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A socio-economic environmental baseline summary for the south Atlantic region between Cape Hatteras, North Carolina and Cape Canaveral, Florida Volume II : Climatology

Virginia Institute of Marine Science

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Recommended Citation Virginia Institute of Marine Science. (1974) A socio-economic environmental baseline summary for the south Atlantic region between Cape Hatteras, North Carolina and Cape Canaveral, Florida Volume II : Climatology. Virginia Institute of Marine Science, William & Mary. https://scholarworks.wm.edu/reports/ 2098

This Report is brought to you for free and open access by W&M ScholarWorks. It has been accepted for inclusion in Reports by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. A SOCIO-ECONOMIC ENVIRONMENT AL BASELINE SUMMARY FOR THE SOUTH ATLANTIC REGION BETWEEN CAPE HATTERAS, NORTH CAROLINA AND CAPE CANAVERAL, FLORIDA

~ . Volume II CLIMATOLOGY

Prepared by the VIRGINIA INSTITUTE OF MARINE SCIENCE Gloucester Point, Virginia 23062 for the BUREAU OF LAND MANAGEMENT United States Department of Interior under Contract No. EQ4AC007 with the Council on Environmental Quality

September 197 4 A SOCIO-ECONOMIC ENVIRONMENTAL BASELINE SUMMARY FOR

THE SOUTH ATLANTIC REGION BETWEEN CAPE HATTERAS,

NORTH CAROLINA AND CAPE CANAVERAL, FLORIDA

Volume II Climatology

prepared by

Evon P. Ruzecki

Virginia Institute of Marine Science Gloucester Point, Virginia 23062

for the

Bureau of Land Management U. S. Department of Interior

under Contract No. EQ4AC007 with the Council on Environmental Quality

September 1974 FOREWORD

The geographic area covered in this report extends from Cape Hatteras, North Carolina, on the north, to Cape Canaveral, Florida, to the·south. Included within this area are portions of the coastal areas of South Carolina and Georgia. All or portions of thirty coastal counties are included within the study area.

Estuaries in this area tend to be partially mixed due to relatively low runoff per mile of coast. The proximity of the Gulf Stream to the continental shelf and the low runoff combine to cause the salinity of the coastal water to be somewhat higher than that of the coastal water north of Cape Hatteras. Surface isotherms parallel the coast and temperatures generally increase seaward. Maximum horizontal gradients and minimum vertical gradients of temperature are usually found during winter.

This coastal region is warm temperate ±n character with a strong maritime influence. There is a tendency toward an annual division into two seasons, with higher precipitation during the sununer than the winter. Local afternoon thunder­ showers produce most of the sununer rainfall. Wind activity is generally low, flowing mainly from the northern quadrants in winter and southern quadrants during sununer. Severe storm development is infrequent throughout the region.

Geologically the area comprises the southern segment of the Atlantic Coastal Plain. The area hetween Cape Hatteras and Cape Romain is distinctive for its three large smooth scallops between Capes Hatteras, Lookout, Fear, and Romain. South of Cape Romain, the area is characterized by extensive salt marshes bordered by a belt of low lying islands, the "Sea Islands" of South Carolina and Georgia. South of the Sea Islands are extensive beaches and associated dunes which create lagoonal flats inland.

iii From a chemical standpoint, the area is characterized by generally low nutrient input from rivers, especially nitrogen, resulting in low phytoplankton production. Heavy·detritus loads from adjacent salt marshes keep the oxygen level in estuaries below saturation. These streams have little capacity to assimilate additional oxygen demand.

Zoogeographically, the area comprises the Carolinian Province. At the northern end, long, narrow barrier islands, well separated from the mainland, are backed by irregularly-. flooded marshes. The enclosed sounds with muddy bottoms and high turbidity, are productive nursery grounds for conunercial fish and shellfish. Along South Carolina and Georgia, the salt marshes provide the base of the food chain for the estuaries. Along t~e remainder of the coast, the mainland is exposed to the sea. The offshore region is sandy throughout with out­ croppings of coral, rock, and other substrates called live- .bottom habitats which are productive of fishery products. The biota is basically temperate with a number of subtropical species.

Economically, the area of the study is generally de­ pressed. The highest degree of urbanization has occurred at the major ports in the area: Wilmington, North Carolina; Charleston, South Carolina; Savannah, Georgia; and Jacksonville, Florida. Per capita income in the area is below u. S. averages in 29 of the 30 counties. Six counties are primarily dependent upon manufacturing as a source of income, six on farming, nine on government (primarily military bases), three on services, and six have no dominant sector.

This area, then, beginning just below the southern limit of the Norih Eastern Megalopolis and extending to the booming Florida peninsula, is one of the largest portions of relatively unspoiled, undeveloped sea coast in the contiguous United States. The possibility of rapid coastal development associated with Outer Continental Shelf resources development should be of prime concern to planners and managers at all levels of government and industry.

It is hoped that this report will be useful to planners and managers as they chart the course of development in the area, and as a data base for preparation of environmental impact statements covering the broad area. There is, however, a seri­ ous need for additional data in various disciplines relative to the entire region, and especially relative to small subsections such as individual estuaries. The present sununary hopefully identifies those subjects and areas requiring further study before planning and management of development can be done on a rational basis.

iv I wish to thank the principal developers of the various portions of this report:

Volume I. Physical Oceanography - Mr. John P. Jacobson

Volume II. Climatology - Mr. Evon P. Ruzecki

Volume III. Chemical and Biological Studies - Dr. Morris H. Roberts, Jr.

Volume IV. Geological Oceanography - Dr. John M. Zeigler and Ms. Martha A. Patton all of the Virginia Institute of Marine Science, and

Volume V. Socio-economic Studies·- ~essrs. Richard May and John Delaplaine and Ms. Margrit Schatz of Planners, Incorporated, Washington, D. C. for their close cooperation and hard labors in completing this study.

Mr. Edward J. Tennyson, Contracting Officers Authorized Representative, of the Bureau of Land Management, has been most responsive and helpful during the course of this study.

Ms. Beverly L. Laird deserves particular mention as the major day to day coordinator in the final prep~ration of this report. She was ably assisted by Ms. Claudia B. Walthall, Melissa A. Forrest, Vickie B. Krahn, and Elaine Poulson, who typed the final manuscript and by various and numerous people in the Department of Information and Education who prepared the art and photographic work for this report.

This report was prepared for the Bureau of Land Manage­ ment under Contract No. EQ4AC007 with the Council on Environmental Quality.

Maurice P. Lynch Senior Marine Scientist Office of Special Programs Virginia Institute of Marine SciencP

15 September 1974

V TABLE OF CONTENTS

Foreword iii

Table of Contents . vi

List of Figures. viii List of Tables ...... xiv

Chapter 1. Introduction

1.1. General ••.•• 1

1.2. Acknowledgments. 1

1.3. Adequacy of Climatological Data in the Region from Cape Hatteras to Cape Canaveral .•..• 2

Chapter 2. Climatology

2.1. General Climatology of the Region Cape Hatteras to Cape Canaveral .•••.. 7

2.2. Climatology of Specific Locations .. . 22

2.2.1. Cape Hatteras, North Carolina 0 22 2.2.2. New Bern, North Carolina .•...... 25 2.2.3. Wilmington, North Carolina ..••...... 27 2.2.4. Charleston, South Carolina •.••• . . . . . 28 2.2.5. Savannah, Georgia. • • . .. 30 2.2.6. Brunswick, Georgia ••.. 31 2.2.7. Jacksonville, Florida •••••• 33 2.2.8. Palatka, Florida •••..•••• 34 2.2.9. Daytona Beach, Florida ••.••• 36 2.2.10. Titusville, Florida •..•••• 37

Chapter 3. Winds

3.1. Medium Scale Weather Systems .•..•.• 39 3.1.1. Basic Information ...•..•...• 39 3.1.2. Cyclogenesis and Frequency and Tracks of Cyclones ....••.••.•.•• 41

vi 3.1.3. Anticyclogenesis and Frequencies and Tracks of Anticyclones •.••••• 66

3.2. Tropical Cyclones, Tropical Storms, Hurricanes and Great Hurricanes .••.••..•. 66

3.3. Tornadoes and Waterspouts. 97

3.4. Local Winds .•..••.•••..•••.•• 99 3.4.1. Winds for Shore Stations, Cape Hatteras to Cape Canaveral. . • • • • . ••••••• 99 3.4.2. Winds for Offshore Areas from Cape Hatteras to Cape Canaveral • . • • •••••.• 129

Chapter 4. Air Temperature .•.••....•••..•. 134

Chapter 5. Precipitation .••. 149

5.1. General .•. 149

5.2. Precipitation at Land Stations, Cape Hatteras to Cape Canaveral ..•.•••••.•.••..•. 149

5.3. Frequency of Occurrence of Precipitation for Offshore Region, Cape Hatteras to Cape Canaveral ••. 165 5.4. Thunderstorms •...... 165

Chapter 6. Relative Humidity, Visibility at Sea, Occurrence of Fog and Severe we·ather Events, Cape Hatteras to Cape Canaveral

6.1. Relative Humidity. 176

6.2. Fog, Smoke and Haze. 182

6.3. Visibility at Sea. 182 6.4. Severe Weather Events...... • 190

Chapter 7. Concluding Remarks ••••.••••••.••• 203

Bibliography •••..•..••••••••••••••• 205

vii LIST OF FIGURES

Figure 1.1. Region between Cape Hatteras, North Carolina and Cape Canaveral, Florida showing locations where meteorological data density in time and space are excellent, good, fair, and poor for compilation of climatological analysis 3

Figure 1.2. SSMO areas from which meteorological data for the off shore region between Cape Hatteras, North Carolina and Cape Canaveral, Florida were used • • • • • • • • • 5

Figure 2.1. Average number of days per year that minimum temperature can be expected to be 320F and below based on data through 1964 ••••.••••••• 8

Figure 2.2. Mean length of freeze free period {days) between last 32°F temperature in Spring and first 320F temperature in Fall based on the period 1921-1950 ••••.•••• 9

Figure 2.3. Mean data of first 32°F temperature in Autumn based on the period 1921-1950 . . . . . 10 Figure 2.4. Mean data on last 32°F temperature· in Spring based on period 1921-195~ . . . . . 11 Figure. 2. 5. Yearly mean temperatures (OF) Cape Hatteras N. C. to Cape Canaveral, Fla. based on the period 1941-1970...... 12 Figure 2.6. Average number of hours per year that surface air temperature exceeds ao°F 13

Figure 2.7. Mean annual number of days that maximum temperatures of 9QOF and above can be expected based on data through 1960 14

Figure 2.8. Normal annual total precipitation (in inches) for Southeastern United States based on period 1931-1960 ••..•. 16

viii Figure 2.9. Monthly mean precipitation in inches for the region Cape Hatteras, N. C. to Cape Canaveral, Fla. based on the period 1941-1970 .•..••••••• . . . . 17 Figure 2.10. Average number of days per year that thunderstorms occur ..•.••.•• 18

Figure 2.11. Average number of days per year that hail has fallen. . . • • . . •• 19

Figure 2.12. Average annual distribution of snow­ fall (in inches) based on 40 years of data • . . . • • • . • . . . • . • . . . . . 20 Figure 2.13. Average number of days per year with fog ...... 21

Figure 2.14. Number of times destruction was caused by Tropical Storms 1901-1955...... 23 Figure 2.15. Tracks of all tornadoes for the period 1916-1950 ...... 24 Figure 3.1. Five stages of development of an extra- tropical cyclone...... • ...... 40 Figures 3.2 through 3.13. Frequency of cyclogenesis. Figure 3.2. January ...... 42 Figure 3.3. February ...... 43 Figure 3.4. March ...... 44 Figure 3.5. April ...... 45 Figure 3.6. May ...... 46 Figure 3.7. June ...... 47 Figure 3.8. July . . 48 Figure 3.9. August ...... 49 Figure 3.10. September ...... 50 Figure 3.11. October ...... 51 Figure 3.12. November ...... 52 Figure 3.13. December ...... 53 Figures 3.14 through 3. 5. frequency and tracks of low pressure areas. Figure 3.14. January ...... 54 Figure 3.15. February ...... 55 Figure 3.16. March ...... 56 Figure 3.17. April ...... 57 Figure 3.18. May ...... 58 Figure 3.19. June ...... 59

ix Figure 3.20. July • • . . • • • • • • • • • • . 60 Figure 3.21. August . • • • . . • • . • • • 61 Figure 3.22. September. • • • • •.•••• 62 Figure 3.23. October •••.•••••••••••• 63 Figure 3.24. November . • • . • • • • • • • • • 64 Figure 3.25. December . • • • . • • • • • • • • 65

Figures 3.26 through 3.37. Frequency of anticyclones. Figure 3.26. January .••••••••••••••• 67 Figure 3.27. February . • . . •.• 68 Figure 3.28. March. • • • . •••••• 69 Figure 3.29. April...... 70 Figure 3. 3 0. 1-1.ay • • • . • • • • • • . • • • 71 Figure 3.31. June • . • • . • . .• 72 Figure 3.32. July .•••.•••••.•••• 73 Figure 3.33. August .•.•.••••••••••• 74 Figure 3.34. September. • ••••••••• 75 Figure 3.35. October. • • • • . • • . . •• 76 Figure 3. 36. November • • • • . . • • • • • • • 77 Figure 3.37. December ••••••••.•••.•• 78 Figures 3.38 through 3.49. Frequency and tracks of high pressure areas. Figure 3.38. January. . .•.•...... 79 Figure 3.39. February . . • . . . . . ••••• 80 Figure 3.40. March ...... •..••• 81 Figure 3.41. April ...... 82 Figure 3. 4 2. May . . . • • • • • . • . . 83 Figure 3. 4 3. June . • . . • • • • • • · • . • • . 84 Figure 3 • 4 4 . July . • • • • . . • • . . • • • • • 85 Figure 3.45. August ••••..•.•••••• 86 Fi.gure 3 . 4 6. September . • • . . • • • . • . • . . . 87 Figure 3.47. October. . • • . •...• 88 Figure 3 • 4 8 • November . • . • . • • • . • . • • 89 Figure 3.49. December . . • • . • . • ..• 90

Figure 3.50. Earliest and latest days of the year that tropical cyclones, hurricanes or great hurricanes have occurred within each 50 mile segment of coastline from Cape Hatteras to Cape Canaveral •.••• 93

Figure 3.51. Percent probability that a tropical storm, hurricane or great hurricane will occur in any year within each of the 50 mile segments of coastline shown in Figure 3. 50 ...... 94

Figure 3.52. Number of tropical storms and hurricanes (by month) affecting each degree of latitude between Cape Hatteras, North Carolina and Cape Canaveral, Florida for the period 1901 to 1963 . . • • . • • • 95-96

X Figures 3.53 through 3.64. Surface winds at shore stations. Figure 3.53. January. . . • • • •••••••. 102 Figure 3.54. February • • • • • • ••••• 103 Figure 3.55. March .•••••••••••.•••• 104 Figure 3.56. April . • • . • ••.•.. • t. 105 Figure 3.57. May. • • • • • • • . . •. 106 Figure 3.58. June . • • • • •••• 107 Figure 3.59. July ••..••••••••••••• 108 Figure 3.60. August .•••••••••••.•.• 109 Figure 3.61. September. • •..•••••••• 110 Figure 3.62. October ••.••.•••..•••.. 111 Figure 3.63. November .•.•••••••• 112 Figure 3.64. December . • • . . • • • . • • • • 113

Figure 3.65. Average monthly wind speed and direction for land stations from Cape Hatteras to Cape Canaveral •••••••••.•• 114-115

Figures 3.66 through 3.78. Wind roses for SSMO areas (Right) and associated land stations Figure 3.66. January. 116 Figure 3.67. February .••• 117 Figure 3.68. March •••• . . 118 Figure 3.69. April 119 Figure 3.70. May . .... 120 Figure 3. 71. June . . . • • • • • • . ., . . 121 Figure 3.72. July 122 Figure 3.73. August ..•.•••• 123 Figure 3.74. September •••. 124 Figure 3~75. October •••••••. 125 Figure 3.76. November ••.•••• 126 Figure 3.77. December ••.•. 127 Figure 3 .-78. Annual 128 Figure 3.79. Winds for SSMO Area 9...... 131 Figure 3.80. Winds for SSMO Area 10 . . . . . 132 Figure 3.81. Winds for SSMO Area 11 ...... 133 Figures 4.1 through 4-.10. -Monthly air temperatures (°F) showing record highe·s·t, average daily maximum, daily mean,_average daily minimum, and record lowest temperatures for each month. Figure 4.1. Cape Hatteras, N. C •••••• • • · 136 Figure 4 • 2. New Bern, N. C. • • • • . • • 137

xi Figure 4.3. Wilmington, N. c...... 138 Figure 4.4. Charleston, s. c. . • ...... 139 Figure 4.5. Savannah, Ga...... 140 Figure 4.6. Brunswick, Ga...... 141 Figure 4. 7. Jacksonville, Fla. . . . . · . 142 Figure 4. 8. Palatka, Fla...... 143 Figure 4.9. Daytona Beach, Fla •...... 144 Figure 4.10. Titusville, Fla •• ...... 145 Figure 4.11. Monthly temperatures in SSMO Area 9 shown as percent of data which was below a given value ••••••••••••• 146

Figure 4.12. Monthly temperatures-in SSMO Area 10 shown as percent of data which was below a given value. • . • • • • • ••• 147

·Figure 4.13. Monthly temperatures in SSMO Area 11 shown as percent of data which was below a given value ••.•••••• • 148

Figure 5.1. Mean number of days with precipitation of 0.1 inch or more ••••••••• 150

Figure 5.2. Maximum precipitation in 24 hour period 153

Figure 5.3. Normal total monthly precipitation and maximum monthly precipitation •. • • 158

Figure 5.4. Normal total monthly precipitation 162

Figure S.S. Normal monthly precipitation (in inches) for the Southeastern United States based on data from 1931-1960 •.•••.•••.•• 166

Figure 5.6. Percent occurrence of all types of pre­ cipitation {by month) in SSMO areas between Cape Hatteras, N. C. and Cape Canaveral, Fla .•••••••••••• 169

Figure 5.7. Mean number of days with thunderstorms, by month • • . . • • . . • • • . • • • • 170

Figure 5.8. Monthly frequency of occurrence of thunder and lightning in SSMO Areas between Cape Hatteras, N. C. and Cape Canaveral, Fla •••••••••••• 174

Figure 6.1. Average relative humidity by month for 1 a.m., 7 a.m., 1 p.m., and 7 p.m. local time ••.•••••• 177

xii Figure 6.2. Per.cent of time relative humidity is over a given% value in SSMO Areas. . . . 181 Figure 6.3. Mean number of days with heavy fo·g . 183

Figure 6.4. Percent occurrence of fog and smoke and haze in SSMO areas~ ••••••• 186

Figure 6.5. Mean percent of time visibility was a given distance (in nautical miles) for SSMO Area 9 ••••••••••• 187 Figure 6.6. Mean percent of time visibility was a given distance (in nautical miles) for SSMO Area 10 ••••••••••••••• 188

Figure 6.7. Mean percent of ,time visibility was a given distance (in nautical miles) for SSMO Area 11 ....••..•••.... 189

xiii LIST OF TABLES

Table 3.1. Number of tropical storms, hurricanes, and totals of both occurring in one degree segments of latitude between Cape Hatteras, North Carolina and Cape Canaveral, Florida for the period January 1901 to December 1963. 98

Table 3.2. Total number of funnel clouds, tornadoes and water spouts reported within each degree of latitude for the coastal area between Cape Hatteras and Cape Canaveral from January 1960 to December 1973 ••••••• 100

Table 6.1. Severe weather events in the region from Cape Hatteras, North Carolina to Cape Canaveral, Florida ••••••••.•• 191

xiv CHAPTER 1 INTRODUCTION

1.1. General

This volume describes the climate of the coastal and con­ tinental shelf regions between Cape Hatteras., North Carolina and Cape Canaveral, Florida and is outlined as follows: This intro­ ductory chapter describes the volume and discusses the adequacy of information used to formulate successive chapters. Chapter 2 presents a general description of the climate of the region from Cape Hatteras to Cape Canaveral and the climatology of specific locations in the region. Chapters 3, 4 and 5 deal with the major weather phenomena: winds, air temperature and pre­ cipitation., which, in concert, determine the climate of the region. Chapter 6 is devoted to non-precipitating atmospheric moisture (relative humidity, fog) and the occurrence of severe weather events in the area. The final chapter contains some concluding remarks and is followed by a bibliography.

In general, descriptions of various climatological fea­ tures within each chapter are ordered from north to south and frqm shore stations to offshore regions. Whenever possible, data ha:W been presented in graphical form and, in some instances, as with wind data in Chapter 3, the same data have been presented in several different graphical formats in an attempt to satisfy various needs.

In order to aid the reader who is not acquainted with meteorological terminology, nontechnical descriptions of various phenomena and their causes have been interjected throughout this report.

1.2. Acknowledgments

Sources of weather and climatological information for this report were numerous;however, heavy reliance on a few requires acknowledgment. Climatological descriptions in Chapter 2 were, for the most part, taken from descriptions prepared by state climatologists and are found in the NOAA Publications: "Local Climatological Data." Weath.er data used in preparation of most of the figures presented here wereobtained from NOAA in various publications which present means and extremes on a monthly basis. Weather information for the offshore region was taken from the Department of Commerce, National Technical Infor­ mation Service Publication: "Summary of Synoptic Meteorological

1 Observations" ( SSMO) • In several instances, maps of isopleths were copied from various publications. In each such instaqce, sources were acknowledged in the text or figure caption. Most of the figures, however, were prepared from tabular data. I am indebted to Ms. Terry Markle and Ms. Marilyn Cavell for the many hours they spent at these tedious tasks. I am also indebted to Ms. Markle for preparing the initial descriptions of tropical cyclones and hurricanes found in Chap­ ter 3 and to Ms. Cavell for extracting and rearrangement of storm data found in Chapter 6. Finally, I would like tq express my thanks to Ms. Shirley Crossley for her diligence and patience while typing the several drafts of this volume.

