Tropical Storm PHILIPPE

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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
 
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