[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT41 KNHC 310246
TCDAT1
HURRICANE TOMAS DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL212010
1100 PM AST SAT OCT 30 2010

THE STRUCTURE OF TOMAS HAS CHANGED LITTLE SINCE THE TIME THE ST.
LUCIA WEATHER SERVICE REPORTED SUSTAINED WINDS ON THAT ISLAND OF AT
LEAST 80 KT AROUND 2130 UTC.  AN EYE HAS NOT BECOME ESTABLISHED ON
INFRARED SATELLITE IMAGERY...ALTHOUGH IT IS WELL DEFINED IN RADAR
DATA FROM MARTINIQUE.  THE INITIAL INTENSITY IS KEPT AT 80 KT SINCE
THERE ARE NO OBVIOUS RECENT CHANGES...BUT IT IS POSSIBLE THIS COULD
BE A BIT CONSERVATIVE.  AN AIR FORCE HURRICANE HUNTER AIRCRAFT IS
SCHEDULED TO INVESTIGATE TOMAS LATER TONIGHT.

THE INITIAL MOTION IS 285/8.  THE CYCLONE IS EXPECTED TO
GRADUALLY GAIN LATITUDE FOR THE NEXT 48 HOURS OR SO DUE TO A MID-
TO UPPER-LEVEL TROUGH THAT IS CURRENTLY LOCATED OVER THE SOUTHWEST
ATLANTIC.  THE TRACK GUIDANCE IS IN GENERALLY GOOD AGREEMENT ON
THIS SOLUTION...BUT THERE IS MUCH GREATER SPREAD AFTER 48 HOURS.
THE GFS...ECMWF...UKMET...AND GFDL SUPPORT A STRONGER MID-LEVEL
RIDGE OVER THE GREATER ANTILLES AND MOVE TOMAS ON A WESTWARD OR
JUST SOUTH OF WESTWARD MOTION ON DAYS 2-4.  THE NOGAPS AND GFDN
SHOW TOMAS MOVING WELL NORTH OF HISPANIOLA BY DAY 5...AND THE HWRF
SHOWS THE CYCLONE STALLING OVER THE EASTERN CARIBBEAN SEA.  THE
LATTER THREE MODELS APPEAR TO BE OUTLIERS.  THE NEW OFFICIAL
FORECAST IS JUST A LITTLE SOUTH OF THE PREVIOUS FORECAST TO COME
INTO BETTER AGREEMENT WITH THE CONSENSUS OF THE MORE SOUTHERN BATCH
OF MODELS.

THERE CONTINUES TO BE LOW CONFIDENCE IN THE INTENSITY FORECAST.
NONE OF THE INTENSITY MODELS SHOW MUCH STRENGTHENING BEYOND ABOUT
90 KT.  THE 200-MB FLOW OVER THE CARIBBEAN SEA SHOULD BE FAVORABLE
FOR STRENGTHENING...ESPECIALLY IF TOMAS MAINTAINS A MORE
SOUTHERN COURSE.  HOWEVER...CROSS-SECTION ANALYSES OF THE GUIDANCE
DOES INDICATE THAT THE CYCLONE VORTEX COULD BECOME A LITTLE TILTED
OVER THE NEXT 48 HOURS OR SO...POSSIBLY DUE TO SHEAR BELOW THE
OUTFLOW LAYER.  BECAUSE OF THESE MIXED SIGNALS...THE OFFICIAL
INTENSITY FORECAST ONLY SHOWS MODEST STRENGTHENING THROUGH 24 HOURS
AND ESSENTIALLY HOLDS THE INTENSITY FAIRLY STEADY THEREAFTER.

FORECAST POSITIONS AND MAX WINDS

INITIAL      31/0300Z 13.6N  62.1W    80 KT
 12HR VT     31/1200Z 14.0N  63.8W    90 KT
 24HR VT     01/0000Z 14.6N  65.9W    95 KT
 36HR VT     01/1200Z 14.9N  68.0W    95 KT
 48HR VT     02/0000Z 15.0N  69.7W    95 KT
 72HR VT     03/0000Z 15.0N  72.5W    95 KT
 96HR VT     04/0000Z 15.5N  74.0W   100 KT
120HR VT     05/0000Z 16.0N  74.5W   100 KT

$$
FORECASTER BERG/FRANKLIN



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