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Tropical Storm PHILIPPE (Text)

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TROPICAL STORM PHILIPPE DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172011
500 AM AST MON SEP 26 2011
 
THE CENTRAL DEEP CONVECTION ASSOCIATED WITH PHILIPPE HAS BEEN
INCREASING IN INTENSITY AND COVERAGE DURING THE PAST SEVERAL
HOURS...WITH CLOUD TOPS AS COLD AS -90C. HOWEVER...THE CURVED BAND
THAT HAS BEEN PRESENT OVER THE WESTERN SEMICIRCLE IS NOW LESS
DISTINCT. THE INITIAL WIND SPEED IS HELD AT 50 KT...WHICH IS THE
AVERAGE OF THE SATELLITE INTENSITY ESTIMATES FROM TAFB...SAB...AND
UW-CIMSS. NIGHT CHANNEL VISIBLE IMAGERY AND A 0453 UTC TRMM
OVERPASS SUGGEST THAT THE LOW-LEVEL CENTER IS LOCATED ON THE
NORTHERN SIDE OF THE CONVECTION.

THE INITIAL MOTION IS 300/11. PHILIPPE IS LOCATED ON THE
SOUTHWESTERN PERIPHERY OF A MID-LEVEL HIGH EXTENDING WESTWARD FROM
WEST AFRICA. THE CYCLONE IS EXPECTED TO TURN NORTHWESTWARD AND SLOW
DOWN DURING THE NEXT COUPLE OF DAYS AS IT BEGINS TO FEEL THE
INFLUENCE OF A DEEP-LAYER TROUGH TO ITS NORTH...AND THE MODELS ARE
IN RELATIVELY GOOD AGREEMENT ON THAT SCENARIO. BEYOND TWO DAYS...
HOWEVER...THE MODELS BECOME QUITE DIVERGENT. THE ECMWF MODEL HAS
SHIFTED EVEN FARTHER WEST...SHOWING A FAIRLY STEADY WEST-NORTHWEST
TO NORTHWEST MOTION. ON THE OTHER HAND...THE GFDL...NOGAPS...AND
GFDN MODELS SHOW PHILIPPE TURNING NORTHEASTWARD BY THE END OF THE
FORECAST PERIOD. THESE DIVERGENT SOLUTIONS APPEAR TO BE ASSOCIATED
WITH THE AMPLITUDE OF THE LONGWAVE TROUGH TO THE NORTH OF PHILIPPE
AND THE VERTICAL INTEGRITY OF THE TROPICAL CYCLONE. THE OFFICIAL
FORECAST...WHICH WAS ADJUSTED SLIGHTLY TO THE WEST...LIES BETWEEN
THE EXTREMES AND ENDS UP NEAR THE GFS AND HWRF MODELS.

THE SHIPS MODEL SHOWS SOUTHWESTERLY SHEAR INCREASING TO 15-20 KT
WITHIN THE NEXT 12 TO 24 HOURS AND PERSISTING THROUGH THE END OF
THE FORECAST PERIOD. THIS LESS FAVORABLE ATMOSPHERIC ENVIRONMENT
AND SLIGHTLY COOLER WATERS ALONG THE FORECAST TRACK ARE NOT
FAVORABLE FOR STRENGTHENING. THEREFORE...THE OFFICIAL FORECAST IS A
LITTLE LOWER THAN THE PREVIOUS ONE AND FOLLOWS THE TREND IN THE
SHIPS/LGEM MODELS...WHICH SHOW A GRADUAL WEAKENING BEYOND 24-36
HOURS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  26/0900Z 14.7N  33.4W   50 KT  60 MPH
 12H  26/1800Z 15.5N  34.5W   55 KT  65 MPH
 24H  27/0600Z 16.4N  35.4W   55 KT  65 MPH
 36H  27/1800Z 17.3N  36.5W   55 KT  65 MPH
 48H  28/0600Z 18.3N  37.8W   50 KT  60 MPH
 72H  29/0600Z 20.8N  40.0W   50 KT  60 MPH
 96H  30/0600Z 23.5N  40.5W   45 KT  50 MPH
120H  01/0600Z 25.5N  40.5W   45 KT  50 MPH
 
$$
FORECASTER CANGIALOSI
 
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