Tropical Storm PHILIPPE

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TROPICAL STORM PHILIPPE DISCUSSION NUMBER  45
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172011
500 AM AST WED OCT 05 2011
 
PHILIPPE CONTINUES TO HAVE A SHEARED PRESENTATION ON SATELLITE
IMAGES...ALTHOUGH THERE IS SOME EVIDENCE OF A VERY RAGGED EYE
OCCASIONALLY.  DVORAK ESTIMATES ARE UNCHANGED FROM SIX HOURS
AGO...SO THE INITIAL INTENSITY WILL REMAIN 55 KT.  MOST OF THE
GLOBAL MODELS SUGGEST THAT PHILIPPE WILL MOVE BENEATH AN UPPER-
LEVEL RIDGE AXIS LATER TODAY...RESULTING IN A PERIOD OF LOWER SHEAR
LASTING FOR A DAY OR SO.  ALL OF THE MODELS SHOW SOME
INTENSIFICATION DURING THAT PERIOD...AND THE OFFICIAL FORECAST
FOLLOWS THAT SOLUTION...ALBEIT ON THE LOWER END OF THE GUIDANCE
SPECTRUM BELOW THE MODEL CONSENSUS.  AFTER THAT TIME...
SOUTHWESTERLY SHEAR SHOULD SIGNIFICANTLY INCREASE DUE TO A LARGE
TROUGH OVER THE WESTERN ATLANTIC.  USUALLY A MORE SIGNIFICANT
WEAKENING WOULD BE CALLED FOR WITH SUCH STRONG SHEAR...BUT ONLY A
MINOR DECREASE IN STRENGTH IS FORECAST DUE TO SIGNIFICANT
BAROCLINIC FORCING.  EXTRATROPICAL TRANSITION IS EXPECTED BY DAY
4...AND IT IS WORTH NOTING THAT MOST OF THE GLOBAL GUIDANCE EVEN
HAVE PHILIPPE EXTRATROPICAL NEAR DAY 3 IN THE LATEST RUNS...BUT I
DID NOT WANT TO SHOW SUCH A LARGE CHANGE FROM THE PREVIOUS
FORECAST.
 
SOME COARSE AMSU DATA SUGGEST THAT THE TROPICAL CYCLONE IS MOVING AT
300/5...ABOUT THE SAME AS PREVIOUS.  A RELATIVELY SHARP TURN TO THE
NORTH AND NORTHEAST IS LIKELY WITHIN A DAY OR SO DUE TO THE
AFOREMENTIONED TROUGH OVER THE WESTERN ATLANTIC.  THIS TROUGH
SHOULD ALSO CAUSE PHILIPPE TO MOVE AT AN INCREASING PACE BY LATE
THURSDAY AS THE TROPICAL CYCLONE IS STEERED BY THE STRONGER
MID-LATITUDE FLOW.  THE NEW FORECAST IS CLOSE TO THE PREVIOUS
ONE...BUT IS A BIT FASTER TO ACCOUNT FOR RECENT MODEL TRENDS.  THE
EXTRATROPICAL TRANSITION APPEARS TO BE A DIFFICULT ONE TO
FORECAST...WITH THE MAIN DISAGREEMENT BEING WHETHER PHILIPPE WILL
BECOME THE MAIN NON-TROPICAL LOW OR BECOME ABSORBED INTO THE LARGER
EXTRATROPICAL CYCLONE.  GIVEN THE SMALL SIZE OF PHILIPPE...THE NHC
FORECAST WILL GO WITH THE ABSORBED SCENARIO.
 
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/0900Z 24.7N  60.8W   55 KT  65 MPH
 12H  05/1800Z 25.3N  61.4W   55 KT  65 MPH
 24H  06/0600Z 26.5N  61.2W   60 KT  70 MPH
 36H  06/1800Z 27.8N  60.1W   65 KT  75 MPH
 48H  07/0600Z 28.9N  58.2W   60 KT  70 MPH
 72H  08/0600Z 31.5N  52.0W   55 KT  65 MPH
 96H  09/0600Z 38.0N  46.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  10/0600Z...ABSORBED
 
$$
FORECASTER BLAKE
 
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