Tropical Storm TOMAS

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TROPICAL STORM TOMAS DISCUSSION NUMBER  34
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL212010
1100 AM EDT SAT NOV 06 2010

A NOAA HURRICANE HUNTER AIRCRAFT REPORTED 850 MB FLIGHT-LEVEL WINDS
OF 69 KT TO THE SOUTHEAST OF THE CENTER OF TOMAS...WITH SFMR WINDS
OF 54 KT.  THE MINIMUM CENTRAL PRESSURE HAS BEEN IN THE 990-992 MB
RANGE DURING THE LAST SEVERAL FIXES.  BASED ON THESE DATA...THE
INITIAL INTENSITY IS NUDGED DOWNWARD TO 55 KT.  THE STORM STILL HAS
A SYMMETRIC BANDED CONVECTIVE PATTERN...AND A RECENT WINDSAT
OVERPASS SHOWS A WELL-DEFINED LOW-LEVEL STRUCTURE.  HOWEVER...
COLD-AIR CLOUDS ARE PRESENT IN SATELLITE IMAGERY NEAR THE WESTERN
EDGE OF CONVECTION...INDICATING THAT A COLD FRONT IS APPROACHING
THE CYCLONE.

THE INITIAL MOTION IS 045/14.  ALL GUIDANCE INDICATES THAT TOMAS
SHOULD SLOW ITS FORWARD MOTION DURING THE NEXT 24 HR AS PRESSURES
RISES TO THE NORTH OF THE CYCLONE AND FALL TO THE EAST OF IT. 
AFTER THAT TIME...ANOTHER ROUND OF BAROCLINIC CYCLOGENESIS SHOULD
OCCUR OVER THE NORTHWESTERN ATLANTIC...WITH A NEW DEEP-LAYER LOW
DEVELOPING TO THE NORTH OF TOMAS.  WHILE THERE ARE SIGNIFICANT
DIFFERENCES IN THE DETAILS BETWEEN THE DYNAMICAL MODELS...THEY ALL
FORECAST THIS NEW SYSTEM TO TURN TOMAS EASTWARD.  THERE REMAINS A
LARGE AMOUNT OF SPREAD IN THE TRACK GUIDANCE AFTER 48 HR...AS THE
GFS/ECMWF FAVORING A SLOWER MOTION AT LOWER LATITUDE...WHILE
GFDL/HWRF/NOGAPS/UKMET/GFS ENSEMBLE MEAN NOW FAVOR A FASTER MOTION
AT HIGHER LATITUDE.  THE NEW FORECAST TRACK IS A BLEND OF THESE
EXTREMES IN BOTH DIRECTION AND SPEED...AND IS SLOWER THAN THE
CONSENSUS MODELS.  THE NEW TRACK IS SHIFTED A LITTLE TO THE WEST OF
THE PREVIOUS FORECAST DURING THE FIRST 24 HR...AND A LITTLE TO THE
NORTH THEREAFTER.

TOMAS HAS BEEN SLOWLY WEAKENING EVEN THOUGH THE VERTICAL WIND SHEAR
REMAINS LIGHT AND THE SEA SURFACE TEMPERATURES WARM.  BASED ON
THIS...LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE FIRST 24 HR
OF THE FORECAST. HOWEVER...GIVEN THE STRUCTURE...THERE IS STILL
SOME CHANCE OF RE-INTENSIFICATION DURING THIS TIME.  TOMAS SHOULD
ENCOUNTER SIGNIFICANT AMOUNTS OF COOLER/DRIER AIR AND INCREASING
WIND SHEAR AFTER 24 HR...WHICH SHOULD CAUSE A STEADY AND POSSIBLY
RAPID WEAKENING.  THE LATTER PART OF THE NEW INTENSITY FORECAST
CALLS FOR THE CYCLONE TO DEGENERATE INTO A REMNANT LOW BY 72 HR AND
TO DISSIPATE COMPLETELY BY 120 HR.  THERE IS A POSSIBILITY TOMAS
COULD UNDERGO EXTRATROPICAL TRANSITION INSTEAD OF
DEGENERATION...ESPECIALLY IF IT TAKES A MORE NORTHERLY COURSE AND
INTERACTS WITH THE WESTERN ATLANTIC BAROCLINIC LOW.
 
TOMAS IS NOW FAR ENOUGH TO THE NORTH AND EAST THAT THE THREAT OF
WIDESPREAD HEAVY RAINS HAS DIMINISHED OVER HAITI AND THE DOMINICAN
REPUBLIC.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/1500Z 23.1N  70.6W    55 KT
 12HR VT     07/0000Z 24.1N  69.9W    55 KT
 24HR VT     07/1200Z 24.8N  69.3W    55 KT
 36HR VT     08/0000Z 25.1N  68.5W    50 KT
 48HR VT     08/1200Z 25.4N  66.5W    40 KT
 72HR VT     09/1200Z 26.5N  62.5W    25 KT...POST-TROP/REMNT LOW
 96HR VT     10/1200Z 28.0N  58.0W    20 KT...POST-TROP/REMNT LOW
120HR VT     11/1200Z...DISSIPATED
 
$$
FORECASTER BEVEN
 
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