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Tropical Storm PHILIPPE


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TROPICAL STORM PHILIPPE DISCUSSION NUMBER  37
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172011
500 AM AST MON OCT 03 2011

THE STRUCTURE OF PHILIPPE HAS CHANGED LITTLE DURING THE LAST SEVERAL
HOURS. MICROWAVE DATA INDICATE THAT THE LOW-LEVEL CENTER IS LOCATED
NEAR THE NORTHWESTERN EDGE OF THE CONVECTIVE MASS...WHICH HAS
EXPANDED SLIGHTLY DURING THE PAST FEW HOURS. AN ASCAT OVERPASS JUST
AFTER 0000 UTC INDICATED THAT MAXIMUM WINDS WERE AROUND 45 KT. THE
LATEST DVORAK CI NUMBERS FROM TAFB AND SAB ARE ALSO 45 KT...
THEREFORE...THE INITIAL WIND SPEED IS HELD AT THAT VALUE.

THE SHIPS MODEL INDICATES THAT ABOUT 30 KT OF NORTHERLY SHEAR IS
CURRENTLY AFFECTING PHILIPPE. HOWEVER...AS MENTIONED IN THE
PREVIOUS DISCUSSION...THERE IS SOME INDICATION THAT THE SHEAR IS
PRIMARILY IN THE HIGHER LEVELS OF THE ATMOSPHERE RATHER THAN
EXTENDING THROUGHOUT THE DEPTH OF THE TROPOSPHERE. THIS COULD BE
THE REASON WHY PHILIPPE HAS NOT WEAKENED SIGNIFICANTLY DURING THE
PAST FEW DAYS DESPITE BEING IN ANALYZED SHEAR OF 30 KT OR HIGHER. 
NONETHELESS...THE SHEAR IS EXPECTED TO LESSEN IN THE 36-72 HOUR
TIME FRAME...AND THAT COULD ALLOW THE TROPICAL STORM TO STRENGTHEN. 
BEYOND A FEW DAYS...SOUTHWESTERLY SHEAR IS ANTICIPATED TO INCREASE
SIGNIFICANTLY AND SHOULD INDUCE WEAKENING.  THE OFFICIAL FORECAST
IS ONCE AGAIN NEAR THE INTENSITY MODEL CONSENSUS AND IS A LITTLE
HIGHER THAN THE PREVIOUS ONE.  

PHILIPPE APPEARS TO NOW BE MOVING A LITTLE SOUTH OF DUE WEST...AND
THE LATEST INITIAL MOTION ESTIMATE IS 265/10. THIS GENERAL MOTION
IS EXPECTED TO CONTINUE FOR THE NEXT 24 TO 36 HOURS AS THE STORM
REMAINS TO THE SOUTH OF A MID-LEVEL RIDGE. THEREAFTER...THE RIDGE
IS EXPECTED TO WEAKEN IN RESPONSE TO A LARGE TROUGH MOVING INTO THE
WESTERN ATLANTIC. THIS SHOULD CAUSE PHILIPPE TO GRADUALLY TURN
NORTHWARD IN 48 TO 72 HOURS...AND THEN NORTHEASTWARD IN THE THREE TO
FIVE DAY TIME PERIOD. ALTHOUGH THE MODELS ARE IN GOOD AGREEMENT ON
THE EVOLUTION OF THE LARGE-SCALE FLOW PATTERN...THERE REMAINS
CONSIDERABLE SPREAD IN THE TRACK GUIDANCE FOR PHILIPPE. THIS SPREAD
IS IN PART DUE TO THE DIFFERENCES IN THE STRENGTH OF PHILIPPE IN
THE MODELS. IN GENERAL...THE GUIDANCE HAS TRENDED A LITTLE FASTER AT
THE END OF THE FORECAST PERIOD AND THE OFFICIAL TRACK FORECAST HAS
FOLLOWED SUIT. 

THE 34-KT WIND RADII HAVE BEEN ADJUSTED BASED ON THE AFOREMENTIONED
ASCAT PASS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  03/0900Z 25.8N  54.9W   45 KT  50 MPH
 12H  03/1800Z 25.6N  56.6W   45 KT  50 MPH
 24H  04/0600Z 25.5N  58.9W   40 KT  45 MPH
 36H  04/1800Z 25.8N  60.7W   40 KT  45 MPH
 48H  05/0600Z 26.5N  61.3W   45 KT  50 MPH
 72H  06/0600Z 28.3N  60.1W   55 KT  65 MPH
 96H  07/0600Z 30.5N  57.0W   45 KT  50 MPH
120H  08/0600Z 33.0N  52.5W   40 KT  45 MPH
 
$$
FORECASTER CANGIALOSI
 
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