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HURRICANE GABRIELLE DISCUSSION NUMBER 24
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT MON SEP 17 2001
AIR FORCE RECON HAS BEEN OUT IN THE SYSTEM THIS MORNING AND FOUND 85
KT 5000-FT FLIGHT-LEVEL WINDS IN DEEP CONVECTION...ALONG WITH A
CENTRAL PRESSURE OF 983 MB. THIS INDICATES THAT GABRIELLE HAS
STRENGTHENED SLIGHTLY SO THE INTENSITY HAS BEEN INCREASED TO 70 KT.
THE INITIAL MOTION ESTIMATE IS 055/17. GABRIELLE HAS MADE A SLIGHT
JOG TO THE LEFT OF THE PREVIOUS MOTION AND FORECAST TRACK...BUT THIS
IS LIKELY JUST A SHORT TERM MOTION...POSSIBLY DUE TO RE-DEVELOPMENT
OF THE LOW-LEVEL CENTER CLOSER TO THE DEEP CONVECTION LOCATED TO THE
NORTHWEST. GABRIELLE IS EXPECTED TO RETURN TO THE PREVIOUS BASE
COURSE OF ABOUT 060 DEGREES AS A LONG FETCH OF WESTERLY MID-TO
UPPER-LEVEL WINDS OVER THE EASTERN U.S. BEGIN TO IMPINGE ON THE
CYCLONE LATER TODAY. THE OFFICIAL FORECAST TRACK IS A LITTLE TO THE
LEFT OF THE PREVIOUS FORECAST THROUGH 24 HOURS AND THEN RETURNS TO
THE PREVIOUS TRACK BY 36 HOURS. THIS SCENARIO IS CONSISTENT WITH
ALL OF THE GLOBAL MODELS...BUT IS CLOSEST TO THE AVN MODEL. THE
NOGAPS MODEL APPEARS TO BE MUCH TOO FAST AND THE UKMET MODEL SEEMS
TOO FAR TO THE LEFT BY TAKING THE CYCLONE ACROSS SOUTHEAST
NEWFOUNDLAND IN THE FACE OF SUCH STRONG WESTERLY FLOW AT THAT
LATITUDE.
THE INTENSITY FORECAST IS RATHER TRICKY SINCE I AM UNCERTAIN AS TO
WHEN THE SYSTEM WILL ACTUALLY MAKE THE EXTRATROPICAL TRANSITION.
HOWEVER...EVEN SOME BAROCLINIC EFFECTS COULD KEEP GABRIELLE FAIRLY
STRONG IN THE LATER PERIODS...SO THE SHIPS INTENSITY MODEL FORECAST
WAS FOLLOWED CLOSELY.
FORECASTER STEWART
FORECAST POSITIONS AND MAX WINDS
INITIAL 17/1500Z 35.8N 65.7W 70 KTS
12HR VT 18/0000Z 37.0N 62.9W 70 KTS
24HR VT 18/1200Z 38.7N 60.2W 65 KTS...BECOMING EXTRATROPICAL
36HR VT 19/0000Z 40.4N 57.8W 60 KTS...EXTRATROPICAL
48HR VT 19/1200Z 42.9N 53.7W 60 KTS...EXTRATROPICAL
72HR VT 20/1200Z 48.0N 43.5W 50 KTS...EXTRATROPICAL
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