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| #6062 (Received by flhurricane at: 10:42 AM 25.Aug.2004) TCDAT1 TROPICAL DEPRESSION SIX DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT WED AUG 25 2004 TROPICAL DEPRESSION SIX IS LOOKING A LITTLE RAGGED THIS MORNING. WHILE STILL ORGANIZED INTO BANDS...THE ASSOCIATED CONVECTION HAS DECREASED SIGNIFICANTLY IN DEPTH AND COVERAGE SINCE SUNRISE. THE REASON FOR THIS IS NOT CLEAR...ALTHOUGH THE SYSTEM MAY BE INGESTING SOME OF THE DRY AIR SEEN NEARBY IN WATER VAPOR IMAGERY. SATELLITE INTENSITY ESTIMATES ARE 35 KT FROM SAB...30 KT FROM TAFB...AND 25 KT FROM AFWA. THE INITIAL INTENSITY REMAINS 30 KT. THE INITIAL MOTION IS NOW 275/15. THE CYCLONE IS CURRENTLY SOUTH OF A SUBTROPICAL RIDGE. LARGE-SCALE MODELS INDICATE THAT A MID/ UPPER-LEVEL LEVEL LOW CURRENTLY SEEN IN WATER VAPOR IMAGERY JUST SOUTHEAST OF NOVA SCOTIA WILL DIVE SOUTHEASTWARD AND WEAKEN THE RIDGE FROM 48-96 HR AND THEN LIFT OUT TO THE NORTHEAST. IF THIS VERIFIES...IT WOULD ALLOW THE TROPICAL DEPRESSION TO TURN NORTHWESTWARD AFTER 24-36 HR...AND THEN POSSIBLY TURNING MORE WESTWARD BY 120 HR AS THE RIDGE REBUILDS TO THE NORTH. THE DYNAMICAL MODELS GENERALLY AGREE WITH THIS SCENARIO. HOWEVER...THE GFS HAS SHIFTED ITS TRACK CONSIDERABLY TO THE SOUTH AND WEST OF THE GFDL...UKMET...AND NOGAPS. THE OFFICIAL FORECAST TRACK ALSO SHIFTS TO THE LEFT OF THE PREVIOUS TRACK...BUT NOT AS FAR AS THE GFS. THE NEW TRACK IS ALONG THE WESTERN EDGE OF THE OTHER DYNAMICAL MODELS IN BEST AGREEMENT WITH THE GFDL AND THE CONSENSUS MODELS. OTHER THAN THE CURRENT RAGGED APPEARANCE...CONDITIONS GENERALLY APEPAR FAVORABLE FOR THE CYCLONE TO INTENSIFY FOR THE FIRST 72-96 HR. THE INTENSITY FORECAST WILL CALL FOR SLOW STRENGTHENING FOR THE FIRST 48 HR OR SO IN AGREEMENT WITH THE CURRENT ORGANIZATION AND TRENDS...THEN CALL FOR FASTER DEVELOPMENT AS THE SYSTEM NEARS HURRICANE STRENGTH. AFTER 72-96 HR...IF THE CYCLONE TRACKS AS FAR NORTH AS FORECAST...IT MAY ENCOUNTER WESTERLY SHEAR TO THE NORTH OF THE UPPER-LEVEL RIDGE FORECAST TO LIE EAST-WEST ALONG 18-19N. THAT WOULD LIMIT STRENGTHENING AS INDICATED IN THE FORECAST. AN ALTERNATE SCENARIO WOULD BE IF THE CYCLONE STAYS SOUTH OF THE RIDGE AXIS...WHICH WOULD ALLOW GREATER STRENGTHENING THAN CURRENTLY FORECAST. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 25/1500Z 11.4N 39.1W 30 KT 12HR VT 26/0000Z 11.8N 41.3W 35 KT 24HR VT 26/1200Z 12.6N 43.7W 40 KT 36HR VT 27/0000Z 13.5N 45.6W 45 KT 48HR VT 27/1200Z 14.5N 47.2W 50 KT 72HR VT 28/1200Z 16.5N 49.5W 65 KT 96HR VT 29/1200Z 18.5N 52.0W 75 KT 120HR VT 30/1200Z 20.5N 55.0W 75 KT |
