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| #151866 (Received by flhurricane at: 11:05 AM 21.Sep.2007) TCDAT5 SUBTROPICAL DEPRESSION TEN DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL102007 1100 AM EDT FRI SEP 21 2007 CONVECTION ASSOCIATED WITH THE NON-TROPICAL LOW IN THE GULF HAS GRADUALLY BECOME BETTER ORGANIZED SINCE YESTERDAY...WITH A WELL-DEFINED BAND IN THE EASTERN SEMICIRCLE AND INTERMITTENT CONVECTION CLOSER TO THE CENTER. ALTHOUGH THE AMOUNT OF CONVECTION PRESENT PROBABLY STRAINS THE DEFINITION A BIT...BECAUSE OF THE POTENTIAL FOR ADDITIONAL DEVELOPMENT RIGHT ALONG THE COASTLINE... ADVISORIES ARE BEING INITIATED ON SUBTROPICAL DEPRESSION TEN. AN AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT FIXED A SMALL CIRCULATION CENTER A SHORT DISTANCE OFFSHORE OF APALACHICOLA...BUT BUOY OBSERVATIONS SUGGEST THAT A LARGER-SCALE CENTER MAY BE FARTHER SOUTH. THE ILL-DEFINED NATURE OF THE SURFACE CIRCULATION...AS WELL AS THE LINGERING UPPER-LOW ALOFT...PROVIDE THE RATIONALE FOR A SUBTROPICAL CLASSIFICATION. THE INITIAL MOTION ESTIMATE IS 325/7. A MID-LEVEL RIDGE OF HIGH PRESSURE STRETCHING FROM TEXAS NORTHEASTWARD IS EXPECTED TO TURN THE DEPRESSION TO THE WEST-NORTHWEST ON A TRACK NEARLY PARALLEL TO THE COASTLINE. MODEL GUIDANCE IS IN GOOD AGREEMENT AND THE OFFICIAL FORECAST FOLLOWS THE DYNAMICAL MODEL CONSENSUS. BECAUSE THE FORECAST TRACK IS NEARLY PARALLEL TO THE COASTLINE...A LANDFALL LOCATION IS DIFFICULT TO PINPOINT...BUT IN ANY EVENT THE CENTER OF A SUBTROPICAL CYCLONE IS RELATIVELY UNIMPORTANT. MOST OF THE WEATHER ASSOCIATED WITH THE SYSTEM IS WELL-DISPLACED FROM THE CENTER. THE UPPER-LOW IS FRAGMENTING...WITH THE MAIN ENERGY SLIDING SOUTHWEST OF THE DEPRESSION. THIS WILL LEAVE THE DEPRESSION UNDER LIGHT SOUTHEASTERLY FLOW OVER THE NEXT DAY OR SO. THE FLOW OF RELATIVELY COOL CONTINENTAL AIR INTO THE GULF AHEAD OF THE SYSTEM...AS WELL AS ITS POOR ORGANIZATION...SHOULD PREVENT EXCESSIVE DEVELOPMENT. THE TROPICAL INTENSITY MODELS ALL SHOW DEVELOPMENT TO A MID-RANGE TROPICAL STORM...WHILE THE GLOBAL MODELS...WHICH MIGHT BE MORE APPROPRIATE TO THIS SITUATION... FORECAST LITTLE STRENGTHENING. THE OFFICIAL FORECAST REPRESENTS A COMPROMISE AMONG THESE SOLUTIONS. FORECAST POSITIONS AND MAX WINDS INITIAL 21/1500Z 29.2N 85.5W 30 KT 12HR VT 22/0000Z 29.7N 86.6W 35 KT 24HR VT 22/1200Z 30.1N 88.1W 40 KT 36HR VT 23/0000Z 30.6N 90.3W 40 KT...INLAND 48HR VT 23/1200Z 31.5N 93.0W 30 KT...INLAND 72HR VT 24/1200Z...DISSIPATED $$ FORECASTER FRANKLIN |
