The Chesapeake: a Boating Guide to Weather. Educational Series Number 25
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DOCUMENT RESUME ED 19B 015 SE 034 410 AUTHOR Lucy, Jon: And Others TITLE The Chesapeake: A Boating Guide to Weather. Educational Series Number 25. TNSTITUTION Virginia Inst. of Mar in:: Science, Gloucester Point, Va. SPONS AGENCY National Oceanic and Atmospheric Administration (DOC), Rockville, Md. National Sea Grant Program. PUB DATE Aug 90 GRANT NA79AA-D-00055 NOTE 27r.: Contains photographs which may not reproduce well. AVAILABLE FP OM Sea Grant Communications Office, Virginia Inst. of Marine Science, Gloucester Point, VA 23062 ($1.001. EDRS PRICE MF01/PCO2 Plus Postage. DESrRTPTORS Accident Prevention: *Boat Operators; Climate: *Meteorology: *Navigation: Safety: *Safety Education: *Weather TDENTTETTTS *Chesapeake Bay ABSTRACT The purpose of this publication is to promote a better understanding of how basic weather features develop on Chesapeake Bav and enable boaters to enjoy the Bay's unique waterways. Sections include:(11 Chesapeake Bay climate: (2) general weather features:f31 seasonal trends: (4)sources of weather information and forecasts:(51 weather service warnings: and (6) weather and boating safety.(Author/C01 *********************************************************************** Reproductions supplied by EDRS are the best that can be made from the original document. *********************************************************************** THE CHESAPEAKE: U.S. DEPARTMENT OF HEALTH, EDUCATION& WELFARE aboating guide to NATIONAL INSTITUTE OF EDUCATION THIS DOCUMENT HAS BEEN REPRO. DUCED EXACTLY AS RECEIVED FROM THE PERSON OR ORGANIZATION ORIGIN- ATING IT POINTS OF VIEW OR OPINIONS STATED DO NOT NECESSARILY REPRE- SENT OFFICIAL NATIONAL INSTITUTEOF WEATHER EDUCATION POSITION OR POLICY jon lucy, terry ritter,ferry larue 1" dt,4. 4" 4 a VAIrre. gfroPo- s-+-. e- --mlistor+Traz ..ajl.Z.P .10 MCme SEA GRANT PROGRAM Virginia Institute of Marine Science College of William and Mary Gloucester Point, Virginia 2 THE CHESAPEAKE a boating guide to WEATHER by Jon Lucy Marine Recreation Specialist Sea Grant Marine Advisory Services Virginia Institute of Marine Science And Instructor, School of Marine Science, College of William and Mary Gloucester Point, Virginia Terry Ritter Meteorologist in Charge National Weather Service Norfolk, Virginia Jerry LaRue Meteorologist in Charge National Weather Service Washington, D.C. Educational Series Number 25 First Printing December 1979 Second Printing August 1980 A Cooperative Publication of V IMS Sea Grant Marine Advisory Services and NOAA National Weather Service 3 Acknowledgements For their review and constructive criticism, appreciation is expressed to Messrs.Herbert Groper, Chief, Community Preparedness Staff, Thomas Reppert, Meteorologist, Marine Weather Services Branch and Michael Mogil, Emergency Warning Meteorologist, Public Services Branch, all of NOAA National Weather Service Head- quarters, Silver Spring, Maryland; also to Dr. Rollin Atwood, Marine Weather Instrrctor, U.S. Coast Guard Auxiliary, Flotilla 33, Kilmarnock, Virginia and Mr. Carl Hobbs, Geological Oceanographer, Vlfv1S.Historical climatological data on Chesa- peake Bay was provided by Mr. Richard DeAngelis, Marine Climatological Services Branch, National Oceanographic Data Center, NOAA Environmental Data Service, Washington, D.C. Thanks go to Miss Annette Stubbs of VIMS Report Center for pre- paring manuscript drafts and to Mrs. Cheryl Teagle of VIMS Sea Grant Advisory Services for com- posing the final text. This work is a result of research sponsored (in part) by the Virginia Institute of Marine Science Institutional Sea Grant Program, supported by the Office of Sea Grant, NOAA, under Grant Number (NA79AA-D-00055). The U.S. Government is authorized to produce and distribute reprints for governmental purposes notwithstanding any copy- right notation that may appear hereon. DESIGN BY DICK COOK Contents P AG E CHESAPEAKE BAY CLIMATE 3 GENERAL WEATHER FEATURES 3 Winds 3 Waves 3 Clouds 5 SEASONAL TRENDS, NOVEMBER THROUGH APRIL.. 5 Fog 6 Cold Air and Water Temperatures 6 Cold Fronts 10 SEASONAL TRENDS, MAY THROUGH JULY 10 Thunderstorms 10 Lightning 12 SEASONAL TRENDS, AUGUST THROUGH OCTOBER 13 Hurricanes 15 Chesapeake Bay Hurricane Holes 15 Waterspouts 17 SOURCES OF WEATHER INFORMATION AND FORECASTS 17 WEATHER SERVICE WARNINGS - WHAT THEY MEAN 20 WEATHER AND BOATING SAFETY 20 ---A-MORE-IDEALBOAT ING-area-than -Otiesapeake --the-need-to-keep-a-close watch-on- weather- condi ) Bay would be difficult to find along the Atlantic, bons. Seaboard With thousands of miles of sheltered The purpose of this publication is to remind shoreline, good water depth and proximity to boatmen that the-Bay has many different weather major urban centers, the Bay is a boatman's par,a- moods, some of which can change quite rapidly. disc. However, the Bay's many protected harbors In addition, it should promote a better under- and relatively narrow width (a boatman normally _standing of how basic weather features develop can keep at least one shore in sight at all times) on the Bay and enable boatmen to enjoy the., tend to produce a feeling of false security about Chesapeake's unique waterways with fewer wea- ther surprises. 