An Investigation of Tropical Rainfall Downwind of Urban Areas Along the United States East Coast

Mississippi State University Scholars Junction

Theses and Dissertations Theses and Dissertations

1-1-2008

An Investigation of Tropical Rainfall Downwind of Urban Areas along the United States East Coast

Ashley Marie Hayes

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Recommended Citation Hayes, Ashley Marie, "An Investigation of Tropical Rainfall Downwind of Urban Areas along the United States East Coast" (2008). Theses and Dissertations. 603. https://scholarsjunction.msstate.edu/td/603

This Graduate Thesis - Open Access is brought to you for free and open access by the Theses and Dissertations at Scholars Junction. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of Scholars Junction. For more information, please contact [email protected]. AN INVESTIGATION OF TROPICAL RAINFALL

DOWNWIND OF URBAN AREAS ALONG

THE UNITED STATES EAST COAST

Ashley Marie Hayes

A Thesis Submitted to the Faculty of Mississippi State University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Geosciences in the Department of Geosciences

Mississippi State, Mississippi

May 2008 AN INVESTIGATION OF TROPICAL RAINFALL

DOWNWIND OF URBAN AREAS ALONG

THE UNITED STATES EAST COAST

Ashley Marie Hayes

Approved:

______P. Grady Dixon Jamie L. Dyer Assistant Professor of Geosciences Assistant Professor of Geosciences (Director of Thesis) (Committee Member)

______Michael E. Brown Christopher P. Dewey Associate Professor of Geosciences Associate Professor of Geosciences (Committee Member) Graduate Coordinator of the Department of Geosciences

______Darrel Schmitz Gary Myers Professor of Geosciences Professor and Interim Dean of the Professor and Head, College of Arts and Sciences Department of Geosciences Name: Ashley Marie Hayes

Date of Degree: May 3, 2008

Institution: Mississippi State University

Major Field: Department of Geosciences (Operational Meteorology)

Major Professor: Dr. Paul Grady Dixon

Title of Study: AN INVESTIGATION OF TROPICAL RAINFALL DOWNWIND OF URBAN AREAS ALONG THE UNITED STATES EAST COAST

Pages in Study: 94

Candidate for Degree of Master of Science

Studies have shown that urban areas enhance mesoscale precipitation but have not revealed if urban areas have the same effect on synoptic scale precipitation. This study used Multi-Precipitation Estimator (MPE) and Next-Generation Weather Radar

(NEXRAD) stage III data to examine the effect of urban areas on rainfall associated with hurricanes and tropical storms from 1976–2005. These urban areas were divided into upwind and downwind areas where 6-hour precipitation totals were calculated and compared. Results displayed that 69.2% of urban areas had greater rainfall in the upwind area. Statistical analyses revealed that there is a larger range of higher precipitation values in the upwind area and a smaller range of lower precipitation values in the downwind area. Based on the results, there is no relationship between urban areas and enhanced rainfall; however, there is a relationship between the distribution of precipitation and urban areas.

DEDICATION

I would like to dedicate this research to my family and friends who have supported me in my dream of becoming a successful meteorologist. I would especially like to thank my mother, Marlene Riley. I will forever be grateful for all the encouragement, support, and love that she has given me throughout the years.

ii ACKNOWLEDGMENTS

I would like to thank my thesis committee Dr. Grady Dixon, Dr. Jamie Dyer, and

Dr. Michael Brown for all of their assistance throughout the course of this research. I would like to thank Dr. Kenneth Johnson and the staff at the National Weather Service

Eastern Region Headquarters for all of their assistance during the summer of 2007. Also,

I would like to personally thank Mr. Paul Trotter and the staff at the National Weather

Service in Slidell, LA for teaching, inspiring, and encouraging me since 2003.

iii TABLE OF CONTENTS

Page

DEDICATION ...... ii

ACKNOWLEDGMENTS ...... iii

LIST OF TABLES ...... vi

LIST OF FIGURES...... viii

CHAPTER

I. INTRODUCTION ...... 1

OBJECTIVE AND HYPOTHESIS ...... 4

II. LITERATURE REVIEW...... 5

Landfall Effects on Tropical Rainfall ...... 5 Urban Effects on Rainfall...... 6

III. DATA AND METHODS...... 10

Research Area and Period ...... 10 Data ...... 12 Data Analyses ...... 16

IV. RESULTS AND DISCUSSION...... 27

Hurricane Bertha – 1996 ...... 27 Baltimore-Towson, MD and Washington-Arlington-Alexandria, DC-VA-MD ...... 28 Raleigh-Cary, NC...... 29 Richmond, VA ...... 30 Virginia Beach-Norfolk-Newport News, VA-NC ...... 31 Hurricane Bonnie – 1998 ...... 32

iv Virginia Beach-Norfolk-Newport News, VA-NC ...... 33 Hurricane Floyd – 1999...... 34 Virginia Beach-Norfolk-Newport News, VA-NC ...... 35 Hurricane Fran – 1996 ...... 36 Greensboro-High Point, NC...... 37 Raleigh-Cary, NC...... 38 Hurricane Gaston – 2004...... 39 Charleston-North Charleston, SC...... 40 Tropical Storm Hermine – 2004 ...... 41 Providence-New Bedford-Fall River, RI-MA, Worcester, MA and Boston-Cambridge-Quincy, MA-NH ...... 42 Hurricane Isabel – 2003 ...... 43 Raleigh-Cary, NC...... 44 Richmond, VA ...... 45 Virginia Beach-Norfolk-Newport News, VA-NC ...... 46 Statistical Analyses ...... 47

V. SUMMARY AND CONCLUSIONS ...... 59

REFERENCES...... 63

APPENDIX

A. REGIONAL VIEW OF 6-HOUR RAINFALL ESTIMATES ASSOCIATED WITH EACH URBAN AREA...... 67

B. FREQUENCY HISTOGRAM FOR EACH URBAN AREA...... 81

v LIST OF TABLES

TABLE Page

3.1 Tropical cyclones that made landfall along the East Coast from 1976–2005 ...... 11

3.2 Saffir-Simpson Hurricane Scale ...... 13

3.3 Urbanized Areas ...... 15

4.1 Downwind and upwind storm total precipitation and the differences ...... 48

4.2 Level of significance for the difference between storm total precipitations in the downwind and upwind area...... 49

4.3 Statistics for the upwind and downwind areas of Baltimore-Towson, MD and Washington-Arlington-Alexandria, DC-VA-MD during Hurricane Bertha...... 51

4.4 Statistics for the upwind and downwind areas of Raleigh-Cary, NC during Hurricane Bertha...... 51

4.5 Statistics for the upwind and downwind areas of Richmond, VA during Hurricane Bertha...... 52

4.6 Statistics for the upwind and downwind areas of Virginia Beach- Norfolk-Newport News, VA-NC during Hurricane Bertha ...... 52

4.7 Statistics for the upwind and downwind areas of Virginia Beach- Norfolk-Newport News, VA-NC during Hurricane Bonnie ...... 53

4.8 Statistics for the upwind and downwind areas of Virginia Beach- Norfolk-Newport News, VA-NC during Hurricane Floyd...... 53

4.9 Statistics for the upwind and downwind areas of Greensboro- High Point, NC during Hurricane Fran ...... 54

vi 4.10 Statistics for the upwind and downwind areas of Raleigh-Cary, NC during Hurricane Fran...... 54

4.11 Statistics for the upwind and downwind areas of Charleston-North Charleston, SC during Hurricane Gaston...... 55

4.12 Statistics for the upwind and downwind areas of Boston-Cambridge- Quincy, MA-NH, Providence-New Bedford-Fall River, RI-MA, and Worcester, MA during Tropical Storm Hermine ...... 55

4.13 Statistics for the upwind and downwind areas of Raleigh-Cary, NC during Hurricane Isabel...... 56

4.14 Statistics for the upwind and downwind areas of Richmond, VA during Hurricane Isabel...... 56

4.15 Statistics for the upwind and downwind areas of Virginia Beach- Norfolk-Newport News, VA-NC during Hurricane Isabel ...... 57

4.16 P values for the variance, skewness, and kurtosis of the downwind and upwind area ...... 58

vii LIST OF FIGURES

FIGURE Page

1.1 The leading causes of tropical cyclone deaths in the U.S. from 1970 to 1999 ...... 2

1.2 Hurricane frequency by year ...... 3

3.1 Eastern Region of the National Weather Service with County Warning Areas (CWAs)...... 10

3.2 Research area displaying rain gauges that provide 15-minute and hourly precipitation data...... 14

3.3 The storm center (H), storm motion (arrow), urban area (brown area), 140-km radius (large circle), and 75-km radius (small circle), upwind half (A), and downwind half (B) ...... 17

