[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 010234
TCDAT1
TROPICAL STORM TOMAS DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL212010
1100 PM AST SUN OCT 31 2010

RECENT MICROWAVE DATA...PARTICULARLY A 0045 UTC SSMIS PASS...
INDICATE THAT THE LOW-LEVEL CENTER OF TOMAS IS NOW LOCATED ABOUT
140 N MI TO THE WEST OF THE DEEP CONVECTION AND HAS BEEN MOVING A
LITTLE SOUTH OF DUE WEST.  DVORAK ESTIMATES HAVE DECREASED TO
T3.0/4.0 FROM TAFB...T2.5/3.5 FROM SAB...AND T3.4/4.3 FROM THE
ADT...AND THE INITIAL INTENSITY IS THEREFORE LOWERED TO 55 KT FOR
THIS ADVISORY.  THIS INTENSITY COULD BE A LITTLE GENEROUS...BUT
ADDITIONAL ADJUSTMENTS CAN BE MADE WHEN THE AIR FORCE HURRICANE
HUNTER AIRCRAFT INVESTIGATES THE CYCLONE LATER TONIGHT.

SIGNIFICANT MODIFICATIONS HAVE BEEN REQUIRED TO THE INTENSITY
FORECAST ON THIS ADVISORY.  STRONG SOUTHWESTERLY SHEAR BELOW THE
OUTFLOW LAYER IS EXPECTED TO CONTINUE TO AFFECT TOMAS FOR THE NEXT
48 HOURS...AS SHOWN BY THE SHIPS GUIDANCE...AND ALL THE INTENSITY
MODELS ARE SHOWING CONTINUED WEAKENING DURING THAT TIME.  THE
OFFICIAL FORECAST HAS BEEN ADJUSTED DOWNWARD...LEVELING THE
INTENSITY AT 40 KT BETWEEN 24 AND 48 HOURS.  THIS IS STILL ABOVE
MOST OF THE INTENSITY GUIDANCE...AND IT IS NOT OUT OF THE QUESTION
THAT TOMAS COULD WEAKEN MORE THAN INDICATED IN THE OFFICIAL
FORECAST.  THE SHEAR IS EXPECTED TO RELAX AFTER 72 HOURS...AND
THERE WILL BE AN OPPORTUNITY FOR TOMAS TO RESTRENGTHEN...POSSIBLY
BACK TO HURRICANE INTENSITY...OVER THE CENTRAL CARIBBEAN SEA.

NOW THAT THE LOW- AND MID-LEVEL CIRCULATIONS OF TOMAS HAVE BECOME
INCREASINGLY DECOUPLED...THE LOW-LEVEL CENTER HAS ACCELERATED OVER
THE PAST FEW HOURS WITH AN INITIAL MOTION ESTIMATED TO BE 270/13.
THE SOUTHWESTWARD ADJUSTMENT OF THE INITIAL POSITION HAS CAUSED THE
NEW FORECAST TRACK TO BE A LITTLE SOUTH AND FASTER THAN THE
PREVIOUS FORECAST.  THE TRACK GUIDANCE IS IN RELATIVELY GOOD
AGREEMENT ON THE FUTURE TRACK OF TOMAS...BUT THERE CONTINUES TO BE
SPEED DIFFERENCES MAINLY ON DAYS 4 AND 5 WHEN A DEEP MID-LATITUDE
TROUGH SWEEPS ACROSS THE GULF OF MEXICO AND NORTHWESTERN CARIBBEAN.
THE GFDN AND HWRF ARE STILL THE FASTEST MODELS...BUT THEY HAVE BEEN
JOINED BY THE ECMWF...MAKING A FASTER SCENARIO A LITTLE MORE
CREDIBLE BY DAY 5.

FORECAST POSITIONS AND MAX WINDS

INITIAL      01/0300Z 14.2N  66.5W    55 KT
 12HR VT     01/1200Z 14.4N  68.1W    45 KT
 24HR VT     02/0000Z 14.7N  69.8W    40 KT
 36HR VT     02/1200Z 14.8N  71.6W    40 KT
 48HR VT     03/0000Z 14.8N  73.1W    40 KT
 72HR VT     04/0000Z 15.1N  74.5W    50 KT
 96HR VT     05/0000Z 16.5N  74.5W    65 KT
120HR VT     06/0000Z 20.0N  72.5W    70 KT

$$
FORECASTER BERG


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