000 WTNT41 KNHC 040841 TCDAT1 TROPICAL STORM TOMAS DISCUSSION NUMBER 25 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010 500 AM EDT THU NOV 04 2010 SATELLITE PICTURES SUGGEST THAT THE CLOUD PATTERN OF TOMAS HAS NOT CHANGED SIGNIFICANTLY DURING THE LAST SEVERAL HOURS. HOWEVER... DATA FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE THAT THE PRESSURE HAS FALLEN TO 997 MB WITH MAXIMUM SURFACE WINDS OF 41 KT. DESPITE THE AIRCRAFT DATA WHICH ARE INDICATIVE OF SLIGHT STRENGTHENING...THE VORTEX HAS BEEN TILTED IN THE VERTICAL BASED UPON COMPARISON OF EARLIER NOAA AND AIR FORCE AIRCRAFT DATA. GIVEN THE SIGNIFICANTLY LOWER CENTRAL PRESSURE FROM THE AIRCRAFT... THE INITIAL INTENSITY IS INCREASED TO 45 KT FOR THIS ADVISORY. THE CURRENT MOTION ESTIMATE REMAINS 330/06. THE FORECAST PHILOSOPHY REGARDING THE TRACK OF TOMAS IS UNCHANGED. TOMAS SHOULD BE STEERED NORTH-NORTHWESTWARD TO NORTHWARD AROUND A LOW- TO MID-LEVEL RIDGE LOCATED OVER THE WEST CENTRAL ATLANTIC TODAY. AFTER THAT...TOMAS SHOULD BEGIN TO ENCOUNTER AN INCREASING SOUTHWESTERLY FLOW ASSOCIATED WITH AN ANOMALOUSLY DEEP MID- TO UPPER-LEVEL TROUGH MOVING ACROSS EASTERN NORTH AMERICA AND TURN NORTHEASTWARD WHILE ACCELERATING. EVEN THOUGH THE SYNOPTIC REASONING HAS NOT CHANGED FROM THE PREVIOUS PACKAGE...THE OFFICIAL FORECAST TRACK IS SHIFTED TO THE LEFT ON ACCOUNT OF THE MOST RECENT AIRCRAFT CENTER FIXES. ALTHOUGH LARGE-SCALE FACTORS OF MODERATELY LOW SHEAR AND WARM WATERS ARE FAVORABLE FOR FURTHER INTENSIFICATION OF TOMAS...THE VERTICAL TILT OF THE VORTEX AND THE BROAD NATURE OF THE CIRCULATION MAY ARGUE AGAINST A RAPID INCREASE IN STRENGTH. INTERESTINGLY...THE SHIPS RAPID INTENSIFICATION INDEX THAT HAD BEEN SHOWING THE POTENTIAL FOR A 30-KT INCREASE WITHIN THE NEXT 24 HOURS IS NOT AS HIGH AS IT WAS BEFORE. THE NEW NHC FORECAST IS SIMILAR TO THE PREVIOUS ONE AND ASSUMES THAT THE LARGE-SCALE ENVIRONMENT SHOULD BE CONDUCIVE ENOUGH TO ALLOW FOR STENGTHENING DURING THE NEXT 24-36 HOURS. BEYOND 36 HOURS...STRONG AND INCREASING SOUTHWESTERLY SHEAR OVER THE WESTERN ATLANTIC IS FORECAST TO CAUSE WEAKENING...PERHAPS AT A MORE RAPID PACE THAN INDICATED IN THE CURRENT FORECAST. THE NEW NHC FORECAST IS REDUCED FROM THE PREVIOUS ONE AT LATER FORECAST TIMES GIVEN THE STRONG FORECAST SHEAR. REGARDLESS OF THE EXACT TRACK AND INTENSITY OF TOMAS...THE MOST SIGNIFICANT THREAT FROM THIS TROPICAL CYCLONE IS 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 04/0900Z 15.8N 76.1W 45 KT 12HR VT 04/1800Z 17.0N 76.0W 55 KT 24HR VT 05/0600Z 18.8N 75.0W 65 KT 36HR VT 05/1800Z 21.0N 73.4W 65 KT 48HR VT 06/0600Z 23.5N 71.5W 55 KT 72HR VT 07/0600Z 26.0N 69.5W 45 KT 96HR VT 08/0600Z 28.0N 67.0W 35 KT 120HR VT 09/0600Z 28.0N 65.0W 25 KT $$ FORECASTER KIMBERLAIN/PASCH