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#36057 (Received by flhurricane at: 4:34 PM 28.Jul.2005) TCDAT1 TROPICAL STORM FRANKLIN DISCUSSION NUMBER 30 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT THU JUL 28 2005 DURING THE PAST 6 HOURS...DEEP CONVECTION HAS DEVELOPED NEAR THE LOW-LEVEL CENTER IN THE NORTHWEST QUADRANT WITH A BAND OF MODERATE CONVECTION WRAPPING AROUND THE EASTERN SEMICIRCLE. SATELLITE INTENSITY ESTIMATES HAVE BEEN FLUCTUATING BETWEEN 45 AND 55 KT FROM TAFB AND SAB...AND AN EARLIER AMSU CIMSS PRESSURE ESTIMATE CAME IN AT 998 MB..OR 48 KT. GIVEN THE OVERALL IMPROVED APPEARANCE OF FRANKLIN AND THE FASTER FORWARD SPEED POSSIBLY ADDING ANOTHER 5 KT TO THE TOTAL WIND FIELD ON THE EAST SIDE...THE INITIAL INTENSITY HAS BEEN INCREASED TO 50 KT. THE INITIAL MOTION ESTIMATE IS 040/15...AS FRANKLIN HAS COME UNDER THE INFLUENCE OF INCREASING DEEP-LAYER SOUTHWESTERLY STEERING FLOW AHEAD OF AN EASTWARD MOVING MID-LATITUDE FRONTAL SYSTEM. THE NHC MODEL GUIDANCE IS IN OUTSTANDING AGREEMENT ON THE DIRECTION OF MOTION...BUT THERE IS A RANGE OF FORWARD SPEEDS WITH THE CANADIAN ...GFS AND GFDL MODELS BEING THE FASTEST...WHILE THE NOGAPS AND GFDN MODELS ARE MUCH SLOWER. THE OFFICIAL FORECAST TRACK LEANS TOWARD THE NOGAPS AND GFDN MODELS GIVEN THEIR BETTER OVERALL PERFORMANCE THUS FAR...AND THE FACT THAT FRANKLIN WILL BE MOVING OVER 13-17C SST WATER BY 36 HOURS WHICH SHOULD CAUSE THE LOW-LEVEL CIRCULATION TO DECOUPLE AND REMAIN BEHIND THE FASTER MOVING MID- TO UPPER-LEVEL CIRCULATION. NOW THAT FRANKLIN IS MOVING NORTHEASTWARD...THE VERTICAL SHEAR ON THE SYSTEM SHOULD REMAIN RELATIVELY LOW FOR ANOTHER 18 HOURS OR SO...WHICH IS ALSO ABOUT THE TIME THAT THE CYCLONE REACHES MUCH COLDER WATER. THEREFORE...SOME ADDITIONAL STRENGTHENING IS POSSIBLE ...WHICH IS ALSO INDICATED NOW BY THE GFDL MODEL. BY 24 HOURS... THOUGH...INCREASING VERTICAL SHEAR AND MUCH COLDER WATER SHOULD INDUCE RAPID WEAKENING...ALONG WITH A TRANSITION TO AN EXTRATROPICAL LOW. IT IS POSSIBLE THAT BY 48 HOURS FRANKLIN COULD ALREADY BE ASORBED BY THE APPROACHING FRONTAL SYSTEM. THE OFFICIAL FORECAST TRACK BRINGS TROPICAL STORM-FORCE WINDS VERY CLOSE TO THE EXTREME SOUTHEASTERN TIP OF NEWFOUNDLAND IN 48 HOURS. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 28/2100Z 37.6N 67.5W 50 KT 12HR VT 29/0600Z 39.3N 65.3W 55 KT 24HR VT 29/1800Z 41.3N 62.0W 50 KT...BECOMING EXTRATROPICAL 36HR VT 30/0600Z 43.2N 57.9W 40 KT...EXTRATROPICAL 48HR VT 30/1800Z 45.3N 53.0W 35 KT...EXTRATROPICAL 72HR VT 31/1800Z...ABSORBED BY FRONTAL SYSTEM |