[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 242056
TCDAT2

TROPICAL STORM PHILIPPE DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172011
500 PM AST SAT SEP 24 2011

A CONVECTIVE BAND WRAPPING AT LEAST HALFWAY AROUND THE WEST SIDE OF
THE CYCLONE HAS DEVELOPED SINCE THE LAST ADVISORY. AS RESULT...THE
INITIAL INTENSITY IS INCREASED TO 35 KT...WHICH IS CONSISTENT WITH
THE 18Z TAFB DVORAK SATELLITE INTENSITY ESTIMATE OF T2.5/35 KT.
UPPER-LEVEL OUTFLOW IS GOOD TO FAIR IN ALL QUADRANTS AND HAS BEEN
SLOWLY IMPROVING.

THE INITIAL MOTION ESTIMATE IS 285/12. THERE IS NO SIGNIFICANT
CHANGE TO THE PREVIOUS TRACK REASONING. PHILIPPE IS EXPECTED TO
MOVE WEST-NORTHWESTWARD AROUND THE SOUTHERN PERIPHERY OF A STRONG
SUBTROPICAL RIDGE LOCATED TO THE NORTH OF THE CYCLONE. BY 48-72
HOURS...A BREAK IN THE RIDGE IS EXPECTED TO DEVELOP BETWEEN 40-45W
LONGITUDE AS A LARGE MID- TO UPPER-LEVEL TROUGH DIGS SOUTHEASTWARD
OVER THE CENTRAL AND EASTERN ATLANTIC. THIS SHOULD RESULT IN
PHILIPPE SLOWING DOWN AND GRADUALLY TURNING TOWARD THE NORTHWEST...
AND THEN TOWARD THE NORTH. THE OFFICIAL FORECAST WAS NUDGED
SLIGHTLY TO THE LEFT OF THE PREVIOUS TRACK DUE TO THE MORE WESTWARD
INITIAL POSITION...AND IS SIMILAR TO THE CONSENSUS MODEL TVCN.

THE BEST OPPORTUNITY FOR PHILIPPE TO STRENGTHEN IS EXPECTED TO BE
DURING THE NEXT 48 HOURS OR SO WHEN THE SHEAR IS THE LOWEST AND THE
THERMODYNAMICS ARE THE GREATEST.  BY 72 HOURS...SOUTHWESTERLY
VERTICAL SHEAR IS FORECAST TO INCREASE TO ABOUT 15 KT...WHICH MAY
NOT BE ENOUGH TO SIGNIFICANTLY INHIBIT THE INTENSIFICATION PROCESS.
AS A RESULT...PHILIPPE IS EXPECTED TO REACH HURRICANE STATUS IN
48-72 HOURS...AND THEN LEVEL OFF SIMILAR TO THAT FORECAST BY THE
SHIPS AND LGEM STATISTICAL-DYNAMICAL MODELS. HOWEVER...IT IS WORTH
NOTING THAT THE GFDL AND EXPERIMENTAL HFIP INTENSITY MODELS MAKE
PHILIPPE A CATEGORY TWO HURRICANE BY DAYS 4 AND 5.

FORECAST POSITIONS AND MAX WINDS

INIT  24/2100Z 11.2N  27.9W   35 KT  40 MPH
 12H  25/0600Z 11.6N  29.6W   40 KT  45 MPH
 24H  25/1800Z 12.5N  31.7W   45 KT  50 MPH
 36H  26/0600Z 13.6N  33.3W   55 KT  65 MPH
 48H  26/1800Z 14.8N  34.9W   65 KT  75 MPH
 72H  27/1800Z 16.8N  36.8W   65 KT  75 MPH
 96H  28/1800Z 19.5N  38.5W   65 KT  75 MPH
120H  29/1800Z 22.0N  39.0W   65 KT  75 MPH

$$
FORECASTER STEWART


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