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| #208251 (Received by flhurricane at: 1:34 PM 18.Aug.2008) TCDAT1 TROPICAL STORM FAY DISCUSSION NUMBER 12 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062008 1100 AM EDT MON AUG 18 2008 THE CENTER OF FAY HAS MOVED INTO THE FLORIDA STRAITS. SATELLITE IMAGERY AND RADAR DATA SHOW STRONG CONVECTIVE BANDING OVER THE EASTERN SIDE OF THE STORM...BUT LITTLE ACTIVITY IN THE WESTERN SEMICIRCLE. THIS ASYMMETRY IS LIKELY DUE TO WESTERLY VERTICAL SHEAR AND DRY AIR ENTRAINMENT. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT MEASURED 850 MB FLIGHT-LEVEL WINDS OF 61 KT...WITH RELIABLE-LOOKING SFMR WINDS OF 45-50 KT. BASED ON THIS AND SIMILAR DOPPLER RADAR WINDS...THE INITIAL INTENSITY IS INCREASED TO 50 KT. THE LATEST MINIMUM PRESSURE REPORTED BY THE HURRICANE HUNTER IS 1003 MB. FAY HAS BEEN MOVING IN FITS AND STARTS FOR THE PAST COUPLE OF DAYS...WITH THE CENTER MOVING FASTER TOWARD THE NORTH-NORTHWEST DURING THE PAST 6 HR. THE INITIAL MOTION IS 335/11. FAY IS ENTERING A BREAK IN THE SUBTROPICAL RIDGE OVER THE EASTERN GULF OF MEXICO AND FLORIDA CAUSED BY A MID/UPPER-LEVEL TROUGH MOVING THROUGH THE SOUTHEASTERN UNITED STATES. BEYOND 36-48 HR...THE TROUGH IS FORECAST TO LIFT OUT...WITH A MID/UPPER-LEVEL RIDGE BUILDING OVER THE EASTERN UNITED STATES AHEAD OF A SECOND TROUGH OVER THE WESTERN GULF COAST STATES. MOST OF THE TRACK GUIDANCE RESPONDS TO THIS EVOLUTION BY FORECASTING FAY TO MOVE GENERALLY NORTHWARD NEAR OR OVER THE FLORIDA PENINSULA AND INTO THE EASTERN UNITED STATES. HOWEVER...THE GFS AND ECMWF BOTH FORECAST FAY TO TURN NORTHEASTWARD INTO THE ATLANTIC AND STALL BY 120 HR...WHILE THE NOGAPS CONTINUES TO CALL FOR A MORE WESTERLY MOTION TOWARD THE FLORIDA PANHANDLE. THE HYDROMETEOROLOGICAL PREDICTION CENTER NOTED THAT THE GFS AND ECMWF ENSEMBLES ARE NOT IN GOOD AGREEMENT WITH THE OPERATIONAL RUNS...SO THESE OUTLIERS ARE IGNORED FOR THE MOMENT. THE NEW FORECAST TRACK WILL FOLLOW THE NORTHWARD SCENARIO...LYING JUST A LITTLE TO THE EAST OF THE CONSENSUS MODELS AND THE CENTER OF THE GUIDANCE ENVELOPE. THE TRACK BRINGS THE CENTER OVER THE SOUTHWESTERN COAST OF FLORIDA IN A LITTLE OVER 24 HR. FAY IS IN A MODERATE SOUTHWESTERLY VERTICAL SHEAR ENVIRONMENT...AND THE UPPER-LEVEL WINDS WILL LIKELY REMAIN LESS THAN IDEAL FOR THE NEXT 24-48 HR. THIS...COMBINED WITH THE DRY AIR AND THE CURRENT STRUCTURE...WILL LIKELY PREVENT RAPID INTENSIFICATION. HOWEVER... THE GUIDANCE SHOWS GRADUAL STRENGTHENING...WITH THE GFDL AND HWRF MODELS MAKING FAY A HURRICANE BEFORE LANDFALL. THUS...THE INTENSITY FORECAST WILL FOLLOW SUIT. AFTER LANDFALL...FAY SHOULD SLOWLY WEAKEN AND BECOME A REMNANT LOW BY 120 HR. THIS INTENSITY FORECAST IS LOW CONFIDENCE...AND THERE IS A DISTINCT CHANCE FAY MIGHT NOT REACH HURRICANE STRENGTH BEFORE LANDFALL...ESPECIALLY IF IT MOVES TO THE RIGHT OF THE FORECAST TRACK. IT SHOULD BE NOTED THAT...SIMILAR TO CHARLEY IN 2004...SMALL DEVIATIONS FROM THE FORECAST TRACK COULD MAKE LARGE DIFFERENCES IN WHEN AND WHERE THE CENTER OF FAY MAKES LANDFALL. FORECAST POSITIONS AND MAX WINDS INITIAL 18/1500Z 23.6N 81.5W 50 KT 12HR VT 19/0000Z 24.6N 81.8W 55 KT 24HR VT 19/1200Z 26.2N 82.1W 65 KT 36HR VT 20/0000Z 27.8N 82.0W 50 KT...INLAND 48HR VT 20/1200Z 29.3N 81.8W 40 KT...INLAND 72HR VT 21/1200Z 31.5N 81.5W 35 KT...INLAND 96HR VT 22/1200Z 33.6N 81.5W 25 KT...INLAND 120HR VT 23/1200Z 35.5N 82.5W 20 KT...INLAND REMNANT LOW $$ FORECASTER BEVEN |