3.4 The storm center (H), storm motion (arrow), urban area (brown area), 140-km radius (large circle), and 75 km radius (small circle), upwind quadrants (A and C), and downwind quadrants (B and D)...... 18

3.5 The urban area (brown area), urban center (•), track points (•), urban area axis (—), tropical cyclone track (—), and extrapolated tropical cyclone track (……)...... 19

3.6 The urban area (brown area), storm track point (•), extrapolated radius (—), storm center (H), storm motion (arrow), 140-km radius (large circles), and 75-km radius (small circle) ...... 19

3.7 Positive vs. Negative skewness (µ=mean) respectively ...... 21

3.8 Low vs. High kurtosis (µ=mean) respectively ...... 21

3.9 Charleston-North Charleston, SC during Tropical Storm Arthur with the green shaded area representing upwind and the red shaded area representing downwind ...... 23

viii 3.10 Charleston-North Charleston, SC during Hurricane Floyd with the green shaded area representing upwind and the red shaded area representing downwind ...... 24

3.11 Omitted urban areas (brown area), Hurricane Bertha storm track (—), Hurricane Floyd storm track (—), and 75-km radius (circle) ...... 25

4.1 Washington-Arlington-Alexandria, DC-VA-MD and Baltimore- Towson, MD with the green shaded area representing upwind and the red shaded area representing downwind...... 28

4.2 Raleigh-Cary, NC Map with the green shaded area representing upwind and the red shaded area representing downwind...... 29

4.3 Richmond, VA with the green shaded area representing upwind and the red shaded area representing downwind ...... 30

4.4 Virginia Beach-Norfolk-Newport News, VA-NC with the green shaded area representing upwind and the red shaded area representing downwind ...... 31

4.5 Virginia Beach-Norfolk-Newport News, VA-NC with the green shaded area representing upwind and the red shaded area representing downwind ...... 33

4.6 Virginia Beach-Norfolk-Newport News, VA-NC with the green shaded area representing upwind and the red shaded area representing downwind ...... 35

4.7 Greensboro-High Point, NC with the green shaded area representing upwind and the red shaded area representing downwind...... 37

4.8 Raleigh-Cary, NC Map with the green shaded area representing upwind and the red shaded area representing downwind...... 38

4.9 Charleston-North Charleston, SC with the green shaded area representing upwind and the red shaded area representing downwind...... 40

4.10 Providence-New Bedford-Fall River, RI-MA, Worcester, MA and Boston-Cambridge-Quincy, MA-NH with the green shaded area representing upwind and the red shaded area representing downwind...... 42

4.11 Raleigh-Cary, NC Map with the green shaded area representing upwind and the red shaded area representing downwind...... 44 ix 4.12 Richmond, VA with the green shaded area representing upwind and the red shaded area representing downwind ...... 45

4.13 Virginia Beach-Norfolk-Newport News, VA-NC with the green shaded area representing upwind and the red shaded area representing downwind ...... 46

x CHAPTER I

INTRODUCTION

Tropical cyclones are large rotating storms that form over warm ocean waters in tropical regions. They can extend over 1000 km from their center while possessing strong winds and torrential rain (Montgomery and Farrell 1993). The intense winds associated with tropical cyclones can damage or destroy vehicles, buildings, bridges, and convert loose objects into deadly projectiles. These tropical cyclones have a distinct season that occurs from June 1st through November 30th, with a peak from late August through

September.

The coasts of the United States are devastated by tropical cyclones yearly with wind and storm-surge flooding thought to be the primary threats. Tropical cyclones are also capable of producing tornadoes, which are accountable for 10% of the total deaths associated with tropical cyclones in the United States (Spratt et al. 1997). Another devastating aspect of a tropical cyclone is the catastrophic amounts of rain. Inland flooding has occurred with many landfalling tropical cyclones and has become the predominant cause of death associated with hurricanes (Elsberry 2002). Rappaport (2000) found that between 1970 and 1999, inland floods claimed 59% of the 600 United States deaths that were associated with tropical cyclones and their remnants (Figure 1.1).

1 Figure 1.1 The leading causes of tropical cyclone deaths in the U.S. from 1970 to 1999.

During the gradual increase of tropical cyclones in the Atlantic Basin (Figure 1.2), more emphasis is being placed upon accurately forecasting precipitation amounts and variability associated with tropical cyclones (Kummerow et al. 1998). A total of 332 tropical cyclones formed in the Atlantic basin from 1976 through 2005.

2 Murty al1995; Baik Westcott Murty Rosenfeld1973; et2004). and 2001; Givati Shepherdand urban islandsheatshown that theirsurroundings influence (Khemani significantly and moremeteorological pronounced.Previouswill local likely studies becomehave effects windand local place, patterns, airAsantemperatures, expansion quality. takes urban microclimates (Shepherdinfuture Thesecreate increase 2005). by the areas affecting is landrapidlyEarth’sof butdensity the isurban,to the of expected considered cities structures.mainUrbanization land-useiscreated Only of the causesone of change. 1.2% increased Urban definedareasof human-are as geographical densities with regions iue12 Hurricanefrequencyby year. Figure1.2

Number of Named Storms As manylandfall make As of these they tropical urban cyclones often areas.strike 10 10 15 20 25 30

0 5

8 4

9 8

8 Frequency Hurricane

8 7

Year 9

0 0

0 5 5

Burian (2003) found evidence that during the warm seasons, rainfall increases 9% – 17% downwind of major cities.

It is well known that urban areas have higher surface temperatures than the surrounding areas (Myrup 1969). Primary factors that determine the magnitude of an urban heat island are the reduction of evaporation, thermal properties of buildings and paving materials, and increased roughness within the city. These factors alter the urban area and surrounding environment due to the fact that the surface heat budgets over two locations differ from each other (Ohashi and Kida 2004).

OBJECTIVE AND HYPOTHESIS

The objective of this study is:

1) To determine the relationship, if any, between urban areas and tropical cyclone

rainfall downwind of the urban area.

The following hypothesis will be tested in this study:

1) The region downwind of an urban area experiences enhanced tropical rainfall

relative to regions upwind of the urban area.

4 CHAPTER II

LITERATURE REVIEW

Landfall Effects on Tropical Rainfall

Forecasting precipitation distribution associated with landfalling tropical cyclones continues to be a challenge. Atallah et al. (2007) found that synoptic-scale dynamics can be used to aid in forecasting precipitation distributions associated with tropical cyclones.

More precipitation can shift to the right or left of a tropical cyclone track if it interacts with a downstream ridge or trough, respectively. Lonfat et al. (2004) found that the storm translation speed also plays an important role in the rainfall asymmetries. The rainfall maxima are typically located in front of the storm center at all speeds, but its amplitude increases with speed.

A tropical cyclone’s circulation, track, translation speed, strength, and precipitation can be influenced by the general topography of an area (Lin et al. 1999).

Rainfall associated with tropical cyclones varies within specific quadrants of the cyclone

(Lonfat et al. 2004). Cerveny and Newman (2000) indicate that weak surface wind speeds are associated with rainfall amounts of 160 mm day-1 while higher wind speeds have higher precipitation amounts in excess of 350 mm day-1 . Therefore, greater intensity cyclones with faster wind speeds should also produce greater amounts of precipitation.

5 Heavy orographic rainfall and deflection of the storm track are effects of a mountain range on a tropical cyclone as it passes. Heavy orographic rainfall may occur prior to the landfall of the tropical cyclone due to the influence of a mountain range on the conditionally unstable airstream associated with the outer circulation of the cyclone

(Lin et al. 2002). Studies have shown a strong relationship between the total rainfall associated with land-falling tropical cyclones and the local distribution of orography.

Bender et al. (1985) conducted a case study on Typhoon Vera, in 1959, which showed the maximum hourly rainfall during landfall to be in the mountain upslope regions. Although this tropical cyclone produced a large amount of precipitation on the upslope side, it began decaying as it produced less precipitation on the downslope side of the mountain.

As with any type of surface orography, a tropical cyclone rapidly weakens as it interacts with the land surface.

Urban Effects on Rainfall

Enhanced turbulence occurs over urbanized areas and contributes to uplift in the atmosphere. The influence that urban areas have on the convective boundary layer indicates that the urban areas are warmer than adjacent rural areas (Hildebrand and

Ackerman 1984). The urban areas are more likely to receive rainfall compared to upwind areas, but also tend to enhance rainfall of existing storms downwind of the urban areas.

