000 WTNT41 KNHC 060848 TCDAT1 TROPICAL STORM TOMAS DISCUSSION NUMBER 33 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010 500 AM EDT SAT NOV 06 2010 AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING TOMAS FOUND 700-MB FLIGHT-LEVEL WINDS OF 63 KT...PEAK SURFACE SFMR WINDS OF 50-55 KT....AND A CENTRAL PRESSURE OF 993 MB. SATELLITE IMAGERY SHOWS THAT THE THE CONVECTIVE STRUCTURE OF THE CYCLONE CONSISTS OF A CENTRAL MASS OF COLD-TOPPED CONVECTION...THOUGH CLOUD TOPS HAVE BEEN WARMING RECENTLY. THE AIRCRAFT OBSERVATIONS ALSO INDICATE THAT THE SURFACE AND FLIGHT-LEVEL CENTERS ARE MORE ALIGNED THAN THEY WERE PREVIOUSLY. WITH NO OBSERVATIONS TO SUPPORT HURRICANE FORCE WINDS...THE INITIAL INTENSITY IS LOWERED TO 60 KT FOR THIS ADVISORY. TOMAS IS EXPECTED TO REMAIN IN RELATIVELY LOW VERTICAL WIND SHEAR FOR UP TO ANOTHER 24 HOURS. HOWEVER...A LOW-LEVEL BAROCLINIC ZONE ASSOCIATED WITH A LARGE DEEP-LAYER TROUGH OVER THE EASTERN U.S. IS IMPINGING ON THE CIRCULATION OF THE HURRICANE. A DRAMATIC INCREASE IN SHEAR IS FORECAST AFTER 24 HOURS...AND THERMODYNAMIC PARAMETERS ARE EXPECTED TO BECOME INCREASINGLY UNFAVORABLE. WEAKENING SEEMS IMMINENT...WITH THE RATE OF WEAKENING LIKELY INCREASING AFTER 36 HOURS...GIVEN THE EXTREME AMOUNT OF VERTICAL WIND SHEAR DEPICTED BY THE LARGE-SCALE MODELS. THE OFFICIAL NHC FORECAST IS SIMILAR TO THE PREVIOUS ONE BUT INDICATES TOMAS BECOMING A REMNANT LOW SOONER. THE INITIAL MOTION IS 050/13...A BIT FASTER THAN THE PREVIOUS ESTIMATE. GLOBAL MODELS CONTINUE TO BE IN GOOD AGREEMENT WITH RESPECT TO THE OVERALL ENVIRONMENTAL SYNOPTIC PATTERN DURING THE NEXT SEVERAL DAYS. THE CYCLONE SHOULD MOVE NORTHEASTWARD DURING THE NEXT 24-36 HOURS IN A DEEP LAYER OF SOUTHWESTERLY FLOW AHEAD OF A MID- TO UPPER-LEVEL TROUGH MOVING FROM THE EASTERN U.S. INTO THE WESTERN ATLANTIC. AFTER THAT...THE TRACK GUIDANCE DIVERGES... WITH SEVERAL OF THE MORE RELIABLE MODELS SHOWING A HEAVILY SHEARED TOMAS MOVING SLOWLY ON AN EASTWARD TRACK AT THE BASE OF THE WESTERN ATLANTIC TROUGH. A SECOND CAMP OF MODELS SHOWS A DEEPER CYCLONE BEING PULLED NORTHWARD AND BECOMING INVOLVED WITH THE BAROCLINIC ZONE ASSOCIATED ASSOCIATED WITH THE SAME TROUGH. THE OFFICIAL FORECAST CONTINUES TO FAVOR THE FORMER GROUP SINCE IT APPEARS UNLIKELY THAT TOMAS WILL BE ABLE TO MANTAIN ITSELF AS A VIABLE TROPICAL CYCLONE FOR LONG. THE NEW NHC FORECAST IS ADJUSTED TO THE RIGHT DURING THE SHORT TERM TO ACCOUNT FOR THE CURRENT MORE NORTHEASTERLY MOTION BUT IS SIMILAR TO THE PREVIOUS FORECAST BEYOND 48 HOURS. EVEN THOUGH THE CENTER OF TOMAS HAS PASSED NORTH OF HISPANIOLA... SOUTHERLY FLOW BEHIND TOMAS WILL RESULT IN THE CONTINUATION OF A HEAVY RAINFALL THREAT FOR THE NEXT DAY OR TWO...WHICH COULD PRODUCE FLASH FLOODING AND LIFE-THREATENING MUD SLIDES OVER PORTIONS OF HAITI AND THE DOMINICAN REPUBLIC. FORECAST POSITIONS AND MAX WINDS INITIAL 06/0900Z 21.9N 71.3W 60 KT 12HR VT 06/1800Z 23.2N 70.2W 60 KT 24HR VT 07/0600Z 24.2N 69.4W 55 KT 36HR VT 07/1800Z 24.7N 68.7W 50 KT 48HR VT 08/0600Z 25.0N 67.5W 40 KT 72HR VT 09/0600Z 25.5N 65.0W 25 KT...POST-TROP/REMNT LOW 96HR VT 10/0600Z 26.5N 60.9W 20 KT...POST-TROP/REMNT LOW 120HR VT 11/0600Z...DISSIPATED $$ FORECASTER KIMBERLAIN/FRANKLIN