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#30187 (Received by flhurricane at: 5:18 PM 05.Jul.2005) TCDAT4 TROPICAL STORM DENNIS DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT TUE JUL 05 2005 DENNIS IS STEADILY BECOMING MORE ORGANIZED. DVORAK CLASSIFICATIONS AT 18Z WERE T2.5/35 KT FROM BOTH TAFB AND SAB...AND THIS WILL BE THE ADVISORY INTENSITY. CONVECTION HAD BEEN A BIT ON THE SPOTTY SIDE EARLIER TODAY...BUT IT HAS SINCE BECOME MORE CONSOLIDATED NEAR THE ESTIMATED CENTER...SO DENNIS SEEMS POISED TO INTENSIFY THIS EVENING. THE CARIBBEAN SEA AHEAD OF THE STORM IS PLENTY WARM...AND THE VERTICAL WIND SHEAR IS EXPECTED TO REMAIN WEAK THROUGHOUT THE FORECAST PERIOD. SHIPS BRINGS THE SYSTEM TO 92 KT...AND GFDL FORECASTS 76 KT...IN 72 HOURS BEFORE THE SYSTEM CROSSES CUBA. DUE TO THE UNCERTAINTIES WITH INTENSITY FORECASTING...INCLUDING IN THIS CASE HOW DENNIS WILL INTERACT WITH THE LARGER ISLANDS OF HISPANIOLA AND CUBA...THE OFFICIAL FORECAST IS LITTLE MORE CONSERVATIVE THAN SHIPS AND GFDL BUT STILL MAKES DENNIS A HURRICANE BY 36 HOURS. DENNIS IS MOVING FAIRLY RAPIDLY...WITH INITIAL MOTION ESTIMATED AT 290/17. MODEL GUIDANCE IS IN TIGHT AGREEMENT ON THIS GENERAL MOTION CONTINUING FOR ABOUT THE NEXT THREE DAYS...WITH THE PRIMARY STEERING MECHANISM BEING THE SUBTROPICAL RIDGE CURRENTLY CENTERED OVER THE NORTHWESTERN BAHAMAS. BEYOND THAT TIME...A WEAKNESS IN THE RIDGE IS ANTICIPATED TO DEVELOP...AS A MID/UPPER LEVEL TROUGH SHARPENS OVER THE EASTERN UNITED STATES. THIS SHOULD INDUCE A GRADUAL DECREASE IN FORWARD SPEED AND A TURN TOWARD THE NORTHWEST LATE IN THE FORECAST PERIOD. THE CURRENT FORECAST IS ALONG BUT A LITTLE FASTER THAN THE PREVIOUS ADVISORY TRACK. BASED ON THE FORECAST...NEW WATCHES AND WARNINGS BE ISSUED FOR THE DOMINICAN REPUBLIC...HAITI...AND JAMAICA. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 05/2100Z 14.2N 68.3W 35 KT 12HR VT 06/0600Z 15.4N 70.6W 45 KT 24HR VT 06/1800Z 17.0N 73.4W 55 KT 36HR VT 07/0600Z 18.4N 75.8W 65 KT 48HR VT 07/1800Z 19.9N 78.4W 70 KT 72HR VT 08/1800Z 22.0N 82.0W 75 KT 96HR VT 09/1800Z 24.0N 84.5W 80 KT 120HR VT 10/1800Z 26.5N 86.5W 80 KT |