1.,3. Adequacy of Climatological Data in the Region from Cape Hatteras to Cape Canaveral A description of the climate of the sector from Cape Hatteras, North Carolina to Cape Canaveral, Florida and extend­ ing· from the coastal region to the continental slope is dependent on the availability of consistent long-term weather information throughout the area. Availability of.such information for this region can be divided into four general categories: A. Excellent - Consistent, long-term records of tempera­ ture, wind, precipitation, fog and unusual·weather events. Such information is readily available from large municipalities with airports servicing regularly scheduled flights, military instal~ lations with airports, agricultural stations, and offshore light stations operat~d by the u. s. Coast·.Guard. B. Good - Consistent long-term, records of temperature and precipitation are usually available from smaller urban areas. c. Fair - Information which can be described as random in space but consistent in time is available from commercial and military maritime reporting. This usually consists of temperature, wind data and the occurrence of precipitation along shipping routes and in military operation areas. D. Poor - Occasional observations in time and space are available o~la-rge areas and long periods. Figure 1.1 gives an indication of availability and gaps in climatological data based on these categories. It is readiiy apparent that the continental shelf, the region of-most interest

2 CLIMATOLOGICAL DATA

EXCELLENT: 1 Cape Hatteras, N.C. 2 Diamond Shoal Light 3 Wilmington, N.C. 4 Five Fathom Bank Light 5 Charleston, S.C. 6 Savannah, Ga. 7 Jacksonville, Fla. 8 Daytona Beach, Fla.

GOOD: A New Bern, N. C. B Brunswick, Ga. C Palatka, Fla. D Titusville, Fla. FAIR: shaded POOR: unmarked

Figure 1.1. Region between Cape Hatteras, North Carolina and Cape Canaveral, Florida showing locations where meteorological data density in time and space are excellent (numbered locations), good (lettered locations), fair (shaded regions), and poor (unmarked regions) for compilation of climatological analysis.

3 to those concerned with development and transport of minerals and fuel resources, is the poorest insofar as available clima­ tological data is concerned. SSMO data for the regionaregrouped into three areas as shown in Figure 1. 2. Comparison of Figures 1.1 and 1.2 indicates that the greater portion·of SSMO areas 10 and 11 are categorized as poor insofar as climatological data are concerned. This poor rating is applied because of the size of the SSMO areas and the assumed lack of data in the specific region of interest (the continental shelf) not because of the quality or quantity of data itself. The assumption that SSMO information is lacking in the region of interest is based on the following information:

1. Although weather observations used to prepare the SSMO reports were taken aboard vessels of varying registry, most of the observations are recent and were taken in conjunction with oceanographic observations. The spatial density of these oceanographic observations is discussed in Volume I of this report (see Chapter 9 of Volume I).

2. As stipulated in the SS'MO (page iii)" ••• it should be noted that these data are based upon observations made by ships in passage. Such ships tend to avoid bad weather when possible, thus biasing our data toward good weather samples."

3. Each SSMO area from Cape Hatteras to Cape Canaveral can be subdivided into three east-west climatological segments:

a. the inner (shelf) segment extending from the coast to the Florida Current - Gulf Stream;

b. the Florida Current - Gulf Stream segment which usually approximates the continental slope area; and;

c. an outer portion east of the Florida Current - Gulf Stream region.

These divisions, although not apparent from the SSMO data in their present formpre strongly suggested by a comparison of the climatological descriptions of successive locations from Cape Hatteras, North Carolina to Daytona Beach, Florida. The climates of all coastal locations in this region are greatly influenced by their proximity to the Atlantic Ocean; however, the climate of Cape Hatteras is less severe than those locations immediately to the South. This apparent anomalous situation can be attributed to the nearness of the Gulf Stream lending credence to the suggested east-west climatological segmentation.

Pertinent meteorological summaries for SSMO areas 9, 10

4 I I , I , I AREA I 09 / / ~' I I I ,~ / ,,,.-""' AREA / /0 _, oo ~tC\ , ,. ,., I ," I I I / I \ AREA J ( II I \ \ \ \ I

Figure 1.2. SSMO areas from which meteorological data for the off shore region between Cape Hatteras, North Carolina and Cape Canaveral, Florida were used.

5 and 11 are presented in this report in graphical form but no attempt has been made to formulate a narrative climatological description for these large areas.

6 CHAPTER 2 CLIMATOLOGY

2.1. General Climatology of the Region Cape Hatteras to Cape Canaveral

The climate of the region from Cape Hatteras to Cape Canaveral is mild and maritime. Average winter temperatures range from 45°F at Cape Hatteras to 60°F at Cape Canaveral with a l.7°F increase per degree of latitude from Cape Hatteras to Savannah, Georgia and a 3.3°F increase per degree latitude from Savannah to Cape Canaveral. The average number of days per year that minimum temperatures below 32 F can be expected ranges from approximately 25 at Wilmington, North Carolina to 2 at Cape Canaveral with somewhat fewer than 20 freeze days per year expected at Cape Hatteras as shown in Figure 2.1. The corillary to this, i.e., freeze-free days to be expected during a year, is shown in Figure 2.2. Mean dates of the first and last 32°F temperatures in fall and spring are shown in Figures 2.3 and 2.4 respectively. Autumn freezes begin as early as 20 November just north of Wilmington, North Carolina and as late as ~O December north of Cape Canaveral with no freeze occurring in the Cape Hatteras region and south of Wilmington in some years. The last date of spring freeze generally occurs between 10 March (again north of Wilmington) and 20 January (north of Cape Canaveral}.

Average sununer temperatures for the entire region range from 78.5°F at Cape Hatteras to 81.SoF at Cape Canaveral. The general variation of isotherms with latitude and time is shown in Figure 2.5.

The intensity of summer heating can be indicated in two ways. Figure 2.6 shows the average number of hours per year that surface air temperatures exceed ao°F. Most of the region between Cape Hatteras and Cape Canaveral will, on the average, experience 1400 to 1800 hours of temperatures over 80°F while the Cape Hatteras region will have from 900 to 1400 hours of these elevated temperatures per year. The number 0£ days per year that temperatures over 90°F can be expected ranges from 5 at Cape Hatteras to over 30 for the region from just .north of Wilmington, North Carolina to Cape Canaveral as shown in Figure 2.7.

The moderate temperatures in the Cape Hatteras region are attributed to the presence of cooler Virginia coastal water which is found between the Cape and the western edge of the Gulf Stream.

7 Figure 2.1. Average number of days per year that minimum temperature can be expected to be 32°F and below based on data through 1964. Source: u. S. Department of Commerce ESSA. Environmental Data Service "Climatic Atlas of the United States."

8 350

300

330 FREEZES OCCUR SOUTH OF THIS DASHED \ LINE IN LESS THAN HALF THE YEAR$

.,...... ·No FREEZE

Figure 2.2. Mean length of freeze free period (days) between last 32°F temperature in Spring and first 32°F temperature in Fall based on the period 1921-1950. Source: U. s. Department of Commerce ESSA. Environmental Data Service "Climatic Atlas of the United States.''

9 80°

NOV 30 SOME YEARS NO AUTUMN FREEZE IN MOST AREAS SOUTH OF THIS DOTTED LINE

FALL FREEZES OCCUR SOUTH OF THIS DASHED LINE IN LESS THAN HALF THE YEARS

25°

..... /NO FREEZE

Figure 2.3. Mean date of first 32°F temperature in Autumn based on the period 1921-1950. Source: U. s. Department of Commerce ESSA. Environmental Data Service, "Climatic Atlas of the United States."

10 •./NO FREEZE

Figure 2.4. Mean data of last 32°F temperature in Spring based on period 1921-1950. A. In some years there is no spring freeze east or south of the dotted lines. B. Spring freezes occur south of the dashed line in less than half of the years. Source: u. s. Department of Commerce ESSA. Environmental Data Service, "Climatic Atlas of the United States."

11 MONTH D J F M A M J J A s 0 N D J I 36 ,~~ I \ ) J70"

z 0 uJ 33 0 ....::> ;:: <[ 32 _J

31

30

29

D J F M A .M J J A s 0 N D J

Figure 2.5. Yearly mean temperatures (°F) Cape Hatteras, N.C. to Cape Canaveral, Fla. based on the period 1941-1970. Source: u. S. Department of Commerce "Climatography of the United States No. 81 (By State) Monthly Normals of Temperature, Precipitation, and Heating and Cooling Degree Days 1941-70.

12 Figure 2.6. Average number of hours per year that surface air temperature exceeds ao°F. Source: Water Atlas· ·o·f ·the· un·ited States.

13 30°

Figure 2.7. Mean annual number of days that maximum temperatures of 90°F and above can be expected based on data through 1960. Source: u. S. Department of Conunerce ESSA. Environmental Data Service, "Climatic Atlas of the United States."

14 Summer temperatures all along the coast are moderated by tne sea breeze effect. During a normal summer day, ground surfaces will heat more rapidly than water surfaces. This rapid heating elevates near surface air temperatures inland. The warmer air rises and, in so doing, draws the somewhat cooler air from over the water toward the coast, thereby depressing coastal temperatures. The reverse procedure operates at night when the land surface cools more rapidly than the adjacent sea surface. An additional effect of thundershower cooling helps to further depress late afternoon temperatures. This is particularly effective in the region from Brunswick, Georgia to Cape Canaveral and can reduce surface air temperatures by as much as 15°F in an afternoon.

Average annual rainfall, as shown in Figure 2.8, ranges from a maximum of over 56 inches just south of Cape Hatteras to a minimum of somewhat less than 48 inches near Charleston, South Carolina. From near Savannah, Georgia to Cape Canaveral annual average rainfall increases again from 48 to over 56 inches. Average monthly rainfall for the coastal region as a function of time and latitude is shown in Figure 2.9. Cape Hatteras has two rainy seasons, late fall-winter and summer. Rains during the late fall-winter period are the result of coastal storms and generally last for prolonged periods while summer rains are due to thunderstorms. South of Cape Hatteras, pre­ cipitation is mainly the result of summer thunderstorms with the rainy season increasing towards the South. Thundershowers occur during one of every three days from June through August at Wil­ mington, North Carolina with frequencies and length•of the rainy season extending to almost daily afternoon thundershowers from June to October near Cape Canaveral. Figure 2.10 shows the average number of days per year that thunderstorms occur. Hail frequently occurs during severe thunderstorms and Figure 2.11 shows the average number of days per year that this phenomenon canbe expected. The average yearly amount of snowfall in this region is less than two inches in the northern portion and an unusual occurrence in Georgia and Florida (see Figure 2.12). Snow that does fall in this coastal region usually lasts less than 2 4 hours.

Fog is most frequent in the region between Wilmington, North Carolina and Cape Canaveral. This length of coast averages 20 to 45 foggy days a year while the Cape Hatteras region experiences between 10 and 20 days with fog each year as shown in Figure 2.13. Fog generally occurs during late fall, winter and early spring and rarely lasts throughout the day.

Average monthly winds for the region range from ten knots in late winter and early spring to eight knots during August. Winds at Cape Hatteras, however, average two knots higher than

15 0 75° )

30°

25°

Figure 2.8. Normal annual total precipitation (in Inches) for Southeastern United States based on period 1931-1960. Source: U. s. Department of Conunerce ESSA. Environ­ mental Data Service, "Climatic Atlas of the United States."

16 MONTH D J F M N D J --4')

z 0

l.&J 0 ::>.... ~ .J Oc

DJ FM AM J JASON DJ

Figure 2.9. Monthl'y mean precipitation in inches for the region Cape Hatteras, N. C. to Cape Canaveral, Fla. based on the period 1941- 1970. Source: u. S. Department of Com­ merce "Climatography of the United States No. 81 (By State) Monthly Normals of Temperature, Precipitation and Heating and Cooling Degree Days 1941-70.

17 85° 80° 75°

30°

25°

so...... ,"~50

Figure 2.10. Average number of days per year that thunderstorms occur. Source: Water Atlas of the United States.

18

I 85° 80° 75°

35°

30°

25°

Figure 2.11. Average number of days per year that hail has fallen. Source: Water Atlas of the United States.

19 35°

30°

. t I 25° .,,,

Figure 2.12. Average annual distribution of snow-· fall (in inches) based on 40 years of data. Source: Water Atlas of the United States.

20 Figure 2.13. Average number of days per year with fog. Source: Water Atlas of the United States.

21 other locations for all months. Summer winds from Cape Hatteras to Charleston are generally out of the south to west-southwest while those in the Savannah-Jacksonville region are from the west and southwest. Summer winds near Daytona Beach range from the east during April and May, the southwest and south~southwest during June and July and blow from an easterly direction again in August and September. Late fall and early winter winds blow from a northerly direction in the region from Cape Hatteras to Savannah while those in the Jacksonville and Daytona Beach areas. are generally from the northwest.

Tropical storms frequent the Cape Hatteras to Cape Cana-· veral area quite readily. Destruction from tropical storms and hurriQanes has been most frequent in the North Carolina region adjacent to Cape Hatteras as shown in Figure 2.14.

Tornadoes are a somewhat rare phenomenon in this region. When they occur, they are most frequently found in the region between Jacksonville and Daytona Beach, Florida. Tornadoes have been reported during each month of the year in this region. (The fewest of tornadoes occur in November and they are most frequent in September.) Figure 2.15 shows locations and tracks of all tornadoes reported for tne period 1916 to 1950.

2.2. Climatology of Specific Locations

This section was taken directly from Climatological Summaries published by the Department of Commerce. When authors have been indicated in these summaries their names appear at the end of the summary.

Date of Summary preparation is indicated in parenthesis.

2.2.1. Cape Hatteras, North Carolina (1972)

Hatteras Island is one of a group of narrow elongated islands comprising the Outer Banks of North Carolina. These islands are separated from one another by inlets varying from 1 to 3 miles wide, and from the mainland by the different sounds varying from 1 to 30 miles wide. While in places sand dunes have built up to 100-feet high, the average elevation of the Outer Banks is less than 10 feet above mean sea level.

Hatteras Island, the largest and easternmost of the islands, extends about 50 miles along its scyth-shaped length and. nearly 4 miles across at its broadest point. The Weather Station is located on the south side of the Village of Buxton, about 1 mile WNW of Cape Hatteras Lighthouse, and about 1~ miles .NW of

22 Figure 2.14. Number of times destruction was caused by Tropical Storms 1901-1955.

23 •

~·

LEGEND

-+ Tornado Track

Location of Tornado • Track too Short to Indicate

0 50 100 150 200 Ml LES

Figure 2.15. Tracks of all tornadoes for the period 1916-1950 (from Weather Bureau Technical Paper No. 20, 1952).

24 the Point of Cape Hatteras.

Hatteras Village, which is located 9 miles West of the Weather Station near Hatteras Inlet, is the largest village on Hatteras Island.

Weather observations have been taken on Hatteras Island, within 10 miles of the present office location, continuously since 1874.

The average path of the Gulf Stream passes offshore at a distance of 20 to 50 miles from Cape Hatteras, ~nd in winter to the southernmost penetration of Virginia coastal water is near the Cape. The waters off Cape Hatteras are a favorite breeding ground for seaborne storms. These storms usually move north - before developing full force and their full fury is often vented on the North Atlantic area, while Hatteras is often only mildly affected.

Tropical hurricanes moving up the Atlantic Coast occasion­ ally pass offshore within a few miles of Cape Hatteras, causing high tides and strong winds over the Island. The vegetation of the·area shows the effect of frequent gales, and the hulls of shipwrecked vessels attest the fury of wind and wave, but there is no record of any casualty or serious injury to any resident being caused by a hurricane.

Cape Hatteras has a maritime climate. Summer days are cooler than the mainland with 90° temperatures a rarity. Winters are warmer than the interior with freezing temperatures only about half as frequent as at inland locations. The influence of the Gulf Stream on winter climate is such that citrus fruits are grown on the Island as a novelty. Over a 30-year period the average date of earliest freeze in fall has been December 18, and the latest in spring, February 25. Rainfall at Cape Hatteras averages greater than that of other long established weather stations at North Carolina coastal points, both to the south and north. The high average rainfall is to a large extent due to heavy and prolonged rains falling in connection with offshore storms. Maximum rainfall occurs during the winter and summer, with spring and fall rain being rather light. Snowfall is rare and when it occurs, usually light in amount, often melting as it falls. Hail is much less frequent than at inland points in North Carolina.

' . ' . .. ~.:· 2.2.2. New Bern, North Carolina (1967)

New Bern is located in the east-central portion of the

25 North Carolina Coastal Plain, near the center of Craven County . .The surrounding terrain is nearly level, sloping gently from the, inland western portion of the county toward the coast on the south and east. The elevation of New Bern is about 15 feet and most of the county lies below 50 feet. Situated on the south bank of the Neuse River where it becomes a broad estuary of Pamlico Sound, New Bern is about 30 miles inland from the Atlantic Ocean at its nearest point on the south. The distance to the Ocean on the east is about 30 miles, while the broad expanse of Pamlico Sound lies about 25 miles to the east and northeast.

The climate of New Bern, and of the entire county, is considerably influenced by the nearby Ocean and Sound, with the maritime effects more pronounced in winter than in sununer. Winds blowing from a southerly or easterly direction have a moderating effect on temperature the entire year. Normal winter temperatures are decidedly mild, averaging about five degrees above those of localities one hundred miles or so inland at the same latitude; the difference in sununer is less than half as great. The lowest the temperature has fallen at New Bern in the past 30 years was 8 degrees above zero; the minimum in the usual winter is con­ siderably above this figure. Only about once in average winter does the mercury fail to rise above the freezing point during the day. Snow is infrequent and usually light, averaging less than one inch in each of the winter months of December through February, most of it melting as it falls or shortly thereafter. Entire winters may pass without any snow being seen in New Bern, and it is a rarity for any snow of consequence to remain on the ground longer than a day or two.

In keeping with the mild winter climate, the yearly freeze­ free period, or "growing season," is long, averaging 235 days. In spring, the average date of the last temperature of 24°F or below is February 24; of 200 or below, March 8; of 32° or below, March 22. The average date of the first autumn temp­ erature of 32° or below is November 12; of 28° or below, Novem­ ber 22; of 24° or below, December 9. In the majority of winters the temperature never drops as low as 15°F.

Summers are long and usually quite warm. Occasional peak afternoon temperatures of 90° begin to occur in May, increase in frequency until July, when maximum afternoon temperatures average 90°, then become infrequent by the latter part of September. Excessively high temperatures are a rarity, however; many entire summers pass without thermometer readings as high as 100°.

Rainfall is usually plentiful in the New Bern area. In fact, average rainfall in this section is higher than in any other portion of the state, except for some places in the

.26 ,.

mountains. In spite of high annual precipitation, prolonged spells of gloomy weather are a rarity. Prolonged or severe drought is virtually unknown, for if dry periods do occur during the growing season, the effects on crops are ameliorated by the relatively high water table which prevails in this area.

Sunshine is plentiful, averaging about 65 percent of the maximum possible amount. The prevailing wind--the direction from which the wind blows most._frequently--is southwesterly most of the year. In the autumn, however, it is somewhat more likely to blow from the northeast than from any other direction. There is much variability in wind direction at all seasons.

Tornadoes are very rare in the New Bern area. Like other localities near the Atlantic Coast, this area is subject to effects of occasional tropical storms. The worst seasons in this respect were 1954 and 1955; during the two years a total of' four hurricanes entered the coast of North Carolina. The great majority of such storms skirt the coastline, remaining some distance offshore.

Cha~les B. Carney Albert V. Hardy State User Service Representative State Climatologist

2.2.3. Wilmington, North Carolina (1972)

Wilmington is located in the tidewater section of south­ eastern North Carolina, near the Atlantic Ocean. T~e City proper is built adjacent to the east bank of the Cape Fear River. Because of the curvature of the coastline, in this area, the ocean lies about 5 miles east and about 20 miles south. The surround­ ing terrain is typical of coastal Carolina. It is low-lying with an average elevation of less than 40 feet, and is charac­ terized by level to gently rolling land with rivers, creeks, and lakes that frequently have considerable swamp or marshland adjoining them. Large wooded areas alternate with cultivated fields.

The maritime location makes the climate of Wilmington unusually mild for its ·1atitude. All wind directions from the east-northeast through southwest have some moderating effects on temperatures throughout the year, as the ocean is relatively warm in winter and cool in sununer. The daily range in tempera­ tures is moderate compared to a continental type of climate. As a rule, summers are quite warm and humid, but excessive heat is rare. Sea breezes, arriving early in the afternoon, tend to alleviate the heat inland beyond Wilmington. Long-term averages show afternoon temperatures reach 90° or higher a third of the days in midsummer, but several years may pass without

27 1000 weather. During the colder part of the year, numerous outbreaks of polar airmasses 'reach the Atlantic Coast, causing sharp drops in temperature. However, together with the warming effects of the ocean air, these cold outbreaks are significantly moderated by their long trajectories from the source regions and the effects of passing over the Appalachian Mountain Range. As a result, most winters are short and quite mild.. Even in the most severe cold spell on record since 1870, the temperature. fell to only s0 , and less than once each winter is there an entire day when the·temperature fails to rise above the freezing point.

Rainfall in this area is usually ample and well distri­ buted throughout the year, the greatest amount occurring in the summer. Summer rainfall comes principally .from thundershowers, and is therefore usually of short duration, but often heavy and unevenly distributed. Thundershowers occur about 1 out of 3 days June through August. Winter rain is more likely to be of the slow, steady type, lasting 1 or 2 day~, generally evenly dis­ tributed and ordinarily associated with large, slow-moving, low-pressure systems. Seldom is there a winter without a few flakes of snow, but several years may pass without a measurable amount, and appreciable accumulation on the ground is rare. Haii occurs less than once a year. Sunshine is abundant, with the area receiving about two-thirds of the sunshine hours possible at its latitude.

Because of these many factors, the growing season is long, averaging 244 days, but records show the range is from 180 days to as long as 302 days. This area is exceptionally good for floriculture. Agricultural pursuits, principally field-grown flowers, nursery plantings, and vegetables, are an important part of the economy. Some types of plants continue to grow throughout the year. The average date of the last occur-· rence in the spring of temperatures as low as 320 is March 17, and the first in the fall is November 16.

In common with most Atlantic Coastal localities, the area is subject to the effects of coastal storms and occasional hurricanes which produce high winds, above normal tides, and heavy rains.

2.2.4. Charleston, South Carolina (1972)

The city of Charleston, prior to expansion that began in 1960, was limited to the peninsula bounded on the west and south by the Ashley River, on the east by the Cooper River, and on the so-µtheast by a spacious harbor. Weather records for the City are from observation sites on the lower portion of the peninsula, while airport records are from sites some 10 miles inland. The

28 terrain is generally level, ranging in elevation from sea level, to 20 feet on the peninsula, with gradual increases in elevation· toward inland areas. The soil is sandy to sandy loam with lesser amounts of loam. The drainage varies from good to poor. Because of the very low elevation, a considerable portfon of this com­ munity and the nearby coastal islands are vulnerable to tidal flooding, though only a few tides have exceeded 8 feet above mean low water.

The climate is temperate, modified considerably by the nearness to the ocean. The marine influence is noticeable during winter when the minimum temperatures are sometimes 10° to 15 higher on the peninsula than at the airport. By the same token, maximum temperatures are dampened 30 lower on the penin~ sula. The wind direction is vital to life and work along the coast. The prevailing winds are northerly in the fall and winter, southerly in the spring and summer.