Some of the urban areas that have been studied extensively include: Houston, TX, St.

Louis, MO, Indianapolis, IN, Cleveland, OH, Tulsa, OK, Washington, D.C., New

Orleans, LA, New York, NY, and Atlanta, GA (Bornstein 1968; Huff and Changnon

6 1973; Bornstein and Lin 2000; Dixon and Mote 2003; Diem and Mote 2005). These urban areas also produce significant wind perturbations, upward flow over the city, and induced surface convergence due to roughness.

Changnon et al. (1976) found that increased precipitation amounts were observed in areas downwind of St. Louis, MO. It was stated that urban areas are a focal point for rain intensification. Squall lines and isolated air mass thunderstorms were also enhanced downwind of the urban area due to increased heat, aerosols, and turbulence. Huff and

Changnon (1973) learned, from previous urban climatic studies, that urban effects did not initiate rainfall, but led to enhancement of rainfall on days when moderate rainfall already existed. Bornstein and Lin (2000) conducted a study on urban induced convective thunderstorms over the Atlanta, GA area from July 26–August 3, 1996. This study showed that the urban area induced a convergence zone that initiated thunderstorms and that a group of buildings could create a bifurcation zone that causes thunderstorms to split and go around cities. This caused a precipitation maximum downwind of the city and a minimum over the city.

METROMEX was a field project designed to study inadvertent weather modification by urban-industrialized effects in St. Louis, MO. Results revealed summer increases in the downwind area rainfall, rain days, strong thunderstorms, as well as hailstorms (Changnon et al. 1971). Braham (1979) found that there was substantial evidence for believing that the microphysics and dynamics of storms can be altered as they pass over an urban-industrial area and that local rainfall can increase. It was stated that urban and topographic enhancements were most pronounced in heavy storms that

7 produced rainfall amounts of 25 mm or more (Huff and Vogel 1978). These storms are an effect of added nuclei from the urban area, which leads to a coalescence process that is more vigorous and frequent than in clouds over rural areas. Mölders and Olson (2004) used a mesoscale model, MM5, to study precipitation patterns in high latitudes. The study showed that additional urbanization, heat, release of aerosols, and moisture also influences precipitation downwind of urban areas.

Shepherd et al. (2002) conducted a 15-month analysis of mean rainfall rates for

Atlanta, GA, Montgomery, AL, Dallas, TX, Waco, TX, and San Antonio, TX. It was found that the average increase in mean rainfall downwind was 28.4% with a range of

14.6%–51.0%. The range was 20–60 km downwind of the edge of the urban area center.

Huff and Changnon (1973) studied the cities of St. Louis, MO, Chicago, IL, Indianapolis,

IN, Cleveland, OH, Washington, D.C., Houston, TX, New Orleans, LA, and Tulsa, OK.

The cities were chosen to differentiate between humid climatic zones, industrial complexes, topography, city sizes, and rate of growth in the 20th century. The climatological study for each city observed precipitation within a radius of 80–120 km around the urban area. The results showed that the maximum urban effect on precipitation was more pronounced in summer months and occurred 15–55 km downwind of the urban area.

Upward trends of 19%–38% were found in warm season precipitation values in

Paris, France, St. Louis, MO, and Chicago, IL, over a 100-year period. The upward trends may be a result of a general climatic shift or the gradual improvements in rainfall measurement techniques (Dettwiller and Changnon 1976). Specific atmospheric

8 measurements of urban effects on weather that extend considerably above the ground level and cause alterations in precipitation processes do not exist in historical records. As a result, evaluation of an urban effect on surface precipitation is conducted by indirect statistical and circumstantial evidence (Huff and Changnon 1972).

CHAPTER III

DATA AND METHODS

Research Area and Period

The research area includes the National Weather Service County Warning Areas

(CWAs) in the eastern portion of the United States that are east of the Appalachian

Mountains and north of Georgia (Figure 3.1). Bender et al. (1985) found that tropical cyclones weaken rapidly when coming in contact with mountain ranges; therefore, the research area will lie east of the Appalachian Mountains to minimize orographic effects on the tropical cyclones. Also there were no tropical cyclones that made initial landfall in a CWA located in Georgia therefore, the research area begins north of Georgia.

Figure 3.1 Eastern Region of the National Weather Service with County Warning Areas (CWAs). 10 The research period includes a 30-year span from 1976 through 2005. This period has an adequate number of tropical cyclones that made initial landfall on the East Coast and in urban areas (Table 3.1). Also, rain gauge and radar estimate data are available during this period to thoroughly study each tropical cyclone after it made landfall.

Table 3.1 Tropical cyclones that made landfall along the East Coast from 1976–2005.

Storm Name Year Belle 1976 Bret 1981 Dean 1983 Diana 1984 Gloria 1985 Henri 1985 Chris 1988 Hugo 1989 Bob 1991 Danielle 1992 Arthur 1996 Bertha 1996 Fran 1996 Bonnie 1998 Dennis 1999 Floyd 1999 Kyle 2002 Isabel 2003 Gaston 2004 Hermine 2004

11 Data

Tropical cyclone data were collected from the National Hurricane Center where the Tropical Cyclone Report provided comprehensive information on each cyclone including synoptic history, meteorological statistics, and the post-analysis best track.

Storm tracks and intensities were obtained from the National Hurricane Center and

NOAA Coastal Services for 1976–2005.

The Next-Generation Weather Radar (NEXRAD) stage III data used in this study were specifically created for River Forecast Centers (Dyer and Garza 2004). Stage III radar data has a temporal resolution of 1 hour and a spatial resolution of 4 km2 and is calibrated with rain gauges and individual radar observations (Wang et al. 2008).

The Multi-sensor Precipitation Estimator (MPE) was also used in this study to determine precipitation amounts. MPE combines radar and satellite rainfall estimates with rain gauge measurements and produces multi-sensor gridded precipitation fields while also having a temporal resolution of 1 hour and a spatial resolution of 4 km2

(Young et al. 2000). The MPE data are currently being used at River Forecast Centers and Weather Forecast Offices of the National Weather Service. Data from the Middle

Atlantic River Forecast Center (MARFC), Northeast River Forecast Center (NERFC), and Southeast River Forecast Center (SERFC) are used in this study. NEXRAD stage III data were used from 1996 until the RFCs switched to MPE in:

• MARFC – October 1999

• NERFC – August 2002

• SERFC – January 2002

12 This study focuses specifically on tropical rainfall associated with hurricanes and tropical storms. The strength of the tropical cyclone used in this study is based on the strength at landfall and not the peak intensity of the storm unless it occurred at landfall.

The Saffir-Simpson hurricane scale displays how tropical cyclones are categorized

(Table 3.2). Neither tropical depressions nor extra-tropical cyclones were included in this study. Tropical depressions were not used since they are not well organized nor is the precipitation concentrated around the center of the system. Also, extra-tropical cyclones were not used due to the fact that these are cyclones that have lost their tropical characteristics due to a change in energy source. These cyclones no longer use the warm ocean waters as their primary source of energy.

Table 3.2 Saffir-Simpson Hurricane Scale

Saffir-Simpson Hurricane Scale

Category Wind speed (mph)

5 156

4 131–155

3 111–130

2 96–110

1 74–95

Tropical Storm 39–73

Tropical Depression 0–38

Rain gauge data were also collected for the years 1976–2005 from the National

Climatic Data Center (NCDC) where 15-minute and hourly precipitation data are 13 available (Figure 3.2). The surface data were used in conjunction with the NEXRAD stage III and MPE data, when available.

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Figure 3.2 Research area displaying rain gauges that provide 15-minute and hourly precipitation data.

The urban areas used in this study can also be referred to as “urbanized areas” or

“metropolitan statistical areas”. These areas are geographic entities defined by the U.S.

Office of Management and Budget (OMB) and they contain a core urban area with a population of 50,000 or more. Each metropolitan statistical area consists of one or more counties, including the counties in which the core urban areas is located, as well as any adjacent counties that have a high degree of social and economic integration with the

14 urban core. Urbanized areas that met or exceed a population of 500,000 are included in this study (Table 3.3).

