Tropical Storm TOMAS

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TROPICAL STORM TOMAS DISCUSSION NUMBER  20
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL212010
1100 PM EDT TUE NOV 02 2010
 
SATELLITE IMAGES INDICATE THAT OVERALL CONVECTION HAS DECREASED
DURING THE PAST SEVERAL HOURS...THOUGH A CURVED BAND HAS BECOME A
LITTLE BETTER-DEFINED RECENTLY.  MICROWAVE DATA SUGGEST THE CENTER
IS ON THE SOUTHEASTERN SIDE OF THAT BAND...AND REMNANTS OF THE OLD
MID-LEVEL CIRCULATION CAN BE SEEN NORTHWEST OF ARUBA.  SATELLITE
INTENSITY ESTIMATES VARY FROM 35-55 KT...AND NO CHANGE WILL BE MADE
TO THE INITIAL WIND SPEED OF 35 KT. AN AIR FORCE HURRICANE HUNTER
WILL BE IN THE AREA IN A FEW HOURS TO CHECK ON THE STATUS OF TOMAS.
 
LARGE-SCALE ENVIRONMENTAL PARAMETERS APPEAR TO BE RATHER FAVORABLE
FOR FUTURE INTENSIFICATION WITH LOW SHEAR AND VERY WARM WATER FOR
THE NEXT FEW DAYS.  IT IS UNCERTAIN...HOWEVER...IF TOMAS CAN TAKE
ADVANTAGE OF THESE CONDITIONS.  A LOOK AT GLOBAL MODEL CROSS-
SECTIONS SHOW A TILTED VORTEX INITIALLY...WITH THE GFS/UKMET
SUGGESTING A MORE FAVORABLE VERTICAL VORTEX STRUCTURE FOR
STRENGTHENING IN A DAY OR TWO.  THE ECMWF MODEL...WHICH WAS ONE
OF THE FEW MODELS THAT PREDICTED THE WEAKENING OF TOMAS IN THE
EASTERN CARIBBEAN...HAS A QUITE DIFFERENT SCENARIO WITH A GOOD DEAL
OF TILT REMAINING FOR THE NEXT FEW DAYS AND ONLY A MODEST INCREASE
IN WINDS UNTIL AFTER THE TROPICAL CYCLONE LEAVES THE CARIBBEAN. 
WITH SUCH DIVERGENCE IN THE GUIDANCE...THE NEW FORECAST IS ABOUT
THE SAME THE PREVIOUS ONE...A LITTLE HIGHER THAN THE MODEL
CONSENSUS.

AN UNCERTAIN INITIAL MOTION ESTIMATE IS 280/7.  A CONTINUED
SLOW-DOWN OF THE TROPICAL CYCLONE IS LIKELY AS RIDGING WEAKENS TO
THE NORTH OF TOMAS.  A DEEP LAYER LOW ENTERING THE GULF OF MEXICO
IS EXPECTED TO ACCELERATE AND TURN TOMAS TO THE NORTH AND NORTHEAST
ON THURSDAY.  WHILE THE MODELS TAKE VARIOUS SPEEDS AND ROUTES TO
GET THERE...THEY REMAIN FOCUSED IN THE DIRECTION OF SOUTHWESTERN
HAITI.  THE NHC FORECAST IS ADJUSTED SLIGHTLY TO THE RIGHT OF THE
PREVIOUS FORECAST DURING THE FIRST COUPLE OF DAYS...AND GENERALLY
LIES TO THE SOUTHEAST OF THE MODEL CONSENSUS.  THE HWRF AND GFDN
HAVE A RATHER DEEP AND INTENSE CIRCULATION...WHICH APPEAR TO BE
OUTLIERS AND BIASING TVCN...THE VARIABLE CONSENSUS MODEL...TOO FAR
TO THE NORTH.   
  
REGARDLESS OF THE EXACT TRACK AND INTENSITY OF TOMAS...IT APPEARS
THAT THE TROPICAL CYCLONE WILL POSE A SIGNIFICANT THREAT OF HEAVY
RAINFALL OVER HAITI AND THE DOMINICAN REPUBLIC LATER IN THE WEEK.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/0300Z 13.7N  75.1W    35 KT
 12HR VT     03/1200Z 14.0N  75.9W    40 KT
 24HR VT     04/0000Z 14.4N  76.5W    50 KT
 36HR VT     04/1200Z 15.0N  76.6W    60 KT
 48HR VT     05/0000Z 16.0N  76.0W    70 KT
 72HR VT     06/0000Z 19.0N  73.9W    80 KT
 96HR VT     07/0000Z 22.0N  71.5W    70 KT
120HR VT     08/0000Z 22.5N  69.5W    60 KT
 
$$
FORECASTER BLAKE
 
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