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| #387735 (Received by flhurricane at: 10:56 PM 04.Nov.2010) TCDAT1 TROPICAL STORM TOMAS DISCUSSION NUMBER 28 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010 1100 PM EDT THU NOV 04 2010 THERE HAS BEEN A SHARP INCREASE IN THE INNER-CORE WIND STRUCTURE AND CONVECTIVE ORGANIZATION OF TOMAS DURING THE PAST 6 HOURS. ALTHOUGH BOTH AIR FORCE RESERVE AND NOAA HURRICANE AIRCRAFT INDICATE THERE IS ABOUT 12 NMI NORTHEASTWARD TILT TO THE VORTEX...THIS HAS NOT PREVENTED THE CENTRAL PRESSURE FROM FALLING AND THE WINDS FROM INCREASING. THE MAXIMUM 850-MB FLIGHT-LEVEL WINDS REPORTED BY THE AIR FORCE WAS 61 KT...AND 58 KT WAS REPORTED AT 700 MB BY THE NOAA HURRICANE HUNTERS. MAXIMUM SFMR WINDS HAVE BEEN AROUND 56-58 KT. THE LATEST NOAA RECON PRESSURE WAS DOWN TO 989 MB...AND THAT WAS WITH 13 KT OF WIND AT THE SURFACE. A COMBINATION OF THESE DATA EASILY SUPPORT INCREASING THE INTENSITY TO 55 KT...WHICH COULD BE A LITTLE CONSERVATIVE GIVEN THAT A WARM SPOT HAS APPEARED INTERMITTENTLY WITHIN A RING OF VERY COLD TOPS OF -80C TO -85C NEAR THE CENTER. THE INITIAL MOTION ESTIMATE IS NOW 030/08. TOMAS HAS NOW MOVED NORTH OF A MID-LEVEL RIDGE THAT LIES EAST-WEST ACROSS THE CENTRAL CARIBBEAN SEA. TOMAS SHOULD CONTINUE TO MOVE AROUND THE WESTERN PERIPHERY OF THE RIDGE AND GRADUALLY ACCELERATE NORTHEASTWARD AS IT COMES UNDER THE INFLUENCE OF MODERATE SOUTHWESTERLY FLOW AHEAD OF A DEEP MID-LATITUDE TROUGH CURRENTLY MOVING EASTWARD ACROSS THE EASTERN U.S....FLORIDA...AND THE EASTERN GULF OF MEXICO. THE TRACK MODELS REMAIN IN EXCELLENT AGREEMENT ON THIS DEVELOPING SCENARIO THROUGH 48 HOURS...AND THE MODEL TRACKS HAVE EVEN SHIFTED MORE TO THE EAST ON THE LATEST FORECAST CYCLE. HOWEVER...AFTER THAT TIME... HOWLING WESTERLY WIND SHEAR IN EXCESS OF 60 KT IS EXPECTED TO SHEAR APART TOMAS AND LEAVE BEHIND A REMNANT LOW PRESSURE SYSTEM THAT SHOULD BE STEERED SLOWLY EASTWARD BY WEAKER LOW-LEVEL WESTERLY FLOW ON THE SOUTH SIDE OF AN EXTRATROPICAL LOW PRESSURE SYSTEM. THE GFDL AND HWRF MODELS TAKE TOMAS OR ITS REMNANTS RAPIDLY NORTHWARD AND MERGE IT WITH A DEEP EXTRATROPICAL LOW NEAR THE NORTHEAST U.S. COAST AND THE CANADIAN MARITIMES. HOWEVER...THE GFS...ECMWF... UKMET...AND NOGAPS MODELS SHOW TOMAS SHEARING APART AND REMAINING JUST NORTH OF THE GREATER ANTILLES. THE LATTER SCENARIO IS PREFERRED GIVEN THE EXTREMELY HOSTILE SHEAR CONDITIONS THAT ARE FORECAST TO AFFECT THE CYCLONE BY 72 HOURS AND BEYOND. THE OFFICIAL FORECAST TRACK HAS BEEN SHIFTED A LITTLE TO THE RIGHT OF THE PREVIOUS TRACK...BUT MAINLY TO ACCOUNT FOR THE MORE EASTERLY INITIAL POSITION. TOMAS HAS ABOUT 24 HOURS OR SO TO STRENGTHEN OVER 29C SSTS AND IN A RELATIVELY LOW SHEAR ENVIRONMENT. HOWEVER...BY 36 HOURS...MID-LEVEL HUMIDITIES ARE FORECAST TO DECREASE BELOW 40 PERCENT...WHICH COULD ACT TO ERODE THE INNER-CORE CONVECTION. AS MENTIONED ABOVE...BY 48 HOURS THE VERTICAL SHEAR IS EXPECTED TO INCREASE SHARPLY AND TOMAS SHOULD BEGIN A STEADY WEAKENING TREND. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO BUT SLIGHTLY LOWER THAN THE SHIPS...LGEM... AND GFDL MODELS. REGARDLESS OF THE EXACT TRACK AND INTENSITY OF TOMAS...THE MOST SIGNIFICANT THREAT FROM THIS TROPICAL CYCLONE WILL BE 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 05/0300Z 17.3N 75.5W 55 KT 12HR VT 05/1200Z 18.8N 74.6W 65 KT 24HR VT 06/0000Z 21.0N 73.1W 70 KT 36HR VT 06/1200Z 23.4N 71.5W 70 KT 48HR VT 07/0000Z 25.1N 70.2W 55 KT 72HR VT 08/0000Z 27.2N 67.9W 40 KT 96HR VT 09/0000Z 28.3N 65.8W 30 KT...POST-TROPICAL 120HR VT 10/0000Z 28.5N 64.0W 30 KT...POST-TROP/REMNT LOW $$ FORECASTER STEWART |