Table 3.3 Urbanized Areas

2000 Population Urbanized Area Population Rank City State New York-Northern New Jersey-Long 1 NY-NJ-PA 18,323,002 Island 4 Philadelphia-Camden-Wilmington PA-NJ-DE 5,687,147 DC-VA- 7 Washington-Arlington-Alexandria 4,796,183 MD 10 Boston-Cambridge-Quincy MA-NH 4,391,344 19 Baltimore-Towson MD 2,552,994 32 Providence-New Bedford-Fall River RI-MA 1,582,997 33 Virginia Beach-Norfolk-Newport News VA-NC 1,576,370 37 Charlotte-Gastonia-Concord NC-SC 1,330,448 44 Hartford-West Hartford-East Hartford CT 1,148,618 46 Richmond VA 1,096,957 51 Bridgeport-Stamford-Norwalk CT 882,567 57 New Haven-Milford CT 824,008 59 Raleigh-Cary NC 797,071 62 Worcester MA 750,963 64 Allentown-Bethlehem-Easton PA-NJ 740,395 68 Springfield MA 680,014 73 Columbia SC 647,158 74 Greensboro-High Point NC 643,430 75 Poughkeepsie-Newburgh-Middletown NY 621,517 84 Greenville SC 559,940 85 Charleston-North Charleston SC 549,033

15 Data Analyses

The rain gauge and rainfall estimate data were analyzed according to the location in which the tropical cyclone made landfall. For each tropical cyclone, urbanized areas in the path of the storm were identified. Upwind and downwind areas, for each urban area, were identified and precipitation data were collected and compared to determine if there was enhanced rainfall in the downwind areas.

Croxford and Barnes (2002) define inner-core strength as the storm-relative, mean tangential wind 60–140 km from the circulation center. Studies have shown that heavier rainfall amounts are concentrated near the center of a tropical cyclone and the rainfall rate is a function of storm intensity, with a tendency for higher rain rates to be associated with stronger storms (Rodgers et al. 1994). Therefore, each storm has a buffer zone of 140 km to the left and right of the storm track which contains the inner-core strength of both small and large tropical cyclones. An urban area was chosen within the buffer zone and a

75-km radius study area was defined around the urban area. This 75-km area surrounding the urban area was then split into halves with the axis lying perpendicular to the storm motion (Figure 3.3). This allows one half to represent upwind and the other half to represent downwind.

16 A B H B A

Figure 3.3 The storm center (H), storm motion (arrow), urban area (brown area), 140- km radius (large circle), and 75-km radius (small circle), upwind half (A), and downwind half (B).

If the tropical cyclone track goes within the 75-km of the urban center, then the buffer zone will be divided into four quadrants (Figure 3.4). This will allow two quadrants to be upwind and two quadrants to be downwind. The upwind and downwind quadrants are chosen based on the wind direction, which is due to the direction that the tropical cyclone is moving. However, if 90% or more of the urban area lies within quadrants A and B then quadrants C and D will be excluded from the study.

17 A D H

B C

Figure 3.4 The storm center (H), storm motion (arrow), urban area (brown area), 140-km radius (large circle), and 75 km radius (small circle), upwind quadrants (A), and downwind quadrant (B).

Tropical cyclones are constantly moving; therefore, the axis that is supposed to be perpendicular to the storm motion will actually only be perpendicular at one instant during the passage of the storm. In order to have more accurate results, each urban area was evaluated for 6 consecutive hours. These hours consist of the three hours as the storm is approaching the urban area and the three hours after the storm has passed the urban area. The time at which the axis is perpendicular to the storm track will be marked as the central point of the 6 hour analysis period. All urban areas do not naturally have an axis that is perpendicular to the storm track; therefore, a track may be extrapolated between two points to create a perpendicular axis (Figure 3.5). An urban area was only analyzed if it remained at tropical storm status, or greater, during the 6 consecutive hours. The

18 hours are given in terms of Hour 1–Hour 24 which state the end time of the period, for example, the data for Hour 1 is collected from 0001 UTC to 0100 UTC.

Figure 3.5 The urban area (brown area), urban center (•), track points (•), urban area axis (—), tropical cyclone track (—), and extrapolated tropical cyclone track (……).

The storm tracks retrieved from the National Hurricane Center are given in 6 hour increments. In some situations, the 140-km radius around the storm track points may not intersect, leaving a space between the buffers. A line is extrapolated in order to connect the buffers and include the urban areas located within the spaces (Figure 3.6).

B A

Figure 3.6 The urban area (brown area), storm track point (•), extrapolated radius (—), storm center (H), storm motion (arrow), 140-km radius (large circles), and 75-km radius (small circle). 19 The storm total precipitation was calculated after all of the urban areas and their upwind and downwind areas had been defined. The storm total precipitation was calculated for the upwind and downwind area separately by adding together the precipitation amount for each hour during the 6 hour analysis period. Paired-samples t- tests were conducted on all of the upwind and downwind totals to determine if there was a statistically significant difference while assuming unequal variances. Finding a significant difference implies that there is statistical evidence that the upwind and downwind rainfall amounts are different. The same tests were conducted on the upwind and downwind totals associated with urban area category to determine if there was a statistically significant difference. Each urban area category is defined in chapter 5.

As precipitation moves from the upwind area to the downwind area it is possible to have a change in the distribution of the precipitation. Therefore, the mean of the storm total precipitation for the upwind and downwind areas were calculated to show the central tendency of the data set along with the variance, which is the average of the squared differences between the precipitation values and the mean. Skewness is a measure of the asymmetry of a distribution (White 1980). A distribution with a skewness value of zero is considered to be a normal distribution. Positive skewness values represent a distribution with a long right tail and negative skewness values represent a distribution with a long left tail (Figure 3.7).

20 Figure 3.7 Positive vs. Negative skewness (µ=mean) respectively.

Kurtosis is a measure used to describe the distribution of data around the mean

(White 1980). Negative kurtosis values indicate that the data cluster less and have shorter tails than those in the normal distribution, while positive kurtosis values indicate that the data cluster more and have longer tails than those in the normal distribution (Figure 3.8).

These statistics were run on the data to show underlying differences in the upwind and downwind areas which may not be visible from the storm total precipitation.

Figure 3.8 Low vs. High kurtosis (µ=mean) respectively.

Hourly and 15-minute rain gauge data were collected for the years 1976–2005 from the National Climatic Data Center (NCDC). While manually looking through the rain gauge data, it became evident that many stations displayed missing data due to the tropical cyclones coming in contact with these stations. It was also evident that some of

21 the remaining data were erroneous and could not be used in this study. After plotting the remainder of the precipitation data for each storm, there was not a sufficient amount of data to conduct analyses. Therefore, due to the large amount of missing and erroneous data, hourly and 15-minute rain gauge data were not used in the analysis of enhanced rainfall downwind of an urban area. This omitted all tropical cyclones prior to 1996, which is when NEXRAD stage III data became available.

During this time period, there were ten storms in which NEXRAD stage III data and MPE data were available. After manually looking through the data, there were several hours with erroneous data that could not be used. In the case of Tropical Storm

Kyle, in 2002, data during hours 18 and 19 were erroneous. This tropical cyclone only affected one urban area, Charleston, SC. The erroneous hours were within the 6 hour period to analyze Charleston, SC for this particular tropical cyclone. Tropical Storm Kyle had to be removed from the study due to the erroneous data in the 6 hour period. During

Hurricane Bertha six urban areas had to be omitted due to erroneous data in hour 1 of the analysis period:

• New Haven-Milford, CT

• Hartford-West Hartford-East Hartford, CT

• Springfield, MA

• Worcester, MA

• Providence-New Bedford-Fall River, RI-MA

• Boston-Cambridge-Quincy, MA-NH

22 Two urban areas were omitted due to the tropical cyclone becoming a tropical depression during the 6 hour analysis period. In the case of Tropical Storm Dennis,

Raleigh-Cary, NC was the only urban area in the storm path. The cyclone was downgraded to a tropical depression during the 6 hours analysis period and was omitted from this study. Virginia Beach-Norfolk-Newport News, VA-NC which is associated with Hurricane Gaston was also omitted due to being downgraded to a tropical depression during the analysis period.

Charleston-North Charleston, SC was omitted from Tropical Storm Arthur

(Figure 3.9) and Hurricane Floyd (Figure 3.10) due to the cyclone being over the ocean and not fully interacting with the urban area despite coming within 75-km of the urban area. Tropical Storm Arthur was omitted from this study because it only had one urban area, Charleston-North Charleston, SC, in its path.

