000 WTNT41 KNHC 050838 TCDAT1 HURRICANE TOMAS DISCUSSION NUMBER 29 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010 500 AM EDT FRI NOV 05 2010 TOMAS HAS REGAINED HURRICANE STRENGTH. THE AIR FORCE HURRICANE HUNTERS FOUND A PEAK 850 MB FLIGHT-LEVEL WIND OF 88 KT AND MAXIMUM SFMR-OBSERVED SURFACE WINDS OF 75 KT. THE LATTER OBSERVATION APPEARED TO BE SOMEWHAT OF A SPIKE IN THE RECORD...AND USING A BLEND OF THE SURFACE AND FLIGHT-LEVEL DATA GIVES 70 KT FOR THE CURRENT INTENSITY ESTIMATE. OBSERVATIONS FROM THE AIRCRAFT AND A TRMM MICROWAVE OVERPASS SUGGEST THAT THE CYCLONE IS TILTED NORTHWARD AS A RESULT OF SOUTHERLY OR SOUTH-SOUTHWESTERLY VERTICAL WIND SHEAR. SATELLITE IMAGERY SHOWS A WELL-DEFINED CENTRAL DENSE OVERCAST...WITH CLOUD TOP TEMPS APPROACHING -90C. THE INITIAL MOTION ESTIMATE IS 035/08. TOMAS IS LOCATED ON THE EAST SIDE OF AN UNUSUALLY DEEP MID- TO UPPER-LEVEL TROUGH CURRENTLY AMPLIFYING OVER THE EASTERN UNITED STATES. THE CYCLONE SHOULD GRADUALLY BECOME EMBEDDED IN AN INCREASING SOUTHWESTERLY WIND FLOW AHEAD OF THIS SYSTEM DURING THE NEXT COUPLE OF DAYS AND MOVE ON A GENERAL NORTHEASTWARD COURSE WITH SOME INCREASE IN FORWARD SPEED. AFTER 48 HOURS...TOMAS SHOULD GRADUALLY SLOW DOWN AND TURN EAST-NORTHEASTWARD AND THEN EASTWARD IN A WEAKER LOW-LEVEL WESTERLY STEERING FLOW AS THE INCREASING SHEAR REDUCES TOMAS TO A SHALLOWER FEATURE. THIS IS THE GENERAL SCENARIO DEPICTED BY THE GFS AND U.K. MET. OFFICE GLOBAL MODELS. AN ALTERNATIVE EVOLUTION IS SUGGESTED BY SOME OF THE OTHER GUIDANCE SUCH AS THE ECMWF. THE LATTER MODEL SHOWS A STRONGER CYCLONE NEAR THE END OF THE FORECAST PERIOD...PRESUMABLY DUE TO BAROCLINIC FORCING...THAT MOVES MORE QUICKLY TOWARDS THE NORTHEAST. THE OFFICIAL NHC TRACK FORECAST IS VIRTUALLY UNCHANGED FROM THE PREVIOUS ONE AND IS ON THE EASTERN SIDE OF THE GUIDANCE ENVELOPE. TOMAS STILL HAS ABOUT 24 HOURS OR SO TO STRENGTHEN IN AN ENVIRONMENT OF RELATIVELY LOW SHEAR...HIGH MOISTURE...AND OVER WARM WATERS. AFTER THAT...A RAPID INCREASE IN SOUTHWESTERLY SHEAR ASSOCIATED WITH THE EASTERN U.S. TROUGH...NOT TO MENTION DRIER AND COOLER ASSOCIATED WITH THE SAME FEATURE IMPINGING ON THE CIRCULATION... SHOULD BRING ABOUT A PRONOUNCED WEAKENING PHASE. THE NEW NHC FORECAST IS LOWER THAN THE SHIPS/LGEM INTENSITY GUIDANCE BUT ABOUT THE SAME AS THE PREVIOUS OFFICIAL FORECAST...INDICATING INTENSIFICATION TO HURRICANE STRENGTH WITHIN 24 HOURS AND WEAKENING TO A REMNANT LOW IN 96 HOURS. WEAKENING AFTER 48 HOURS COULD BE MORE RAPID THAN INDICATED...CONSIDERING THAT THE SHEAR COULD BE HIGHER THAN 60 KT AFTER 60 HOURS. REGARDLESS OF THE EXACT TRACK AND INTENSITY OF TOMAS...THE MOST SIGNIFICANT THREAT FROM THIS TROPICAL CYCLONE SHOULD CONTINUE TO BE HEAVY RAINFALL...WHICH COULD PRODUCE FLASH FLOODING AND LIFE- THREATENING MUD SLIDES OVER PORTIONS OF HAITI AND THE DOMINICAN REPUBLIC DURING THE NEXT COUPLE OF DAYS. FORECAST POSITIONS AND MAX WINDS INITIAL 05/0900Z 18.1N 74.9W 70 KT 12HR VT 05/1800Z 19.8N 73.9W 75 KT 24HR VT 06/0600Z 22.1N 72.4W 75 KT 36HR VT 06/1800Z 24.4N 70.9W 65 KT 48HR VT 07/0600Z 25.8N 69.6W 50 KT 72HR VT 08/0600Z 27.5N 67.5W 35 KT 96HR VT 09/0600Z 28.5N 65.0W 25 KT...POST-TROP/REMNT LOW 120HR VT 10/0600Z 28.5N 63.0W 25 KT...POST-TROP/REMNT LOW $$ FORECASTER KIMBERLAIN/PASCH