Summer is warm and humid. Temperatures of 100° or higher are infrequent. Maximum temperatures are generally several degrees lower along the coast than inland due to the cooling effect of the sea breeze. Summer is the rainiest season with 41 percent of the annual fall. The rain, aside from occasional tropical storms, is generally of a shower or thundershower nature, producing variable amounts over scattered areas.

The fall season passes through the warm "Indian Summer" period to the prewinter cold spells which begin late in Novem­ ber. From late September to early November the weatner is mostly sunny and extremes of temperature are rare. Late summer and early fall, however, is the period of maximum threat to the South Carolina coast from hurricanes. Some memorable hurricanes that have affected the Charleston area occurred in August 1885, August 1893, August 1911, July 1916, September 1928, August 1940, August 1952, and September 1959. The highest storm tide of record for which accurate heights were obtained was 11.2 feet above mean low water in the August 1893 storm.

The winter months, December through February, are mild with rainfall averaging 18 percent of the annual total. The winter rainfall is generally of more uniform type, although a few thundershowe·rs do occur. There is some chance of a snow flurry, with the best probability of its occurrence ih January, but a significant amount is rarely measured. An average winter would experience less than one cold wave and severe freeze. Temperatures of 200F or less on the peninsula and along the coast are very unusual.

The most spectacular time of the year, weather.wise, is spring with its rapid changes from windy and cold in March to

29 warm and pleasant in May. The spring rainfall represents about 20 percent of the total annual rain. Severe local storms are more likely to occur in the spring than in other seasons; however, some of the most destructive local storms of the 20th century wre a series of severe tornadoes on Septeml:!>er,29, 1938, and a single7 small tornado accompanying a hurricane on September 11 1960. I

The average date of the first freeze in the fall is December 10, and the average date of the last freeze before spring is February 19, giving an average growing season of 294 days. Freeze has been reported in the inunediate inland areas as late as April 16 (1962} and as early as October 24, (1937}.

2.2.5. Savannah, Georgia(1972}

Savannah is surrounded by flat terrain, low and marshy to the north and east, rising to several feet above sea level to the west and south. About half the land to the west and south is cle~red and the other half in woods, much of the latter lying in swamp. The area has a temperate climate, with a seasonal mean temperature of 510F. in winter, 64°F. in spring, ao°F. in summer, and 66° F. in autumn. The growing season averages 273 days, from an average date of last freeze in spring of February 26, to a first in autumn on November 26. Killing frost has occurred as late as April 16 and as early in autumn as October 25. During the history of the station, the lowest temperature · recorded was so F., and the highest 105° F. Sununer temperatures are moderated almost every afternoon by thundershower activity. Of the normal 48.91 inches of rain, about half falls in the thunderstorm season of June 15 through September 15. The remainder, produced principally by squall-line and frontal showers, is spread over the other 9 months with a minor peak in March. Considerable periods of fair, mild weather are experienced in October, November, April, and to a less extent, in May. Snow is a rarity and even a trace does not occur on an average of once a year. The greatest recorded fall was 3.6 inches in February 1968. Severe tropical storms affect this area about once in 10 years. Rainfall from these storms con­ stitute the heaviest sustained precipitation. Instances of this are the 22.79 inches in August 1898, and 22.88 inches in Septem­ ber 1924, most of which was from tropical storms.

The present exposure of the thermometers gives readings more nearly conunensurate with those of suburban street levels of Savannah than was the case of previous locations atop various

30 buildings. Then, especially on still, clear radiation nights, temperatures near the ground and in lower inland places were as much as 15° lower than official minima. Present differences on 0 comparable nights range from 3° to a • The extreme minima for the winter months are considered representative- of the area, because they occurred at times with considerable wind. Extreme maxirraalso are repre~entative of the area.

Sunshine is adequate at all seasons and seldom are there two or more days in succession without it. Sea- and land-breeze effect is usually not felt in Savannah, though it is a daily feature on the nearby islands. Dry, continental air masses reach this area in summer mostly by sliding down the Atlantic coast and giving cooler northeast winds. Such masses reaching this area from the northwest or west in summer bring mostly clear skies and our highest temperatures.

2.2.6. Brunswick, Georgia (1970)

Brunswick is located on Georgia's southeast coast, in the southern part of Glynn County. It is bounded on three sides by coastal waters and is four to five miles from the Atlantic Ocean. The surface is flat with an elevation of 10 to 15 feet. Much of the surrounding area is marsh land.

The coastal waters have a moderating effect on Brunswick temperatures. Summer maxima are generally lower and winter minima higher than at inland points at or near the same latitude. On clear, calm winter nights the variation in minimum temperatures is quite large within short distances. Readings along and near the water may be several degrees higher than in the more inland parts of the city farthest removed from the open water.

Summers are warm and humid but unusually high temgeratures are rare. The afternoon maximum reaches, or exceeds, 90 on less than two-thirds of the days in June, July and August and a read­ ing of 100° is recorded during only about one-half the summers. The upward march of temperature is frequently interrupted by afternoon thundershowers. The sea breeze during the warmest part of the day also tends to hold maximum temperatures below those experienced at inland locations. The highest temperature of record is 1040 in July 1942 and in June 1952. Summer nights are usually pleasant, the temperature dropping to the mid or low ?O's, and sometimes below 70, by early morning. A minimum tem­ perature as high as ao 0 is rare. The Brunswick area enjoys mild and relatively short winters. A minimum temperature of freezing, or below, occurs.on only 11 days during an average winter and only 4 winters in the

31' last 30 have had a temperature under 200. The lowest temperature of record is 13° in February 1895. The cold spells that drop early morning temperatures to freezing, or slightly below, are short and aiternate with longer periods of mild, open weather. Daytime ,temperatures usually rise to comfortable levels even during the coldest weather. The average maximum for the three winter months is 65.5° and afternoon readings in the upper ?O's are not unusual in mid-winter. Since late fall and winter is also the dry season, there is little interruption of construction work or other outside activities at this time.

The average dates of the last freezing temperature in spring and the first freezing temperature in fall are February 10, and December 7, respectively, giving an average freeze- free growing season of 300 days. Freezing has occurred as late in spring as March 27, (1955) and as early in autumn as November 3, (1954). No freezing temperatures occurred during winter of 1949-50.

Brunswick's latitude and coastal location result in a pronounced summer and early autumn rainfall maximum. About 53 .percent of the annual total normally occurs during the four months June through September. This is due partly to the heavy rains that occasionally occur in connection with tropical storms. The full effect of these storms is seldom felt in Brunswick but it is not too unusual for them to bring heavy rains to the area. Late fall and winter is the driest part of the year. Less than one-fifth of the yearli rainfall occurs from November •through February, and long periods of mild sunny weather are· common during this season. Annual rain­ fall totals have ranged from 79.15 inches in 1953 to only 31.92 inches in 1931. The largest monthly total is 22.86 inches in September 1953. Three different months have had no rain. Snow­ fall is rare in Brunswick. Amounts greater than a trace have occurred only two times during the long period of record. The last measurable amount fell in February 1958 and was recorded as about 1.5 inches.

Several tornadoes have been reported in Glynn County. However, they have caused no loss of life and only light property damage. Locally strong winds accompany some of the more severe thunderstorms.

Relative humidity averages range from 87 to 93 percent in the early morning and from 59 to 69 percent in early afternoon. The higher averages for both morning and afternoon occur in late summer and early autumn. Average wind speeds range from about 7 mph in August to around 9 mph in February. Prevailing- direc­ tions vary but are usually southerly in summer and northerly in winter.

32 Horace S. Carter Climatologist for Georgia Agricultural Engineering Center University of Georgia Athens, Georgia

2.2.7. Jacksonville, Florida (1972)

Jacksonville, located on the St. Johns River, about 16 miles inland from the Atlantic Ocean, is near the northern bound­ ary of the trade winds. The surrounding terrain is level, and easterly winds blowing about 40 percent of the time produce a maritime influence that modifies to some extent the heat of summer and the cold of winter. Also being situated south of the usual path of winter storms, the City seldom experiences strong winds or severe cold waves. Cold waves venturing into the southeastern states usually assume a northeasterly course before reaching this longitude, and the cool, dry, invigorating air in the lower quadrants of these waves lends a measure of variety to an otherwise humid climate. Exceptional weather in Jacksonville is occasioned by infrequent "nor-easters" along the·northeast Florida coast, marked by winds 20-30 mph, low stratus clouds, and drizzle. These occur mainly in late summer and fall, and sometimes persist for several days at a time.

The annual mean temperature for Jacksonville is between 69° and 70°. June, July and August are the hottest months, with temperatures averaging above 80°; December, January,•and February are the coolest months, with mean temperatures near the middle fifties. On clear, hot days either an afternoon thundershower or a southeasterly sea breeze usually reaches this area shortly after midday, and temperatures in summer are usually comfortable, very rarely failing to drop below 80°. Temperatures fall to freezingor below about 12 times a year, but it is rare indeed that the temperature does not rise above freezing during the day, in fact, there have been only five occasions on which it failed to do so. Most notable of these was during the great freeze of February 13, 1899, when the maximum for the day was only 27°.

The earliest recorded date of freezing temperature in fall is November 3, 1954, and the latest date in spring, March 31, 1964.

The greatest rainfall, mostly in the form of local thunder­ showers, occurs during the late .·summer months when a measurable amount can be expected 1 day in 2. Rainfall of an inch or more in 24 hours normally occurs about 14 times a year, and very infrequently heavy rains, associated with tropical storms, reach

33 amounts of several inches with durations of more·than 24 hours.

The atmosphere is moist, with an average re.lative humidity of about 75 percent, ranging from about 90 percent in early morning hours to about 55 percent during the afternoon. The average daily sunshine runs from 5.5 hours in December to 9.0 hours in May. Lowest temperatures occur with fair weather, and snow has fallen in measurable amounts twice since 1871: 1.9 inches on February 12-13, 1899, and 1.5 inches on February 13, 1958. Heavy sleet and freezing rain occurred January 4-5, 1879, and nearly 16 hours of freezing rain and freezing drizzle January 11-12, 1962, produced the City's worst glaze storm. These two are the only ice storms on record.

Prevailing winds are northeasterly in the fall and winter months, and southwesterly in spring and sununer. Wind movement, which averages slightly less than. 9 mph, is 2 to 3 miles higher in spring than in other seasons of the year. Although this area is in the Hurricane Belt, this section of the coast has been very fortunate in escaping hurricane-force winds until September 9, 1964, when the center of Hurricane Dora passed just south and west of the City, producing hurricane-force winds of 82 mph from the· north. Most hurricanes reaching this latitude have tended to move parallel to the coastline, keeping well out to sea, or to lose much of their force moving over land before reaching this area.

2.2.8. Palatka, Florida (1960)

Palatka, county seat of Putnam County, is in the eastern portion of the county on the west bank of the St. Johns River and about 25 miles from the Atlantic Ocean. Terrain in Putnam County is gently rolling west of the river but is mostly flat east of the river. There are numerous small lakes and ponds in the central and western sections of the county and a large portion of that area is also wooded. Soils in the county are mostly sandy and low in natural fertility. The nearness to the Atlantic Ocean causes some climatic differences in the county: the frequency of frost or freezing is somewhat greater in the western county area than at Palatka and in fall, especially October, rainfall is somewhat more frequent in the Palatka area than in the western sections of the county.

Summers are long, warm and relatively humid; winters although punctuated by periodic invasions of cold air, are mild and relatively dry. In summer, there is little temperature difference from one section to another. Although sununer after­ noon temperatures reach 90° or higher with great regularity, temperatures of 100° or higher are quite rare, averaging only

34 1 or 2.per summer. In winter, daily maximum temperatures through­ out the county closely follow those reported at Palatka. Winter minimums, especially during cold periods, average somewhat higher in the eastern portion of the county than those in the west. In the farming areas of east Putnam County, temperatures of 32° or lower occur 8 to 10 times per winter, on the average. About half the years have experienced freezing in fall on or before December 1 and in spring, about half the years have experienced freezing after February 24. Freezing has occurred in fall as early as November 3 and in spring as late as March 26. The lowest temper­ ature ever recorded at Palatka is 18° on January 28, 1940. Early records at Federal Point, located on the east side of the St. Johns River, indicate a temperature of 130 in February 1899.

The 4~ month period June through mid-October constitutes the "rainy season" at Palatka which, in an average year, pro- duces about 60 percent of the annual rainfall. The major portion of the summer rain falls from frequent, short duration after- noon or early evening "local" thundershowers which occur, on the average, on about half the days. Thundershowers occur in all seasons but the greatest frequency is in summer. Thundershowers usually reduce temperatures to comfortable levels very quickly; temperature drops of 100 to 15° often occur during these showers. Thundershowers are occasionally heavy and sometimes produce 3 or more inches of rain in an hour or two. The more severe thunder­ storms may be attended by strong winds and in spring occasionally produce .hail. Hail is usually small and seldom causes much damage. Rainfall frequency diminishes quite.markedly after early October in the Palatka area. Day long rains in summer are usually associated with tropical storms, hence infrequent. Precipitation during the drier months of the year is usually associated with large-scale weather developments, hence does not display any marked tendency to odcur during any particular part of the day. Twenty-four hour rainfall amounts of near 5 inches can be ex­ pected to occur at any given place in the county about once every two years, mid-morning fleecy clouds begin to appear and by noo:q.time skies are usually more than half covered with clouds. On most summer days clouds increase during early afternoon and by mid-afternoon local thundershowers may be occurring in the county. Skies usually clear again soon after sundown. Many winter days have abundant sunshine; there is, however, a higher frequency of overcast days in winter and day long rains occa­ sionally occur in winter and early spring. Snow is very rare in Putnam County. The only report of measureable snow at Palatka during the period of available record is 1.0 inch on February 2-3, 1951. 2.0 inches of snow was reported at Crescent City on this same date.

Tropical storms are not considered great hazards in Putnam County because the overland movement of storms from the Gulf of

35 Mexico or Caribbean Sea to this area effectµally reduces storm severity. Historically, Atlantic storms have not approached this area sufficiently close to give sustained high winds. Tropical storms, however, do occasionally produce copious rain­ fall in the area. Tornadoes occasionally occur and, according to available records, have caused damage in the county on 4 occasions during the period 1916-1960. Tornado paths have been short and narrow, hence damages have not been extensive.

Observations of relative humidity are not available for any-point in Putnam County. Records compiled at other points in northeast Florida indicate an early morning average of 90 to 95 percent and early afternoon averages ranging from 40 to 50 percent in spring to close to 60 percent during the "rainy season." Fog forms quite frequently at night during the winter and early spring. These fogs, however, usually dissipate or thin out by mid-morning and day long fogginess is seldom observed. Pr-evailing winds are northerly in fall and winter and southerly in spring and sununer. Wind speeds generally range from 12-18 mph during the day and mostly under 8 mph at night.

2. 2·. 9. Daytona Beach, Florida (1972)

Daytona Beach is located on the Atlantic Ocean, with the Halifax River, part of Florida's Inland Waterway, running through the City. Terrain in the area is flat, soil is mostly sandy, and elevations in the area range from 3 to 15 feet above m.s.l. near the ocean to near 31 feet at the airport and along a ridge running along the western city limits.

Nearness to the ocean results in a climate tempered by the effect of land and sea breezes. In the sununer, while maxi­ mum temperatures reach 900 or above during the late morning or early afternoon, the number of hours of 90° or above is relatively small due to the beginning of the sea breeze near midday and the occurrence of local afternoon convective thundershowers which lower the temperature to the comfortable eighties. Winters, although subject to invasions of cold air, are relatively mild due to the nearness of the ocean and latitudinal location.

The "rainy season" from June through mid-October pro­ duces 60 percent of the annual rainfall. The major portion of the summer rainfall occurs in the form ·of local convective thundershowers. These showers are occasionally heavy and pro­ duce as much as 2 or 3 inches of rain. The more severe showers may be attended by strong gusty winds. Almost all rainfall dur­ ing the winter months is associated with frontal passages.

36 Long periods of cloudiness and rain are infrequent, usu­ ally not lasting over 2 or 3 days. These periods are usually associated with a stationary front with waves, a so-called "nor­ easter," or a tropical disturbance.

Tropical disturbances or hurricanes are not considered a great threat to this area of the state. While not outside the hurricane belt, past history indicates the chance of having hurricane force winds in any given year to be about 1 in 30. Generally hurricanes in this latitude tend to pass well off­ shore or lose much of their intensity while crossing the state before reaching this area. Only in gusts have hurricane force winds ever been recorded at this station.

Heavy fog occurs mostly during the winter and early spring. These fogs usually form by radiational cooling at night and dissipate soon after sunrise. On rare occasions se.a fog moves in from the ocean and persists for two or three days.

There is no significant source in the area for air poliution.

2.2.10. Titusville, Florida (1968)

Titusville, county seat of Brevard County, is located on the east coast of the central Florida peninsula. ·To the east, across the Indian River, is the Kennedy Space Center NASA. The northward-flowing St. Johns River lies about 10 miles west. The surrounding terrain is low and slightly rolling. There are many lakes west of the city.

Summers in Titusville are long, warm and relatively humid; winters are mild and relatively dry. In summer, there is little day to day variation in temperature. Afternoon temperatures reach the high 80's or low 90's with great regularity but seldom exceed 95° and almost never reach 100°. In winter, afternoon temperatures usually vary between 60° and 80° and seldom fail to reach 50° even on the coldest days. Winter minimums range mostly between 45° and 650 and very seldom fall below 30°. Nearby locations in the colder areas experience a temperature of 26° or lower about one winter in four.

The June through October "rainy" season produces about 65% of the annual rainfall total in Titusville~ The major por­ tion of the summer rain falls from frequent short duration afternoon and evening thundershowers. Thunderstorms average about 80 per year with 60% occurring in the months of June,

37 July and August. Showers are occasionally heavy and sometimes produce three inches of rain or more in an hour or two. Day long rains in summer are infrequent and when they occur, are usually associated with a tropical storm. Rainfall during the drier seasons is usually associated with large-scale weather develop­ ments and does not display any marked tendency to occur during any particular part of the day.

A typical summer day begins with clear skies; during the morning, fleecy clouds begin to appear and by noontime skies are often more than half covered by clouds. On most summer days, clouds increase during the afternoon and by mid-afternoon, local thunderstorms may be occurring in the area. Skies usually clear again after sunset. Although the frequency of overcast conditions is about the same in summer and winter, the incidence of clear skies is twice as great in winter as in summer.

Tropical storms, which occur in late sununer and fall, affect the area infrequently and at irregular intervals. The chances of hurricane force winds (74 mph or greater) in any given year are about 1 in 25. Tropical storms occasionally produce copious rainfall in the area, however, twenty-four hour rains of 6~ inches or more may be expected to occur about once every 5 years on the average.

Prevailing winds are from the southeast to east in spring and sununer, northeast in the fall, and quite variable in winter. Wind speeds average about 10 mph and exceed 25 mph less than 3% of the time. Relative humidity ranges ·from early morning averages near 90% in all seasons to an afternoon low near 50% in late spring and 60% in the rainy season. Heavy fog forms on 30 to 35 days per year. These fogs form at night and dissipate by mid-morning. Day long fogginess is seldom observed. About two-thirds of the fogs occur during the period November through March. Jack E. Mickelson, State Climatologist ESSA Weather Bureau P.O. Box 14376, University Station Gainesville, Florida 32601

March 1, 1968.

\

38 CHAPTER 3 WINDS

3.1. Medium Scale Weather Systems

3.1.1. Basic Information

This section is devoted to a brief explanation of cyclones and anticyclones and their formation. It is -intended for the reader who may be unfamiliar with meteorological terminology and concepts.

Medium scale weather systems are categorized as cyclones or anticyclones. Centers or areas of low pressure are called cyclones and centers or areas of high pressure are called anti­ cyclones. Cyclones are usually somewhat circular and may be as large as 1,000 miles in diameter while anticyclones are somewhat larger and more eccentric, having in some cases elongated axes of 2,000 miles or more. ~n the northern hemis­ phere, winds around a cyclone are counterclockwise while those around an anticyclone are clockwise. Winds in a cyclone are almost always stronger than those in an anticyclone of the same size. The formation of an extratropical cyclone (one formed in temperate latitudes) is illustrated in Figure 3.1 and occurs when a wave forms along a frontal zone [as shown in (a) of Fig­ ure 3.1] separating westerly winds from easterly winds. As the wave increases in amplitude (b) a cyclone of increasing in­ tensity forms around it. The air, in adjusting itself towards equilibrium, pushes towards this weak point in the front and develops a cyclonic circulation centered at the wave crest (c). As the development progresses, the westerly winds shift to come from a southwesterly direction and push a segment of the original front ahead to form a warm front. The opposite side of the original wave is also moved by the westerly winds to form a cold front penetrating into the warmer section. The cold front moves faster than the warm front and closes the warm sector to form a combined front(called an occluded front) as shown by the dashed line in (d). As this process of occlusion is begin­ ning, the cyclone reaches its greatest intensity. The process continues until the low pressure area is essentially "pinched off" as shown in (e). This process of cyclone formation is· called cyclogenesis and applies only to extratropical cyclones. Tropical cyclones are quite different from extratropical cyclones and will be discussed in a later section.

The formation of anticyclones (termed anticyclogenesis) is most usually the result of cooling of surface air. This

39 EASTERLY WINDS ~ COLD___ AIR____, HIGH PRESSURE--- FRONTAL ZONE

WARM------AIR HIGH PRESSURE

COLD FRONT (a) ( b)

( C)

HIGH

Figure· 3.1. Five stages of development of an extratropical cyclone. See text for description of process.

40 cooling, most characteristic over land masses in winter and water masses in summer, increases the density of surface air. A high pressure area is thus formed and air movement towards the peripheral lower pressure regions, coupled to a spinni·ng earth, results in clockwise movement of air around the high pressure region in the northern hemisphere.

3.1.2. Cyclogenesis and Frequency and Tracks of Cyclones

Monthly development of low pressure systems, or cyclo­ genesis, for the eastern half of the United States is shown in Figures 3.2 through 3.13. Isopleths indicate the number of cyclones that originated within unit boxes during the 20 year period 1909-14 and 1924-37. Only the location of the low at 1230 GMT on the first day of its existence was considered. The frequencies were counted in boxes 5° latitude in length and of varying widths to produce areas roughly equal to that of a box 50 latitude by 5o longitude at 470N. Isopleths are drawn at intervals of 4 (solid lines) with selected inter­ mediate dashed lines at intervals of 2.

In the region between Cape Hatteras and Cape Canaveral, cyclones were spawned every month. Lowest frequency of cyclo­ genesis appears to occur during September (Figure 3.10) while the months of highest frequency are January (Figure 3.2) and August (Figure 3.9).