1200 ! ! ! ! ! ! ! ! ! ! ! ! ! SC ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 0600 ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! GA

Figure 3.9 Charleston-North Charleston, SC during Tropical Storm Arthur with the green shaded area representing upwind and the red shaded area representing downwind. 23 NC

600

SC ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 0000 GA

1800 FL

Figure 3.10 Charleston-North Charleston, SC during Hurricane Floyd with the green shaded area representing upwind and the red shaded area representing downwind.

Urban areas in the northeast are very close to one another and it is difficult to determine a clear upwind or downwind area (Figure 3.11). In this case there is part of the upwind area intersecting the downwind area of a different urban area or vice versa.

Therefore, 14 urban areas were omitted:

• Hurricane Bertha

o Allentown-Bethlehem-Easton, PA-NJ

o Bridgeport-Stamford-Norwalk, CT

o New York-Northern New Jersey-Long Island, NY-NJ-PA

o Philadelphia-Camden-Wilmington, PA-NJ-DE

o Poughkeepsie-Newburgh-Middletown, NY

24 • Hurricane Floyd

o Boston-Cambridge-Quincy, MA-NH

o Bridgeport-Stamford-Norwalk, CT

o Hartford-West Hartford-East Hartford, CT

o New Haven-Milford, CT

o New York-Northern New Jersey-Long Island, NY-NJ-PA

o Poughkeepsie-Newburgh-Middletown, NY

o Providence-New Bedford-Fall River, RI-MA

o Springfield, MA

o Worcester, MA

VT NH !

MA !

! ! !

! ! RI

! CT

! PA

Figure 3.11 Omitted urban areas (brown area), Hurricane Bertha storm track (———), Hurricane Floyd storm track (———), and 75-km radius (circle).

25 There are two instances where urban areas were combined to create a clear upwind and downwind area. Washington-Arlington-Alexandria, DC-VA-MD and

Baltimore-Towson, MD were combined for Hurricane Bertha and Boston-Cambridge-

Quincy, MA-NH, Providence-New Bedford-Fall River, RI-MA and Worcester, MA were combined for Tropical Storm Hermine. A center point between the combined urban areas served as the middle point for the 6 hour analysis period as well as the axis perpendicular to the storm track. The 75-km radius around the urban areas remained and the axis perpendicular to the storm track divided the area into an upwind and a downwind half.

26 CHAPTER IV

RESULTS AND DISCUSSION

There were 21 urban areas associated with 20 tropical cyclones that made landfall along the United States East Coast from 1976 to 2005. After removing all tropical cyclones and urban areas that could not be accurately analyzed, the dataset was reduced to 13 urban areas associated with 7 tropical cyclones. Images displaying radar estimates for each urban area are given in Appendix A.

Hurricane Bertha – 1996

Bertha originated from a tropical wave just off the coast of Africa on July 1st and was named a hurricane on July 7th. As Bertha tracked across the Atlantic Ocean, it became a category 2 hurricane on July 9th with maximum sustained winds of 100 knots.

The storm made landfall near Wrightsville, NC on July 12th at 2000 UTC as a category 1 hurricane. Before being downgraded to an extratropical storm, on July 14th, it passed within 140-km of 4 urban areas:

• Baltimore-Towson, MD and Washington-Arlington-Alexandria, DC-VA- MD

• Raleigh-Cary, NC

• Richmond, VA

• Virginia Beach-Norfolk-Newport News, VA-NC 27 Baltimore-Towson, MD and Washington-Arlington-Alexandria, DC-VA-MD

As Bertha tracked over these urban areas it produced a total of 273.410 mm of precipitation in the downwind area and 836.320 mm in the upwind area (Figure 4.1). This urban area was analyzed for July 13th from Hour 11–Hour 16 (1001–1600 UTC).

1800 PA

0600

Figure 4.1 Washington-Arlington-Alexandria, DC-VA-MD and Baltimore-Towson, MD with the green shaded area representing upwind and the red shaded area representing downwind.

28 Raleigh-Cary, NC

As Hurricane Bertha passed over this area it produced a total of 865.550 mm of precipitation in the downwind area and 1138.650 mm in the upwind area (Figure 4.2).

This urban area was analyzed for July 12th and July 13th from Hour 23–Hour 4 (2201–

0400 UTC).

VA 0600

1800

Figure 4.2 Raleigh-Cary, NC Map with the green shaded area representing upwind and the red shaded area representing downwind.

29 Richmond, VA

In this area, total precipitation amounts reached 331.120 mm in the downwind area and 919.390 mm in the upwind area (Figure 4.3). This urban area was analyzed for the same time as Virginia Beach-Norfolk-Newport News, VA-NC for July 13th from

Hour 6–Hour 11 (0501–1100 UTC).

1200

WV ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! VA ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! 0600

0000

Figure 4.3 Richmond, VA with the green shaded area representing upwind and the red shaded area representing downwind.

30 Virginia Beach-Norfolk-Newport News, VA-NC

This urban area was analyzed for July 13th from Hour 6–Hour 11 (0501–1100

UTC) and received a total of 848.430 mm of precipitation in the downwind area and

521.290 mm in the upwind area (Figure 4.4).

1200

! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! VA ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 0600 ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

0000

Figure 4.4 Virginia Beach-Norfolk-Newport News, VA-NC with the green shaded area representing upwind and the red shaded area representing downwind.

31 Hurricane Bonnie – 1998

Bonnie developed from a low to mid-level cyclonic circulation that moved over

Dakar, Senegal and into the warm Atlantic waters. Convection began developing and

Bonnie was named a tropical storm on August 20th at 1200 UTC. As Bonnie moved westward toward the Leeward Islands and into a more favorable environment it was upgraded to a category 1 hurricane on August 22nd at 0600 UTC. Bonnie made landfall near Wilmington, NC on August 27th as a category 2 hurricane with maximum sustained winds of 100 knots. It quickly weakened into a tropical storm while encountering only one urban area, Virginia Beach-Norfolk-Newport News, VA-NC, before turning northeast and reentering the ocean and regaining strength.

32 Virginia Beach-Norfolk-Newport News, VA-NC

As Bonnie headed back towards the ocean it passed over this urban area producing a total of 1586.260 mm of precipitation in the downwind area and 6140.500 mm in the upwind area (Figure 4.5). This urban area was analyzed for July 27th and July

28th from Hour 23–Hour 4 (2201–0400 UTC).

! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! VA ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 1200 ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 600

0000

NC 1800

1200

Figure 4.5 Virginia Beach-Norfolk-Newport News, VA-NC with the green shaded area representing upwind and the red shaded area representing downwind.

33 Hurricane Floyd – 1999

The genesis of Floyd can be traced back to a tropical wave that emerged from western Africa in early September. As this wave proceeded westward across the Atlantic it became better organized north of the Leeward Islands and was name a tropical storm on September 8th at around 0600 UTC. Floyd slowly strengthened to a hurricane on

September 10th at 1200 UTC and had several intensity fluxes from a category 1 to category 3 hurricane. On September13th, Floyd reached its maximum strength at the top end of category 4 intensity with maximum sustained winds of 135 knots. By the time

Floyd made landfall near Cape Fear, NC, it had weakened to a category 2 hurricane with maximum sustained winds near 90 knots. Floyd came within 140 km of one urban area,

Virginia Beach-Norfolk-Newport News, VA-NC, before making the transition into an extratropical storm on September 17th at 1200 UTC Floyd.

34 Virginia Beach-Norfolk-Newport News, VA-NC

This urban area was analyzed for September 16th from Hour 13–Hour 18 (1201–

1800 UTC) and received a total of 13293.780 mm of precipitation in the downwind area and 13360.060 mm in the upwind area (Figure 4.6).

WV DE MD

1800

! VA ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

NC 1200

Figure 4.6 Virginia Beach-Norfolk-Newport News, VA-NC with the green shaded area representing upwind and the red shaded area representing downwind.

35 Hurricane Fran – 1996

Fran formed from a tropical wave associated with deep convection on August

22nd. It was named a tropical storm east of the Lesser Antilles on August 27th at 1200

UTC and gained hurricane strength on August 29th just before being downgraded to a tropical storm. As Fran moved closer to the mid-Atlantic coast, it regained hurricane strength on August 31st. It became a category 3 hurricane with maximum sustained winds of 105 knots when it was located northeast of the central Bahamas on September 4th.

When Fran made landfall on the North Carolina coast it had maximum sustained winds of

100 knots. Fran came within 140 km of two urban areas, Raleigh-Cary, NC and

Greensboro-High Point, NC, before being downgraded to tropical depression on

September 6th at 1800 UTC.

