000 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