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| #34798 (Received by flhurricane at: 11:03 PM 22.Jul.2005) TCDAT1 TROPICAL STORM FRANKLIN DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT FRI JUL 22 2005 AN AIR FORCE HURRICANE HUNTER AIRCRAFT MEASURED NEAR 00Z AND 02Z A MINIMUM CENTRAL PRESSURE OF 1003 MB... DOWN ABOUT 4 MB COMPARED TO EARLIER THIS AFTERNOON. MAXIMUM 850 MB FLIGHT LEVEL WINDS WERE 53 KT IN A BURST OF CONVECTION JUST SOUTHEAST OF THE CENTER. THESE DATA... ALONG WITH DVORAK ESTIMATES OF 45 KT FROM TAFB AND SAB... SUPPORT MAINTAINING THE ADVISORY INTENSITY AT 45 KT. THE OVERALL APPEARANCE ON SATELLITE IMAGERY REMAINS UNIMPRESSIVE. THE LARGE UPPER-LEVEL ANTICYCLONE OVER THE YUCATAN DISTURBANCE CONTINUES TO PRODUCE WESTERLY WINDS ACROSS FLORIDA THAT ARE IMPOSING SHEAR ON FRANKLIN... RESULTING ESSENTIALLY IN HALF OF A TROPICAL STORM... WITH MOST OF THE WINDS AND CONVECTION IN THE EASTERN SEMICIRCLE. THE AIRCRAFT MEASURED 45 KT FLIGHT LEVEL WINDS IN A BAND FARTHER OUT IN THE SOUTHEASTERN QUADRANT ABOUT 50-75 NMI FROM THE CENTER. THE 34 KT WIND RADII WERE EXPANDED TO THE SOUTHEAST ACCORDINGLY. THE RECON FIXES INDICATE THAT FRANKLIN HAS SLOWED DOWN SLIGHTLY AND IS NOW MOVING JUST EAST OF DUE NORTH... WITH ESTIMATED INITIAL MOTION OF 010/7. FRANKLIN IS MOVING SLOWLY THROUGH A SLIGHT WEAKNESS IN THE SUBTROPICAL RIDGE. WATER VAPOR IMAGERY DEPICTS A MIDLATITUDE SHORTWAVE TROUGH THAT IS JUST ABOUT TO EMERGE OFF THE MID-ATLANTIC EAST COAST OF THE UNITED STATES... WHICH IS EXPECTED TO SHARPEN WHILE MOVING FAIRLY QUICKLY EASTWARD OVER THE WESTERN ATLANTIC. LITTLE DOUBT REMAINS THAT THIS FEATURE WILL TURN FRANKLIN TOWARD THE NORTHEAST... BUT MUCH UNCERTAINTY EXISTS REGARDING HOW FAST FRANKLIN WILL MOVE DURING THE NEXT FEW DAYS. THE NWS MODELS... GFS AND GFDL... ARE BY FAR THE FASTEST. THE GFS SOLUTION APPEARS TOO FAST EVEN INITIALLY SINCE IT SHOWS NEARLY AN IMMEDIATE DECOUPLING OF THE LOW AND MID LEVEL CIRCULATIONS... WHICH DOES NOT SEEM TO YET BE OCCURRING. THE UKMET AND THE NAVY MODELS... NOGAPS AND GFDN... ARE MUCH SLOWER. IN FACT... THE 18Z NOGAPS IS QUITE A BIT SLOWER THAN THE 12Z RUN. THEREFORE... THE OFFICIAL FORECAST WILL REMAIN SLOWER THAN THE DYNAMICAL MODEL CONSENSUS BUT FASTER THAN THE PREVIOUS ADVISORY. THE VERTICAL SHEAR MIGHT ABATE A LITTLE DURING THE NEXT DAY OR SO... BUT NORTHERLY SHEAR SHOULD BEGIN THEREAFTER AS FRANKIN MOVES FARTHER NORTH AND THE MIDLATITUDE TROUGH COMES OFF THE EAST COAST. GIVEN THIS ENVIRONMENT AND THE PRESENT LACK OF ORGANIZATION... THE DEVELOPMENT RATE IS EXPECTED TO REMAIN LIMITED. IN FACT... ESPECIALLY GIVEN ITS SMALL SIZE... FRANKLIN COULD VERY WELL BECOME SHEARED APART IN 2-3 DAYS. ALONG THE OFFICIAL FORECAST TRACK... THE TROPICAL STORM WILL REACH SUB-27C SSTS ON DAYS FOUR AND FIVE... SO A WEAKENING TREND IS INTRODUCED LATE IN THE FORECAST. THE INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND LIES IN BETWEEN THE SHIPS AND GFDL SOLUTIONS. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 23/0300Z 28.4N 76.5W 45 KT 12HR VT 23/1200Z 29.5N 75.7W 50 KT 24HR VT 24/0000Z 30.7N 74.1W 55 KT 36HR VT 24/1200Z 31.5N 72.2W 60 KT 48HR VT 25/0000Z 32.2N 69.9W 60 KT 72HR VT 26/0000Z 33.5N 65.5W 60 KT 96HR VT 27/0000Z 35.5N 60.5W 55 KT 120HR VT 28/0000Z 38.0N 55.0W 50 KT |
