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| #365670 (Received by flhurricane at: 10:40 AM 03.Aug.2010) TCDAT4 TROPICAL STORM COLIN DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042010 1100 AM EDT TUE AUG 03 2010 COLIN HAS A VERY RAGGED APPEARANCE THIS MORNING. THE CONVECTIVE BANDING SEEN EARLIER HAS WEAKENED...LEAVING A SMALL CONVECTIVE MASS NEAR THE CENTER AND A SECOND CONVECTIVE MASS TO THE NORTH. SATELLITE INTENSITY ESTIMATES ARE 35 KT FROM TAFB AND 30 KT FROM SAB...AND BASED ON THIS THE INITIAL INTENSITY REMAINS 35 KT. IT SHOULD BE NOTED THAT IT IS HARD TO FIND WESTERLY WINDS IN THE LOW CLOUD MOTIONS SOUTH OF THE CENTRAL CONVECTION...AND THERE IS SOME QUESTION AS TO WHETHER COLIN STILL HAS A CLOSED CIRCULATION. THE SYSTEM HAS TURNED A LITTLE TO THE LEFT DURING THE PAST SEVERAL HOURS. THE INITIAL MOTION IS 280/21...AND THE SHORT-TERM MOTION MAY BE EVEN FASTER. COLIN IS ON THE SOUTH SIDE OF THE LOW/ MID-LEVEL BERMUDA HIGH...AND IN 48-72 HR SHOULD BE APPROACHING A WEAKNESS OR BREAK IN THE HIGH CAUSED BY A MID/UPPER-LEVEL TROUGH NEAR THE SOUTHEASTERN COAST OF THE UNITED STATES. THIS PATTERN SHOULD INITIALLY STEER COLIN RAPIDLY TOWARD THE WEST-NORTHWEST... FOLLOWED BY A TURN TOWARD THE NORTHWEST WITH A DECREASE IN FORWARD SPEED AFTER 48 HR. THE MODEL GUIDANCE GENERALLY AGREES WITH THIS SCENARIO. HOWEVER...THERE IS A CONSIDERABLE SPREAD IN THE TRACKS BY THE END OF THE FORECAST PERIOD. THE GFDL AND HWRF FORECAST AN EAST OF NORTH MOTION ON THE RIGHT EDGE OF THE GUIDANCE ENVELOPE BY 120 HR...WHILE THE CANADIAN AND GFDN ARE ON THE LEFT EDGE WITH NO NORTHWARD TURN BEFORE 120 HR. THE NEW FORECAST TRACK IS SHIFTED 60-90 N MI TO THE SOUTHWEST BASED ON THE INITIAL POSITION AND MOTION. IT IS IN BEST AGREEMENT WITH THE ECMWF AND LIES TO THE LEFT OF THE CONSENSUS MODELS AND THE CENTER OF THE GUIDANCE ENVELOPE. CURRENTLY...COLIN IS EXPERIENCING WESTERLY VERTICAL SHEAR LIKELY CAUSED BY THE LOWER PART OF THE STORM OUTRUNNING THE UPPER PART. THIS IS FORECAST TO CONTINUE FOR THE NEXT 24-36 HR DUE TO THE RAPID MOTION. AFTER THAT TIME...THE SYSTEM IS EXPECTED TO ENCOUNTER INCREASING UPPER-LEVEL WESTERLY WINDS CAUSED BY THE WESTERN ATLANTIC TROUGH. THIS PATTERN DOES NOT APPEAR FAVORABLE FOR SIGNIFICANT STRENGTHENING...AND THE ONLY INTENSITY GUIDANCE THAT CURRENTLY CALLS FOR COLIN TO BECOME A HURRICANE IS CLIMATOLOGY/ PERSISTENCE. GIVEN THE CURRENT TRENDS AND THE FORECAST SHEAR...THE INTENSITY FORECAST IS A LITTLE WEAKER THAN THE PREVIOUS FORECAST... WITH AN INTENSITY OF 45 KT THROUGH MOST OF THE FORECAST PERIOD. AN ALTERNATIVE SCENARIO IS THAT COLIN COULD DEGENERATE TO AN OPEN WAVE DUE TO A COMBINATION OF ITS RAPID MOTION AND WESTERLY SHEAR. INTERESTS IN THE NORTHERN LEEWARD ISLANDS AND THE VIRGIN ISLANDS SHOULD FOLLOW THE PROGRESS OF COLIN. FORECAST POSITIONS AND MAX WINDS INITIAL 03/1500Z 14.2N 49.5W 35 KT 12HR VT 04/0000Z 15.0N 52.7W 40 KT 24HR VT 04/1200Z 16.5N 56.6W 45 KT 36HR VT 05/0000Z 18.3N 60.4W 45 KT 48HR VT 05/1200Z 20.2N 63.7W 45 KT 72HR VT 06/1200Z 23.0N 67.5W 45 KT 96HR VT 07/1200Z 26.5N 69.5W 45 KT 120HR VT 08/1200Z 29.0N 70.5W 50 KT $$ FORECASTER BEVEN |
