TROPICAL STORM TOMAS DISCUSSION NUMBER 27

By: National Hurricane Center
By: National Hurricane Center

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WTNT41 KNHC 042056
TCDAT1
TROPICAL STORM TOMAS DISCUSSION NUMBER 27
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010
500 PM EDT THU NOV 04 2010

THIS AFTERNOON...TOMAS CONTINUES AS A SHEARED TROPICAL STORM WITH
MOST OF THE DEEP CONVECTION LOCATED EAST OF A LOW-LEVEL SWIRL.
DESPITE APPEARANCES THAT THE SWIRL IS THE CIRCULATION CENTER...THE
AIR FORCE C-130 OBSERVATIONS INDICATE THAT THIS FEATURE HAS BEEN
ROTATING AROUND A BROADER MEAN CENTER. THE RECONNAISSANCE ALSO
OBSERVED A CENTRAL PRESSURE OF 995 MB AND EQUIVALENT WINDS AT THE
SURFACE OF ABOUT 45 KT...THOUGH THIS WIND VALUE COULD BE SLIGHTLY
GENEROUS.

THE MOTION OF THE CYCLONE IS 350 DEGREES AT 4 KT AS IT IS PRIMARILY
BEING STEERED TO THE NORTH AROUND THE WESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE. A VIGOROUS SHORT-WAVE TROUGH CURRENTLY OVER THE
GULF OF MEXICO SHOULD INDUCE RECURVATURE OF TOMAS TOWARD THE
NORTH-NORTHEAST AND ACCELERATION OF ITS FORWARD SPEED DURING THE 36
HR OR SO. THE TRACK MODELS ARE IN EXCELLENT AGREEMENT ON THIS
POINT AND THE OFFICIAL FORECAST THROUGH 36 HR IS CLOSE TO THE MODEL
CONSENSUS AND THE PREVIOUS ADVISORY. AT 48 HR AND
BEYOND...HOWEVER...THE EVENTUAL TRACK OF TOMAS IS QUITE UNCERTAIN.
ONE GROUP OF MODELS...INCLUDING THE GFS...GFS ENSEMBLE
MEAN...NOGAPS...HWRF...AND GFDL...CONTINUE TO SPEED THE CYCLONE
NORTH-NORTHEASTWARD AND HAVE IT BECOMING EXTRATROPICAL AS IT
ENCOUNTERS A STRONG COLD FRONT. ANOTHER SCENARIO...SHARED BY THE
ECMWF AND UKMET MODELS...IS THAT THE CYCLONE WOULD BECOME SHEARED
AND SHALLOW...NOT PICKED UP BY THE TROUGH AND FRONT...AND MEANDER
EASTWARD FOR A COUPLE DAYS. THE CONSENSUS TECHNIQUES...BY
DESIGN...SPLIT THE DIFFERENCE...WHICH IS NOT VERY LIKELY TO BE
CORRECT. IN A SOMEWHAT UNCOMFORTABLE COMPROMISE...THIS TRACK
FORECAST IS NEARLY IDENTICAL TO THE PREVIOUS ADVISORY BUT IS
SOMEWHAT EQUATORWARD OF THE MODEL CONSENSUS.

TOMAS HAS ABOUT A DAY OR TWO TO INTENSIFY UNDER THE INFLUENCE OF
MODERATE SOUTHERLY VERTICAL SHEAR...A MOIST ENVIRONMENT...VERY WARM
WATERS...AND A SOMEWHAT UNSTABLE ATMOSPHERE. BEYOND TWO DAYS...THE
CYCLONE SHOULD EXPERIENCE STRONG WESTERLY SHEAR AND INCREASINGLY
COOLER WATERS. THE INTENSITY PREDICTION IS QUITE CLOSE TO A
CONSENSUS OF DECAY-SHIPS...LGEM...AND GFDL MODELS AND NEARLY THE
SAME AS THE PREVIOUS ADVISORY. IT SHOULD BE NOTED THAT IF THE
TRACK DOES TAKE THE CYCLONE DIRECTLY OVER EITHER EASTERN CUBA OR
HISPANIOLA FOR MORE THAN A FEW HOURS...THE CYCLONE WOULD BE WEAKER
THAN INDICATED HERE.

REGARDLESS OF THE EXACT TRACK AND INTENSITY OF TOMAS...THE MOST
SIGNIFICANT THREAT FROM THIS TROPICAL CYCLONE IS HEAVY RAINFALL...
WHICH COULD PRODUCE FLASH FLOODING AND LIFE-THREATENING MUD SLIDES
OVER HAITI AND THE DOMINICAN REPUBLIC DURING THE NEXT COUPLE OF
DAYS.

FORECAST POSITIONS AND MAX WINDS

INITIAL 04/2100Z 16.6N 76.0W 45 KT
12HR VT 05/0600Z 17.8N 75.6W 50 KT
24HR VT 05/1800Z 20.1N 74.3W 60 KT
36HR VT 06/0600Z 22.6N 72.5W 65 KT
48HR VT 06/1800Z 24.8N 71.1W 55 KT
72HR VT 07/1800Z 27.5N 69.0W 40 KT
96HR VT 08/1800Z 28.5N 66.5W 30 KT
120HR VT 09/1800Z 29.0N 64.5W 30 KT...POST-TROP/REMNT LOW

$$
FORECASTER LANDSEA/BEVEN


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