1. f...a'l.ye. ,,,. .. Ad.,........4.. li, ......, . D.../.. '' ..". ''. .... --.1......30 0-7z;.edir.,..r.,11=710, ...... ..", .. .5.: 7.......r."a: ',..'.. ...... r --,.......-. _ _ '6:1....ei .-1-=t- , -.."-/- 7 .......- ;;' ..,...---:. ---.....-- ,.- ---',..- '.../11FL' -'. .1- T-C: -.._ .- - - - 1,. -....- ...y -' .-*- -.'' ."7'4... ,.7 -'11..--Z.--,----1- .....7--__-,.,..... - 11. -,..---... :.."jilu---Agniiiiri- Tr...4 -..a.,.....---..- -- 7 ...71E.114.../. ... ......_. 7..'7-. - je.... Sicd-............,.ti.....;... ,.......70, - .--,.6....s.. .....Zio . .- .01,., ' - - - .. "'"-- ' IL:jiP.I.ailir.;_. ...7-..........". -". ........ _.. ".""";%;." .......... '."'-....--_,.........--......'""r. ....7 .'" --=.1., CHESAPEAKE BAY CLIMATE to be southerly during warm months and northerly during the cold portion of the year. However, the The climate of the Bay is established by its many smaller bays, inlets, islands and tributaries of location in mid latitudes on the eastern edge of the Chesapeake interfere with prevailing wind flow the North American continent.This location patterns, resulting in local winds which can differ results in winter climate being regulated by the drastically from the general pattern. polar continental influence, while summer is Differences in Bay water temperature and air characterized by continental tropical weather temperature influence wind direction and speed, with infrequent invasions of cooler air.The particularly as compared to patterns over adjacent climate is tempered by marine influences which land surfaces. During cooler months, the passage of most noticeably result in milder winter tem- light, warm prevailing winds over cold water can peratures than those found inland at similar result in reduced winds on the Bay as compared to latitudes. winds inland, unless the warm winds are strong. Fall, winter and spring are characterized by During warmer months, whenever cold air moves occasional storm systems producing wind gusts over warm Bay water, winds will be stronger and of over 50 knots*, rarely up to 70 knots, about much more gusty over the Bay than over adjacent once a year.Such winds usually come from land surfaces, due to the unstable situation of cold the south, northwest or north, but about once in air overlying rising air warmed by the water. ten ?ears strike the area from the east, causing Another characteristic of winds around the Bay unusually high storm surges. is the sea breeze effect. Occurring during warmer Summers are characterized by weak low pres- months, sea breeze is caused by differences be- sure systems rarely producing winds as high as 30 tween air temperatures over the land and water. knots. The Bay also experiences the majority of Basically, air warmed over heat-absorbing land its annual average of 30 thunderstorm days during areas is lighter than adjacent air over relatively summer, and these, of course, may produce the cooler Bay water. The lighter air rises, causing the higher winds noted formerly. Often associated cooler air over the Bay to move towards land to with cold fronts, these storms occur most fre- fill the void. Sea breeze is noticeable when the two quently from May through August. air masses differ by as little as 5°F (about 3°C) and Hurricanes are experienced in the Bay about increases as differences become greater. once every ten years, generally coming in the latter The sea breeze effect is largely responsible for half of the boating season (August-October). the strong diurnal variation in wind speeds over the The Bay's configuration and orientation signifi- Bay during the boating season. When no major cantly affect wind and weather patterns important weather disturbances are governing the Bay's wind to boatmen (Fig. 1). The relatively straight course patterns, winds will tend to be very light at night, of the Bay extends in a north-south direction for increasing in strength during the late morning. nearly 200 miles (332 kilometers). The western Maximum winds occur in mid afternoon when shore of the lower Bay is cut deeply by five tri- air mass temperatures over land and water differ butaries varying 2-8 miles (3-13 kilometers) in the most, with wind speed falling off rapidly at width at their mouths and exhibiting northwest dusk. Such winds are generally stronger near fetches of as much as 20-40 miles (32-64 kilo- the shore, especially where