I Frequencies of low pressure areas, in unit ar~as based on 5o by 50 squares at 47°N, as well as tracks of low pressure areas are shown in Figures 3.14 to 3.25. The frequencies of lows.are based on the number of extratropical cyclones lo­ cated within unit boxes at 1230 GMT during the 20 year period covered by the years 1909-14 and 1924-37. No one cyclone was counted more than once in the same box regardless of how many days it stayed there. Solid isopleths are at intervals of 10 while selected dashed isopleths are at intervals of 5.

The prevailing direction of motion of cyclones in Figures 3.14 to 3.25 is indicated by the arrows. Solid lines denote primary tracks--those which are most frequent and generally indicated by most data sources; dashed lines denote secondary, less frequent, and less well-defined tracks. All arrowheads, except those near the margins of the figures, end in areas where cyclone frequency is a local maximum. At this ending point, tracks may cross, branch and merge, although they are not specifically so drawn. Locally preferred regions of cyclogenesis are indicated where secondary or primary tracks begin.

41 FREQUENCY OF CYCLOGENESIS. -JANUARY-

\ \ \ ~2."J\ c;.O -- '

Figure 3.2. F'igure 3.J. FREQUENCY OF CYCLOGENESIS. -MARCH-

I \

'. \ \

80° Figure 3.4. FREQUENCY OF CYCLOGENEsrs . -APRIL -

Figure 3.5. 80° FREQUENCY OF CYCLOGENES1s· -MAY-

I \ \ ----v,oo\ \ ------\ --\----- \ \ \ \ ' z..,c..O . -----··\ \ ----- ' J------': ------t--o \ --- I \ I \

80° Figure 3.6.

\ '30° -- ...... ------\ '

E'igure 3 .. 8. FR£QIJ£Ncy OF CYCLOG£Nes,s -,4uGusr-

Figure 3.9.

80° FREQUENCY OF CYCLOGENESIS .

\ \

\ \ \ c=. 0 ). ?,;.J \ \ _..\ -- 01 - - ' 0

_...... ---· -- ' --

\ I \

Figure 3.10. Figure 3. 11. FREQUENCY OF CYCLOGENESIS . f:?.~_,_ -NOVEMBER- ~Oo

40°

\

_: .. ~~'.) .- lJl \ N

. 00 _..---"\ ~ I \ \ \

,::-::- ·:. -:/-.'- . 4 I ~-:• .-:. ·:. ·:.\ ' ! l \ l \ '!, o {\:{·\Id ------< : t:·.:-::::-::::-::y·· / . \ '.' \ I ----~.2 ... ·:. ·:."•::) ' I \.:.'• ·:. ·:. ' ,C:~ 1) i , ' j • -- \ /.\·:\\\ ----f __ _ j \3\ t I :_ .. 2 "1.--- \ /::\\\:\ // ! ------+------>+-l~~------t·--·- \ \ /f!f!:}}1 _, I 6 . ···, :., ~).J \ \ · \ Ooo ~-~ __ j -:·...... :~p-:-,1({\·\·.:.'=""::~ I) £j' 0 '\. \ __ J,oo 950______/:((:§:)?{:~ Li ~ I> '""'<.··...... \·-~...... di O L 1 ____1~--- 600 9ocr~·.-.· ------_J__ ····:_\}~-:·.:-:·::-... . --100 ------s . aso --- aoo ----- ·- 750 Figure 3.12. F'RE:Q!JE:,vcy OF CYc_lOGE:fV£s1s· -OEcEMaER -

Figure 3.13.

80° FREQUENCY PRINCIPAL T OF LOWS RACKS OF LOWS

I .... ····-~"?,':>I) .. .·· .. . ··

--:------:------'- ' ' -¥-..--:------· •• •! ...... ·10- •.

' 0 .. ---- __ ,;.. '2'=>

-·----~-.--- -··--- -

f:JSJ0h :~~:-:~-,\;;:_~:. ··.~ --.-~ » cP 90 0--..:.-·(_ •• • f~\·:.··:,.t . • ' •••••• • .. • • • I I ...... ·:.. • 0. ...~ - _J__ - \:1,-.-::-:-::~ •• •• @ ~ , :.·····\:: •••• 850 .. .-·- L - 2.-,.:.~·;.,::••i~.. ·:.··.. -..:-;l,. , • • e e e e •• • .~L • ••• • 0• aoo ·-- 6!> =75° -·· ------10° -- Figure 3.14. -JANUARY- Notation Used to Indicate Changes in Tracks of Cyclones and Anticyclones

An area of frequent genesis is indicated by either of the following two track symbols (all motion from left to right):

..... ____ A single secondary track changes to a single primary track.

Two secondary tracks merge to form a primary track, with a break between dashed and solid line.

Other track representations occasionally used, none of which represent genesis, are illustrated below (again all motion from left to right).

Two secondary tracks merge to form a primary track, without a break between dashed and solid line.

A secondary track merges with a primary track, with­ out a break between dashed and solid line.

Two secondary tracks merge to form another secon­ dary track.

Two primary tracks merge.

A primary track decreases in frequency to a ----- secondary track.

A secondary track branches off from a primary track.

$1 A primary track splits into two primary branches.

--:::::.;- A secondary track splits into two secondary Qranches. ' ~ FREQUENCY f:.f·:.,.. PRfNCf PA OF LOW ,...... L TRA . S , ..,·.~·:::,_-.-.:· .. :· CI( S .

01 01

·· .. .. Figure 3.15. 10°

-FEBRUARY- FREQUENCY OF LOWS ~ PRINCIPAL TRACKS OF LOWS ,;Oo l?:'>c--, - -~

U1 O'\

\ \ ------...... - \

\ --\\ 2'50 \ ------\ . - ---t"\ \ ( J .' -- --J. \ - ---r-- \. ·:-:·:-:-:-:-:-~·--·:1 •• I I • "' : I • ,, 0 ... ·.. .•, 0 /.:-.-.:-.-.:-.-.:-.-t-f • • • • .· . . i \ . . ~ ·r. .. . yz. o ~,,·._..-._..-._.:._-:... . : ' =-"""·-~~ . ~ I D "" ••.• · • • ?--:'"• IOo~.:.·::.··.\1 __ J ,.,~.:.··.·:·:····:··::··.:_.·:·_.··:·:~::·..:·::·::···:::::··:::· ... ·.:·:.·:::····:····.··~ _iJ0;:•t:J:\{ii~~ ~ ~.,.• \ . \__~- 60 ~ 5 0 - ---- \:\\{\/:::Ji; ,· /"° ' f'\;t::::f:!-?-:-.• •••••?...... _l-- . --- 6!> 0 . 9QO ··-- _J/ L 2;_}):·(J;··. --- 10° · ss0 · ------·aoo ···----· ·- 75° Figure 3.16. -MARCH - · · · · · · FREQUENCY OF LOWS ~ PRINCIPAL TRACKS' OF LOWS

U1 ....J

80° Figure 3.17. - APRIL - \

\ \ \ "100 . ---, J \ I \

--- - "' .. -- ... ------t--- \

Figure 3.18. -MAY - FREQUENCY OF LO.Ws -;;a-_ PRINCIPAL TRACKS OF LOWS

..

,,; ...... \. . . : ~() . d': 85° . Figure 3.19. 80°

-JU NE - FREQUENCY OF LOWS ~ PRINCIPAL TRACKS OF LOWS 1500

°'0

--.~00 __ .,...

- t-·- \ -· --+---· ' \

•••• ' \ 0 ' • •• : ••••••••••••••••• • ..,.-.2!> ·······~· .. .··· ------·, .·.::-::-::·:-( ---"! -..... • \ ~Q ••• •\•·11·4··.\i G.'.") ·2, •·.• • •• • • • • • •••• • .,/\\\) / :.~------!_. •• •• L····· \:{/fi· ...... ij:;.··· \ ~_:~------.. -:.·:.·· .. ·.. • •• •• •• ----- "' ~. J. o :i1 ~ I !?/\:{\ . .T-----·~-.,~- ·t- - ~- 1S i \

6/Ji/J / \· ... i .... ·.. ;::,-·~>:,l "''~ \ , IOoo... :..·:-.:'.·~ ' ~' .P:~:::-:.:-:·.;.~~ \ D 00 ~ \ \.._.--- --910----- L&JH(Jf\,i ~ . f'~\L2b\.::::-.:·.. :-,,). di ·_l------€,,;O 9QO._,,.;./___ ~ i ::·~:;;;.,~--- 70° 85°_____ -too--~ -- 75°

Figure 3. 20. - JULY - Figure 3.21. 75°

-AUGUST- · ··· ... FREQUENCY OF LOWS ~ PRINCIPAL TRACKS OF LOWS . . ~00

Figure 3.22. ·•· · • · · FREQUENCY OF LOWS -i..- PRINCIPAL TRACKS OF LOWS . . 50 0

O'\ w

Figure 3.23. 80°

-OCTOBER - FREQUENCY OF LOWS PRINCIPAL TRACKS OF LOWS !,Oo ~- -~-:-J

• . \ . \ ... \ 00 ~~

--r-

,----:----:-l I I , 1-:-:--:-\ I ' ' / _.:)){/1-: / I • \)/} i • .

/:.\::it:f1 --,-- i \l}t:::::; ~\v \ / :.:·:-:·:.:·:-:·:: I · - l ··:-:-:: i ~: __ -J--- -t-- --·. --- :-:-:-:-:-:-:-:-:j , I ·------1-- ~ ~"+-,1),.2...__: --/ '. \ /:/_}\\:~ I / i --- .. I '°\ I ,->:--:--:-·········.··-:--.. l I •• i·········o • • •; • • • • • •• ' ~¥. \' <;_-:-t-:-\\ / .• I ' ~5:/:-_r::-______a, ' 'oo N--":,_--_ j : rdm,= ;~;-;;;;:- ~;(-:-;-:-:--:- "'~ 1 /J ·-,, • 1 -~so·-.. ·-.\ifl~ __ _.J·~--~· • 'f4 S~i(-~- ~----:fo --·- aso----- ·iooL2f!:_ rs• 0 Figure 3.24. - NOVEMBER - ...... FREQUENCY PRINCIPAL OF LOWS TRACKS OF LOWS

\ 2.!>o \ \ \ \ \ \ ••••••• 2.00 ~o \ I . ••• 600 __l_.------65 ° Figure 3.25. 80° 70°

- DECEMBER - A key to track representations is presented prior to Figure 3 .15.

The region from Cape Hatteras to Cape Canaveral was affected by a total of at least 10 cyclones·during each month of the years studied except September (Figure 3.22). However, it should be remembered that tropical cyclones (including hurricanes) are not included in these particular data. During all months~ the highest residency of cyclones occurs in the Cape Hatteras region. All months spow either primary or secondary paths of cyclones proceeding generally from south to north within this area of interest.

3.1.3. Anticyclogenesis and Frequencies and Tracks of Anticyclones

Regions of formation of anticyclone_s in the eastern United States for all months are shown in Figures 3.26 to 3.37. Periods of time covered and methods of compilation and data presentation are identical to those discussed under cyclogenesis. Figure 3.31 shows that no anticyclones were generated between Cape Hatteras and Cape Canaveral during the Junes investigated. The months with most frequent anticyclone development in this area are April, July, August, November and December as shown in Figures 3.29, 3.32, 3.33, 3.36, and 3.37.

Frequencies of anticyclones in the same 5° by 5° unit areas and principal and secondary tracks of anticyclones on a monthly basis are shown in Figures 3.38 to 3.49. June, July, August and September are the only months that show fewer than 10 anticyclones in the region of interest (see Figures 3.43 to 3.46. Highest frequencies were in February, April, October, November and December as shown in Figures 3.39, 3.41, 3.47, 3.48 and 3.49. Unlike cyclones, anticyclones tend to cross the region from west to east. The least amount of anti­ cyclone movement through the area (indicated by a lack of tracks) occurs in the same months that show less than 10 highs in the region (June, July, August and September). Information on genesis, frequencies and tracks of cyclones and anticyclones was obtained from Klein (1957).

3.2. Tropical Cyclones, Tropical Storms, Hurricanes and Great Hurricanes

Tropical cyclones differ from extratropical cyclones in that extratropical cyclones obtain their energy from the variances of temperature and moisture in air masses within the circulation: whereas tropical cyclones obtain energy from

66 FREQUENCY OF

\ 0 ~\'?,!>o ' ------\:: --*--·I .- \\ \ \ \

--+----i

Figure 3.26. FREQUENCY OF ANTI CYCLOGENE SIS

Figure 3.27. FREQUENCY OF

Figure 3.28. FREQUENCY Of ANTICYCLOGENESIS

.....J 0

_.. -

- ---·-+-- -- t - - 0\\. ------G!>o L ---- 95~---- 100

Figure 3.29. OF

0 Figure 3.Jo. FREQUENCY OF ANTICYCLOGE NE Sl·S ,,.._ -JUNE - ,_... _.... ~ ,;Oo

,...... j / .·.···.. ·.·· I \ . . • ') ;·

Figure 3. 31. FREQUENCY

Figure 3.32. FREQ U·ENCY OF ANTICYCLOGENESiS

-AUGUST-

----\\ __ .---\\ __ -

Figure 3. 33.

FREQUENCY

Figure 3.35. FREQUENCY OF ANTICYCLOGENESIS -NOVEMBER-

0

""' \ ----· 65° Figure 3.36. 70° . fREOUENcv OF ANTICYCLOGENES1s

-....J CX>

Figure 3.37. \ • I \ I -~-.._,j1-----:-----~--,-,.,,,- \ ----r \ •• •• \ •• \ I .•• .• ••I •••• .. I •• \ \ ...... '2.!>o . o·· . . ··...... \

Figure 3.38 . ' -JANUARY - FREQUENCY ~ PRINCIPAL T OF HIGHS RACKS OF HIGHS

CX> 0

.di

Figure 3 • 39. 10°

-FEBRUARY-. ~ FREQUENCY OF HIGHS /.:·::-:.·. PRINCIPAL TRACKS . OF HIGHS

.. ( ..- .. :·... : IO •• ·f...... :• Jif.it ------1----- I ·"\@{ = ~t ••.. • ;,':-.'.'(,·-:-::; I -----f---.____._,s"-+-...,1.\.~~-i------r-- 10~'/'\\\ / I .. . . t <>

~~ i---\·-:····>>:\.{-.'.,:-.~1-,, I/) O' !i"~ah--_ · \::-:;\t<----· .. d ~, Figure 3.40. 70°

-MARCH - ..,. - \ .. / \ . 0 .~ .: _...... --\~'=>o\

/ . ----·-- -\ - . -- ~ : ·\·· .. .., \ ~00

I I ...\.•···· . •••• ••••• I • •• •

Figure 3. 41. -APRIL- ....~ ··· FREQ UENCY OF HIGHS :>. PRINCIPAL TR ACKS· OF HIGHS

0) w

eo 0

Figure 3.42. -MAY- Figure 3. 43. 80°

-JUNE - ...... FREQUENCY OF H.IGHS ~ PRINCIPAL TRACKS OF HIGHS

0 f!J?-,.. -~\!)0 -<~~t\:::'.;:';,:l&tx~ c.:. ':.t ...... :... :...... -~\~ ~~·.:·,·71(:¥? ~ 1...... , ...... ,., ...... t~ , ...... ,...... ·...... ,.3~·di··· ..... Cf~.. t} 4 s0

... ••• /:-.-...... : ..-.-. . ·.; ... ,o , ~:·.-.-.-.,.-,,_ i I I \ tXt<·· I I 'JI I' \ o. · · \ft· ,~,1rr ...... ····· ~ .. 95u --..._ __ • •• .. .. .a· ••

Figure 3.44. 80°

-JULY - ...... FREQUENCY OF PRINCIPAL TR HIGHS :~ --==-- ACKS OF HIGHS

co O'\ FREQUENCY OF HI_GHS ~ PRINCIPAL TRACKS· OF HIGHS

co -...J

\ I I

• ••••••••••• ... 200 60° Figure 3.46.

~SEPTEMBER - ~ FREQUENCY -~.. PRINCIPAL T~AF HIGHS

I··· ...... #_ C f

Q) co

-OCTOBER- Figure 3.48. -NOVEMBER - FREQUENCY OF HIGHS ~ PRINCIPAL TRACKS OF 11·•.;.-::-:-,-. HIGHS " 500

I •• : ti' ··\·· .. •• .. \ •• 1?":\}.J!f{ff ········::-: ..,:[~:-:.:;-:;-::•.\if. ••• •• ~ Af2ff _., / -:·.-._,.-.: ----.~@k. .. ··~; I ' .. \ ·10 i ••• • /.. ,:-:-.:-:f ; .....•... I '-:-:-.:-:·.\.:-: -.. .. \ .. \ ...... \ ···~\ ...,o ".. t. • • ······· ·--•• \

I) o, \I •••,ta.. ~o (!;J •••••

Figure 3.49. 80°

-DECEMBER- latent heat of condensation of water vapor. The average diameter of a tropical cyclone is between 60 and 600 miles at maturity. Cyclones of the middle latitudes may have winds ranging from very weak to highly intense; whereas, the max­ imum wind speed near the center of a tropical cyclone usually exceeds 200 mph in well-developed hurricanes. Extensive torrential rainfall is corrunon to tropical cyclones of all intensities and the coastal area tides resulting from an intense hurricane may average 10 to 25 feet above normal. In addition, the wind pattern of a tropical cyclone creates a central "eye," an area with a radius of 5 to 10 miles in which there is little rain or wind and greater temperatures and less moisture than in the encircling region.

Tropical cyclones are classified by stages according to the sustained surface wind speeds.

A. The most intense stage, called a great hurricane, has winds in excess of 125 mph.

B. The hurricane has sustained surface winds from 74 to 124 mph.

C. Tropical storms have sustained winds 39-73 mph.

D. Tropical depressions have sustained winds not exceeding 38 mph.

Location and environment determine the development and dissipation of tropical cyclones. They form only in ocean areas having a high surface temperature, 780 to 81°F and only during certain seasons, with the greatest number occurring in the late surruner and early fall in the Northern Hemisphere. They are seldom observed within 5° of the equator. A storm begins in an area of a pre-existing disturbance. After formation, the pull of the Easterlies results in a tropical cyclone making a curved path from east to west. In some instances, tropical cyclones will reverse their direction of travel, a phenomenon called "recurving." If the storm's track crosses overland, the storm quickly dies, due to the removal ·of the oceanic energy source. If the storm remains at sea, it will usually become an extratropical wave cyclone and eventually blow itself out as warm water, the energy source, becomes unavailable ..Extratropical stages occur when the tropical cir­ culations are modified by moving into an area of complex inter­ action of atmosphere I·ayers. This results in the expahsion of circulation area, decrease in the speed of maximum winds and destruction of the symmetrical distributuion of winds, rainfall, and temperatures around the center characteristic of a tropical cyclone. Some characteristics of a tropical cyclone, such as a

91 small area of intense central winds, remnants of the "eye" and heavy rainfall .. may continue for a considerable period of time . Because winds of the semicircle to the right of the storm's eye coincide with the cyclone direct~on its~lf in the Northern Hemisphere, this part of the hurricane is the most dangerous. It is possible for this side to have winds 60 knots faster after recurvature.

The coastal region between Cape Hatteras and Cape Cana­ veral has experienced tropical·cyclones of one type or another as early as 28 May and as late as 2 December. Figure 3.50 modified from Simpson and Lawrence (1971) shows the earliest and latest dates that tropical storms, hurricanes or great hurricanes have occurred.in 50 mile segments of this coastline .. The probability (in percent) that a tropical storm, hurricane, or great hurricane will occur in any one year in the same 50 mile coastal segments is shown in Figure 3.51 which has also been modified from Simpson and Lawrence (1971). The portion of the region near Cape Hatteras is the most likely to have a hurricane in any one year (11% probability). The region between Cape Hatteras and approximately Beaufort, South Carolina has an average probability of hurricane occurrence within any given year of 7%. In the ·region south of Beaufort, this probability is slightly more than 2%.

Because of the size of a tropical cyclone (600 mile average diameter), the frequency of their presence 300 miles inland and 300 miles seaward of the continental shelf should be considered when activities on the continental shelf are planned. 1 For this reason, Figure 3 • 52 was prepared from information furnished by Cry (1965). Figure 3.52 is composed of ten sub­ figures, each dealing with a one degree latitude segment. Each subfigure indicates, by month, the number of tropical cyc~ones inland within 300 miles of the coast (circles); crossing the coast (triangles); and at sea but within 300 miles of the edge of the continental shelf (squares). Open figures represent tropical storms and closed figures represent hurricanes. The period of time covered is 1901 to 1963. The earliest tropical cyclone, considering the 300 mile criteria, occurred in February, was offshore, and reached hurricane intensity between 31 and 32°N. During March and April no tropical cyclones were reported in the region of interest, while one tropical storm in December was inland up·to 29°N crossed the coast as a hurricane between 290 and 30°N, and decreased in intensity north of 32°N.

Figures 3.51 and 3.52 do not display the same information. Figure 3.51 is concerned with tropical storms and hurricanes which affect the coastal region while Figure 3.52 indicates tropical

92 35°

EARLIEST LATEST I II JUL 16 SEP 2 25 JUN 8NOV 3 12 JUN 2DEC 4 17 AUG 310CT 5 5 JUL 310CT 6 8 JUL 230CT 7 II AUG 15 OCT 8 28 MAY 19 OCT 9 15 JUL 60CT 10 31 AUG 17 SEP 30° 11 6 JUN 170CT 12 27 JUL 210CT 13- 27 JUL 13 SEP 14 28 JUN 17 SEP ~13

•14 80° 75° Figure 3.50. Earliest and latest days of the year that tropical cyclones, hurricanes or great hurricanes have occurred within each 50 mile segment of coastline from Cape Hatteras to Cape Canaveral. Modified f~om Simpson and Lawrence (1971).

93 LEGEND WIND SPEEDS (m.p. h.}

ALL TROP. CYCL. TROP. CYCL. 39-73 ALL HURR. ~ HURR. 74-124 GREAT HURR. ii GREAT HURR. > 125

20

.... 15 -z LL.I (.) 0:: LLJ a. -....>- .J 10 CD <( CD 0 0:: a.

5

COASTAL SECTOR 14 13 12 II 10 9 8 7 6 5 4 3 2 ALL TROPICAL CYCLONES II 7 7 7 4 5 16 8 8 13 7 14 18 9 ALL HURRICANES 8 5 2 2 7 8 5 6 6 5 11 8

GREAT HURRICANES 5 - 2 2 - 2 4

Figure 3.51. Percent probability that a tropical storm, hur­ ricane or great hurricane will occur in any year within each of the 50 mile segments of coastline shown in Figure 3.50. Modified from Simpson and Lawrence (1971). 94 Figure 3.52. Number of tropical storms and hurricanes (by month) affecting each degree of latitude between Cape Hatteras, North Carolina and Cape Canaveral, Florida for the period 1901 to 1963. Open figures indicate tropical storms; closed figures indicate hurricanes. For each one degree of latitude, circles represent inland storms within 300 miles of the coast, triangles represent storms that crossed the coast and squares represent storms at sea but within 300 miles of the edge of the continental shelf. Source: Cry, George W., 1965, "Tropical Cyclones of the North Atlantic Ocean," Technical Paper No. 55, U. S. Department of Commerce, Weather Bureau.

