Hurricane TOMAS

ZCZC MIATCDAT1 ALL
TTAA00 KNHC DDHHMM
HURRICANE TOMAS DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL212010
1100 AM AST SAT OCT 30 2010
 
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING TOMAS
THIS MORNING FOUND MAXIMUM 700 MB FLIGHT-LEVEL WINDS OF 68 KT IN
THE SOUTHEAST QUADRANT ALONG WITH SEVERAL 64-66 KT RELIABLE SFMR
WINDS. IN ADDITION...A DROPSONDE IN THE NORTHEAST EYEWALL INDICATED
A SURFACE WIND OF 72 KT. HOWEVER...THE BOUNDARY-LAYER WIND PROFILES
SUGGEST A SLIGHTLY LESSER SURFACE WIND SPEED ESTIMATE OF AROUND 66
KT. A COMBINATION OF THIS DATA EASILY SUPPORTS A 65-KT HURRICANE...
AND TOMAS HAS BEEN UPGRADED ACCORDINGLY.

THE INITIAL MOTION ESTIMATE IS 290/13. THE LATEST RECON FIX
POSITIONS HAVE COME IN RIGHT ON THE PREVIOUS ADVISORY TRACK. 
UPPER-AIR DATA FROM SAN JUAN REVEALED 30-METER 500 MB HEIGHT
INCREASES DURING THE PAST 24 HOURS...WHICH CLEARLY INDICATES THAT
MID-LEVEL RIDGING TO THE NORTH OF TOMAS HAS STARTED AS THE
DEEP-LAYER TROUGH THAT HAS CAPTURED HURRICANE SHARY LIFTS RAPIDLY
TO THE NORTHEAST AWAY FROM THE CARIBBEAN REGION. LOW- TO MID-LEVEL
RIDGING IS FORECAST BY ALL OF THE GLOBAL MODELS TO CONTINUE
BUILDING WESTWARD ACROSS THE LESSER AND GREATER ANTILLES FOR THE
NEXT 72-96 HOURS. THIS SHOULD GRADUALLY FORCE TOMAS ON A MORE
WESTERLY TRACK...ESPECIALLY AFTER 48 HOURS. HOWEVER...BY DAY 5...A
BROAD MID-TROPOSPHERIC TROUGH CURRENTLY LOCATED ALONG THE U.S. WEST
COAST IS FORECAST TO MOVE EASTWARD INTO THE CENTRAL U.S. BY DAYS
2-3 AND THEN DIG MORE SOUTHEASTWARD AFTER THAT...AND INTO THE GULF
OF MEXICO AND SOUTHEASTERN MEXICO BY DAY 5. THIS IS EXPECTED TO
RESULT IN A SIGNIFICANT EROSION OF THE WESTERN PORTION OF THE RIDGE
AND A WEAKENING OF THE STEERING CURRENT ACROSS THE WESTERN AND
CENTRAL CARIBBEAN SEA. THIS WEAK FLOW REGIME SHOULD ALLOW TOMAS TO
SLOW DOWN AND GRADUALLY MOVE NORTHWARD. THE OFFICIAL FORECAST TRACK
IS JUST AN UPDATE AND EXTENSION OF THE PREVIOUS ADVISORY TRACK...
AND REMAINS ALONG THE SOUTHERN EDGE OF THE NHC GUIDANCE ENVELOPE.

TOMAS HAS DEVELOPED A 30-40 NMI DIAMETER EYE NOTED IN RECENT RADAR
IMAGES FROM MARTINIQUE. THE UPPER-LEVEL OUTFLOW PATTERN IS WELL
ESTABLISHED AND CONTINUES TO IMPROVE. A COMBINATION OF THE
AFOREMENTIONED FEATURES ALONG WITH DEEP WARM WATER AHEAD OF THE
CYCLONE SHOULD RESULT IN CONTINUED STRENGTHENING FOR THE NEXT 24
HOURS OR SO. AFTER THAT...HOWEVER...WESTERLY 300 MB WINDS ARE
EXPECTED TO UNDERCUT THE IMPRESSIVE OUTFLOW LAYER AND INDUCE SOME
SHEAR ON TOMAS...WHICH MAY HALT THE INTENSIFICATION PROCESS. 
USUALLY WITH WESTERLY SHEAR COMES DRY AIR MID-LEVEL AIR...AND THIS
INHIBITING FACTOR WAS CLEARLY INDICATED IN UPPER-AIR DATA WEST OF
65W LONGITUDE THIS MORNING. BY 72 HOURS...ENVIRONMENTAL CONDITIONS
ARE EXPECTED TO IMPROVE AS TOMAS SLOWS DOWN...AND A INTENSIFICATION
IS EXPECTED TO RESUME. THE OFFICIAL INTENSITY FORECAST IS ABOVE THE
SHIPS/LGEM MODELS...AND IS SIMILAR TO THE PREVIOUS FORECAST AND
LAST TWO GFDL MODEL RUNS...WHICH MAKES A TOMAS A MAJOR HURRICANE
SOUTH OF HISPANIOLA.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      30/1500Z 13.3N  60.7W    65 KT
 12HR VT     31/0000Z 13.8N  62.5W    75 KT
 24HR VT     31/1200Z 14.4N  64.8W    80 KT
 36HR VT     01/0000Z 14.8N  67.2W    80 KT
 48HR VT     01/1200Z 15.2N  69.2W    85 KT
 72HR VT     02/1200Z 15.6N  72.3W    90 KT
 96HR VT     03/1200Z 16.0N  74.0W   100 KT
120HR VT     04/1200Z 16.5N  75.0W   100 KT
 
$$
FORECASTER STEWART
 
NNNN