ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM GABRIELLE DISCUSSION NUMBER 16 NATIONAL WEATHER SERVICE MIAMI FL 11 AM EDT SAT SEP 15 2001 GABRIELLE HAS MOVED OFF THE FLORIDA COAST DURING THE MORNING. THE STORM CURRENTLY MORE RESEMBLES A SUBTROPICAL CYCLONE...WITH THE STRONGEST WINDS AND CONVECTION WELL REMOVED FROM THE CENTER AND AN UPPER LEVEL CYCLONE OVER THE SURFACE CENTER. DESPITE THE LACK OF CENTRAL CONVECTION...THE CENTRAL PRESSURE REMAINS 998 MB WITH AIRCRAFT MEASURED WINDS OF 59 KT IN THE SOUTHEAST QUADRANT AND 58 KT IN THE NORTHWEST QUADRANT. THE MAXIMUM INTENSITY IS SET TO 40 KT BASED ON THE AIRCRAFT WINDS AND AN OBSERVATION OF 42 KT FROM THE ST. AUGUSTINE C-MAN STATION. THE INITIAL MOTION IS 070/6...AND RADAR AND AIRCRAFT FIXES SINCE 12Z SUGGEST IT MAY BE MOVING EVEN FASTER. WATER VAPOR IMAGERY SHOWS THAT GABRIELLE IS BECOMING EMBEDDED IN THE WESTERLIES... WITH A DEEP-LAYER RIDGE TO THE SOUTHEAST OF THE SYSTEM AND A BROAD MID/UPPER LEVEL TROUGH OVER THE EASTERN UNITED STATES. THIS PATTERN SUPPORTS A GENERAL EAST TO NORTHEAST TRACK...AND NHC HURRICANE GUIDANCE IS CLUSTERED AROUND AN EAST-NORTHEASTWARD MOTION. THE TRACK FORECAST IS DOWN THE MIDDLE OF THE GUIDANCE AND IS JUST A LITTLE FURTHER SOUTH OF THE PREVIOUS PACKAGE. SOME ADJUSTMENT OF THE TRACK MAY BE NECESSARY IN THE NEXT PACKAGE IF GABRIELLE IS ACTUALLY MOVING FASTER THAN 6-8 KT. THERE ARE SEVERAL POSSIBILITIES REGARDING THE INTENSITY OF GABRIELLE. THE FIRST IS THAT THE MID/UPPER LEVEL DRY AIR OVER THE LOW LEVEL CENTER WILL INHIBIT CONVECTION AND PREVENT RE-DEVELOPMENT. THE SECOND IS THAT CONVECTION WILL RETURN AND SOME STRENGTHENING WILL OCCUR. THE INTENSITY FORECAST IS A COMBINATION OF THESE TWO POSSIBILITIES...CALLING FOR NO CHANGE IN STRENGTH FOR THE FIRST 12 HR FOLLOWED BY SLOW STRENGTHENING. A THIRD POSSIBILITY IS THAT THE CENTER MIGHT TRY TO REFORM CLOSER TO ONGOING CONVECTION TO THE NORTHEAST...WHERE GABRIELLE IS INTERACTING WITH A FRONTAL ZONE. IF THIS OCCURS...GABRIELLE MIGHT RE-INTENSIFY AS A HYBRID SYSTEM. ONE FINAL POSSIBILITY IS THAT GABRIELLE MIGHT MERGE WITH THE FRONTAL ZONE AND BECOME EXTRATROPICAL. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 15/1500Z 28.8N 79.8W 40 KTS 12HR VT 16/0000Z 29.2N 78.9W 40 KTS 24HR VT 16/1200Z 30.2N 76.7W 45 KTS 36HR VT 17/0000Z 31.9N 73.7W 50 KTS 48HR VT 17/1200Z 33.7N 70.5W 50 KTS 72HR VT 18/1200Z 37.0N 64.0W 50 KTS NNNN