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#463905 (Received by flhurricane at: 4:38 PM 03.Oct.2011) TCDAT2 TROPICAL STORM PHILIPPE DISCUSSION NUMBER 39 NWS NATIONAL HURRICANE CENTER MIAMI FL AL172011 500 PM AST MON OCT 03 2011 PHILIPPE IS TILTED FROM NORTH TO SOUTH WITH HEIGHT DUE TO CONTINUED NORTHERLY SHEAR. DVORAK INTENSITY ESTIMATES ARE NOW T3.5...OR 55 KT...FROM BOTH TAFB AND SAB...AND THAT WILL REMAIN THE INTENSITY FOR THIS ADVISORY. THE SMOOTHED INITIAL MOTION REMAINS 255 DEGREES AT 10 KT. THE CURRENT WEST-SOUTHWESTWARD MOTION SHOULD BEGIN TO VEER TO THE WEST AND WEST-NORTHWEST OVER THE NEXT 24 TO 36 HOURS AS PHILIPPE REACHES A WEAKNESS IN THE SUBTROPICAL RIDGE CREATED BY A LARGE CUT-OFF LOW NEAR THE CANADIAN MARITIMES. RE-CURVATURE AHEAD OF THE LOW IS EXPECTED BY 48-72 HOURS...BUT THE TRACK GUIDANCE FROM THE 12 UTC MODELS HAS SHIFTED WESTWARD AND TRENDED SLOWER. BASED ON THIS CHANGE...THE NEW FORECAST IS SHIFTED WEST OF THE PREVIOUS ONE THROUGH 72 HOURS AND THEN SLOWED DOWN ON DAYS 4 AND 5. PHILIPPE HAS ABOUT ANOTHER 36 HOURS OF BEING IN A HIGH-SHEAR ENVIRONMENT...AND NO SIGNIFICANT CHANGES IN INTENSITY ARE EXPECTED DURING THAT TIME. BY 48 HOURS...THE CYCLONE SHOULD ENTER AN AREA OF UPPER-LEVEL RIDGING...WHICH COULD FAVOR SOME STRENGTHENING. ALL OF THE INTENSITY MODELS SHOW THIS SCENARIO...AND THE STATISTICAL MODELS HAVE COME INTO BETTER AGREEMENT WITH THE DYNAMICAL MODELS SHOWING PHILIPPE BECOMING A HURRICANE AT THE LATTER PART OF THE FORECAST PERIOD...EVEN THOUGH STRONG WESTERLY SHEAR IS FORECAST TO DEVELOP BY THAT TIME. IT IS STILL A LITTLE DISCONCERTING THAT THE 12 UTC CYCLE OF THE ECMWF MODEL CONTINUES TO DISSIPATE THE SURFACE CIRCULATION OF PHILIPPE AHEAD OF A COLD FRONT BY 48 HOURS. HOWEVER...THE UPPER-LEVEL PATTERN IN THAT MODEL SUGGESTS THAT THE LEFTOVER VORTEX COULD BE LOCATED IN A FAVORABLE AREA OF UPPER-LEVEL DIFFLUENCE. IF THE TRACK OF PHILIPPE CONTINUES TO TREND SLOWER AND FARTHER SOUTH...THEN THERE COULD BE A DELAY BEFORE IT IS NEGATIVELY AFFECTED BY THE DEVELOPING SHEAR. THE OFFICIAL FORECAST THEREFORE ALLOWS PHILIPPE TO BECOME A HURRICANE AROUND DAY 4...BUT IT IS STILL LOWER THAN THE STATISTICAL GUIDANCE AT THAT TIME. FORECAST POSITIONS AND MAX WINDS INIT 03/2100Z 24.6N 56.6W 55 KT 65 MPH 12H 04/0600Z 24.5N 58.5W 55 KT 65 MPH 24H 04/1800Z 24.8N 60.5W 55 KT 65 MPH 36H 05/0600Z 25.2N 61.6W 55 KT 65 MPH 48H 05/1800Z 25.8N 61.9W 55 KT 65 MPH 72H 06/1800Z 27.5N 61.0W 60 KT 70 MPH 96H 07/1800Z 29.0N 58.0W 65 KT 75 MPH 120H 08/1800Z 30.5N 54.5W 55 KT 65 MPH $$ FORECASTER BERG |