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| #268421 (Received by flhurricane at: 10:55 AM 28.May.2009) TCDAT1 TROPICAL DEPRESSION ONE DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL012009 1100 AM EDT THU MAY 28 2009 DEEP CONVECTION ASSOCICATED WITH THE AREA OF LOW PRESSURE OFF THE MID-ATLANTIC COAST HAS BEEN PERSISTENT SINCE ABOUT 04Z THIS MORNING WHILE THE SYSTEM MOVES OVER THE 25-26C WATERS OF THE GULF STREAM. DVORAK CLASSIFICATIONS FROM TAFB AND SAB AT 12Z WERE T2.0 AND T1.5...RESPECTIVELY. AN AMSU PASS AT 1033Z HELPS TO PLACE THE CENTER ON THE NORTHWEST EDGE OF THE DEEP CONVECTION. BASED ON THESE DATA...THE SYSTEM IS BEING UPGRADED TO A TROPICAL DEPRESSION...THE FIRST OF THE ATLANTIC HURRICANE SEASON. THE INITIAL MOTION IS 050/15. THE DEPRESSION IS EMBEDDED IN A SOUTHWESTERLY STEERING CURRENT AHEAD OF A DEEP-LAYER TROUGH OVER THE CENTRAL UNITED STATES. THIS BASIC PATTERN IS EXPECTED TO PERSIST...AND THE DYNAMICAL MODEL GUIDANCE IS IN PRETTY GOOD AGREEMENT...AT LEAST THROUGH 36 HOURS...WHEN THE SYSTEM BEGINS TO LOSE DEFINITION IN MUCH OF THE GUIDANCE. VERTICAL SHEAR OVER THE SYSTEM IS LIGHT...AND THE CYCLONE IS LIVING OFF THE NARROW GULF STREAM WATERS. AS LONG AS IT REMAINS THERE SOME STRENGTHENING IS POSSIBLE. ALTHOUGH THE SHIPS GUIDANCE DOES NOT SHOW THE SYSTEM REACHING TROPICAL STORM STRENGTH...THE INITIAL SST INPUT TO THE MODEL APPEAR TOO COLD. AS A RESULT...THE OFFICIAL FORECAST WILL CALL FOR THE SYSTEM TO BECOME A TROPICAL STORM OVER THE NEXT DAY OR SO. AFTER THAT...A LOSS OF CONVECTION...AND TROPICAL CHARACTERISTICS...IS EXPECTED. FORECAST POSITIONS AND MAX WINDS INITIAL 28/1500Z 37.3N 71.0W 30 KT 12HR VT 29/0000Z 38.5N 68.4W 35 KT 24HR VT 29/1200Z 40.2N 64.6W 35 KT 36HR VT 30/0000Z 41.5N 60.0W 30 KT 48HR VT 30/1200Z 43.0N 55.0W 25 KT...EXTRATROPICAL 72HR VT 31/1200Z 46.0N 46.0W 25 KT...EXTRATROPICAL 96HR VT 01/1200Z...DISSIPATED $$ FORECASTER FRANKLIN/BEVEN |
