[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 272037
TCDAT2

TROPICAL STORM PHILIPPE DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172011
500 PM AST TUE SEP 27 2011

WESTERLY WIND SHEAR ASSOCIATED WITH AN UPPER-LEVEL TROUGH HAS
DISPLACED THE DEEP CONVECTION MORE THAN 100 NM TO THE EAST OF THE
LOW-LEVEL CENTER. GIVEN THE DECREASE IN ORGANIZATION OF THE
CYCLONE...THE INITIAL INTENSITY IS LOWERED TO 35 KT IN AGREEMENT
WITH THE FINAL-T NUMBERS FROM TAFB AND SAB. OUTPUT FROM THE SHIPS
MODEL SUGGESTS THAT THE SHEAR WILL BE RATHER RELENTLESS OVER
PHILIPPE DURING THE FORECAST PERIOD...ONLY DROPPING BELOW 15 KT
BRIEFLY IN A COUPLE OF DAYS. THE SHEAR COMBINED WITH MARGINAL SSTS
SHOULD RESULT IN SLOW WEAKENING OF PHILIPPE DURING THE NEXT DAY OR
SO...AND LITTLE CHANGE THEREAFTER. THE NEW NHC FORECAST IS CLOSE TO
THE LGEM MODEL THROUGH THE PERIOD...AND WELL BELOW THE DYNAMICAL
HURRICANE MODELS WHICH CONTINUE TO INSIST ON STRENGTHENING THE
CYCLONE DESPITE THE HOSTILE ENVIRONMENT. IT IS POSSIBLE THAT
PHILIPPE COULD BECOME A POST-TROPICAL REMNANT LOW DURING THE PERIOD
IF THE CONVECTION BECOMES DISPLACED EVEN FARTHER FROM THE CENTER.

THE INITIAL MOTION IS NOW TOWARD THE WEST-NORTHWEST...OR 285/6...
TAKING PHILIPPE A LITTLE TO THE LEFT OF THE PREVIOUS NHC TRACK.
PHILIPPE CONTINUES TO BE STEERED BY A NARROW MID-LEVEL RIDGE TO THE
NORTH...AND SHOULD CONTINUE MOVING AROUND THE PERIPHERY OF THIS
FEATURE DURING THE PERIOD. THIS SHOULD RESULT IN A GENERAL WEST-
NORTHWEST OR NORTHWEST MOTION OVER THE NEXT COUPLE OF DAYS...WITH A
BEND BACK TO THE LEFT AND FASTER FORWARD SPEED AT THE END OF THE
PERIOD AS THE RIDGE AMPLIFIES NORTH OF PHILIPPE. THE GUIDANCE FOR
HAS SHIFTED QUITE A BIT TO THE LEFT AND IS ALSO FASTER FOR THIS
CYCLE. THE NEW NHC TRACK FORECAST IS SIGNIFICANTLY TO THE LEFT OF
AND FASTER THAN THE PREVIOUS ONE DUE TO THE INITIAL MOTION AND THE
TREND IN THE GUIDANCE. EVEN WITH THIS ADJUSTMENT TO THE LEFT...THE
NEW NHC TRACK STILL LIES TO THE RIGHT OF MOST OF THE RELIABLE
MODELS AND THE NEW MULTI-MODEL CONSENSUS. IF PHILIPPE IS BECOMING A
SHALLOWER CYCLONE...A TRACK EVEN MORE TOWARD THE WEST THAN SHOWN
HERE IS POSSIBLE...SIMILAR TO THAT OF THE ECMWF.


FORECAST POSITIONS AND MAX WINDS

INIT  27/2100Z 16.0N  36.0W   35 KT  40 MPH
 12H  28/0600Z 16.4N  37.0W   35 KT  40 MPH
 24H  28/1800Z 17.5N  38.5W   35 KT  40 MPH
 36H  29/0600Z 18.9N  39.9W   30 KT  35 MPH
 48H  29/1800Z 20.3N  41.0W   30 KT  35 MPH
 72H  30/1800Z 22.6N  42.7W   30 KT  35 MPH
 96H  01/1800Z 24.0N  44.5W   30 KT  35 MPH
120H  02/1800Z 25.5N  47.5W   30 KT  35 MPH

$$
FORECASTER BRENNAN



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