Hurricane TOMAS

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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
 
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