[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 050236
TCDAT2

TROPICAL STORM PHILIPPE DISCUSSION NUMBER  44
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172011
1100 PM AST TUE OCT 04 2011

THE STRUCTURE OF PHILIPPE HAS AGAIN CHANGED LITTLE SINCE THE LAST
ADVISORY.  CONVENTIONAL AND MICROWAVE SATELLITE DATA SHOW THAT THE
LOW-LEVEL CENTER IS LOCATED NEAR THE NORTHWESTERN EDGE OF THE
CONVECTION...WITH THE MICROWAVE IMAGERY SUGGESTING A MID-LEVEL EYE
IS SOUTHEAST OF THE SURFACE CENTER.  SATELLITE INTENSITY ESTIMATES
ARE 55 KT FROM TAFB AND 45 KT FROM SAB...AND...BASED ON THIS AND
THE LACK OF CHANGE IN ORGANIZATION...THE INITIAL INTENSITY REMAINS
55 KT.

PHILIPPE HAS BEGUN ITS FORECAST NORTHWARD TURN WITH THE INITIAL
MOTION NOW 300/6.  THE CYCLONE IS NEAR THE WESTERN END OF THE
SUBTROPICAL RIDGE...WITH WATER VAPOR AND INFRARED IMAGERY SHOWING A
DEEP-LAYER TROUGH AND ASSOCIATED SURFACE COLD FRONT TO THE
NORTHWEST.  ALL GUIDANCE AGREES THAT PHILIPPE SHOULD RECURVE ON THE
EASTERN SIDE OF THE TROUGH DURING THE NEXT 48-72 HOURS.  HOWEVER...
THERE IS A SIGNIFICANT SPREAD IN THE TRACK GUIDANCE BASED ON THE
MODEL FORECASTS OF THE EVENTUAL FATE OF PHILIPPE.  THE GFS...
CANADIAN...NOGAPS...GFDL...AND HWRF MODELS SHOW THE CYCLONE
REMAINING STRONG THROUGH EXTRATROPICAL TRANSITION AND FORECAST A
NORTHWARD OR EVEN WEST OF NORTH MOTION BY 120 HOURS AS PHILIPPE
MERGES WITH THE TROUGH.  THE ECMWF AND UKMET SHOW A MUCH WEAKER
PHILIPPE MOVING EASTWARD AHEAD OF THE COLD FRONT THAT EVENTUALLY
ABSORBS THE TROPICAL CYCLONE.  THE OFFICIAL FORECAST FOLLOWS THE
EXTRATROPICAL TRANSITION SCENARIO AND SHOWS PHILIPPE TURNING
NORTHWARD BY 120 HOURS.  THE NEW FORECAST IS FASTER THAN THE
PREVIOUS FORECAST...BUT IS SLOWER THAN THE MODEL CONSENSUS.

WHILE PHILIPPE REMAINS UNDER NORTHERLY VERTICAL WIND SHEAR...
ANALYSES FROM THE SHIPS MODEL AND CIMSS AT THE UNIVERSITY OF
WISCONSIN SUGGEST THE SHEAR IS GRADUALLY DECREASING.  THE DYNAMICAL
MODELS SUGGESTS THERE WILL BE A 36-48 HOUR WINDOW OF MORE FAVORABLE
CONDITIONS AS THE CYCLONE PASSES THROUGH AN UPPER-LEVEL RIDGE...AND
MOST OF THE INTENSITY GUIDANCE RESPONDS TO THIS BY FORECASTING
INTENSIFICATION.  AFTER 48 HOURS...THE SHEAR SHOULD INCREASE
AGAIN...WITH EXTRATROPICAL TRANSITION FORECAST TO START AT AROUND
96 HOURS AND FINISH BY 120 HOURS.  THE NEW INTENSITY FORECAST IS
UNCHANGED FROM THE PREVIOUS ADVISORY AND IS IN BEST AGREEMENT WITH
THE SHIPS AND LGEM MODELS.  IT SHOULD BE NOTED THAT THE GFDL AND
HWRF MODELS FORECAST A HIGHER PEAK INTENSITY THAN SHIPS AND
LGEM...SO IT CANNOT BE RULED OUT THAT PHILIPPE COULD BE STRONGER
THAN CURRENTLY FORECAST.

FORECAST POSITIONS AND MAX WINDS

INIT  05/0300Z 24.6N  60.4W   55 KT  65 MPH
 12H  05/1200Z 25.3N  61.1W   55 KT  65 MPH
 24H  06/0000Z 26.1N  61.5W   60 KT  70 MPH
 36H  06/1200Z 27.2N  60.9W   65 KT  75 MPH
 48H  07/0000Z 28.4N  59.6W   65 KT  75 MPH
 72H  08/0000Z 30.5N  54.5W   60 KT  70 MPH
 96H  09/0000Z 35.0N  48.0W   55 KT  65 MPH
120H  10/0000Z 40.5N  45.5W   55 KT  65 MPH...POST-TROP/EXTRATROP

$$
FORECASTER BEVEN



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