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TROPICAL STORM GABRIELLE DISCUSSION NUMBER  30
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT TUE SEP 18 2001
 
THE PRESSURE AT BUOY 44141 IS 977.6 MB...SO THE CENTRAL PRESSURE
IS 975 MB OR SO AND FALLING.  I ASSUME THAT THE MAXIMUM WIND
REMAINS 60 KNOTS AS IN THE LAST ADVISORY.  975 MB WOULD SUPPORT A
HURRICANE UNDER NORMAL CONDITIONS.  BUT SSTS OF 20 DEG C AND 
VERTICAL 
WIND SHEAR OF NEAR 50 KNOTS IS NOT NORMAL.  A RECENT QUIKSCAT SHOWED 
WINDS SPEEDS IN THE 60 KNOT RANGE.  THE GUIDANCE SUGGESTS THAT THE 
WIND SPEEDS COULD REMAIN NEAR 60 KNOTS FOR A DAY OR SO AND ANY 
WEAKENING WILL BE SLOW.
 
THE INITIAL MOTION ESTIMATE IS 040/18...MAYBE A LITTLE FASTER.  THE
TRACK SCENARIO IS THE SAME AS EARLIER.  GABRIELLE IS CAUGHT UP IN
THE WESTERLIES AND SHOULD ACCELERATE NORTHEASTWARD FOR 72 HOURS.  
THE FORECAST TRACK IS ADJUSTED SLIGHTLY LEFT OF THE PREVIOUS 
ADVISORY BASED ON A CONSENSUS OF THE MOST SKILLFUL MODELS.
 
THERE IS NO DEEP CONVECTION ANYWHERE NEAR THE CENTER...ALL CLOUD
TOPS ARE WARMER THAN -50C BASED ON GOES8 IR IMAGERY.  THERE IS
HOWEVER WHAT MIGHT BE SHALLOW CONVECTION NEAR AND NORTH OF THE
CENTER.  NEARBY SSTS WILL SOON FALL BELOW 20 DEGREES C.  PENN STATE
PHASE ANALYSIS IS NEAR NEUTRAL BASED ON 18Z AVN MODEL.  THE LATEST
AMSU EXPERIMENTAL PRODUCTS ARE 12 HOURS OLD.  GABRIELLE IS BECOMING 
EXTRATROPICAL AND FUTURE INFORMATION ON THIS STRONG STORM WILL BE
CONTAINED IN THE HIGH SEAS FORECAST FROM THE MARINE PREDICTION
CENTER UNDER WMO HEADER FZNT01 AND UNDER AWIPS HEADER NFDHSFAT1.
 
FORECASTER LAWRENCE
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     19/0300Z 42.3N  56.7W    60 KTS...BECOMING EXTRATROPICAL
12HR VT     19/1200Z 44.5N  54.0W    60 KTS...EXTRATROPICAL
24HR VT     20/0000Z 47.3N  49.5W    60 KTS...EXTRATROPICAL
36HR VT     20/1200Z 50.2N  44.6W    60 KTS...EXTRATROPICAL
48HR VT     21/0000Z 53.0N  39.0W    55 KTS...EXTRATROPICAL
72HR VT     22/0000Z 54.0N  32.0W    45 KTS...EXTRATROPICAL
 
 
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