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TROPICAL STORM GABRIELLE DISCUSSION NUMBER  20
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT SUN SEP 16 2001
 
AIR FORCE RECON REPORTS AND SATELLITE DATA INDICATE THAT GABRIELLE 
HAS BECOME BETTER ORGANIZED THIS MORNING AND HAS STRENGTHENED 
SLIGHTLY.  A RECON REPORT AT 16/1140Z INDICATED A CENTRAL PRESSURE 
DOWN TO 995 MB...WHILE THE 16/1328Z REPORT INDICATED 1500 FT 
FLIGHT-LEVEL WINDS OF 67 KT NORTHWEST OF THE CENTER IN DEVELOPING 
CONVECTION.  THERFORE...THE INTENSITY HAS BEEN INCREASED TO 55 KT 
FOR THIS ADVISORY.  RECON ALSO INDICATED THE TEMPERATURE IN THE 
CENTER HAS WARMED AND SATELLITE IMAGERY INDICATES INCREASING 
ANTICYCLONIC OUTFLOW IN THE NORTHWEST SEMICIRCLE...ALL OF WHICH 
SUGGEST THAT GABRIELLE IS STILL A WARM-CORE TROPICAL CYCLONE.

THE INITIAL MOTION IS 065/17. THE NHC MODEL GUIDANCE REMAINS IN 
EXCELLENT AGREEMENT ON TAKING GABRIELLE TO THE NORTHEAST THROUGHOUT 
THE FORECAST PERIOD.  THE FORWARD SPEED IS EXPECTED TO DECREASE AS 
AN APPROACHING SHORTWAVE TROUGH WEAKENS AND GRADUALLY LIFTS OUT TO 
THE NORTHEAST OF THE CYCLONE. THE NEXT TROUGH TO FINALLY PICK UP THE 
SYSTEM IS FORECAST TO DROP SOUTHEAST OUT OF THE NORTHERN PLAINS 
STATES AND GRADUALLY ACCELERATE GABRIELLE TO THE NORTHEAST.  THE 
OFFICIAL FOREACST IS JUST AN UPDATE OF THE PREVIOUS FORECAST TRACK 
AND IS CLOSE TO THE AVN-UKMET-NOGAPS MODEL ENSEMBLE AVERAGE.
 
SURFACE ANALYSES OVER THE PAST 24 HOURS INDICATE THAT THE COLD HIGH 
PRESSURE SYSTEM OVER THE NORTHERN U.S. HAS WEAKENED CONSIDERABLY AND 
THAT THE COLD FRONT TO THE NORTHWEST OF GABRIELLE HAS MADE LITTLE 
PROGRESS TO THE SOUTHEAST.  IT IS QUITE POSSIBLE THAT THE CYCLONE 
MAY STAY ON THE WARM SIDE OF THE FRONTAL BOUNDARY AND REMAIN MORE 
TROPICAL-LIKE FOR THE NEXT 24 TO 36 HOURS...UNTIL THE NEXT SHORTWAVE 
TROUGH FINALLY PICKS UP THE SYSTEM AND MAKES GABRIELLE MORE 
BAROCLINIC...OR AT LEAST SUBTROPICAL IN NATURE.  UNLESS DEEP 
CONVECTION DEVELOPS DIRECTLY OVER THE CENTER...LITTLE ADDITIONAL 
INTENSIFICATION SHOULD OCCUR. THERE IS LESS DRY AIR SURROUNDING THE 
SYSTEM TODAY...SO MORE CONVECTIVE DEVELOPMENT IS A POSSIBILITY.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     16/1500Z 31.9N  74.1W    55 KTS
12HR VT     17/0000Z 32.7N  71.5W    55 KTS...BECOMING EXTRATROPICAL
24HR VT     17/1200Z 33.9N  68.2W    50 KTS...EXTRATROPICAL
36HR VT     18/0000Z 35.3N  65.5W    50 KTS...EXTRATROPICAL
48HR VT     18/1200Z 36.7N  63.3W    50 KTS...EXTRATROPICAL
72HR VT     19/1200Z 40.0N  57.0W    50 KTS...EXTRATROPICAL
 
 
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