TROPICAL STORM TOMAS DISCUSSION NUMBER 26

WTNT41 KNHC 041537
TCDAT1
TROPICAL STORM TOMAS DISCUSSION NUMBER 26...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010
1100 AM EDT THU NOV 04 2010

CORRECTED INITIAL INTENSITY TO 45 KT

SATELLITE IMAGERY...ALONG WITH REPORTS FROM AIR FORCE RESERVE AND
NOAA HURRICANE HUNTER AIRCRAFT INDICATE THAT THE CENTER OF TOMAS IS
LOCATED NEAR THE WESTERN EDGE OF THE MAIN CONVECTIVE MASS. THE
NOAA PLANE HAS MEASURED 700 MB FLIGHT-LEVEL WINDS OF 44 KT...AND A
RECENT DROPSONDE SUGGESTS SURFACE WINDS AROUND 40-45 KT AND A
CENTRAL PRESSURE BELOW 997 MB. BASED ON THESE DATA...THE INITIAL
INTENSITY REMAINS 45 KT. THE CIRRUS OUTFLOW IS CURRENTLY GOOD OVER
THE NORTHEASTERN SEMICIRCLE AND POOR ELSEWHERE.

THE INITIAL MOTION IS NOW A SOMEWHAT UNCERTAIN 350/7. A LARGE
DEEP-LAYER TROUGH AND ASSOCIATED COLD FRONT SHOULD CAUSE TOMAS TO
MOVE NORTHWARD TO NORTHEASTWARD FOR THE NEXT 48 HR OR SO...WITH THE
CENTER PASSING NEAR OR OVER JAMAICA...HAITI...EASTERN CUBA...AND
THE SOUTHEASTERN BAHAMAS. THE TRACK GUIDANCE IS IN GOOD AGREEMENT
WITH THIS SCENARIO...AND THIS PART OF THE FORECAST TRACK IS AN
UPDATE OF THE PREVIOUS TRACK. AFTER 48 HR...THE GUIDANCE IS
DIVERGENT AND INCONSISTENT. THE ECMWF SHOWS TOMAS MOVING ALONG THE
SOUTHERN PERIPHERY OF THE DEEP-LAYER TROUGH...AND THIS IS
CONSISTENT WITH ITS PREVIOUS RUN. THE GFS...GFDL...AND HWRF NOW
CALL FOR TOMAS TO MOVE RAPIDLY NORTHWARD AND BE ABSORBED INTO THE
TROUGH...WHICH IS A MAJOR CHANGE FROM THE 6 HOUR OLD RUNS. ON THE
OTHER HAND...THE NOGAPS...WHICH 6 HR AGO WAS CALLING FOR A
CONTINUED NORTHWARD MOTION...NOW CALLS FOR AN EASTWARD TURN SIMILAR
TO THE ECMWF. OVERALL...THE GUIDANCE ENVELOPE HAS SHIFTED
NORTHWARD FROM THE PREVIOUS ADVISORY. THE 72-120 HR PORTION OF THE
TRACK WILL ALSO BE SHIFTED NORTHWARD...BUT IS WELL SOUTH OF THE
CONSENSUS MODELS AND THE CENTER OF THE GUIDANCE ENVELOPE. THIS
PART OF THE FORECAST TRACK IS LOW CONFIDENCE.

TOMAS IS EXPERIENCING 10-15 KT OF SOUTH-SOUTHWESTERLY VERTICAL WIND
SHEAR...AND THE CYCLONE SHOULD REMAIN IN A LIGHT/MODERATE SHEAR
ENVIRONMENT FOR THE NEXT 36-48 HR. THIS SHOULD ALLOW STRENGTHENING
AS LONG AS THE CENTER REMAINS OVER WATER. THIS PART OF THE NEW
INTENSITY FORECAST IS ONLY SLIGHTLY CHANGED FROM THE PREVIOUS
ADVISORY AND IS CLOSEST TO THE SHIPS MODEL. AFTER 48 HR...THE
INTENSITY AND EVENTUAL FATE OF TOMAS ARE STRONGLY TIED TO ITS
TRACK. A NORTHWARD TRACK WOULD RESULT IN A RAPID EXTRATROPICAL
TRANSITION AND ABSORPTION BY THE DEEP-LAYER TROUGH. AN EASTWARD
TRACK WOULD KEEP THE SYSTEM NEAR OR JUST AHEAD OF THE COLD FRONT IN
AN AREA OF STRONG WIND SHEAR. EITHER WAY...TOMAS SHOULD WEAKEN
DURING THIS TIME AND THIS IS REFLECTED IN THE INTENSITY FORECAST.
THE 120 HR FORECAST NOW CALLS FOR EXTRATROPICAL TRANSITION...AND
THIS COULD OCCUR EARLIER IF THE CYCLONE MOVES FARTHER NORTH THAN
FORECAST.

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 04/1500Z 16.3N 76.1W 45 KT
12HR VT 05/0000Z 17.5N 75.9W 50 KT
24HR VT 05/1200Z 19.5N 74.7W 60 KT
36HR VT 06/0000Z 21.8N 73.1W 65 KT
48HR VT 06/1200Z 24.3N 71.3W 55 KT
72HR VT 07/1200Z 28.0N 69.0W 40 KT
96HR VT 08/1200Z 29.5N 66.5W 30 KT
120HR VT 09/1200Z 29.5N 63.5W 30 KT...POST-TROP/EXTRATROP


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