Hurricane ISABEL
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HURRICANE ISABEL DISCUSSION NUMBER 51
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT THU SEP 18 2003
ISABEL MADE LANDFALL ON THE OUTER BANKS OF NORTH CAROLINA NEAR DRUM
INLET...BETWEEN CAPE LOOKOUT AND OCRACOKE ISLAND...NEAR 17Z THIS
AFTERNOON...WITH WINDS ESTIMATED NEAR 85 KT. A GPS DROPSONDE
REPORTED SURFACE WINDS OF 83 KT ABOUT AN HOUR BEFORE LANDFALL A FEW
MILES FROM CAPE HATTERAS IN THE NORTHEAST EYEWALL. THE STEPPED
FREQUENCY MICROWAVE RADIOMETER ON BOARD THE NOAA P-3 AIRCRAFT
REPORTED SURFACE WINDS OF 90 KT AT 1707Z IN THE SAME AREA...AND
ANOTHER MEASUREMENT OF 82 KT WAS REPORTED ABOUT AN HOUR EARLIER.
RECONNAISSANCE AIRCRAFT MEASURED PEAK FLIGHT-LEVEL WINDS OF 118 KT.
THE AIRCRAFT MEASUREMENTS WERE CONFIRMED BY GROUND-BASED DOPPLER
RADARS. A LARGE NUMBER OF DROPSONDES IN ISABEL INDICATE THAT
SURFACE WINDS WERE AVERAGING ABOUT 70% OF THE FLIGHT-LEVEL VALUES
OVER THE LAST DAY OR TWO...AND THIS ALSO YIELDS ABOUT 83 KT FOR A
PEAK SURFACE WIND ESTIMATE.
ISABEL CONTINUES INLAND...AND WHILE THERE HAS BEEN SOME SHARPENING
UP OF THE EYEWALL AFTER LANDFALL...THE MAXIMUM WINDS SHOULD BE
DECREASING. GIVEN THE PRESENT ORGANIZATION OF THE CORE AND THE
LARGE AND STRONG CIRCULATION ALOFT...THE FORECAST DECREASE OF WIND
IS SLOWER THAN INDICATED BY THE DECAY SHIPS MODEL GUIDANCE. THE
STRONG WINDS ALOFT WILL BE FELT IN THE FORM OF HURRICANE FORCE WIND
GUSTS WELL INLAND OVER THE ELEVATED TERRAIN OF NORTHERN VIRGINIA
AND WESTERN MARYLAND...AS WELL AS ON HIGH RISE BUILDINGS AND OTHER
STRUCTURES IN MAJOR METROPOLITAN AREAS NEAR AND ESPECIALLY EAST OF
THE PATH OF ISABEL.
THERE HAS BEEN LITTLE CHANGE TO THE FORECAST TRACK. ISABEL IS
EXPECTED TO BECOME EXTRATROPICAL WITHIN 36 HOURS AND BE ABSORBED
AFTER 48 HOURS.
FORECASTER FRANKLIN
FORECAST POSITIONS AND MAX WINDS
INITIAL 18/2100Z 36.2N 77.1W 80 KT
12HR VT 19/0600Z 39.0N 78.6W 55 KT...INLAND
24HR VT 19/1800Z 43.5N 79.7W 35 KT...INLAND
36HR VT 20/0600Z 49.5N 79.6W 30 KT...EXTRATROPICAL
48HR VT 20/1800Z 55.5N 76.5W 25 KT...EXTRATROPICAL
72HR VT 21/1800Z...MERGED WITH EXTRATROPICAL LOW
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