ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM GABRIELLE DISCUSSION NUMBER 18 NATIONAL WEATHER SERVICE MIAMI FL 11 PM EDT SAT SEP 15 2001 WITH AN INITIAL MOTION ESTIMATE OF 055/12...GABRIELLE SEEMS TO BE RIGHT ON THE PREVIOUS FORECAST TRACK. THE GUIDANCE AGREES CLOSELY ON A CONTINUED NORTHEAST OR EAST-NORTHEASTWARD TRACK FOR THE NEXT 72 HOURS AS THE STORM IS NOW EMBEDDED IN THE WESTERLIES. THE OFFICIAL FORECAST TRACK IS CHANGED LITTLE FROM AND IS AN UPDATE OF THE PREVIOUS ADVISORY. SHIPS REPORTS INDICATE THE WINDS ARE UP TO 50 KNOTS NORTHWEST OF THE CENTER NOT FAR FROM THE US EAST COAST. THERE IS ALSO EVIDENCE OF 50 KNOT WIND SPEEDS IN OTHER QUADRANTS FROM RECON AND GOES CLOUD DRIFT WINDS. MOST OF THE GUIDANCE HOLDS ON TO 50 KNOTS OR SO THROUGH 72 HOURS. ONLY THE GFDL FORECASTS SIGNIFICANT STRENGTHENING. GABRIELLE DOES NOT APPEAR VERY TROPICAL ON INFRARED IMAGES. ALL OF THE CONVECTION IS NORTH OR EAST OF THE CENTER AND THE VERTICAL SHEAR IS 30 KNOTS OR MORE IN THE AVIATION MODEL. SO IF GABRIELLE DOES MAINTAIN ITS STRENGTH...IT WILL PROBABLY DO SO AS AN EXTRATROPICAL SYSTEM WITH A BAROCLINIC ENERGY SOURCE...UNLESS THE WARM GULFSTREAM SSTS PLAY A ROLE. FORECASTER LAWRENCE FORECAST POSITIONS AND MAX WINDS INITIAL 16/0300Z 30.8N 77.3W 50 KTS 12HR VT 16/1200Z 31.8N 75.3W 50 KTS...EXTRATROPICAL 24HR VT 17/0000Z 33.3N 72.6W 50 KTS...EXTRATROPICAL 36HR VT 17/1200Z 34.7N 70.0W 50 KTS...EXTRATROPICAL 48HR VT 18/0000Z 36.1N 67.3W 50 KTS...EXTRATROPICAL 72HR VT 19/0000Z 39.0N 62.0W 50 KTS...EXTRATROPICAL NNNN