Hurricane TOMAS

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HURRICANE TOMAS DISCUSSION NUMBER  38
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL212010
500 AM AST SUN NOV 07 2010
 
AROUND 06Z...A BURST OF DEEP CONVECTION WITH TOPS COLDER THAN -80C
DEVELOPED NEAR THE CENTER...AND A WARM SPOT OR EYE FEATURE BRIEFLY
BECAME EVIDENT IN INFRARED IMAGERY. SINCE THAT TIME...HOWEVER...
CLOUD TOPS HAVE WARMED AND THE UPPER-LEVEL OUTFLOW HAS BECOME
FLATTENED ON THE WEST SIDE AS WESTERLY SHEAR HAS STARTED TO IMPINGE
ON THE CYCLONE. A SATELLITE INTENSITY ESTIMATE OF T4.0/65 KT FROM
TAFB ALONG WITH AODT AND UW-CIMSS ADT ESTIMATES OF T4.3/72 KT
SUPPORT MAINTAINING A SYNOPTIC INTENSITY OF 70 KT AT 06Z.
HOWEVER...GIVEN THE RECENT DISHEVELED APPEARANCE TO THE CONVECTIVE
CLOUD MASS...THE 09Z ADVISORY INTENSITY IS BEING LOWERED TO 65 KT.

THE INITIAL MOTION ESTIMATE IS 040/06. SATELLITE IMAGERY DURING THE
PAST COUPLE OF HOURS SUGGESTS THAT TOMAS HAS SLOWED DOWN AND TURNED
TOWARD THE NORTHEAST SINCE THE 06Z FIXES. A TURN TOWARD THE
EAST-NORTHEAST IS EXPECTED WITHIN THE NEXT 12 HOURS OR SO AS
INCREASING WEST-SOUTHWESTERLY MID-/UPPER-LEVEL FLOW AHEAD OF A
BROAD EASTWARD-MOVING TROUGH GRADUALLY DECOUPLES THE LOW- AND
UPPER-LEVELS CIRCULATIONS...LEAVING THE LOW-LEVEL CIRCULATION TO BE
STEERED EASTWARD BY WEAKER FLOW AHEAD OF A COLD FRONT. BY 48
HOURS...TOMAS IS FORECAST TO DEGENERATE INTO A NON-CONVECTIVE
REMNANT LOW PRESSURE SYSTEM...WHICH IS THEN EXPECTED TO BE
CAPTURED BY AND PULLED NORTHEASTWARD INTO A LARGE EXTRATROPICAL
CYCLONE AFTER 72 HOURS. MOST OF THE NHC MODEL GUIDANCE IS IN GOOD
AGREEMENT ON THIS DEVELOPING SCENARIO. THE OFFICIAL FORECAST TRACK
IS SIMILAR TO THE PREVIOUS ADVISORY TRACK AND LIES ALONG THE
NORTHERN EDGE OF THE GUIDANCE ENVELOPE.
 
WATER VAPOR IMAGERY AND SATELLITE-DERIVED WINDS INDICATE 40-50 KT
WEST-SOUTHWESTERLY MID-LEVEL FLOW IS BEGINNING TO UNDERCUT THE
HIGH-LEVEL OUTFLOW LAYER OF TOMAS. AS A RESULT...ASSOCIATED STRONG
VERTICAL WIND SHEAR SHOULD INDUCE WEAKENING WITHIN THE NEXT 6-12
HOURS...AND TROPICAL CYCLONE DISSIPATION SHOULD BE COMPLETE BY 48
HOURS. THE OFFICIAL INTENSITY FORECAST TRACK IS SIMILAR TO THE
PREVIOUS ADVISORY AND IS CLOSE TO A BLEND OF THE SHIPS AND LGEM
INTENSITY MODELS. HOWEVER...THE COMBINATION OF STRONG WESTERLY
SHEAR AND VERY DRY MID-LEVEL AIR COULD RESULT IN MORE RAPID
WEAKENING THAN CURRENTLY FORECAST. 
 
THE 34-KT WIND RADII AND 12-FT SEAS RADII HAVE BEEN EXPANDED IN THE
WESTERN SEMICIRCLE BASED ON REPORTS FROM NOAA BUOYS 41047 AND
41047. THE INCREASE IN THE OUTER WIND FIELD IS DUE TO A STRONG COLD
FRONT AND HIGH PRESSURE SYSTEM MOVING CLOSER TO TOMAS...WHICH HAS
ACTED TO TIGHTEN UP THE PRESSURE GRADIENT ON THE WEST SIDE OF THE
HURRICANE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0900Z 26.2N  68.8W    65 KT
 12HR VT     07/1800Z 26.5N  68.2W    60 KT
 24HR VT     08/0600Z 26.8N  66.6W    50 KT
 36HR VT     08/1800Z 27.5N  64.2W    40 KT
 48HR VT     09/0600Z 28.6N  61.3W    30 KT...POST-TROP/REMNT LOW
 72HR VT     10/0600Z 33.0N  55.5W    25 KT...POST-TROP/REMNT LOW
 96HR VT     11/0600Z...DISSIPATED
 
$$
FORECASTER STEWART
 
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