95 a1• ao• 78° 77° 76°

\ \. ______

34° ~----4------+------l-

I]--

l

96 storms and hGrricanes affecting the region ext~nding 300 miles inland from the coast to 300 miles seaward of the continental slope. This latter region is slightly greater than 600 miles wide near Cape Hatteras and Cape Canaveral (where the continental shelf is narrow) to over 700 miles wide near Charleston where the shelf is widest, hence, storms with a north easterly set from south of Cape Canaveral will be considered in only the southern and northern portions of Figure 3.51 but will be considered in all portions of Figure 3.52.

Table 3.1 summarizes the data presented in the various portions of Figure 3.52. Between 1901 and 1963 the dis­ tributuion of tropical storms along the coast is bimodal with peaks between 33° and 35°N and 30° and 32°N. The distribution of hurricanes in the same region peaks at 31° to 32°N.

All latitude segments experienced more than 100 tropical cyclones of storm or greater intensity during this period of time with the greatest number occurring between 31 and 32°N.

3.3. Tornadoes and Waterspouts

Funnel clouds, tornadoes and water spouts are different types of the same phenomenon; the latter two being funnel clouds which have extended downward to the ground or water surface respectively. A total of 208 of these meteoro­ logical features have been reported in the coastal area between Cape Hatteras and Cape Canaveral between 1960 and 1972; hence, they are not necessarily unusual.

Tornadoes are usually associated with cyclones (both tropical and extratropical) and, when they occur, develop in the southeast quadrant of the foreward periphery of the cyclone. Movement of over 60% of tornadoes reported in the United States is generally from southeast to northwest. Although highly destructive tornadoes are the smallest of severe weather dis­ turbances, and are limited in duration as well as length and width of path. These paths vary from a few yards to several hundred yards in width and can extend from a few hundred yards to over three hundred miles. The average width and length of tornado paths in the United States are 400 yards and 16 miles respectively. ·

Tornadoes generally travel at speeds of about 40 miles per hour; however, these foreward speeds range from zero to 68 mph. Wind speeds within tornadoes have not been measured (no anemometer has survived a tornado) but are estimated to be in excess of 500 mph. Pressure drops as great as 2.42 inches

97 Table 3.1 Number of Tropical Storms, Hurricanes and Totals of both occurring in one degree segments of latitude between Cape Hatteras, North Carolina and Cape Canaveral, Florida for the period January 1901 to December 1963.

Latitude Segment Tropical Storms Hurricanes Total (degrees north)

35-36 77 31 108

34-35 86 39 125

33-34 84 48 132

32-33 70 53 123

31-32 83 58 141

30-31 83 57 140

29-30 76 58 134

28-29 69 49 118

27-28 61 46 107

98 of mercury over a distance of seven blocks have been recorded within tornadoes. They therefore act as giant vacuum cleaners and, if they pass over a structure, can cause it to literally explode.

Table 3.2 lists the frequency of occurrence of funnel clouds, tornadoes and waterspouts for each degree of latitude _in the coastal region from Cape Hatteras to Cape Canaveral for the period 1960 to 1972.

3.4. Local Winds

Local winds, for the purpose of this report, are con­ sidered to be those measured at a particular location as opposed to general wind systems determined by upper atmosphere circulation, or medium scale wind systems discussed in the previous section. Two categories of local winds are treated: those measured over long periods of time at a particular land station, and winds averaged over the large SSMO areas (see Figure L2 from many readings taken by various ships.

3.4.1. Winds for Shore Stations, Cape Hatteras to Cape Canaveral

Mean monthly winds and fastest mile winds for Cape Hatteras and Wilmington, North Carolina; Charle?ton, South Carolina; Savannah, Georgia and Jacksonville and Daytona Beach, Florida are presented in Figures 3.53 through 3.64. Fastest mile winds are one minute averages of fastest wind velocity recorded during any of the twelve individual months during the period of record. Periods of record range from 15 years at Cape Hatteras to 31 years at Jacksonville. These data, less fastest mile data, are graphically shown in Figure 3.65 as monthly averaged wind speed and direction for each of the six stations. Monthly and annual wind roses for land stations at Charleston and Jacksonville and all three SSMO areas are presented in Figures 3.66 through 3.78. The land stations and SSMO area wind roses have been combined to facilitate com­ parisons. Wind data from Cape Hatteras were not amenable to wind rose analysis and do not appear in these figures. The reader should note that winds for land stations are in miles per hour while those for SSMO areas are in knots (a choice of speed ranges dictated by formating of available data). An approximate conversion from miles per hour to knots can be obtained by multiplying miles per hour by 0.87. The opposite conversion may be obtained by multiplying knots by 1.15 to obtain miles per hour.

99 Table 3.2 Total number of funnel clouds, tornadoes and water spouts reported within each degree of latitude for the coastal area between Cape Hatteras and Cape Canaveral from January 1960 to December 1973. Source: NOAA publication "Storm Data" Vol. 2 #1 to Vol. 15 #12. 1960 to 1973.

Number Number Number of Latitude of Funnel Clouds of Tornadoes Waterspouts

35-36° 2 8 4

34-35° 3 10 12 33-34° 3 12 4

32-33° 12 16 14

31-32° 13 4 6

30-31° 18 13 12

29-30° 13 14 15

Total 64 77 67

100 Figures 3.53 to 3.64. Average winds and fastest mile for each month at six locations. Average monthly winds are wide arrows pointing as the wind moved with the head of the arrow at the recording station. Average wind speed in miles per hour is indicated at the tail of the arrow. Fastest mile winds (thin arrows) indi­ cate one-minute averages of the fastest winds recorded at each station for the month. Directions and magni­ tudes of fastest mile winds are indicated in a fashion similar to those for average winds. Locations and number of years of record are as follows (from North to South):

Cape Hatteras, North Carolina, 15 years; Wilmington, North Carolina, 21 years; Charleston, South Carolina, 30 years; Savannah, Georgia, 22 years; Jacksonville, Florida, 31 years; Daytona Beach, Florida, 29 years.

Source of data: U.S. Department of Commerce, "Local Climatological Data, Annual Summary with Comparative Data."

101 85° 80° 75°

Figure 3.53. Surface winds at shore stations for January.

102 85° 80° 75°

Figure 3.54. Surface winds at shore stations for February.

103 85° 60° 75°

7~-l-~-+----+-----r---,350

Figure 3.55. Surface winds at shore stations for March.

104 85° 80° 75°

71

-l--+--+---,--, 35°

61 30°

Figure 3.56. Surface winds at shore stations for April.

105 85° 80° 75°

42 --lL--~+---4----+--.35° 52

Figure 3.57. Surface winds at shore stations for May.

106 85° 80° 75°

54

t..=:::!:::::==t::::=--'---~:=J.:...J. __L...__..L_,_--'----J--L--'--=::::±==::i 250 ,

Figure 3.58. Surface winds at shore stations for June.

107 85° 80° 75°

Figure 3.59. Surface winds at shore stations for July.

108 85° 75°

?igure 3.60. Surface winds at shore stations for August.

109 85° 80° 75°

Figure 3.61. Surface winds at shore stations for September.

110 85°

Figure 3.62. Surface winds at shore stations for October.

111 75°

Figure 3.63. Surface winds at shore stations for November.

112 75°

Fi~ure 3.64. Surface winds at shore stations for December.

113 20 CAPE HATTERAS,N.C. 18 AVG. MONTHLY WINDS -:x:: 16 N :E Cl. 0- _ -0- - -0---0 14 z ~ I 0 -0 12 E ~ w \ 10 ·---· I n, w \ C') a. \ ----·----·------~' CJ) 8 s -f \ -0- / 0 0 z 6 0---0---0-- --0---0 z - 4 w ~ 2 0 N

J F M A M J J A s 0 N D

20 WILM ING TON, N.C. 18 AVG. MONTHLY WINDS ~ 16 N =E Cl. z ~ 14 0 0 12 E o w ::0 w 10 n, Cl. CJ) 8 0---0---0---0---0-_ • • • • s ~ 0 6 / -0 0 z / \ 4 / \ wz ~ / \ 2 .,,.0 \ .,,. \ 0 0.,,. 0---0---0---0 N

J F M A M J J A s 0 N D

20 CHARLESTON,S. C. 18 AVG. MONTHLY WINDS ~ 16 ..,,.---0 ..... N :E Cl. 0 0-- -0- -'"'-0 I z :E 14 I ' 0 I \ I -0 12 I \ I E o w I W 10 ::0 Cl. \ f'T1 CJ) 8 \ __ 0--- s C') 0---0- -I 0 6 z 0 ~ 4 wz 2 o N

Figure 3.65. Average monthly wind speed (e~-•) and direction ( 0----0 ) for land stations from Cape Hatteras to Cape Canaveral.

114 20 SAVANNAH, GA. 18 AVG. MONTHLY WINDS ~ 16 N ~ 0---0 a. 14 0------0 z 2: 0 0 I \ I E o -O 12 I \ I ::0 ~ 10 !__a !I • IT1 .__., - \ ~~ I (") 55 8 I \ I \ -· • s -I I \ IL ...... __~•---••-· 0 6 I I \ 0 z I \ I \ I z I \ I (:)- - - (:)- - - 0 - - - 0 w ~ 4 0 0 2 0 N

J F M A M J J A s 0 N D

20 JACKSONVILLE, FLA. 18 AVG. MONTHLY WINDS £ 16 N ~ a. z ::E 14 0---0 0 I \ -O 12 I \ E o :ij ~ 10 IT1 .------;~ • '1 • 55 8 s ~ I ' I \ • 0 6 0 II \ 0' - - 0- - - 0 - - - 0 \ 0 z ., ' \ z ~ 4 /,, ', I \ w 2 G" '0 C>---0 0 N

J F M A M J J A s 0 N D

20 DAYTONA BEACH, FLA. 18 AVG. MONTHLY WINDS £ 16 N ~ a. z ~ 14 ~0 0 \ o 12 0----0 0---0' ~-- \ E o / \ I w .:0 W 10 Q. .---• •---re~// ~ IT1 (/) 8 /I . \ / ~ \ -•-~• s (") -I 0 6 p '0---· \ z I , \ 0 I \ wz ~ 4 I \ 2 0---d 0---0 0 N

Figure 3. 65. (Cont'd). Average monthly wind speed ( •--• ) and direction ( 0----e ) for land stations from Cape Hatteras to Cape Canaveral.

115 WIND WIND

40 8209

35

30

25 !z I.LI 20 ~ a..I.LI AREA g· / 15

10

5 /f

·"'"'· I I I I I 0 IO 20 3040 50 6070 80 c::::n90 100 0

9208

-'1{ AREA 10 ~~~CHARLESTON

~ .. ,,,;.~ 0 IO 20 30 40 50 60 70 80 90 IOO I "77 , I 111111111 0 10 20 30 40 50 60 70 80 90 IOO

AREA II c:::J~i/ 2 -c=-(] / f'JAOOONVILLE

,"m'r/ I • I I I I I I I r;:;;i o I02t>36 40 £ 60 % so 90 ~o 0 IO 20 30 40 50 60 70 80 90 IOO

Figure 3.66. January wind roses for SSMO areas (Right) and associated land stations. Percent calm is· shown in center of each rose and total number of observations j= shown at the top of each rose. 116 WIND WIND

MPH KNOTS 9~~ (>I .i,, km~ ~~ iJI~~8 ~

40 7767

35

30

25 I-z LLJ 20 ~ LI.I a. AREA 9 c:::::J 1.0-==-0 15 "/ 10

5 /f' 17Fif I I I I I I c::::l 0 IO 20 30 40 5060 70 80 90 IOO 0

8564

AREA 10 /f' r'n' I I I I I I I I r;::::71 0 IO 20 3040 50 60 70 80 90 00

~IT/ CJ AREA II /i~~LLE

,7777, , , I I I "'I 0 10 20 30 40 50 60 70 80 90 100

Figure 3.67. February wind roses for SSMO areas (Right) and associated land stations. Percent calm is shown in center of each rose and total number of observations is shown at the top of each rose~ 117 WIND WIND

MPH KNOTS

~- OI ..!,, F3 iZ5 ~~ c,; ~ ~ ~

40

35

30

25 zI- LL.I 20 ~ AREA 9 D LL.Ia.. 15 "/ 10 /[' 5 6"""10 20 3040 50 J, 70 80 ~ 0

AREA 10 c::J

,;::;-;:?, I I I I I I I ;:::::, 0 0 20 30 40 50 60 70 80 90 100 O :0 20 30 40 50 60 70 80 90 IOO

AREA II

1"FnTf ji i jii I i i j i q 0 IO 20 30 40 50 60 70 80 90 IOO 0 IO 20 30 40 50 60 70 80 90 100 Figure 3.68. March wind roses for SSMO areas (Right) and associated land stations. Percent calm is shown in center of each rose and total number of observations is shown at the top of each rose. 118 WIND WIND

40 9

35

30

25 ~ AREA 9 I.LI 20 ~ I.LI a.. 15

10

5

,"""'i' I I Cl 0 0 10 20 30 40 50 60 70 80 90 IOO

AREA 10

,.--,,; I I I I I ,-.ii 0 10 20 30 40 50 60 70 80 90 IOO

AREA II (]

,i'ii'rji'1 I I I I I I I I I q 0 10 20 30 40 50 60 70 80 90 100 0 IO 20 30 40 50 60 70 80 90 IOO

Figure 3.69. April wind roses for SSMO areas (Right) and associated land stations. Percent calm is shown in center of each rose and total number of observations is shown at the top of each rose. 119 WIND WIND

40

35

30

25 AREA 9 ffi 20 ~ LLJ 0.. 15

10

5

0 i~• I a 0 IO 20 30 40 50 60 70 80 90 IOO

AREA 10

0 10 20 30 40 50 60 70 80 90 100

AREA 11

0 IO 20 30 40 50 60 70 80 90 100

Figure 3.70. May wind roses for SSMO areas (Right) and associated land stations. Percent calm is' shown in center of each rose and total number of observations is shown at the top of each rose. 120 WIND WIND

MP.H KNOTS

~ ~tll ffi~ t

40

35

30 AREA 9 ~I~1/ 25 I-z ILi 20 ~ ILi 0.. 15 /' 10

5

I a 0 0 i8 2b 3Cl 40 50 60 1o 80 90 IOO

7200

<\J/ AREA 10 ~J/ ~E~N 7'

I# ' ' I I I I ' " 0 IO 20 3Cl 40 50 60 70 80 90 100 6 1()20304050607b~s'o~

AREA II

...... I I I I I ~ 0 IO 20 3Cl 40 50 60 70 80 90 IOO

Figure 3.71. June wind roses for SSMO areas (Right) and associated land stations. Percent calm is' shown in center of each rose and total number of observations is shown at the top of each rose. 121 WIND WINO

MPH KNOTS

~ ~iii~!

40

35 AREA 9 30

25

ILi!z 20 ~ ILi Q. 15

10

5

0 6 b 20 3040506070804:,&,

7440

AREA 10 ~'1L 11-==-l.8J/ -4 ~ESTON '

0 IO 20 30 40 50 60 70 80 90 100

AREA II S/

0 IO 20 3040 50 60 70 8090 JOO

Figure 3.72. July wind roses for SSMO areas (Right) and associated land stations. Percent calm is shown in center of each rose and total number of observations is shown at the top of each rose. 122 WIND WIND

MPH KNOTS

~c,, -., Fii 1115 ~~ifiN_,.8 ...., 0

40 8448 35

30

25 AREA 9 ~J/ !z LI.I 20 ~ LI.I 0.. 7~~ 15

10

5

0 6 ib 2.cdo 4o oo so io ~ sk> ~ 7440

AREA 10 /~~~ON~ Ila===-~r/ " 0 10 20 30 40 50 60 70 80 90 IOO 0 10 203040506070eb~I~

'\V AREA II IJa===:,----3.6~J/ /l~~LLE /f' I I I I I I I I I """"' 6'720 304050~ioeo~oo 0 IO 20 30 40 50 60 70 80 90 100

Figure 3.73. August wind roses for SSMO areas (Right) and associated land stations. Percent calm is - shown in center of each rose and total number of observations is shown at the top of each rose. 123 WIND WIND

MPH . ~t~~,

40 8

30

25 ffi 20 u ffi AREA 9 a. 15

10

5

I I I I I I I I I I q 0 IO 20 30 40 50 60 70 80 90 IOO 0

7200

AREA 10

o 6'2030405o60708090~

;r AREA II /i~--==J=-ACKSON-ae=Vl=L:::::iLE

0 IO 20 30 40 50 60 70 80 90 IOO

Figure 3.74. September wind roses for SSMO areas (Right) and associated land stations. Percent calm is shown in center of each rose and total number of observations is shown at the top of each rose. 124 WIND WIND

MPH KNOTS

~I I 7' • ~ Oliii~~o

40 8642 35

30

25 ~ LL.I 20 ~ LL.I a. 15 AREA 9 10 ,/I] 1.7 I] 5 /f' 0 ,"""'i9 I I I I I I I lq 0 10 20 30 40 50 60 70 80 90 100 7440

9789

AREA 10

O lb2030405060708090i6o 17ri77 I I I I I , , ,q 0 K> 20 3040 50 6070 8090 00

7440

AREA 11

o'4:> 20 30 40 50 60 io ao 90,X,

Figure 3.75. October wind roses for SSMO areas (Right) and associated land stations. Percent calm is shown in center of each rose and total number of observations is shown at the top of each rose. 125 WIND WIND

40 8818 35

30

25 !z I.I.I 20 (.) a:: I.I.I Q. 15 AREA 9

10

5

0

7200 94 7

AREA 10 • ~l~CHARLESTONw

,""""T' I I I I I I ,q 0 10 20 :30 40 50 60 70 80 90 IOO 6 lb20:304o~6070~9()~

7218 7200

AREA II

Figure 3.76. November wind roses for SSMO areas (Right) and associated land stations. Percent calm is shown in center of each rose and total number of observations is shown at the top of each rose. 126 WIND WIND

40 78 I

35

30

25 ffi 20 ~ w · AREA 9 Q. 15

10

5 '""'""II I I I I I~ 0 IO 20 30 40 50 60 70 00 90 100 0

8924 7440

AREA 10 D

I .,,, I I I I I 11111! 0 IO 20 30 40 50 60 70 80 90 100

6970

AREA 11

Figure 3.77. December wind roses for SSMO areas (Right) and associated land stations. Percent calm is shown in center of each rose and total number of observations is shown at the top of each rose. 127 WIND WIND

MPH KNOTS

~c.,, ~ rG m ~O>oi~ 0 40 102636 35

30

25 zt- LIJ 20 ~ AREA 9 LIJ ~ 15 "/ 10

5 /~'

0 ,~.II I I I ,q 0 IO 20 30 40 50 60 70 80 90 100

AREA 10

,r-::; 1 1 1 1 1 I I I q 0 IO 20 30 40 50 60 70 80 90 IOO

/l~~LLE"1/ AREA 11

0 10 20 30 40 50 60 70 80 90 IOO

Figure 3.78. Annual wind roses for SSMO areas (Right) and associated land stations. Percent calm is shown in· center of each rose and total number of observations is shown at the top of each rose. 128 Wind roses were constructed as follows:

a. Each arm of a rose represents the accumulated 9ercent of time winds of various speed ranges blew from the direction towards which the arm extends (i.e., the arm pointing towards the top of the page represents winds blowing from the north).

b. Segments of each arm represent various speed ranges. Speed ranges are ordered such that the segment of the arm nearest the center of the rose represents the slowest winds.

c. The number in the center of the rose indicates the percent of time no appreciable wind blew (the ~er­ cent calm).

d. The number at the top of the rose represents the num­ ber of wind readings-used to formulate the wind rose.

e. The vertical scale is used to determine percent values for each segment of the arms.

f. The horizontal scale shows cumulative percent values of all wind speeds (from all directions) for each speed range.

3.4.2. Winds for Offshore Areas from Cape Hatteras to Cape Canaveral

Available SSMO wind data have been treated three ways:

a. Wind roses for each month presented in Figures 3.66 to 3.78.

b. Wind constancy and resultant direction for each month.

c. Percentiles of wind speed for each month.

Wind constancy (sometimes called the steadiness of the wind) is a measure of how constantly the wind blows from any given direction. Constancy is determined by taking the square root of the sum of the squares of the time averaged northerly and westerly components of the wind for a given period (in this case for one month) and dividing by the time averaged speed of the wind for the same period. A constancy of 100% indicates

129 the wind always blew from the same direction. A constancy of zero indicates the time integrated wind was variable.

The reader should be cautioned to avoid comparisons between wind constancy and averaged winds as well as com­ parisons between resultant directions and averaged directions. Constancy and resultant directions involve integrations over time; whereas, averages generally do not. As an example, if the winds blows from the north at 50 knots for half the time and then blows from the south at 5 knots for half the time, the constancy is 82% and the resultant direction! is north. If, however, the wind blows from the north at 50 knots for half. the time and from the east at 5 knots for the remainder of the time, the constancy is now 91% and the resultant direction is s0 to the east of north.

Percentiles of wind indicate the percent of the time th·at wind speed was a given value or less during the period 6f

1

interest. In the case at hand, the 1st, 5th , 25th, 50th, 75th, 95th and 99th percentiles and maximum winds are shown for each SSMO area on a monthly basis. ~ Figures 3.79, 3.80 and 3.81 bhow wind Qonstancy and re- sultant direction in portion a) and wind percentiles in portion b) for SSMO areas 9, 10 and 11 respectively (see Figure 1.2 for locations). Median winds in the SSMO areas range from 10 to 17 knots with weakest winds from March to August. Winter winds are strongest in the two northernmost areas. Wind constancy for all three areas has somewhat the same yearly trend.· The southern­ most area (area 11) has the widest range of wind constancy, from near zero (variable winds) in April to 50% in October'when winds are predominantly out of the northeast. All three areas show peaks of constancy in July and October with the July peak most prominant in area 9.

Resultant wind direction is similar for all three areas going from west during winter to predominantly southerly during summer months.

130 ·----c- + + --m-- .. -a ... .. 50 .. 1' ... w .. ,[:J DJR +',, ccr,oN + z Q + ' + 40 ' .. [:] .... - - t:l .. , , t- + s~ -~ 0::: ~ 30 + 0 (.)>- z t- 20 \ + Ez ~ \ en \ ... ~:.,.J z 'c:l, .::> 0 10 ... + .... U) (.) 'El, w + + ' N o::: ~ ' 0 ... ' '[;J + + '--~----.

