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| #386308 (Received by flhurricane at: 5:01 PM 29.Oct.2010) TCDAT1 TROPICAL STORM TOMAS DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010 500 PM AST FRI OCT 29 2010 AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT INVESTIGATING THE VIGOROUS TROPICAL WAVE LOCATED SOUTHEAST OF THE WINDWARD ISLANDS FOUND A CLOSED SURFACE CIRCULATION...ALONG WITH FLIGHT-LEVEL WINDS AND UNCONTAMINATED SFMR SURFACE WINDS THAT SUPPORT A 35-KT TROPICAL STORM. AS A RESULT...ADVISORIES HAVE BEEN INITIATED ON TROPICAL STORM TOMAS...THE NINETEENTH NAMED STORM OF THE 2010 SEASON. THE INITIAL MOTION IS AN UNCERTAIN 295/15...DUE TO THE POSSIBILITY OF REFORMATION OF THE LOW-LEVEL CENTER WITHIN THE CENTRAL DEEP CONVECTION. TOMAS IS EXPECTED TO CONTINUE MOVING WEST-NORTHWESTWARD FOR THE NEXT 48 HOURS...PASSING THROUGH THE WINDWARD ISLANDS IN ABOUT 24 HOURS OR SO. AFTER THAT...THE BROAD TROUGH THAT IS LOCATED OFF THE U.S. EAST COAST AND THE BAHAMAS IS FORECAST TO LIFT OUT TO THE NORTHEAST...WHICH ALLOWS A RIDGE TO BUILD TO THE NORTH OF TOMAS ACROSS THE GREATER ANTILLES...THE BAHAMAS...AND FLORIDA. THE EASTERLY FLOW ON THE SOUTH SIDE OF THE RIDGE SHOULD FORCE TOMAS ON MORE OF A WESTERLY TRACK THROUGH 96 HOURS. BY DAY 5...A SECOND MUCH DEEPER TROUGH IS EXPECTED TO DIG SOUTHWARD INTO THE SOUTHERN PLAINS AND SOUTHEASTERN U.S. AND CAUSE THE RIDGE AND ASSOCIATED STEERING CURRENTS TO WEAKEN. THE RESULT SHOULD BE A SHARP DECREASE IN FORWARD SPEED BY 120 HOURS. THE NHC MODEL GUIDANCE IS IN GOOD AGREEMENT ON THIS DEVELOPING SCENARIO...EXCEPT FOR THE GFDL AND HWRF MODELS...WHICH ARE CONSIDERED TO BE OUTLIERS AT THIS TIME. THE OFFICIAL FORECAST TRACK IS ALONG THE SOUTHERN EDGE OF THE GUIDANCE ENVELOPE...BUT NOT AS FAR SOUTH AND WEST AS THE GFS... ECMWF...AND UKMET MODELS...WHICH ARE DEPICTING A MUCH WEAKER AND SMALLER TROPICAL CYCLONE THAN IS EXPECTED. RECON AND SATELLITE DATA INDICATE THE LOW-LEVEL AND UPPER-LEVEL CIRCULATIONS ARE NOT YET VERTICALLY ALIGNED...WHICH SHOULD RESULT IN ONLY SLOW INTENSIFICATION IN THE NEAR TERM. HOWEVER...WITH A CENTRAL PRESSURE OF 998 MB...VERY MOIST MID-LEVELS...AND LOW VERTICAL SHEAR...IT WOULD NOT TAKE MUCH FOR TOMAS TO INTENSIFY AT A FASTER THAN NORMAL RATE. WHILE NOT EXPLICITLY INDICATING RAPID INTENSIFICATION...THE OFFICIAL INTENSITY FORECAST REFLECTS THESE FAVORABLE ENVIRONMENTAL CONDITIONS...AND IS ABOVE THE SHIPS/LGEM INTENSITY MODEL GUIDANCE. FORECAST POSITIONS AND MAX WINDS INITIAL 29/2100Z 11.1N 57.5W 35 KT 12HR VT 30/0600Z 12.0N 59.5W 40 KT 24HR VT 30/1800Z 12.9N 61.8W 50 KT 36HR VT 31/0600Z 13.5N 64.0W 60 KT 48HR VT 31/1800Z 14.1N 66.2W 70 KT 72HR VT 01/1800Z 14.8N 70.4W 90 KT 96HR VT 02/1800Z 15.2N 74.0W 100 KT 120HR VT 03/1800Z 16.0N 76.0W 100 KT $$ FORECASTER STEWART |