36 Greensboro-High Point, NC

In this urban area, Hurricane Fran produced a total of 3499.930 mm of precipitation in the downwind area and 7995.990 mm in the upwind area when analyzed for September 6th from Hour 9–Hour 14 (0801–1400 UTC) (Figure 4.7).

1800 WV

! ! ! ! ! ! !! ! 1200 ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! NC ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 600

Figure 4.7 Greensboro-High Point, NC with the green shaded area representing upwind and the red shaded area representing downwind.

37 Raleigh-Cary, NC

As Hurricane Fran passed by, it produced total precipitation amounts of

15665.310 mm in the downwind area and 12944.580 mm in the upwind area (Figure 4.8).

This urban area was analyzed for September 6th from Hour 6–Hour 11 (0501–1100

UTC).

VA 1200

TN ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! NC ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 0600

0000

Figure 4.8 Raleigh-Cary, NC with the green shaded area representing upwind and the red shaded area representing downwind.

38 Hurricane Gaston – 2004

Gaston originated from a cold front that moved off the coast of the Carolinas and into the Atlantic Ocean. This frontal zone was associated with convection and organized into Tropical Storm Gaston on August 28th. As the storm began moving toward east coast it became better organized and reached hurricane strength just before making landfall near Awendaw, SC on August 29th around 1400 UTC. Before weakening to a tropical depression, Gaston affected one urban area, Charleston-North Charleston, SC.

39 Charleston-North Charleston, SC

As Hurricane Gaston made landfall it produced a total of 8568.510 mm of precipitation in the downwind area and 13152.780 mm in the upwind area (Figure 4.9).

This urban area was analyzed for August 29th from Hour 11–Hour16 (1001–1600 UTC).

0 NC

! ! 1800 SC ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 1200 ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! GA 600

1200

1800 0 0 1800 1200 600

Figure 4.9 Charleston-North Charleston, SC with the green shaded area representing upwind and the red shaded area representing downwind.

40 Tropical Storm Hermine – 2004

Hermine initiated from the same frontal zone that produced Hurricane Gaston just a few days earlier. Some of the convection became detached from the frontal zone and later gained tropical storm status on August 29th at 1200 UTC with its peak wind speed of

50 knots. Hermine never reached hurricane strength due to Tropical Storm Gaston which was still located over the eastern United States. Hermine came within 140-km of 3 urban areas, Providence-New Bedford-Fall River, RI-MA, Worcester, MA and Boston-

Cambridge-Quincy, MA-NH, before becoming extratropical on August 31st at 1200 UTC.

41 Providence-New Bedford-Fall River, RI-MA, Worcester, MA and Boston-Cambridge- Quincy, MA-NH

As Tropical Storm Hermine tracked over these urban areas it produced a total of

1379.980 mm of precipitation in the downwind area and 1485.320 mm in the upwind area

(Figure 4.10). This urban area was analyzed for August 31st from Hour 6–Hour 11 (0501–

1100 UTC).

NH ME VT 1200 ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! NY ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! MA ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! RI ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! CT ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 0600 ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

0000

Figure 4.10 Providence-New Bedford-Fall River, RI-MA, Worcester, MA and Boston- Cambridge-Quincy, MA-NH with the green shaded area representing upwind and the red shaded area representing downwind.

42 Hurricane Isabel – 2003

Isabel originated form a tropical wave that moved off of the African coast in early

September. As this storm moved westward it became better organized and was named a tropical storm on September 6th near 0600 UTC. Isabel became moving toward the northwest and soon became a hurricane on September 7th and would continue to strengthen into a category 5 hurricane on September 11th with maximum wind speeds of

145 knots. Isabel began to weaken to a category 2 hurricane on September 16th until it made landfall near Drum Inlet, NC on September 18th near 1700 UTC. As the storm weakened it came within 140-km of 3 urban areas, Virginia Beach-Norfolk-Newport

News, VA-NC, Raleigh-Cary, NC, and Richmond, VA, before becoming extratropical on September 19th near 1200 UTC.

43 Raleigh-Cary, NC

As Hurricane Isabel tracked over this urban area it received a total of 1922.740 mm of precipitation in the downwind area and 4628.620 mm in the upwind area (Figure

4.11). This urban area was analyzed for September 18th and September 19th from Hour

22–Hour 3 (2101–0300 UTC).

600 DE MD WV

0000

1800

Figure 4.11 Raleigh-Cary, NC with the green shaded area representing upwind and the red shaded area representing downwind.

44 Richmond, VA

Hurricane Isabel passed over this urban area producing a total of 24589.380 mm of precipitation in the downwind area and 23088.300 mm in the upwind area (Figure

4.12). This urban area was analyzed for September 18th and September 19th from Hour

24–Hour 5 (2301–0500 UTC).

MD DE 600 WV

! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! VA ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 0000

1800 SC

Figure 4.12 Richmond, VA with the green shaded area representing upwind and the red shaded area representing downwind.

45 Virginia Beach-Norfolk-Newport News, VA-NC

As Hurricane Isabel passed by, it produced total rainfall amounts of 16038.800 mm in the downwind area and 11228.900 mm in the upwind area (Figure 4.13). This urban area was analyzed for September 18th and September 19th from Hour 21–Hour 2

(2001–0200 UTC).

600 DE

WV MD

VA ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 0000 ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

1800

Figure 4.13 Virginia Beach-Norfolk-Newport News, VA-NC with the green shaded area representing upwind and the red shaded area representing downwind.

46 Statistical Analyses

In total, there were 13 urban areas involved in this study with 69.2% having greater rainfall amounts in the upwind area. The differences between the upwind and downwind areas were calculated by subtracting the upwind storm total precipitation from the downwind storm total precipitation. This allows for positive numbers to show that the downwind rainfall is greater and negative numbers to show that the upwind rainfall is greater. Table 4.1 shows the storm total precipitation amounts, in millimeters (mm), for the upwind and downwind area along with the difference.

Paired-samples T-tests were calculated to determine if there were significant differences between the downwind and upwind area of each urban area. Table 4.2 displays the level of statistical significance at p < 0.01 or p < 0.05. The only strong storms in this study were category 3 hurricanes; therefore, “strong storms” category and

“category 3” hurricanes category are identical. There was only one tropical storm; therefore, a statistical significance could not be calculated for the tropical storm category.

The category of “urban areas with greater upwind precipitation” was significantly different at p <0.05; however, there were no categories that were significantly different at p < 0.01.

47 Table 4.1 Downwind and upwind storm total precipitation and the differences.

Difference in Total Total Downwind and Tropical Downwind Upwind Urban Area Upwind Cyclone Precipitation Precipitation Precipitation (mm) (mm) (mm) Bertha Baltimore-Towson, MD and Washington-Arlington- 273.410 836.320 -562.910 Alexandria, DC-VA-MD Raleigh-Cary, NC 865.550 1138.650 -273.100

Richmond, VA 331.120 919.390 -588.270 Virginia Beach-Norfolk- 848.430 521.290 327.140 Newport News, VA-NC Bonnie Virginia Beach-Norfolk- 1586.260 6140.500 -4554.240 Newport News, VA-NC Floyd Virginia Beach-Norfolk- 13293.780 13360.060 -66.280 Newport News, VA-NC Fran Greensboro-High Point, NC 3499.930 7995.990 -4496.060

Raleigh-Cary, NC 15665.310 12944.580 2720.730 Gaston Charleston-North 8568.510 13152.780 -4584.270 Charleston, SC Hermine Boston-Cambridge-Quincy, MA-NH, Providence-New 1379.980 1485.320 -105.340 Bedford-Fall River, RI-MA, and Worcester, MA Isabel Raleigh-Cary, NC 1922.740 4628.620 -2705.880

Richmond, VA 24589.380 23088.30 1501.080 Virginia Beach-Norfolk- 16038.800 11228.090 4810.710 Newport News, VA-NC

48 Table 4.2 Level of significance for the difference between storm total precipitations in the downwind and upwind area.

Storm Category Significance

All Storms

Weak Storms

Strong Storms

Tropical Storm

Category 1 Hurricane

Category 2 Hurricane

Category 3 Hurricane

Day Landfall

Night Landfall

Coastal Urban Areas

Non-Coastal Urban Areas

Large Urban Areas

Small Urban Areas

Urban Areas with Greater Downwind Precipitation Urban Areas with Greater * Upwind Precipitation

*Indicates significance at p < 0.05 **Indicates significance at p < 0.01

49 Tropical cyclones are considered weak storms if they were less than or equal to a category 2 hurricane and strong storms if greater than or equal to a category 3 hurricane.