D J F M A M J J A s 0 N D J MONTH

50 + MAX I I

40

-U) t- 0z 30 ~ 0 -w w a.. U) 0 20 + z 3: 75%

10 25°/c

5% 0 1%

D J F M A M J J A s 0 N D J MONTH

Figure 3.79. Winds for SSMO Area 9. (a) Upper figure shows constancy and resultant direction, (b) Lower figure shows wind speed per- centiles. See text for explanation. 131 - ---i!J,.----e- + • --... "'1:l... + ....,, + w 50 + z ~ 0 t' ' \ t- ' , ~ 40 ... ' 'm.. ____ q s ~ -0 >- 0::: -(.) 0 z 30 1-

D J F M A M J J A S - 0 N D J MONTH

50 +

40

-en 99% bz 30 ~ 0 -w .w 95% a.. en 20 0z 75% 3: 50% 10 + 25°/c 5% 0 1%

D J F M A M J J A s 0 N D J MONTH Figure 3.80. Winds for SSMO Area 10. (a) Upper figure shows constancy and resultant direction, (b) Lower figure shows wind speed per­ centile. See text for explanation.

132 + .... 50 + + wz 0 40 .... (.) ~ ~ w >- 30 s~ (.) 0 z + t-z i=! ~ Cl) 20 z ' E ~:..J 0 ' \ + ::> (.) ' Cl) 10 'a, D1~ w ... , ...... a- 'ec-r 0::: ...... J.OAJ 0 ... + ...... N ''Q. ... + ...... D J F M A M J J A s 0 N D J MONTH

50 + + MAX

-Cl).... 0 z 30 ~ 0 -w IJJ a.. en 0z 20 3:

10 0% +

0

D J F M A M J J A 0 N D J MONTH

Figure 3.81. Winds for SSMO Area 11. {a) Upper figure shows constancy and resultant direction, (b) Lower figure shows wind speed per­ centile. See text for explanation. 133 CHAPTER 4 AIR TEMPERATURE

Air temperature data, as presented for land stations in "Local Climatological Data, Annual Summary with Comparative Data" are plotted as mean, normal maximum and minimum, and record high and low temperature·s (°F) by month for stations from C,ape Hatteras to Cape Canaveral. These plots are shown in Figures 4.1 to 4.10. The monthly temperature range for Cape Hatteras is the smallest for all months and is between 120F for winter and 11°F for sununer. Monthly temperature ranges for all stations south of Cape Hatteras averaged 21°F in winter and 19. s°F in sununer except for Daytona Beach, Florid.a which has a temperature range of 12°F in September. Extremes for both record high and record low temperatures were at New Bern, North Carolina. These were: 98°F for June and 9°F for December, January, and February.

Similar treatment of SSMO temperature data was not possible because of the large areas covered and spatial in- ' consistencies of collection. SSMO temperature data are presented in Figures 4 .11, 4 .12 and 4 .13 for areas 9,, 10 and 11 respectively. These figures show the percent of reported temper­ atures falling below a given value, maximum, mean and minimum temperatures.

134 Figures 4.1 to 4.10. Air temperature data {°F) showing record highest, average daily maximum, monthly normal, average daily minimum, and record lowest temperatures by month. Number with single asterisk indicates years used to determine average values. Number with double asterisk indicates years considered for record high and low values. Source: U. s. Department of Commerce: "Local Climatological Data, Annual Summary with Com­ parative Data." Figure 4.1. Cape Hatteras, North Carolina 29* 15** 4.2. New Bern, North Carolina 30* 30** 4.3. Wilmington, North Carolina 29* 9** 4.4. Charleston, South Carolina 29* 30** 4.5. Savannah, Georgia 29* 8** 4.6. Brunswick, Georgia 30* 30** 4.7. Jacksonville, Florida 29* 31** 4.8. Palatka, Florida 30* 30** 4.9. Daytona Beach, Florida 29* 29** 4.10. Titusville, Florida 30* 30**

135 110

100

90

80

70 -LL. ~ LI.I a:: 60 ::> ....er UJ a.. 50 ~ 1.1..1.... 40 I 30 I ...... 20 ......

10

0

J F M A M J J A s 0 N

Figure 4.1. Monthly air temperatures (°F) for Cape Hatteras, N. C. showing (top to bottom) record highest, average daily maximum, daily mean, average daily minimum, and record lowest temperatures for each month.

136 / ...... __ / ' ' ...... ' '

-LL 0 -w 0:: ::, ~ 0:: w 50 a.. ~ w .... 40

30

20

10

0

J F M A M J J A s 0 N D

Figure 4.2. Monthly air temperatures (°F) for New Bern, N. c. showing (top to bottom)reccrd highest, average daily maximum, daily mean, average daily minimum, and record lowest tempera­ tures for each month.

13"/ 110

-LL ~ L&J a: 60 :::> ~ a: wQ. 50 :E: .....L&J 40

30

20

10

0

J F M A M J J A s 0 N

Figure 4.3. Monthly air temperatures (°F) for Wilmington, N.C. showing (top to botto~) record highest, average daily maximum, daily mean, average daily minimum, and record lowest temperatures for each month.

138 110

...... 100 / ,,,,,,.·--.--· ...... ' ' ·, 90 ' ·, . 80 '

70 LL. 0 LJJ a:: 60 ::, ~ . 0:: I.IJ \ 50 ',,, \ a.. \ "· :E I.IJ ' \ •,, .... 40 ......

30

20

10

0

J F M 'A M J J A s 0 N D

Figure 4.4. Monthly air temp~ratures (°F) for Charleston, s.c. showing (top to bottom) record highest, average daily maximum, daily mean, average daily minimum, dnd record lowest temperatures for each month..'

139 80

70 Ll- 0 w a: ::, 60 ~ a:: LL.J Q. 50 :E w I- 40

30

J F M A M J J A s 0 N D

0 Figure 4.5. Monthly, air temperatures ( F) for Savannah, Ga. showing (top to bottom) record highest, average daily maximum, daily mean, average daily minimum, and record lowest temperatures for each month. II 0

..,... .._ -. ---...... -... •"' -· . / / ' y..\G't. • ' ·, ~~ .;,, .,,, ..... ~(jO//' ----·-----·, • ~..,.... / ' ' • ' _.,,,., / ·""' ' / ' '· / / ----·-· ' ' ·,, ~~/ . ' . / ~·· . ~(;:,·/ ',,, ~ ~ .,,,. / .----·----· ', .,,, . , , "" , ·,, u.. \, . ''' -0 -·-" / ' "" . - ~~/ ,/· w ·- ' ',. • 0::: ,/ //--\ ' :::> ~- ' .... . ' • <( .---· ~t;' ' ' a= ~<::,·/ / ' ' ~ ,,• • w , , / '"' , .. CL , \ :E /. • ' ' '• w .---- -· .... 40 ./ 0~; "" • 30 ~v/ \ cP /. \ 20 ~'-<;/ • ..,,,. __,,...• ' • 10 '

J M A M J J A s 0 N

Figure 4.6. Monthly air temperatures (°F) for Brunswick, Ga. showing (top to bottom) record highest, average daily maximum, daily mean, average daily minimum, and record lowest temperatures for each month.

141 110

100

90

80

70 LL 0 I.LI Q: 60 => ~ 0:: uJ a.. 50 ~ uJ t- 40

30 . 20 "- 10 "·

0

J F M A M J J A s 0 N D

Figure 4.7. Monthly air temperatures (°F) for Jacksonville Fla. showing (top to bottom) record highest, average daily maximum, daily mean, average daily minimum, and record lowest temperatures for each month.

142 110

-LL ~ LU a:: :::> ti a:: LU 50 a.. :E LU t-

10

0

J F M A M J J 0 N

Figure 4.8. Monthly air temperatures (°F) for Palatka, Fla.· showing (top to bottom) record highest, average daily maximum, daily mean, average daily minimum, and record lowest temperatures for each month.

143 J F M A M J J A s 0 N D

Figure 4.9. Monthly air temperatures (°F) for Daytona Beach, Fla. showing (top to bottom) record highest, average daily maximum, daily mean, average daily minimum, and record lowest temperatures for each month.

144 110

100

-u.. ~ LIJ a:: :::::, 60 ~ a:: w 50 0.. :E ....w

J F M A M J J A s 0 N D

Figure 4.10. Monthly air temperature$ (°F) for Titusville, Fla. showing (top to bottom) record highest, average daily maximum, daily mean, average daily minimum, and record lowest temperatures for each month.

145 - - --•- - - • - - - • MAX •, /. ' / ' / ' ./ / .99°/o '• / / ·---. ', ·-- /// /' 95°/o·--·~ "'- ',.____ , -·- - - . . ·, "'- ././:~er---~~-~·~.·--- / / 7501,/ .-~~------...... ·-----:/'/: • 25%. 5% -~-~~ ·----...... ·-LL 70 0 w -a:: ::, ~ 60 a:: MEA~---cf/ / / / \ • • w ~ ~ a. :E w Q:.;.::;:~;;;..-/·/.<_,// \ -~~. ~ 50 .----·~

'J F M A M J J A 0 N MONTH

Figure 4.11. Monthly temperatures in SSMO Area 9 shown as percent of data which was below a given value.

146 100,

~ a: ::) ~ 60 a: LLJ a. ~ LLJ .- 50

40

30

20

J A M J J A s 0 N D MONTH

Figure 4.12. Monthly temperatures in SSMO Area 10 shown as percent of data which was below a given value.

147 ---· MAX ._ .------...... -•, ,,,.// ~~·---...... ·--- .-- - ·---· / ,./""~· /:==·~·...... ______,99°/o ...... '•---· ./.--·~ • 75% • 95% "" ~ / ----·/"50% \, / \_\ "·~ :i!: w -· / \ I \ \, • t- 50 --•--- I I ,I• \ \ ~ . \ / '· . •---..._ / I '- • I '-, I '• ·------.------.I

J F M A M J J A s 0 N MONTH

Figure 4.13. Monthly temperatures in SSMO Area 11 shown as percent of data which was below a given value.

148 CHAPTER 5 PRECIPrJ'ATION

5 • 1. Genera 1

Availability of precipitation data in the region between Cape Hatteras and Cape Canaveral is similar to temperature data in that there is an abundance of information relative to land stations--maximum, minimum and mean quantities on an hourly, daily, monthly and yearly basis--whereas in the SSMO areas, precipitation data are merely records of occurrence or non­ occurrence. This is understandable because the SSMO data ~re based on mariners' reports and oceangoing vessels equipped with rain gauges are a rarity. Also, a ship underway, measuring rainfall would be similar to measuring rain from a moving auto~ mobile: you may pass through the shower area or you may move along with it. In either case, the measurement is not repre­ sentative of what happens at a fixed point and, for normal climatological purposes, of questionable value.

5.2. Precipitation at Land Stations Cape Hatteras to Cape Canaveral

The average number of days per year that .. 01 inch or more of rain is recorded ranges from 109 days at Charleston, South Carolina to 155 days at Wilmington, North Carolina, as shown in Figure 5.1. The greatest number of rain days occurs during the summer with rain experienced for nearly half ·the days of July at Charleston, Savannah, Jacksonville and Daytona Beach. South of Cape Hatteras, the fewest rainy days per month occur in late fall and early winter. From Savannah south, a minimum in rainy days is also seen in April. It appears that "April showers" are more likely to occur in July and August.

Maximum precipitation recorded during a 24-hour period for land stations between Cape Hatteras and Cape Canaveral is shown in Figure 5.2. The greatest 24-hour rain was recorded in New Bern, North Carolina with 12.5 inches falling 'in September. Stations from Brunswick south have experienced 24-hour rains of around 10 inches during the fall of the year.

Normal total monthly precipitation for all land stations and maximum monthly precipitation for major stations is shown in Figures 5.3 and 5.4. Wettest months are July, August, and September with maxima of nearly 20 inches of rainfall recorded at stations from Savannah south. Winter months are

149 Figure 5.1. Mean number of days with precipitation of 0.01 inch or more. Number in parentheses indicates years used to obtain mean. Sourc¢: U.S. Department of Commerce, "Local Climatological Data, Annual Summary with Comparative Data."

A. Cape Hatteras, North Carolina (15) B. Wilmington, North Carolina (21) C. Charleston, South Carolina (21) D. Savannah, Georgia (22) E. Jacksonville, Florida (31) F. Daytona Beach, Florida (29)

150 15 A. CAPE HATTERAS, NORTH CAROLINA

. ·--- 10 •-...._./ Cl) ·-·--- .~. / ." ..---·-...... _. __ . >­

0 .______.J J F M A M J J A s 0 N D MONTH

15 B. WILMINGTON, NORTH CAROLINA • / '-... 10 Cl) ·--·--· ---· ~ ~. ----· "'· . 0 ---. ---. ---- 5

0 ---,,--r---r---T"----,r---...------.----...... ------' J F M A M J J A s 0 N D MONTH

C. CHARLESTON, SOUTH CAROLIN/•"-•

10 Cl) >- ·-./·" __ ./·

J F M A M J J A N 0 MONTH

Figure 5.1. Mean number of days with precipitation of 0.1 inch or more.

151 15 0. SAVANNAH, GEORGIA /. 10 ."' / . " . ·-·-·". /""'. " 5 "·--·---- .

J F M A M J J 0 N D MONTH

E. JACKSONVILLE, FLORIDA /•--•".

10 en / . ~ . 0 "' ·-· -·~./· "'·/· 5

o.______....,.. ___,______,--~-~-~--..-- J F M A M J J A s 0 N 0 MONTH

15 F. DAYTONA BEACH, FLORIDA •--·--- ./ ."' 10

.---·-·" • /'/ '""· -· 5

0 '------..-----,,------~------..---.--J F M A M J J A s 0 N D ..... MONTH

Figure 5.1. (Cont'd) Mean number of days with precipitation of 0.1 inch or more.

152 Figure 5.2. Maximum precipitation (inches) in a 24 hour period by month. Number in parentheses indicates years considered. Source: u. s. Department of Commerce: "Local Climatological Data, Annual Summary with Comparative Data."

A. Cape Hatteras, North Carolina (1957-1972) B. New B~rn, North Carolina (1938-1967) C. Wilmington, North Carolina (1951-1972) D. Charleston, South Carolina (1942-1972) E. Savannah, Georgia (1950-1972) F. Brunswick, Georgia (1941-1970) G. Jacksonville, Florida (1941-1972) H. Palatka, Florida (1931-1960) I. Daytona Beach, Florida (1943-1972) J. Titusville, Florida (1938-1967).

153 A. CAPE HATTERAS, NORTH CAROLINA 10 en w . :::c:: u .--:_ /" z 5 ·---.-//'------./ . ·--·-·---......

J F M A M J J A s 0 N MONTH

B. NEW BERN, NORTH C~ROLINA ./'\ 10 en w :::c:: u z 5 . / ""·/ . ~--·-·----· ~·-·

M J J s 0 N MONTH

C. WILMINGTON, NORTH CAROLINA 10 en w u:::c:: z 5

0 J F M A M J J A s 0 N D ------MONTH

Figure 5.2. Maximum precipitation in 24 hour period.

154 0. CHARLESTON, SOUTH CAROLINA en 10 LiJ :J: (.) z 5

J F M A M J J A s 0 N MONTH

E. SAVANNAH, GEORGIA 10 en LiJ :J: (.) "'-.... z 5 .---· _..,.,,...... ---· ---- I ----· -· ~' " t ~ I

0 J F M A M J J A s N MONTH

F. BRUNSWICK, GEORGIA 10 en LiJ :J: (.) z 5

M M J J s 0 N D MONTH

Figure 5.2. Maximum precipitation in 24 hour period.

155 G. JACKSONVILLE, FLORIDA iO Cl) w :I: u .-·, /'"-..../·~-- z 5 ./ "-.--·--· .".

0 ------....----.-----.~-....------r----...J J F M A M J J A s 0 N D MONTH

H. PALATKA, FLORIDA 10 Cl) w :I: /. 0 z 5 ·-·-· /·-· \ .-- ~ ...... ---·--· .---·

M A M J J A s 0 N MONTH

I. DAYTONA BEACH, FLORIDA 10 Cl) LLI u'.l: z 5

0 -----r--~....-----,------...J J F M A M J J A s 0 N D MONTH

Figure 5.2. Maximum precipitation in 24 hour period.

156 J. TITUSVILLE, FLORIDA. 10 Cl) IJJ :c 0 z 5 /\./.--·-·-."" . ·-·--·---.--· o...___,,--,----,---,--.,----,---,---,ro---.,----,----,r---'T""-'""'T-- J F M A M J J s N D MO~TH

Figure 5.2. Maximum precipitation in 24 hour period.

157 Figure 5.3. Normal total precipitation (solid line) and maximum monthly precipitation (dashed line). Number with one asterisk indicates years of record used to determine monthly normals. Number with two asterisks indicates years considered for maximum values. Source: U. s. Department of Commerce, "Local Climatological Data, Annual Summary with Comparative Data."

A. Cape Hatteras, North Carolina 29* 15** B. Wilmington, North Carolina 29* 21** C. Charleston, South Carolina 29* 30** · D. Savannah, Georgia 29* 22** E. Jacksonville, Florida 29* 31** F. Daytona Beach, Florida 29* 29**

158 20 A. CAPE HATTERAS, NORTH CAROLINA

15 .,,,• ~"' \ en ,•, .,, •"' \ I.LI / ·--- ., ' .,, \ ~ 10 / ·- --..,, ' .,, \ z ...... / '·"' . ' ·- --·- -- - ./ 5 / ·-·---·---...... ~~, - ·------.---· - . --·-­

0 J F M A M J J A s 0 N D MONTH

20 8. WILMINGTON, NORTH CAROLINA

15

en ~ 10 (.) ..- -- ~·~ ·~ ...... ~ ' ·-- -.- - ·- -- /·----·-·""- ',,. 5 --. ----. . "' .----· ...... ---· ·-·-· 0 J F M A M J J A s 0 N D MONTH

Figure 5.3. (1) Normal total monthly precipitation. (2) Maximum monthly precipitation.

159 20 C. CHARLESTON, SOUTH CAROLINA ...... ,,,,...... ,,,, '·-- -· \ 15 I \ I \ I \ en • I \ LI.I /",, I '. 5 10 / .... z / ·---· ' ...___ ...... ---· ·---·/ / ---· 5 / ----. ·----·-·---.----· ----· ' "" .--. ---· 0 J F M A M J J A s 0 N D MONTH

20 0. SAVANNAH, GEORGIA • I' I \ I I ' I ' 15 ,, • ' / ·- -. en / LIJ / ' :I: 10 • ' (.) .,,...... / / ' ~ ..,,...... ,./ ' • -- ' ·- ----·--. -...._..._ ' 5 • • ' ' ·- --· .----·-·-· --~ "' ·--·--· 0 J F M A M J J A s 0 N D MONTH

Figure 5.3. (Cont'd) (1) Normal total monthly precipitation. (2) Maximum monthly precipitation.

160 E. JACKSONVILLE, FLORIDA 20 ,• / \ / \ ·- - -·/ \ / ' 15 / ' / ' ./ ·, (/) /~ \ LI.I / \ ::i:: 10 (.) \ z _.---·---·- --· ' .- - .----·----.---·" ' ·---· 5 / . ---·-·-· ~ ·-· / " .--. 0 '------..--..--~----J F M A M J J A s 0 N D MONTH

20 F. DAYTONA BEACH, FLORIDA /\• / / ' \ 15 I·- --•/ ' I ·- -- ...... I .... (/) ..... I • ~ 10 I (.) ,,• ....._' I ~ ' / '•---•- I ' ," --· ---·-·--·-...... _ ' 5 ' .----·. ---·--·--· /. ."' ·---. 0 J F M A M J J A s 0 N D MONTH

Figure 5. 3. (Cont'd) (1) Normal total monthly precipitation. (2) Maximum monthly precipitation.

161 Figure 5.4. Normal total precipitation for four substations. Normals are based on 30 years of data. Source: U.S. Department of Commerce, "Local Climatological Data, Annual Summary with Comparative Data."

A. New Bern, North Carolina B. Brunswick, Georgia C. Palatka, Florida D. Titusville, Florida

162 A. NEW BERN, NORTH CAROLINA

15

Cl) w 510 z ·~ 5 / ·-· ·-·--·---.--·--· "' ·-·---· 0 J F M A M J J A s 0 N MONTH

8. BRUNSWICK, GEORGIA

(/') ~ 10 (.) ~ -~·-·-----·~ __ ...... / •--- . --..... • ---- ·,. ---- • 0 M A M J J A s 0 N D MONTH

Figure 5.4. Normal total monthly precipitation.

163 20 C. PALATKA, FLORIDA

15

Cl) w ~ 10 z ------·-·-· 5 . " .~·-·-·-·/ ·,'.~· 0 J F M A M J J A s 0 N D MONTH

20 0. TITUSVILLE, FLORIDA

15

Cl) w ::c 10 u ~

5 / .-·-.----/"" . ·-· --·--·-· "' ·-· 0 ~------.------....--..... ---.--or---,--- J F M A M J J A s 0 N D MONTH

Figure 5.4. (Cont'd) Normal total monthly precipitation.

164 tlE dryest with all stations except Cape Hatteras reporting less than 5 inches per month.

Normal monthly precipitation for the southeastern United States is shown in Figure 5.5 as isopleths of precipitation in inches for each month.

5.3. Frequency of Occurrence of Precipitation for Offshore Region, Cape Hatteras to Cape Canaveral

As previously mentioned, only the occurrence of precipi­ tation in the SSMO areas is recorded. Available records show occurrence of rain, rain showers, drizzle, freezing precipi­ tation and hail. These have all been combined in Figure 5.6, which shows the percent of time precipitation of any type was observed while other meteorological parameters were being measured.

Unlike land stations in this region, the greatest fre­ quency of precipitation offshore occurs in January and February for the northernmost two areas (9 and 10), as shown in Figure 5.6, while the southernmost area, area 11, has the highest frequency of precipitation in September. Minimal frequencies of precipitation occur in all areas in April, although this minimum is least pronounced in area 11.

Frequencies of precipitation decrease from north to south in this region with annual frequencies of 5.7% in area 9, 5.1% in area 10 and 3.7% in area 11.

5.4. Thunderstorms

Thunderstorms result from cumulus clouds passing over an area bringing their associated thunder, lightning, strong gusty winds and downpours. In fact, cumulus clouds are thunder­ storms. Cumulus cloud formations in the Cape Hatteras to Cape Canaveral region generally result from strong atmospheric convection. Convection will take place when substantial differences in surface air temperature develop in relatively small areas such as over small bodies of water, plowed fields, or in regions where surface water shows a substantial horizontal temperature gradient.

