[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 252047
TCDAT2

TROPICAL STORM PHILIPPE DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172011
500 PM AST SUN SEP 25 2011

THE APPEARANCE OF PHILIPPE ON VISIBLE IMAGERY HAS IMPROVED OVER THE
PAST FEW HOURS. CONVECTION HAS PERSISTED ALONG A CURVED BAND
LOCATED TO THE WEST AND SOUTH OF THE MAIN CENTER OF CIRCULATION...
AND A CDO-LIKE CENTRAL CONVECTIVE FEATURE HAS ALSO DEVELOPED.
DVORAK ESTIMATES OF INTENSITY HAVE INCREASED SINCE THE LAST
ADVISORY...AND A BLEND OF THESE ESTIMATES YIELDS AN INITIAL
INTENSITY OF 50 KT.

PHILIPPE IS MOVING TO THE NORTHWEST TOWARD A WEAKNESS IN THE
SUBTROPICAL RIDGE.  THIS MOTION IS EXPECTED TO CONTINUE FOR THE
NEXT COUPLE OF DAYS...AND THERE IS GOOD AGREEMENT AMONG THE MODELS
THROUGH 48 HOURS. BEYOND THAT TIME...THE UNCERTAINTY INCREASES AS
SOME MODELS RECURVE THE TROPICAL CYCLONE TOWARDS THE NORTHEAST...
WHILE OTHERS ALLOW THE RIDGE TO REBUILD...RESULTING IN A MORE
WESTWARD TRACK. THIS DISCREPANCY IS LIKELY RELATED TO THE INTENSITY
OF PHILIPPE...AS A DEEPER AND STRONGER SYSTEM WILL LIKELY MOVE
FARTHER NORTH...WHILE A WEAKER SYSTEM WILL BE STEERED TO THE WEST
BY LOWER LEVEL EASTERLIES. OVERALL...THE GUIDANCE ENVELOPE HAS
SHIFTED WESTWARD...AND THE TRACK HAS BEEN NUDGED IN THAT DIRECTION
ACCORDINGLY.

THE ENVIRONMENT AROUND PHILIPPE CONTINUES TO BE CONDUCIVE FOR
INTENSIFICATION. THIS FAVORABLE ENVIRONMENT IS EXPECTED TO PERSIST
FOR THE NEXT 24 TO 36 HOURS. AFTER THAT...PHILIPPE WILL BEGIN
INTERACTING WITH AN UPPER-LEVEL TROUGH...WHICH SHOULD RESULT IN A
SUBSTANTIAL INCREASE IN THE VERTICAL WIND SHEAR. ADDITIONALLY...
THE CYCLONE WILL BEGIN MOVING OVER COOLER SSTS AND INTO A MORE
STABLE ENVIRONMENT. THE OFFICIAL INTENSITY FORECAST HAS NOT CHANGED
SUBSTANTIALLY...AND THE FORECAST STILL CALLS FOR PHILIPPE TO
APPROACH HURRICANE INTENSITY WITHIN THE NEXT COUPLE OF DAYS.

FORECAST POSITIONS AND MAX WINDS

INIT  25/2100Z 13.2N  31.7W   50 KT  60 MPH
 12H  26/0600Z 14.0N  33.1W   55 KT  65 MPH
 24H  26/1800Z 15.1N  34.7W   60 KT  70 MPH
 36H  27/0600Z 16.1N  35.9W   65 KT  75 MPH
 48H  27/1800Z 17.3N  36.9W   60 KT  70 MPH
 72H  28/1800Z 20.0N  38.7W   55 KT  65 MPH
 96H  29/1800Z 22.5N  39.5W   55 KT  65 MPH
120H  30/1800Z 25.0N  39.5W   50 KT  60 MPH

$$
FORECASTER ZELINSKY/STEWART



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