Day landfalls are the tropical cyclones that made landfall from 1200 UTC to 0000 UTC and night landfalls made landfall from 0001 UTC to 1159 UTC. Tropical cyclones that affected coastal urban areas were considered coastal if they were less than or equal to 20 km from the ocean and all other affected urban areas were considered non-coastal urban areas. If an urban area had an area greater than 1000 square kilometers it was considered a “large” urban area while all other urban areas were considered “small” urban areas.

Several descriptive statistics were calculated for the upwind and downwind area of each urban area. The numbers of grid points in the upwind and downwind area are shown in Tables 4.3–4.15 along with the variance, skewness, and kurtosis. Frequency histograms were also created to visually display the descriptive statistics (Appendix B).

There were a few patterns that stood out, such as:

• 100% of the kurtosis values are negative in the upwind area for urban areas with greater downwind precipitation. This implies that as the precipitation moved across the urban area the range of precipitation values became smaller. • 92.3% of the upwind kurtosis values were smaller than the downwind kurtosis values. This also implies that as the precipitation moved across the urban area the range of precipitation values became smaller. • 84.6% of the upwind variance values are larger than the downwind variance values. This implies that the precipitation values upwind have a larger range of precipitation values and the range becomes smaller once the precipitation has moved over the urban area.

50 Table 4.3 Statistics for the upwind and downwind areas of Baltimore-Towson, MD and Washington-Arlington-Alexandria, DC-VA-MD during Hurricane Bertha.

Baltimore-Towson, MD and Washington-Arlington-Alexandria, DC-VA-MD

Upwind Downwind

Number of Grid Points 410 348

Mean Precipitation (mm) 2.040 0.786

Variance 3.442 1.103

Skewness 1.576 2.039

Kurtosis 2.887 4.652

Table 4.4 Statistics for the upwind and downwind areas of Raleigh-Cary, NC during Hurricane Bertha.

Raleigh-Cary, NC

Upwind Downwind

Number of Grid Points 205 213

Mean Precipitation (mm) 5.554 4.064

Variance 17.335 11.181

Skewness 1.129 0.925

Kurtosis 1.417 0.437

51 Table 4.5 Statistics for the upwind and downwind areas of Richmond, VA during Hurricane Bertha.

Richmond, VA

Upwind Downwind

Number of Grid Points 366 382

Mean Precipitation (mm) 2.512 0.867

Variance 4.391 1.108

Skewness 1.243 2.381

Kurtosis 1.000 7.684

Table 4.6 Statistics for the upwind and downwind areas of Virginia Beach-Norfolk- Newport News, VA-NC during Hurricane Bertha.

Virginia Beach-Norfolk-Newport News, VA-NC

Upwind Downwind

Number of Grid Points 408 381

Mean Precipitation (mm) 1.278 2.227

Variance 1.299 2.801

Skewness 0.643 0.892

Kurtosis -0.538 0.922

52 Table 4.7 Statistics for the upwind and downwind areas of Virginia Beach-Norfolk- Newport News, VA-NC during Hurricane Bonnie.

Virginia Beach-Norfolk-Newport News, VA-NC

Upwind Downwind

Number of Grid Points 254 240

Mean Precipitation (mm) 24.033 6.609

Variance 312.005 56.618

Skewness 0.402 1.933

Kurtosis -0.300 4.472

Table 4.8 Statistics for the upwind and downwind areas of Virginia Beach-Norfolk- Newport News, VA-NC during Hurricane Floyd.

Virginia Beach-Norfolk-Newport News, VA-NC

Upwind Downwind

Number of Grid Points 300 309

Mean Precipitation (mm) 44.534 43.022

Variance 498.048 289.098

Skewness 0.005 0.015

Kurtosis -1.315 -0.931

53 Table 4.9 Statistics for the upwind and downwind areas of Greensboro-High Point, NC during Hurricane Fran.

Greensboro-High Point, NC

Upwind Downwind

Number of Grid Points 340 352

Mean Precipitation (mm) 23.518 9.943

Variance 151.549 108.018

Skewness 0.274 1.118

Kurtosis -0.922 0.833

Table 4.10 Statistics for the upwind and downwind areas of Raleigh-Cary, NC during Hurricane Fran.

Raleigh-Cary, NC

Upwind Downwind

Number of Grid Points 288 261

Mean Precipitation (mm) 44.946 60.020

Variance 192.122 256.683

Skewness 0.151 0.126

Kurtosis -0.457 0.309

54 Table 4.11 Statistics for the upwind and downwind areas of Charleston-North Charleston, SC during Hurricane Gaston.

Charleston-North Charleston, SC

Upwind Downwind

Number of Grid Points 435 446

Mean Precipitation (mm) 30.236 19.212

Variance 283.607 280.363

Skewness 0.920 2.088

Kurtosis 0.579 4.495

Table 4.12 Statistics for the upwind and downwind areas of Boston-Cambridge-Quincy, MA-NH, Providence-New Bedford-Fall River, RI-MA, and Worcester, MA during Tropical Storm Hermine.

Boston-Cambridge-Quincy, MA-NH, Providence-New Bedford-Fall River, RI-MA, and Worcester, MA Upwind Downwind

Number of Grid Points 550 569

Mean Precipitation (mm) 2.701 2.425

Variance 5.621 5.599

Skewness 0.960 2.135

Kurtosis 0.352 6.000

55 Table 4.13 Statistics for the upwind and downwind areas of Raleigh-Cary, NC during Hurricane Isabel.

Raleigh-Cary, NC

Upwind Downwind

Number of Grid Points 193 183

Mean Precipitation (mm) 23.982 10.507

Variance 161.271 53.234

Skewness 0.869 1.858

Kurtosis 0.930 4.395

Table 4.14 Statistics for the upwind and downwind areas of Richmond, VA during Hurricane Isabel.

Richmond, VA

Upwind Downwind

Number of Grid Points 414 402

Mean Precipitation (mm) 55.769 61.168

Variance 489.587 321.137

Skewness 0.415 0.520

Kurtosis -1.050 -0.335

56 Table 4.15 Statistics for the upwind and downwind areas of Virginia Beach-Norfolk- Newport News, VA-NC during Hurricane Isabel.

Virginia Beach-Norfolk-Newport News, VA-NC

Upwind Downwind

Number of Grid Points 239 209

Mean Precipitation (mm) 46.979 76.741

Variance 848.110 130.488

Skewness 0.863 0.821

Kurtosis -0.047 2.066

After noticing patterns in the descriptive statistics, the p values were assumed for the variance, skewness, and kurtosis values for the upwind and downwind storm total precipitation of each urban area to determine if are statistically different (Table 19). The categories previously used in Table 4.2 area also used in Table 4.16. “All storms” and

“weak storms” showed that the skewness and variance were significantly different at p <

0.01. Several storm categories showed that the skewness and kurtosis were significantly different with the exception of “Coastal Urban Areas” which only showed the kurtosis being significantly different. There were no storm categories with a variance that was significantly different. Overall, there is a statistical difference between the upwind and downwind skewness and kurtosis values for several storm categories.

57 Table 4.16 P values for the variance, skewness, and kurtosis of the downwind and upwind area.

Variance Skewness Kurtosis Storm P P P Significance Significance Significance Category Value Value Value All Storms 0.074 0.005 ** 0.002 **

Weak Storms 0.111 0.008 ** 0.003 **

Strong Storms 0.513 0.433 0.141

Tropical — — — Storms Category 1 0.093 0.100 0.117 Hurricanes Category 2 0.109 0.182 0.051 Hurricanes Category 3 0.513 0.433 0.141 Hurricanes

Day Landfalls 0.111 0.020 * 0.009 **

Night Landfalls 0.480 0.195 0.174

Coastal Urban 0.145 0.144 0.034 * Areas Non-Coastal 0.236 0.024 * 0.031 * Urban Areas Large Urban 0.092 0.032 * 0.011 * Areas Small Urban 0.532 0.118 0.117 Areas

* Indicates significance at p < 0.05 ** Indicates significance at p < 0.01

58 CHAPTER V

SUMMARY AND CONCLUSIONS

As the concern grows about the impact of natural processes on the environment, it is important to address the interactions between the urban environment and precipitation.