Development rarely occurs during the cold season. Hence, thunderstorm activity shoQld be expected during the summer season in the Cape Hatteras to Cape Canaveral region. Figures 5.7 and 5.8 show thunderstorm occurrence for the land and off­ shore portions of this region respectively. For land stations

165 85° 80° 85° 80°

6 ,,,---, tt 35° l ,. \ ...... ~ ...,. '-./) "/' ~6 "/ r / I ,,, 5 .....- / { I I I _I - I 5 I I 30° 30°

2 JANUARY 25° FEBUARY

85° 80° 85° -, 4 ...... /,,,-7 i., / 5 35° I t I \~-...;;...,..., r=~,c;7 ' a /'1 r !,.".,. J \ \ .... 6 I' ,, / 6 .I " I I ) '--1 I s- .... I '1 r, I I {"'5' \ I J ( \ ' 30° l 30° \ ) ) /

25° MARCH APRIL

Figure 5.5. Normal monthly precipitation (in inches) for the Southeastern United States based on data from 1931 to 1960. Source: U. s. Department of Commerce ESSA. Environmental Data Service, "Climatic Atlas of the United States."

166 85°

35°

JUNE

85° 80° 85° 80° C. 1 ... ~ .,, , -5 / ' '-? ,,;fu, / / t.3,,1 I i'~ 35° I <- J/ _, / ,, - ., t\ I J ('- I ii I ( \. ~ .J I / \ ~- .., J ' , /jt'-') I 5 \ 5- _.I <.:- rca/ 1/''6., / ) "' \6 / / \ &' l~;I / 6 I r,: \ I \. .,,, ".., / I /"/ ,,,. 5""' - I ~ / ,/ "' ""'./ / ,,- ,/ ~ I / ,. - 5 '._. I .,s--. --/ / - 30° 30°

25° JULY 25° AUGUST

Figure 5.5. (Cont'd)

167 85° 80° ., / / ) / 35° -, / r~ J / \., / ~5 ., I 1(J ~ .,, 4 . / '3 - / l I'.// ---

~) 4 30° tJ 30°

SEPTEMBER 25° OCTOBER 25°

85° 80° 85° 80° 3 '):.." J I I/ '

NOVEMBER 25° DECEMBER 25°

Figure 5.5. (Cont'd)

168 10 SSMO AREA 9 /" . ~- /·----.-----· 5 ""·---. ---·--·-·--.

0

z J F M A M J J A s 0 N D o 10 ~ a:l- SSMO AREA 10 u Lu a:: a.. ·--·--. J_ lJ.. 5 0 /. . ~· Lu ·--·-·----·"" u ./' / z \

5 ."' . /·~. "-~·"' ·-·/----·--. ~.-·

0 J F M A M J J A s N MONTH

Figure 5.6. Percent occurrence of all types of precipitation (by month) in SSMO areas between Cape Hatteras, N. C. and Cape Canaveral, Fla.

169 Figure 5.7. Mean number of days with thunderstorms. Number in parentheses indicates years used to determine mean. Source: U.S. Department of Commerce, "Local Climato­ logical Data, Annual Summary with Comparative Data."

A. Cape Hatteras, North Carolina (15) B. Wilmington, North Carolina (21) C. Charleston, South Carolina (30) D. Savannah, Georgia (22) E. Jacksonville, Florida (31) F. Daytona Beach, Florida (28)

170 A. CAPE HATTERAS, NORTH CAROLINA 5 15 4 .,, l'T1 U) 10 3 :::0 (") ~ /·--. l'T1 0 2 z -4 5 .----.-· \ . ----·-· / ·---·---•~-• 0 J F M A M J J A s 0 N D MONTH

8. WILMINGTON, NORTH CAROLINA 15

U> 10 ~ 0 5

0 --T"--T---,---,,---....---.,---...---....--...... ------' J F M A M J J A s 0 N D MONTH

Figure 5.7. Mean number of days with thunderstorms, by month.

171 C. CHARLESTON, SOUTH CAROLINA 15 /·'----. 4 en 10 ~ 0 ./' \ 5 / . ·---~ ·--·--. o'----....,---.....---.---.,---~-,---,---~-..----,----,r------· ----· "" J F M A M J J A s o N D MONTH

0. SAVANNAH 1 GEORGIA • 15

Cl) 10 I"'· ~ .~/ 0 \ 5 / . ·--· ,,,,,,.-· "" ·--·--· J F M A M J J A s 0 N MONTH

Figure 5.7. (Cont'd) Mean number of aays with thunderstorms, by month.

172 E. JACKSONVILLE, FLORIDA 5 15 4 "tJ en 1·"'· 3~ 10 ~ ...,("') 0 /' \ 2Z • • ~ 5 / /·-· •--· 0 ·----·--· J F M A M J J A s""' 0 N D MONTH

F. DAYTONA BEACH, FLORIDA/' ...... 15

en 10 /' \ ~ 0 5 .---./· ·""'· ' 0 .---- .---- " ·---· J F M M J J A s 0 N D ------MONTH

Figure 5.7. (Cont'd) Mean number of days with thunderstorms, by Month.

173 I I I I ' ' . SSMO AREA 9 5~

4 . /r-• - 2 .. /.-· \ . -----· ·-·~ (!) I - .---· ·----. z o- .---- - ~ :x: I ' . l l l . (!) J F M A M J J A S 0 N D ...J I I ' I ' I 0 ' z 6-- . <( SSMO AREA 10 a:: 5- - w 0z ::> :x: . I- .,,..,--· __ ./"\ LL 0 2.- ' /" . - I.LI () ~- ~. z I ~ ---· ~- .. <( , . a:: .--· " a:: o- - ::::, () I . l I I I l I (.) J F M A M J J A s 0 N D 0 I . 1- ' ' z SSMO AREA 11 - w () . ct: 5 ... I.LI Q. . .

2,. .

I - . o- -

. l l l J F M A M J J A s 0 N D MONTH

Figure 5.8. Monthly frequency of occurrence of thunder and lightning in SSMO Areas between Cape Hatteras, N. C. and Cape Canaveral, Fla.

174 (Figure 5.7), data are presented as mean number of thunderstorms per month. In order to compare this information with thunder­ storm data for the SSMO regions (which arepresented as percent occurrence) the right hand scale for Figures 5.7A, C and E (Cape Hatteras, Charleston and Jacksonville) have been annotated with appropriate percent scales.

Maximum thunderstorm activity at land stations centrally iocated within the SSMO areas are 3% in July at Cape Hatteras 4.5% in July at Charleston and 5% in July at Jacksonville. Corresponding maximum activity in the SSMO areas are 3.5% in June and July for area 9 and 4% in August for areas 10 and 11.

Minimal thunderstorm activity in all areas occurs during the winter (November to February) period.

175 CHAPTER 6 RELATIVE HUMIDITY, VISABILITY AT SEA, OCCURRENCE OF FOG, AND SEVERE WEATHER EVENTS IN THE REGION FROM CAPE HATTERAS TO CAPE CANAVERAL

Parameters used to indicate the quantity of non-precipitat­ ing water in the atmosphere are grouped together because of their direct or indirect importance to operations, particularly move­ ment, on land and water surfaces. This section, therefore, deals with relative humidity, visibility at sea and occurrence of fog smoke or haze in the region from Cape Hatteras to Cape Canaveral. A sub-section on the occurrence of severe weather events in the region is included.

6.1. Relative Humidity

The quantity of water vapor that a given parcel of air can absorb is a function of the temperature of the air. Warm air can hold more water vapor than cool air. When air is saturated with water vapor, its relative humidity is 100% thus warm air with a given relative humidity contains more water than cool air with the same relative humidity. When warm moist air cools, its relative humidity increases to slightly higher than 100%, then the excess water in the,air condenses on fine particulate matter in the air (in coastal areas this particulate matter is generally sea salt resulting from evaporation of salt spray) and forms fog.

The daily variation of monthly average relative humidity at land stations from Cape Hatteras to Cape Canaveral exceeds the annual variation at any one time of day as shown in Figure 6.1, which gives average monthly values for 1 am, 7 am, 1 pm, and 7 pm. The general daily trend in relative humidity shows a decrease as the air is warmed during the day. With the exception of Savannah and Jacksonville, winter humidities are highest during the early morning hours before warming has begun while summer humidities are highest at night. The smallest daily range in relative humidity occurs at Cape Hatteras where average January· humidities range through 12 percent and those in July through 20 percent. Largest ranges are at Jacksonville with 38 percent in April and 30 percent in September. Average humidities range from evening values of 46% at Savannah in March to 1 am values of 92% at Charleston and Daytona Beach in August.

Relative humidity in the SSMO areas show the same daily variation as land stations. Average daily humidities for these areas increase during the summer months as shown in Figure 6.2

176 Figure 6.1. Average relative humidity by month for 1 a.m., 7 a.m., 1 p.m., and 7 p.m. local time. Number in parentheses indicates number of years used to determine average. Source: U. S. Department of Commerce, "Local Climatological Data, Annual Summary with Com­ parative Data."

A. Cape Hatteras, North Carolina (15) B. Wilmington, North Carolina (9) C. Charleston, South Carolina (30) D. Savannah, Georgia (8) E. Jacksonville, Florida (36) F. Daytona Beach, Florida (28)

177 A. CAPE HATTERAS , NORTH CAROLINA /.-·-. • /· _.-G--G~ e:::: / _....@- _@- -- • ----...... ' ~ ·-~,..c____,,______,,,_.... • -----. ------0-...... _ - 0 ---. ---- •----- • -- I-----•-~ ___-0:::::--• -- • --:::...0 ->- 1- 0 ~ -- .---·- ·- ::) -·- -...... - -- J: '...... // ·­--.---· .J ·---·""" w a::: --· lam - -07am ----· 1pm - - -· 7pm

J F M A M J J A s 0 N D MONTH

B. WILMINGTON , NORTH CAROLINA ----· ---·-;ci>-~

- . .----- .- ----·-----. --, 1- Q ',,,_ . ~ ·, ,,' ---- ::) :I: ·-----·- ," / ·---· ...... / ...... ' I ,/ d·a::: ' ' /.- -- ' / ·---·---· -/ /

J F M A M J J A s 0 N D MONTH

Figure 6 .1.

178 C. CHARLESTON , SOUTH CARO LINA

@- .---·-·~ ~--e...... • ....:::._~~/GY-@-_,.{Y =-e...... _-- ',,. . -----· e 10 -- ,, ~ -- ,," ::::> .-----· :I: ,,,,,,,,,·- --·- "' ,,-"' - -·, .,,, ·--·lam ', • ...... ______,,,,,, - --07am '...... ---- · 1pm ', ' .,,,.. - -· 7pm .,~

D

O. SAVANNAH ' GEORGIA

~ 0 ,,,, .... ,,' .- .... _ '>=' ...... ,,,• ·---- ...... , 9 70 ,, . .. ~ ... .. ,,' ::::> .. .. J: ...... , .. ,,.. • ,,·-...... ,. .. --- ' .... ; .,...; -.. -.., .---- -...... -.. .,... --~~ ..... '-.. -... ___ .,,,,. ·, ' '

D

Figure 6 .1. (Cont'd)

179 E. JACKSONVILLE, FLORIDA 0.--G>-~-~- ~~ ~-~-~--·--:~---e ---. ----~~ ·--· ~0 80 --. ___ ...... ----·-- ~ --·----·----· t- ,, ... •' ' ' , 9 70 ' .... , :E ' ...... , , :::> .. , ::c .... ----· ----· _j .... ------· ...... , w ., ...... -- ... 0::: ', ..,""' .... _ ,,,,, ...... • ' , ,,," " --· I am - ·""' ...... _ __./ - --07am -.- --- - · 1pm - - -· 7pm 40

J F M A M J J A s 0 N D MONTH

F. DAYTONA BEACH, FLORIDA

@- --G--0 • ----0"'~--0-._ ·---. : __ : -:=<;)~0- • • ------:: ::c _j w ·­ 0::: --·- --......

40

J F M A M J J A s 0 N D MONTH

Figure 6 .1. (Cont'd)

180 D • N 0 s A :c SSMO AREA t- J 9 ~ J :E M A M F J 0 10 20 30 40 50 60 70 80 90 100 D • N 0 s A SSMO AREA ~ J 10 ~ J ~M A M F J 0 10 20 30 40 50 D . N 0 s SMO AREA A II :c t- J 2 0 J :EM A M F J 0 10 20 30 40 50 60 70 80 90 100 PERCENT OF TIME

Figure 6.2. Percent of time relative humidity is over a given % value in SSMO Areas.

181 where isopleths of constant average relative, humidity are plotted as functions of time and percent of time that humidities were greater than those indicated by the isopleths. Humidities of 90% or greater occur most frequently in area 9 and least in area 11 while lower humidities show the opposite north south trend for all months.

6.2. Fog, Smoke and Haze The occurrence of heavy fog at land stations between Cape Hatteras and Cape Canaveral varies from an average of six days during January at'Daytona Beach to less than one day a month at Cape Hatteras during July and September as shown in Figure 6.3. Heavy fog is most frequent at Savannah with an average of 44 days a year and least frequent at Wilmington with an average of 25 days a year. As with thunderstorms, the right hand scales of graphs for Cape Hatteras, Charleston and Jacksonville have been augmented with a percent frequency scale to facilitate com­ parisons with adjacent SSMO areas. The frequency of fog in the SSMO areas is substantially less than that for associated shore stations. Figure 6.4 shows that SSMO area 11 has the highest frequency of fog. (Fog frequencies are shown on the left scale). This occurs between January and June, when fog has been reported between 2 and 3 percent of the time. Other months in area 9 and all months in areas 10 and 11 have fog less than one percent of the time.

Smoke and haz.e are more frequent than fog in the SSMO areas also shown in Figure 6.4 (right scale) with highest occurrences reported during the summer months in all areas and highest occurrences always reported in area 9.

6.3. Visibility at Sea

Visibility at sea in SSMO areas 9, 10 and 11 is shown in Figures 6.5, 6.6 and 6.7 respectively. Each figure has three parts showing percent of time visibility was (from bottom to top) less than one half nautical mile, between one half and one nautical mile, from one to two nautical miles, from two to five nautical miles, from five to ten nautical miles and more than ten nautical miles.

Visibility of over ten nautical miles is achieved least in area 9 (where it varies from 70 to 85 percent of the time) and most in area 11 (85 to 95 percent of the time) which agrees with information for fog, smoke and haze for these areas.

182 Figure 6.3. Mean number of days with heavy fog. Numbers in parentheses indicate years of data considered. Source: U. S. Department of Commerce, "Local Climatological Data, Annual Summary with Comparative Data."

A. Cape Hatteras, North Carolina (15) B. Wilmington, North Carolina (21) C. Charleston, South Carolina (23) D. Savannah, Georgia (22) E. Jacksonville, Florida (28) F. Daytona Beach, Florida (28)

183 6 20 5 A. CAPE HATTERAS, NORTH CAROLINA 15 -o Cl) 4 l'T1 3 10 ~ ~ l'T1 0 2 z ·-·"·-·-·" /. . 5 -4 I ·-...... _.-,,-·"' ~·-· 0 • • 0 .

J F M A M J J A s N D MONTH

6 20 5 B. WILMINGTON, NORTH CAROLINA 15 4 Cl) ~ 3 10 Q 2 ·-·-·-·-·-· /·"·/·-· 5 I 0 "·-· 0 J F M A M J J A s 0 N D MONTH

6 20 5 c. CHARLESTON, SOUTH CAROLINA 15 .,, 4 . fTI Cl) ·--· ::n >- 3 / IO o ~ l'T1 Q / 2 ~ z ·--·-·-·-· 5 -4 " ·--· / 0 0

J F M A M J J A s 0 N D MONTH

Figure 6.3. Mean Number of Days with Heavy Fog.

184 6 20 SAVANNAH, GEORGIA 5 15 en 4 .""'D ·-·----·-· ~ 3 ·-·-·-·-· 10 0 ./ 2 5 I / 0 0

J F M A M J"" J A 0 N D s MONTH

6 20 5 • "-.. E. JACKSONVILLE, FLORIDA ·-· . 15 -o (/) 4 / 1'11 ~ 3 10~ ·-· 1'11 0 2 " 5~ I " " ·--·-·-· / 0 0

J F M A M J J A s 0 N D MONTH

6 20 5 DAYTONA BEACH, FLORIDA . 15 (/) 4 / ~ 3 10 0 2 5 I 0 0

J F M A M J J A s 0 N D MONTH

Figure 6.3. (Cont'd)

185 10

5 SSMO AREA 9 /\ ~ / \ / \ CJ) / \ 3: (.!) / \ // ' 0 0 /---· \/ ' '\ LL / \ 5 "I'll ~ ~-,.._. '\. zJ> C . / ' :c . -----·// .---· ----· -·\ ' ~, l> / '·~· N ·--.----·----.../· -- . I'll 0 0

J F M A M J J A s 0 N D 10

SSMO AREA 10 cf!. 5 CJ) 3:: 0 (.!) 0 5 "I'll LL J> 0~ /·, z ," ' /,·--- ·, C ,,,.. .. • ' / ' :c ·---·""/ ,./ ' J> / N ·----. / ' ·, 1'11 0 . -- ---~------. ----. ------·-----·--.------·-----. ___::- :-;:.--c::- ~ 0

J F M A M J J A s 0 N D 10

5 SSMO AREA II 0~ CJ) 3:: 0 5 "l"1 zJ> C :c ., .. ·---., l> / ' -·---· N _..... " '.-- ...... 1'11 0 ·---··------·~ ·:::...-... --...... ------·----·-·--•-,-·~==-==: , ...... 0

J F M A M J J A s 0 N D MONTH

Figure 6.4. Percent occurrence of fog~-·, and smoke and haze---·, in SSMO Areas.

186 SSMO AREA 9

100

...... ______...... ---· ,,,~·----~---·---·----·---· t­ z ~50 50 a:: w Cl..

. ·-·-·-----·-----· ~ ...... ·-·------·---·-· c.)----

J F M A M J J A s 0 N D

6 6

5 5

t-z 4 ., ...... 4 w .,,, ...... (.) 3 ,, 3 a:: . -...... w -·- ...... ----' Cl.. 2 2 ' ' , ...... ,, ,·---·- ---·--··-----· l­ ·----·...... •--..._ . . ..------·--·------...----·-· - - 0 o b.)

J F M A M J J A s 0 N D 1.0 ./·-\ zt­ w (.) .5 .5 a:: LLJ a. ,.,,·---·,, ·-·"' . /"/" ·' ...... ' ~,,·,,~ _/·-----:,·-·---· ;, ---· ...... ,, ·' -~-- ·"' 0 a.) 0

J F M A M J J A s 0 N D MONTH Figure 6.5. Mean percent of time visibility was a given distance (in nautical miles) for SSMO Area 9. (a) <.5 b) -·.l to 2 c) --· .5 to 10 . 5 to 1 2 to 5 ---·>10

187 SSMOAREAIO

100 --·-----·- ,,,,,,,,_.,,,,,.•---· - -- ·--- _.,,,,,,,...... __ ;.,,.,,. ·--- ·---·""'.,,, --·- - - ....- t­ z ~50 50 · er:: w 0.

c).--·--·-- ·--·-·--.--·--·--·--·--· 0 J F M A M J J A s 0 N D

6 6

5 5

t- 4 4 z LI.I u 3 3 er:: Lu 0. 2 2 ·---·---·...... ___ __. ...._ __ .------·"'""- .---· ...... ___ .----- ...... ___ .

0 b)·-·--·--. -· ---·--·--·--·-·---- •---· 0

J F M A M J J A s 0 N D

1.0 1.0

t­ z lJ.Ju a: .5 w a.

0 J F M A M J J A S . 0 N D MONTH Figure 6.6. Mean percent of time visibility was a given distance (in nautical miles) for SSMO Area 10. (a)--· <.5 b) --· .1 to 2 c) --· .5 to 10 - - - · . 5 to 1 - --· 2 to 5 - - - · > 10

188 SSMO AREA II

100 ·--- -·---·------·---·---·------·---·--- ...... - --·------·-- -- .

t- z 50 UJ U50 a:: LLJ 0..

.) ·--·--·--- . C -·--·---- .------·--·--·-· 0 0 J F M A M J J A s 0 N D

6 6

5 5

4 zt- 4 LLJ u 3 3 a:: ~ 2 2 ·- --·---·---· _,,,,.,,,,,·------·-- .... -·-- -· ...... _,,,,,,,, ...... -- -- -·-----·--...... -- .,- . . 0 0 b)·-·--·--·--·------·-·-·-----·---

J F M A M J J A s 0 N D

1.0 1.0

t­ z LLJ u .5- .5 0:: LLJ 0.. 4·,-·~ ·--·--·---•...... ______...-~·~·--· / ', ·~· a ) .... ·----:·--- . .--- ...... ___ . / .__ ' ·-- -·--..___...__.. 0 ______-- -- - _____ - 0 J F M A M J J A s 0 N D MONTH Figure 6.7. Mean percent of time visibility was a given distance (in nautical miles) for SSMO Area 11. (a) --· <. 5 b) --· .1 to 2 c) --· .5 to 10 ---· . 5 to 1 2 to 5 ---· >10

189 6.4. Severe Weather Events

The occurrence of tropical storms, hurricanes, tornadoes, and thunderstorms in the region between Cape Hatteras and Cape Canaveral has been discussed previously. This region is prone to other weather phenomena which cause loss of life and property damage. Table 6.1 is a listing of all types of severe weather'. events which have affected this area from January 1960 to Dec­ ember 1973. The table is arranged chronologically for each degree of latitude from north to south and generally covers the distance from the coast to approximately fifty miles inland. The date, event, and estimates of damage are given. Those events marked with an asterisk were statewide and estimates of damage should be appropriately reduced for the region of interest con­ sidered. Data were obtained from the NOAA publication "Storm Data."

