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TROPICAL STORM GABRIELLE DISCUSSION NUMBER  10
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT THU SEP 13 2001

FIXES FROM THE AIR FORCE RESERVE HURRICANE HUNTER MONITORING
GABRIELLE EARLIER THIS EVENING INDICATED AN ERRATIC MOTION...
FIRST JUMPING ABOUT 20 NM TO THE WEST AND THEN ABOUT 30 NM TO THE
EAST.  THE CENTRAL PRESSURE DROPPED TO 996 MB...WITH A SECOND
LATER FIX OF 997 MB AND 52 KT FLIGHT LEVEL WINDS.  SATELLITE IMAGERY
INDICATES THAT THE STORM IS AT LEAST SOMEWHAT SHEARED...WITH BURSTS
OF CONVECTION DEVELOPING TO THE EAST OF THE CENTER.  THE INITIAL
INTENSITY IS 45 KT IN AGREEMENT WITH ALL SATELLITE INTENSITY
ESTIMATES AND THE AIRCRAFT WINDS.
 
THE INITIAL MOTION IS VERY UNCERTAIN BUT IS ESTIMATED TO BE 055/4.
WATER VAPOR IMAGERY AND DATA FROM THE NOAA G-4 JET SHOW A SHARP
MID/UPPER LEVEL TROUGH JUST WEST OF THE CYCLONE...WHILE LOW LEVEL
RIDGING SURROUNDS THE SYSTEM.  THE RIDGING SUGGESTS THE MOTION
SHOULD REMAIN SLOW...AT LEAST INITIALLY.  NHC HURRICANE GUIDANCE
AGREES ON A SLOW NORTHEASTWARD MOTION FOR THE FIRST 36-48 HR WITH
SOME ACCELERATION THEREAFTER.  THE TRACK FORECAST FOLLOWS THE
GUIDANCE AND IS BASICALLY AN UPDATE OF THE PREVIOUS PACKAGE.  SOME
ERRATIC MOTION IS LIKELY AS THE CENTER RE-FORMS DUE TO THE
CONVECTIVE BURSTS.
 
THE G-4 DATA INDICATES CONSIDERABLE UPPER LEVEL DIFLUENCE OVER
GABRIELLE FROM THE UPPER LEVEL TROUGH AND AN UPPER LEVEL RIDGE
TO THE SOUTHEAST.  WHILE LARGE-SCALE MODELS INDICATE THAT SOME
WESTERLY SHEAR SHOULD CONTINUE OVER THE STORM...DIVERGENCE FROM
THE TROUGH AND ASSOCIATED UPPER LEVEL WIND MAXIMA WILL LIKELY
MAINTAIN STRONG CONVECTION WITH THE SYSTEM AND ALLOW FOR SOME
STRENGTHENING.  THE INTENSITY FORECAST BRINGS GABRIELLE TO 60
KT AT LANDFALL...AND THERE IS A CHANCE IT COULD BE A HURRICANE AT
THAT TIME.
 
AT THIS TIME...IT APPEARS THAT THE MAIN THREAT FROM GABRIELLE IS
VERY HEAVY RAINFALL AND POTENTIAL FLOODING.  HEAVY RAINBANDS ARE
ALREADY SPREADING ONSHORE OVER THE SOUTHERN FLORIDA PENINSULA AND
KEYS.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     14/0300Z 25.5N  84.0W    45 KTS
12HR VT     14/1200Z 26.0N  83.4W    50 KTS
24HR VT     15/0000Z 27.0N  82.4W    60 KTS
36HR VT     15/1200Z 28.1N  81.4W    50 KTS
48HR VT     16/0000Z 29.0N  80.5W    45 KTS
72HR VT     17/0000Z 31.0N  77.0W    50 KTS
 
 
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