It has been documented that urban areas create a microclimate and can have effects on the surrounding areas (Khemani and Murty 1973; Westcott 1995; Baik et al 2001; Givati and Rosenfeld 2004). In several studies, it has been shown that urban areas tend to have enhanced rainfall downwind of cities (Bornstein 1968; Huff and Changnon 1973;

Bornstein and Lin 2000; Dixon and Mote 2003; Diem and Mote 2005). The enhanced rainfall has been specifically associated with squall lines or mesoscale systems and not with tropical systems. Based on previous research, it is reasonable to believe that tropical rainfall will also increase downwind of an urban area.

The primary goal of this study is to determine if there is a relationship between urban areas and tropical rainfall due to the fact that research has not yet been on conducted enhanced tropical rainfall downwind of urban areas. The research period included a 30-year span from 1976 through 2005 and consisted of 20 tropical cyclones making landfall along the east coast of the United States where there are 21 urban areas in the eastern region.

59 Initially, 15-minute and hourly precipitation data were going to be used in conjunction with radar data until a large of amount of missing data were identified while conducting a quality control on the data. This eliminated 20 years, but only 10 tropical cyclones, due to lack of sufficient data. The remaining 10 tropical cyclones occurred from 1996 through 2005 and had sufficient amounts of radar data to analyze each urban area thoroughly. Quality control was also conducted on the radar data and storms that were affected by missing or erroneous data were omitted from the study. In total, there were 13 urban areas involved in this study.

Each urban area was analyzed for 6 consecutive hours with three hours as the storm is approaching the urban area and the other three hours as the storm is moving away from the urban area. Total precipitation amounts were calculated, during this time period, for each urban area. There were 62.5% of the urban areas that displayed greater storm total precipitation upwind of the urban area which did not support the hypothesis.

A paired-samples t-test assuming unequal variance was used to determine if there was a statistically significant difference between the upwind and downwind areas associated with each set of urban area. The statistics showed that urban areas with greater precipitation downwind are significantly different at p < 0.05. Although this does not support the hypothesis it is implying that something has changed between the upwind and downwind storm total precipitation when there is greater rainfall upwind of the urban area.

In order to find underlying changes in the data sets, statistics such as the mean, variance, kurtosis and skewness were calculated. These descriptive statistics display facts

60 about the data set of the upwind and downwind area associated with each urban area. The mean was used to display the central point of each dataset, as well as to calculate the variance. Based on the variance values, there is a larger range of precipitation values in the upwind areas and the range becomes smaller as the precipitation moves across the urban area in which 84.6% of the variances were greater for the upwind area.. Since variance and kurtosis are closely related it was expected that kurtosis values would show similar results. The results displayed that 92.3% of kurtosis values were greater downwind which implies that the precipitation has become more equally dispersed and has a smaller range of precipitation values compared to upwind. Skewness values for both the upwind and downwind areas were all positively skewed; however, 76.9% of the downwind skewness values were more positively skewed than the upwind areas. This indicates that the precipitation weakened as it moved over the urban area.

The statistics show that there is a difference between the upwind and downwind skewness and kurtosis values of several tropical cyclone categories. This relationship implies that there is a larger range of higher precipitation values in the upwind area and a smaller range of lower precipitation values in the downwind area. Therefore, instead of the urban area enhancing the tropical rainfall it is actually weakening the rainfall. This weakening could be cause by the increased friction of the urban area. Another possibility stated by Bornstein and Lin (2000) is that thunderstorm can sometimes split and go around an urban area.

Based on the results of this study, there is no relationship between urban areas and enhanced tropical rainfall in the downwind area. However, there is a statistical

61 relationship between the distribution of precipitation upwind and downwind of urban areas along the United States East Coast. For future research, higher temporal resolution rainfall estimates could be used to observe tropical rainfall as it approaches and interacts with an urban area in order to determine how the distribution of precipitation changes on a smaller time scale.

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66 APPENDIX A

REGIONAL VIEW OF 6-HOUR RAINFALL ESTIMATES

ASSOCIATED WITH EACH URBAN AREA

67 A.1 Six hour rainfall estimates for Baltimore-Towson, MD and Washington-Arlington- Alexandria, DC-VA-M during Hurricane Bertha.

68 A.2 Six hour rainfall estimates for Raleigh-Cary, NC during Hurricane Bertha.

69 A.3 Six hour rainfall estimates for Richmond, VA during Hurricane Bertha.

70 A.4 Six hour rainfall estimates for Virginia Beach-Norfolk-Newport News, VA-NC during Hurricane Bertha.

71 A.5 Six hour rainfall estimates for Virginia Beach-Norfolk-Newport News, VA-NC during Hurricane Bonnie.

72 A.6 Six hour rainfall estimates for Virginia Beach-Norfolk-Newport News, VA-NC during Hurricane Floyd.

73 A.7 Six hour rainfall estimates for Greensboro-High Point, NC during Hurricane Fran.

74 A.8 Six hour rainfall estimates for Raleigh-Cary, NC during Hurricane Fran.

75 A.9 Six hour rainfall estimates for Charleston-North Charleston, SC during Hurricane Gaston.

76 A.10 Six hour rainfall estimates for Boston-Cambridge-Quincy, MA-NH, Providence- New Bedford-Fall River, RI-MA, and Worcester, MA during Tropical Storm Hermine. 77 A.11 Six hour rainfall estimates for Raleigh-Cary, NC during Hurricane Isabel.

78 A.12 Six hour rainfall estimates for Richmond, VA during Hurricane Isabel.

79 A.13 Six hour rainfall estimates for Virginia Beach-Norfolk-Newport News, VA-NC during Hurricane Isabel.

80 APPENDIX B

FREQUENCY HISTOGRAM FOR EACH URBAN AREA

81 B.1 Upwind precipitation for Baltimore-Towson, MD and Washington-Arlington- Alexandria, DC-VA-MD during Hurricane Bertha.

B.2 Downwind precipitation for Baltimore-Towson, MD and Washington-Arlington- Alexandria, DC-VA-MD during Hurricane Bertha. 82 B.3 Upwind precipitation for Raleigh-Cary, NC during Hurricane Bertha.

B.4 Downwind precipitation for Raleigh-Cary, NC during Hurricane Bertha.

83 B.5 Upwind precipitation for Richmond, VA during Hurricane Bertha.

B.6 Downwind precipitation for Richmond, VA during Hurricane Bertha.

84 B.7 Upwind precipitation for Virginia Beach-Norfolk-Newport News, VA-NC during Hurricane Bertha.

B.8 Downwind precipitation for Virginia Beach-Norfolk-Newport News, VA-NC during Hurricane Bertha. 85 B.9 Upwind precipitation for Virginia Beach-Norfolk-Newport News, VA-NC during Hurricane Bonnie.

B.10 Downwind precipitation for Virginia Beach-Norfolk-Newport News, VA-NC during Hurricane Bonnie. 86 B.11 Upwind precipitation for Virginia Beach-Norfolk-Newport News, VA-NC during Hurricane Floyd.

B.12 Downwind precipitation for Virginia Beach-Norfolk-Newport News, VA-NC during Hurricane Floyd. 87 B.13 Upwind precipitation for Greensboro-High Point, NC during Hurricane Fran.

B.14 Downwind precipitation for Greensboro-High Point, NC during Hurricane Fran.

88 B.15 Upwind precipitation for Raleigh-Cary, NC during Hurricane Fran.

B.16 Downwind precipitation for Raleigh-Cary, NC during Hurricane Fran.

89 B.17 Upwind precipitation for Charleston-North Charleston, SC during Hurricane Gaston.

B.18 Downwind precipitation for Charleston-North Charleston, SC during Hurricane Gaston. 90 B.19 Upwind precipitation for Boston-Cambridge-Quincy, MA-NH, Providence-New Bedford-Fall River, RI-MA, and Worcester, MA during Tropical Storm Hermine.

B.20 Downwind precipitation for Boston-Cambridge-Quincy, MA-NH, Providence- New Bedford-Fall River, RI-MA, and Worcester, MA during Tropical Storm Hermine. 91 B.21 Upwind precipitation for Raleigh-Cary, NC during Hurricane Isabel.

B.22 Downwind precipitation for Raleigh-Cary, NC during Hurricane Isabel.

92 B.23 Upwind precipitation for Richmond, VA during Hurricane Isabel.

B.24 Downwind precipitation for Richmond, VA during Hurricane Isabel.

93 B.25 Upwind precipitation for Virginia Beach-Norfolk-Newport News, VA-NC during Hurricane Isabel.

B.26 Downwind precipitation for Virginia Beach-Norfolk-Newport News, VA-NC during Hurricane Isabel. 94