ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM 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 NNNN