000 WTNT41 KNHC 070848 TCDAT1 HURRICANE TOMAS DISCUSSION NUMBER 38 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010 500 AM AST SUN NOV 07 2010 AROUND 06Z...A BURST OF DEEP CONVECTION WITH TOPS COLDER THAN -80C DEVELOPED NEAR THE CENTER...AND A WARM SPOT OR EYE FEATURE BRIEFLY BECAME EVIDENT IN INFRARED IMAGERY. SINCE THAT TIME...HOWEVER... CLOUD TOPS HAVE WARMED AND THE UPPER-LEVEL OUTFLOW HAS BECOME FLATTENED ON THE WEST SIDE AS WESTERLY SHEAR HAS STARTED TO IMPINGE ON THE CYCLONE. A SATELLITE INTENSITY ESTIMATE OF T4.0/65 KT FROM TAFB ALONG WITH AODT AND UW-CIMSS ADT ESTIMATES OF T4.3/72 KT SUPPORT MAINTAINING A SYNOPTIC INTENSITY OF 70 KT AT 06Z. HOWEVER...GIVEN THE RECENT DISHEVELED APPEARANCE TO THE CONVECTIVE CLOUD MASS...THE 09Z ADVISORY INTENSITY IS BEING LOWERED TO 65 KT. THE INITIAL MOTION ESTIMATE IS 040/06. SATELLITE IMAGERY DURING THE PAST COUPLE OF HOURS SUGGESTS THAT TOMAS HAS SLOWED DOWN AND TURNED TOWARD THE NORTHEAST SINCE THE 06Z FIXES. A TURN TOWARD THE EAST-NORTHEAST IS EXPECTED WITHIN THE NEXT 12 HOURS OR SO AS INCREASING WEST-SOUTHWESTERLY MID-/UPPER-LEVEL FLOW AHEAD OF A BROAD EASTWARD-MOVING TROUGH GRADUALLY DECOUPLES THE LOW- AND UPPER-LEVELS CIRCULATIONS...LEAVING THE LOW-LEVEL CIRCULATION TO BE STEERED EASTWARD BY WEAKER FLOW AHEAD OF A COLD FRONT. BY 48 HOURS...TOMAS IS FORECAST TO DEGENERATE INTO A NON-CONVECTIVE REMNANT LOW PRESSURE SYSTEM...WHICH IS THEN EXPECTED TO BE CAPTURED BY AND PULLED NORTHEASTWARD INTO A LARGE EXTRATROPICAL CYCLONE AFTER 72 HOURS. MOST OF THE NHC MODEL GUIDANCE IS IN GOOD AGREEMENT ON THIS DEVELOPING SCENARIO. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY TRACK AND LIES ALONG THE NORTHERN EDGE OF THE GUIDANCE ENVELOPE. WATER VAPOR IMAGERY AND SATELLITE-DERIVED WINDS INDICATE 40-50 KT WEST-SOUTHWESTERLY MID-LEVEL FLOW IS BEGINNING TO UNDERCUT THE HIGH-LEVEL OUTFLOW LAYER OF TOMAS. AS A RESULT...ASSOCIATED STRONG VERTICAL WIND SHEAR SHOULD INDUCE WEAKENING WITHIN THE NEXT 6-12 HOURS...AND TROPICAL CYCLONE DISSIPATION SHOULD BE COMPLETE BY 48 HOURS. THE OFFICIAL INTENSITY FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND IS CLOSE TO A BLEND OF THE SHIPS AND LGEM INTENSITY MODELS. HOWEVER...THE COMBINATION OF STRONG WESTERLY SHEAR AND VERY DRY MID-LEVEL AIR COULD RESULT IN MORE RAPID WEAKENING THAN CURRENTLY FORECAST. THE 34-KT WIND RADII AND 12-FT SEAS RADII HAVE BEEN EXPANDED IN THE WESTERN SEMICIRCLE BASED ON REPORTS FROM NOAA BUOYS 41047 AND 41047. THE INCREASE IN THE OUTER WIND FIELD IS DUE TO A STRONG COLD FRONT AND HIGH PRESSURE SYSTEM MOVING CLOSER TO TOMAS...WHICH HAS ACTED TO TIGHTEN UP THE PRESSURE GRADIENT ON THE WEST SIDE OF THE HURRICANE. FORECAST POSITIONS AND MAX WINDS INITIAL 07/0900Z 26.2N 68.8W 65 KT 12HR VT 07/1800Z 26.5N 68.2W 60 KT 24HR VT 08/0600Z 26.8N 66.6W 50 KT 36HR VT 08/1800Z 27.5N 64.2W 40 KT 48HR VT 09/0600Z 28.6N 61.3W 30 KT...POST-TROP/REMNT LOW 72HR VT 10/0600Z 33.0N 55.5W 25 KT...POST-TROP/REMNT LOW 96HR VT 11/0600Z...DISSIPATED $$ FORECASTER STEWART