[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 301452
TCDAT2

TROPICAL STORM PHILIPPE DISCUSSION NUMBER  26
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172011
1100 AM AST FRI SEP 30 2011

FINALLY...WE CAN CLEARLY SEE THE CENTER OF PHILIPPE.  A SERIES OF
MICROWAVE PASSES FROM OVERNIGHT SUGGEST THAT THE PREVIOUSLY
ESTIMATED CENTER DISSIPATED...AND A NEW CENTER FORMED FARTHER
NORTH...CLOSER TO THE DEEP CONVECTION.  NOW THERE IS NO DOUBT SINCE
THE CENTER HAS RECENTLY POPPED OUT OF THIS DEEP CONVECTION.
BECAUSE OF THE POSSIBLE RE-FORMATION...THE CENTER IS MOVING AT AN
UNCERTAIN 325 DEGREES AT 11 KT.  PHILIPPE IS STILL GAINING SOME
LATITUDE AS IT MOVES AROUND THE SOUTHWESTERN PERIPHERY OF A
MID-LEVEL ANTICYCLONE...BUT A NEW ANTICYCLONE IS ALREADY BUILDING
FARTHER NORTH AND SHOULD FORCE THE STORM ON A WEST-NORTHWESTWARD
HEADING OVER THE NEXT 48 HOURS.  THE MODEL GUIDANCE IS TIGHTLY
CLUSTERED DURING THIS PERIOD.  THEREAFTER...THE GFS AND ECMWF
INDICATE THAT THE MID-LEVEL HIGH WILL BUILD FARTHER SOUTH AND FORCE
PHILIPPE ON A WEST TO JUST SOUTH OF DUE WEST HEADING ON DAYS 3 AND
4.  ON THE OTHER HAND...MANY OF THE OTHER MODELS DO NOT BUILD THE
RIDGE AS MUCH AND ALLOW THE CYCLONE TO CONTINUE GAINING LATITUDE.
DESPITE THESE DIFFERENCES...PHILIPPE SHOULD HAVE MADE ENOUGH
WESTWARD PROGRESS BY DAY 5 TO START FEELING THE INFLUENCE OF A DEEP
LONGWAVE TROUGH OVER THE WESTERN ATLANTIC...AND ALL THE MODELS SHOW
SOME DEGREE OF A NORTHWARD TURN BEGINNING AT THAT TIME.  THE
OFFICIAL FORECAST DIVERGES TO THE SOUTH OF THE TVCA CONSENSUS AFTER
48 HOURS IN THE DIRECTION OF THE GFS AND ECMWF...AND ENDS UP VERY
CLOSE TO THE PREVIOUS FORECAST.

A 1212 UTC ASCAT PASS SHOWED A FEW 40-KT WIND VECTORS JUST TO THE
NORTH OF THE CENTER...AND THE INITIAL INTENSITY IS RAISED TO 45 KT.
HOWEVER...PHILIPPE WILL LIKELY NOT MAINTAIN THIS INTENSITY NOW THAT
VERTICAL SHEAR IS INCREASING OVER THE SYSTEM.  BELLIGERENT
NORTHERLY SHEAR OF AT LEAST 30 KT IS EXPECTED TO AFFECT PHILIPPE
OVER THE NEXT SEVERAL DAYS...AND THIS COULD CAUSE THE SYSTEM TO
WEAKEN TO A DEPRESSION.  THE SHEAR COULD RELAX A BIT BY DAY 5 ONCE
THE CYCLONE REACHES AN AREA OF UPPER-LEVEL RIDGING BETWEEN THE
HOSTILE NORTHERLY WINDS OVER THE CENTRAL ATLANTIC AND THE DEEP
TROUGH OVER THE WESTERN ATLANTIC.  THE FORECAST THEREFORE ALLOWS
FOR PHILIPPE TO REGAIN TROPICAL-STORM STATUS AT THAT TIME.  IN
GENERAL...THE OFFICIAL INTENSITY FORECAST LIES BETWEEN THE LGEM AND
THE SHIPS MODEL...THE LATTER OF WHICH MAINTAINS PHILIPPE AS A
TROPICAL STORM THROUGHOUT THE FORECAST PERIOD.

FORECAST POSITIONS AND MAX WINDS

INIT  30/1500Z 22.9N  45.3W   45 KT  50 MPH
 12H  01/0000Z 23.8N  46.7W   40 KT  45 MPH
 24H  01/1200Z 24.6N  48.5W   40 KT  45 MPH
 36H  02/0000Z 25.3N  50.2W   40 KT  45 MPH
 48H  02/1200Z 25.7N  51.8W   35 KT  40 MPH
 72H  03/1200Z 25.5N  55.5W   30 KT  35 MPH
 96H  04/1200Z 25.0N  60.0W   30 KT  35 MPH
120H  05/1200Z 26.0N  62.5W   35 KT  40 MPH

$$
FORECASTER BERG



This weather bulletin was brought to you by:
www.nashvilleweather.net