[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 282037
TCDAT2

TROPICAL STORM PHILIPPE DISCUSSION NUMBER  19
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172011
500 PM AST WED SEP 28 2011

THE APPEARANCE OF PHILIPPE ON GEOSTATIONARY SATELLITE IMAGERY IS
UNCHANGED SINCE THIS MORNING. CONVECTION IS LIMITED TO THE NORTHERN
SEMICIRCLE OF THE STORM...AND THE LOW-LEVEL CENTER HAS BEEN
PERIODICALLY EXPOSED DURING THE AFTERNOON. THE INITIAL INTENSITY
REMAINS 35 KT BASED ON A BLEND OF DVORAK ESTIMATES FROM TAFB AND
SAB.

PHILIPPE CONTINUES TO MOVE TOWARD THE WEST-NORTHWEST AT ABOUT 10 KT.
THE GLOBAL MODELS ALL SUGGEST THAT A WEAKNESS IN THE SUBTROPICAL
RIDGE...INDUCED BY A LARGE MID-LATITUDE TROUGH OVER THE NORTHERN
ATLANTIC...WILL ALLOW PHILIPPE TO MOVE NORTHWESTWARD OVER THE NEXT
TWO DAYS. AFTER THAT...THE RIDGE IS FORECAST TO REBUILD...RESULTING
IN A TURN BACK TOWARD THE WEST. MOST OF THE MODEL GUIDANCE NOW
SUGGESTS A SLIGHTLY STRONGER RIDGE...RESULTING IN AN MORE WESTWARD
MOTION AND AN INCREASED FORWARD SPEED OF THE CYCLONE. THEREFORE...
THE OFFICIAL FORECAST HAS BEEN ADJUSTED IN THAT DIRECTION TOWARD
THE NEW MULTI-MODEL CONSENSUS.

AN UPPER-LEVEL TROUGH CONTINUES TO PRODUCE STRONG VERTICAL SHEAR
OVER PHILIPPE....WHICH IS EXPECTED TO CONTINUE FOR THE NEXT 12 TO
24 HOURS. THE SHIPS MODEL NOW SUGGESTS THAT THE SHEAR COULD BRIEFLY
DECREASE BETWEEN 24 AND 48 HOURS...WHICH SHOULD ALLOW PHILIPPE TO
MAINTAIN ITS INTENSITY FOR THE NEXT 2 OR 3 DAYS. GIVEN THIS...THE
THE OFFICIAL FORECAST NOW MAINTAINS PHILIPPE AS A MINIMAL TROPICAL
STORM FOR 72 HOURS. AFTER THAT...THE SHEAR IS EXPECTED TO INCREASE
SUBSTANTIALLY...AND PHILIPPE IS FORECAST TO WEAKEN TO A REMNANT LOW
BY THE END OF THE PERIOD.

FORECAST POSITIONS AND MAX WINDS

INIT  28/2100Z 17.0N  39.7W   35 KT  40 MPH
 12H  29/0600Z 17.9N  41.0W   35 KT  40 MPH
 24H  29/1800Z 19.3N  42.7W   35 KT  40 MPH
 36H  30/0600Z 20.9N  44.3W   35 KT  40 MPH
 48H  30/1800Z 22.1N  46.1W   35 KT  40 MPH
 72H  01/1800Z 23.6N  49.3W   35 KT  40 MPH
 96H  02/1800Z 25.0N  53.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  03/1800Z 25.0N  56.5W   30 KT  35 MPH...POST-TROP/REMNT LOW

$$
FORECASTER BRENNAN/ZELINSKY



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