190 Table 6.1. Severe Weather Events in the Region from Cape Hatteras, North Carolina to Cape Canaveral, Florida.

Damage in Thousands Date Occurrence of Dollars

35°-36° NORTH

1960 May tornado (1 injured) 5-50 (p~ 1 1961 June hail storm 5-50(c)2 1961 Aug. wind and rain 50-500 (p) , 50-500 (c) 1963 May tornado (2 injured) 50-500(p) 1963 Sept. tornado 5-50(p) 1965 Mar. electrical storm 50-500(p) 1966 July electrical storm 5-50(p) 1968 Mar. tornado 50-500(p) 1968 Apr. tornado 5-50(p) 1968 May wind storm 50-500 (p) , 50-500 (c) 1968 June hail, electrical storm 5-50(p), 50-500(c) 1968 July tornado 50-500(p) 1969 Apr. tornado .5-5(p) 1970 July wind and electrical storm 5-50(p) 1970 Nov. funnel cloud 1971 Apr. funnel cloud 1971 May tornado 50-500(p) 1971 June electrical storm (3 injured) 50-500(p) 1971 Aug. waterspout 1971 Aug. waterspout 1972 June waterspout 1972 Dec. wind storm .5-5(p) 1973 May wind and hail storm ·. 5-5 (c) 1973 July waterspout

34°-35° NORTH

1960 Mar. snow and sleet (greatest on record for March) 1960 June hail, electrical storm 5-50(p) 1960 July electrical storm .5-5(p) 1960 July electrical storm (1 dead) 1960 July tropical storm Brenda 50-5oo (p), 5o-5oo (c) 1960 Sept. Hurricane Donna (8 dead; 5000-50000 (p) , 100 injured) 5000-50000(c) ------1 (p) represents damage to property 2(c) represents damage to crops

191 Table 6 .1. (Cont'd)

Damage in Thousands Date Occurrence of Dollars

1961 Feb. tornado .5-5(p) 1961 Apr. electrical storm; winds up 5-50 (p) * to 80 mph; rain 1961 May hail and electrical storm 5-50 (p) , 50-500 (c) 1961 June hail 5-50(c) 1961 June hail; wind; rain 50-500 (p) , 500-5000 (c) 1961 July rain 50-500 (p), 500-5000 (c) 1961 Sept. Hurricane Esther 50-5000(p) 1962 Apr. electrical and wind storm 50-500(p) (4 dead) 1962 June tornado 5-50(p) 1962 June rain; wind; high tides 50-500 (p) , 5000-50000(c) l9q2 July rain; wind (3 injured) 50-500 (p), 5000-50000(c) 1962 Aug. tropical storm Alma . 5-5 (p), 5-50 (c) 1962 Oct. Hurricane Ella 5·-5o (p), 5-50 (c) 1962 Nov. rain; wind 50-500(p) 1962 Nov. wind; high seas, tides 5()()-5000 (p) 1963 Apr. electrical; hail and wind 50-500 (p), • 5-5 (c) storm 1963 May tornado (2 injured) 5-50 (p) 1963 May tornado .5-5(p) . 1963 July hail 5-50(c) 1963 Aug. wind, electrical 5-50(p) 1963 Aug. electrical. (2 injured) 1963 Aug. waterspout 1963 Oct. Hurricane Ginny 50-500 (p) , 50-500 (c) :J.9_6J .Oct. hail 5-50 (p) , . 5-5 (c) 1964 Feb. wind and waves s~so (p) 1964 Feb. wind and electrical storm 5-50(p) 1964 Feb. wind 5-50(p) 1964 Mar. late freeze great damage to crops 1964 May wind, rain 5-50(p) 1964 June wind 5-50(p) 1964 June hail 5-50 (c) 1964 Aug.. Hurricane Cleo (rain) 50-500 (p), 50-500 (c) * 1964 Sept. waterspout 5-50(p) 1964 Sept. Hurricane Dora 5-50 (p), 5-50 (c) 1964 Sept. tornado 5-50(p) 1964 Sept. Hurricane Gladys 50-500 (p), 5-50 (c) 1964 Sept. rain (2 dead, 10 injured) 5000-50000 (p) , 5000-SOOOO(c)* 1964 Oct. Hurricane Isbell 50-500 (p), 50-500 (c) 1965 Mar. tornado (2 dead, 100 injured) 500...;.5000 (p)

192 Table 6 .1. (Cont'd)

Damage in Thousands Date Occurrence of Dollars

1965 June hail 5-50(c) 1965 June rain 50-500(p)~ 50-500(c) 1965 July electrical, rain, wind 5-50(p) 1965 July waterspout 196 6 May waterspout 1966 June rain and wind 5-50 (p) 1966 Aug. electrical storm and rain 5-50(p) (1 injured) 1967 Aug. hail 5-50(p) 1967 Aug. waterspout 1967 Nov. wind and electrical storm 50-500(p) (4 injured) 1967 Dec. wind and rain 50-500(p) 1967 Dec. waterspout 50-500(p) 1968 May wind and hail 5-50(p) 1968 July waterspouts 1968 July lightning 1968 July wind, rain, electrical storm 50-500(p) 1968 Aug. waterspout 1968 Aug. electrical, wind, and rain 50-500(p) storm 1968 Oct. Hurricane Gladys 5-50 (p), 5-50 (c) 1968 Dec. wind, low pressure storms 50-5QO(p) 1969 May rain 5-50(p) 1969 May hail, electrical, wind storm 5-SO(p) 1969 July electrical (2 dead) .5-S(p) 1969 Aug. tornado 5-SO(p) 1969 Nov. wind and rain (1 dead) 50-500 (p), 5-50 (c) 1970 June hail and electrical storm 5-50 (p), 5-50 (c) 1970 July electrical storm 5-SO(p) 1970 Aug. wind, riptides (70 mph winds) 50-500(p) (4 dead) 1970 Oct. waterspout 1970 Oct. rain, wind, tides 50-500 (p) , 5-50 (c) * 1970 Dec. wind 5-SO(p) 1971 Jan. glazing (1 dead) 50-500(p)* 1971 June electrical, rain, hail storm 5-SO(p) 1971 July waterspout 1971 July waterspout .5-5(p) 1971 July electrical and wind storm 5-50(p) 1971 July wind 5-SO(p) 1971 Aug. rain, wind 50-500 (p), 50-500 (c) 1971 Aug. waterspout and funnel cloud 1971 Aug. tropical storm Doria, 69 mph 50-500 (p), 50-500 (c) winds, rain

193 Table 6.1. (Cont'd)

Damage in Thousands Date Occurrence of Dollars

1971 Sept. tropical storm Ginger, 92 mph 5000-50000 (c) , winds 50-500(p) 1971 Oct. wind (2 dead) 5-50 (p) 1971 Oct. rain 5-50 (p), 5-50 (c) 1972 Jan. wind, high seas 5-50(p) 1972 Jan. fog 5-50 (p) 1972 Jan. wind, high seas (3 dead) 5-50(p) 1972 Apr. wind (1 dead), fire 5-50 (p), 500-5000 (c) 1972 July hail and wind 5-50(p), .-5-5(c) 1972 July funnel cloud 1972 July electrical and wind storm 5-50(p) 1972 Aug. small funnel 19.72 Aug. electrical, hail, wind storm 5-50(p) (1 injured) 1972 Aug. electrical storm .5-5(c) 1972 Sept. electrical and wind storm 5-50 (p) 1972 Sept. tornado 1972 Oct. tornado 50-SOO(p) 1973 Feb. snow and wind (2 dead, 500-5000(p), 3 injured) 50-500(c)" 1973 Mar. wind and high seas 50-500(p) 1973 Mar. rain, wind, electrical storm 500-5000(p) 1973 Apr. tornado 5-50(c) 1973 May wind and thunderstorm 5-50 (p). 1973 June flash flood 5-50(p) 1973 July lightning 5-50(p)

33°-34° NORTH

1960 Feb. tornado 50-500(p) 1960 Apr. extreme turbulence 1960 July wind .05-.5(p) 1960 Sept. tornado 5-SO(p) 1960 Sept. Hurricane Donna 1962 Mar~ wind storm and high tides 50-500(p) (1 dead) 1962 Aug. tornado 5-50(p) 1962 Aug. tropical storm Alma 1962 Sept. waterspout 1962 Nov. wind and tides 50-500(p) 1963 July lightning (1 dead) 1963 July lightning (1 dead) 1963 Oct. hail .5-5(p)

194 Table 6 .1. (Cont'd) Damage in Thousands Date Occurrence of Dollars

1963 Oct. Hurricane Ginny no damage 1964 Mar. late freeze great damage to crops* 1964 May hail -1964 June heavy rain 50-500 (p) , 500-5000 (c) 1964 June funnel cloud - . ~ .. - . 1964 July electrical storm. (1 dead, 1 injured) 1964 July funnel cloud 1964 July waterspout 1964 Aug. funnel cloud 1964 Aug. Hurricane Cleo 50-500 (p) , 50-500 (c) * 1964 Sept. tropical storm Dora 5-50 (p), 5-50 (c) 1964 Sept. waterspouts 1964 Sept. tornado 5-50(p) 1964 Sept. Hurricane Gladys 1964 Oct. rain (1 dead) 500-5000 (p), 500- 5000 (c) 1964 Oct. rain from Hurricane Isbell 50-500(c) 1965 May tornado 5-50(p) 1965 July lightning (1 dead) 1965 Aug. tornado (46 injured) 50-500(p) 1966 July hail and rain 5-50(c) 1967 May tornado <.05(p) 1967 June tropical depression 5-~0(p), .05-.5(c) 1967 Aug. waterspout 1967 Nov. tornado and wind (1 injured) 5-50(p), .05-.5(c) 1967 Dec. tornado (1 injured) 5-50(p) <.05(c) 1968 Mar. tornado .05-.5(p) 1968 Aug. tornado <.05(p) 1968 Dec. tornado 5-50(p) 1969 Nov. wind and rain (cyclone) 50-500 (p), . 5-5 (c) (1 dead, 2 injured) 1970 Dec. cyclone, high wind, tides 5-50(p)* 1970 June windstorm (2 injured) 50-500(p) 1970 July thunderstorms, hail, wind, 50-500(c) ahd rain 1970 July · lightning (3 injured) 1970 Nov. thunderstorm and wind 5-50(p) 1971 Dec. rain and wind 500-5000 (p), 500-5000(c) 1972 July thunderstorm, wind, hail 5-SO(p) 1973 Feb. flood 5-50(p), .05-.5(c) 1973 Sept. high tides 5-50 (p)

1960 Feb. ice and wind 5-SO(p)

195 Table 6 .1. (Cont'd)

Damage in Thousands Date Occurrence of.Dollars

1960 Mar. wind 1960 July wind 5-50(p) 1960 July funnel cloud 1960 July tropical storm Brenda 1960 Sept. tornado associated with 500-5000(p) Donna (10 injured) 1960 Oct. waterspout 1961 Jan. wind 5-50(p) 1961 Apr. wind 5-50(p) 1961 Apr. wind (1 dead, 12 injured) 50-500(p) 1961 Apr. tornado 5-50(p) 1961 Apr. tornado 50-500(p) 1961 Apr. waterspout 1961 June hail 1961 July funnel cloud 1961 July funnel cloud 1961 July funnel cloud 1961 Aug. lightning (1 injured) 1961 Sept. high winds (1 injured) .5-5(p) 1961 Sept. tornado 5-50(p) 1962 Jan. ice storm 5-50(p) 1962 Mar. ice storm 1962 May hail 1962 July wind and rain 5-50 (p.) 1963 June heavy rain 500-5000(c) 1963 June rain 50-500(p) 1963 July thunderstorm 5-SO(p) 1963 July lightning (1 dead) 1963 Oct. Hurricane Ginny 5-50(p) 1964 Mar. cold wave 5-50(p)~, 500-5000(c)* 1964 May hail 1964 July rain 50-500(p) 1964 Aug. tornado .5-5(p) 1964 Oct. funnel cloud 1965 Mar. wind 5-50(p) 1965 June lightning 50-500(p) 1965 July tornado .5-5(p) 1965 Oct. tornado 50-500(p) 1966 Apr. tornado <.05(p), <.05(c) 1966 July wind, hail, electrical storm 5-50(p) 1966 July wind, hail, electrical storm 5-SO(p) 1966 July tornado .5-5(p) 1966 Aug. tornado 5-SO(p) 1966 Sept. tornado .5-5(p) 1967 Jan. funnel clouds (2) 1967 Feb. cold wave (1 dead)

196 Table 6 .1. (Cont'd)

Damage in Thousands Date Occurrence of Dollars

1967 Mar. wind 5-SO(p) 1967 Apr. hail and wind 50-SOO(p) 1967 Apr. funnel cloud ·-1967 May wind and rain .5-S(p) 1967 July lightning (1 dead, 2 injured) 1968 Jan. turbulence (2 injured) 1968 Apr. wind 5-SO(p) 1968 June wind, rain, lightning (1 dead) .5-S(p) 1968 June funnel cloud 1968 June waterspout 1968 June tropical storm Abby (SO mph 5-SO(p), .5-S(c) on coast) 1968 June windstorm 5-SO(p), .5-S(c) 1968 July tornado 1968 Aug. funnel cloud 1968 Aug. wind and lightning (1 injured) .5-S(p) 1968 Sept. thunderstorm (1 dead) .5-S(p) 1969 May heavy rain 50-500 (p), 50-500 (c) 1969 May hail 1969 June waterspout 1969 July lightning 5-50(p) 1969 Aug. waterspout 1969 Sept. tornado 1970 Mar. hail 1970 Mar. hail 5-50 (p) , . 5-5 (c) 1970 May tornado 5-50(p) 1970 May tornado .5-S(p) 1970 July waterspout 1970 July funnel cloud 1970 July windstorm 5-50(p) 1970 Aug. windstorm 5-SO(p) 1970 Aug. heavy rain 500-SOOO(p) 1971 May lightning (1 injured) 5-SO(p) 1971 June funnel cloud 1971 July thunderstorms, lightning 5-SO(p) 1971 July waterspout 1971 July waterspout 1971 Aug. . funnel cloud 1971 Aug. heavy rains 50-SOO(p) 1971 Aug. lightning (1 injured) 1971 Aug. waterspout 1971 Aug. waterspout 1971 Oct. waterspout 1972 Feb. cyclone (4 injured) .5-S(p) 1972 June thunderstorm 5-SO(p) 1972 July waterspout

197 Table 6 .1. (Cont'd)

Damages in Thousands Date Occurrence of Dollars

1973 May wind, hail, electrical (1 500-5000(p), 5-50(c) dead, 3 injured) 1973 May waterspout 5-50(p) 1973 May wind (3 injured) 5-50(p) 1973 June flood 1973 July waterspout 1973 Aug. electrical storm 50-500(p) 1973 Nov. tornado 5-50(p)

31°-32° NORTH

1960 Feb. wind 5-50(p) 1960 Sept. Hurricane Donna 5-50(p) 1962 Jan. ice and glaze 5-50(p) 1962 May wind and hail 5-50 (p) , • 5-5 (c) 1962 Aug. funnel cloud 1963 Feb. wind and rain 5-50(p) 1963 May tornado 5-50 (p) 1963 June waterspout .5-5(p) 1964 Mar. wind, rain, electrical 50-500(p) storm (2 dead) 1964 Aug. waterspout 1964 Aug. Hurricane Cleo (44 mph winds) 50-500 (p) , 5-50 (c) 1964 Sept. Hurricane Dora 5000-50000 (p) , 50-500(c) 1965 Jan. hail and wind . 5-5 (p) 1965 Mar. tornado .5-5(p) 1965 Sept. rain and wind 50-500 (p) , • 5-5 (c) * 1966 May waterspout 1966 May funnel cloud 1966 May funnel cloud 1966 June Hurricane Alma 50-500 (p), 50-500 (c) 1966 July tornado 50-500(p) 1966 Aug. funnel cloud 1966 Aug. funnel cloud 1967 Aug. funnel cloud 1968 May waterspout 1968 May hail .5-S(p), .5-5(c) 1968 Sept. funnel cloud 1968 Oct. funnel cloud 1969 May heavy rain .5-5(p) 1969 July windstorm 5-SO(p) 1969 July funnel cloud 1969 Nov. heavy rain (2 injured) 50-SOO(p&c)

198 Table 6 .1. (Cont'd)

Damages in Thousands Date Occurrence of ·oollars

1970 Feb. funnel\ cloud 1970 Sept. waterspout 1971 Apr. tornado 5-SO(p) ·1971 June thunderstorm 5-SO(p) 1971 Oct. funnel cloud 1971 Dec. wind, rain, tides 50-SOO(p) 1972 Mar. lightning .5-S(p) 1972 May wind, rain, hail, funnel cloud 5-SO(p) 1972 May waterspout 1972 May subtropical cyclone (65 mph 50-SOO(p) winds) 1973 May funnel cloud 1973 May hail .5-S(p&c) 1973 June funnel cloud

30°-31° NORTH

1960 Feb. tornado (1 injured) 5-SO(p) 1960 Feb. tornado 5-SO(p) 1960 Sept. funnel cloud 1960 Oct. tornado . 05-. 5 (p) 1961 Feb. funnel cloud 1961 Mar. tornado .5-S(p) 1961 July tornado 1961 Aug. funnel cloud 1961 Aug. funnel cloud 1962 May lightning (1 injured) 1962 May lightning (1 dead) 1962 Aug. funnel cloud 1962 Aug. lightning (1 dead, 1 injured) 1962 Aug. waterspouts (2) 1962 Sept. waterspout 1962 Nov. wind and tides 500-SOOO(p) 1963 Feb. wind 500-SOOO(p) 1963 May . !l(ightning (1 dead) 1963 July tornado .5-5 (p) 1963 Aug. lightning (1 dead) 1963 Oct. waterspout 1964 Jan. tornado 1964 Mar. wind and lightning (1 dead, 3 injured) 1964 May tornado 1964 June tornado 50-SOO{p)

199 Table 6 .1. (Cont'd)

Damage in Thousands Date Occurrence of Dollars

1964 July funnel cloud 1964 Aug. Hurricane Cleo minor damage 1965 June waterspout 1965 Aug. funnel cloud 1965 Aug. lightning (3 injured) 1965 Aug. lightning (2 injured) 1966 Feb. funnel clouds ( 2) 1967 May waterspout 1967 July waterspouts (3) 1967 Aug. lightning (1 dead) 1968 Apr. hail 1968 July funnels aloft 1968 July funnels aloft 1968 Aug. funnels aloft 1968 Aug. funnels aloft 1968 Aug. rain and flooding 50-SOO(p) 1968 Sept. tornado .5-S(p) 1968 Oct. funnels aloft 1968 Oct. funnels aloft 1969 June tornado .5-5(p) 1969 Aug. wind and rain 1969 Sept. lightning .5-5(p) 1969 Oct. rain and flooding 50-SOO(p) 1969 Nov. thunderstorm and flood 5-50(p~ 1969 Dec. funnel aloft 1970 Feb. heavy rain, floodings 50-500(p) 1970 June lightning (2 injured) 1970 June waterspout 1970 July lightning (4 injured) 1970 July tornado .5-5(p) 1971 Apr. hail 1971 June lightning 5-SO(p) 1971 July lightning 5-50(p) 1971 Aug. lightning 5-50(p) 1971 Aug. lightning (3 injured) 1971 Sept. wa1:-erspout 1972 Jan. funnel aloft 1972 Mar. lightning 5-50(p) 1972 Apr. waterspout 1972 June lightning 5-SO(p) 1972 June lightning 5-50(p) 1972 July lightning (1 injured) 1972 July tornado (4 injured) 1972 Oct. funnel aloft

200 Table 6 .1. (Cont'd)

Damage in Thousands Date Occurrence of Dollars

29°-30° NORTH

1960 Mar. hail 1960 June waterspout 1960 July tornado 1960 July tornado 1961 Aug. funnel clouds 1961 Aug. waterspout 1961 Aug. tornado 5-SO(p) 1961 Sept. waterspout 1961 Sept. waterspout 1962 Aug. waterspouts (2) 1962 Aug. lightning (1 injured) 1962 Sept. waterspout 1962 Sept. waterspout 1963 July lightning (1 injured) 1963 July tornado .5-S(p) 1963 Aug. tornado .5-S(p) 1964 Jan. tornado .5-S(p) 1964 June lightning (2 injured, 1 dead) 1964 July funnel cloud 1964 Aug. · tornado .5-S(p) 1964 Aug. Hurricane Cleo minor damage 1965 Aug. funnel cloud 1965 Sept. funnel cloud 1966 Apr. funnel cloud 1967 May funnel aloft 1967 Aug. waterspout 1968 June waterspout 1968 Aug. lightning (1 injured) 1968 Aug. tornado 5-SO(p) 1968 Aug. tornado 5-SO(p) 1968 Nov. funnel aloft 1969 July tornado .5-S(p) 1969 Sept. waterspouts (2) 1969 Oct. tornado 1969 Oct. funnels aloft ( 2) 1969 Dec. . damaging winds .5-S(p) 1970 June lightning, hail, flooding 5-SO(p) (1 injured) 1970 July lightning (1 dead) 1970 July lightning (1 injured) 1970 July lightning (1 injured) 1970 July tornado .05-.S(p) 1970 Aug. lightning (1 dead) 1971 Feb. tornado 50-SOO(p)

201 Table 6 .1. (Cont'd)

Damage in Thousands Date Occurrence of Dollars

1971 Feb. hail .5-S(p) 1971 Feb. wind, snow (3 injured) 50-SOO(p)* 1971 Mar. hail 1971 Mar. hail 1971 June funnels aloft 1971 July lightning (1 dead) 1971 July wind and lightning (1 dead) 1971 Sept. waterspout 1971 Oct. funnel aloft 1971 Oct. waterspout 1972 Mar. wind (1 injured) .05-.S(p) 1972 July wind 5-SO(p) 1972 Aug. lightning (1 injured) 1972 Aug. lightning (1 injured) 1972 Aug. waterspout 1972 Aug. tornado 5-SO(p) 19 72 Dec. funnel aloft 1973 Jan. funnel aloft

* Statewide

202 CHAPTER 7 CONCLUDING REMARKS

The general yearly trends of climatic features of the coastal region between Cape Hatteras, North Carolina and Cape ·canaveral, Florida have been described. The climate of the region is mild and substantially regulated by rather warm coastal waters. The most undesirable climatic feature of the region is the high frequency of hurricanes. In general, there is a greater than 5 percent probability that a hurricane will enter the coastal region in any given year. This probability is greatest at Cape Hatteras (11%) and just south of Cape Canaveral (8%) and least in the region between Jacksonville and Savannah (1 to 2%).

Climatological data are readily available for the land area of this region; however, weather records for the offshore portion have been condensed for the somewhat large SSMO areas which, most likely, cover three climatic subregions: nearshore, Gulf Stream-Florida Current, and the region east of the Gulf Stream-Florida Current. The broad east-west extent of the SSMO areas allows for, at best, a very general description of the climate of the continental shelf-slope portion of the region. Additionally, most of the offshore weather data is obtained from ships in transit and is poorly suited for climatological analysis for several reasons:

a) Spatial and temporal irregularity.

b) The tendency of ships to avoid bad weather, thus producing a bias towards fair weather data.

c) The condition that ships transecting the continental shelf in this region have just left port or are pre­ paring to enter port and shipboard activities are other than routine.

Because of these factors, the climatological description of the continental shelf portion of this region should be con­ sidered as somewhat crude. It can be improved to some degree by reordering the original SSMO data to conform with the three eas~­ west regions previously discussed.

Any attempt to "extrapolate" terrestrial climatological descriptions out on to the continental shelf should be made with caution. Physical features and movement of air over land can be substantially different from those over water because ·of energy and mass exchanges as well as surface roughness. The former will affect the stability of the air because of heat and moisture

203 transfers while the latter affects the vertical profile of horizontal velocity.

The overall problem produced by poor climatological information ori the shelf area can best be solved by long-term consistent meteorological measurements at fixed points. At present, such information is not readily available.

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211