[Tropical] Tropical Cyclone Discussion

[Nashville EMWIN]

WTNT43 KNHC 122040
TCDAT3
HURRICANE CHARLEY DISCUSSION NUMBER  14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT THU AUG 12 2004

CHARLEY CONTINUES TO STRENGTHEN AND BECOME BETTER ORGANIZED BASED ON
DATA FROM RECONNAISSANCE AIRCRAFT...SATELLITE IMAGES...AND RADARS
FROM CUBA. WHILE THE CENTRAL PRESSURE HAS ONLY DECREASED TO 980 MB
...THE HURRICANE IS MOVING INTO A REGION OF HIGHER THAN AVERAGE
SURFACE PRESSURES FOR THIS TIME OF THE YEAR. THEREFORE...THE USUAL
PRESSURE-WIND RELATIONSHIP MAY NOT BE VALID...AT THIS TIME. THE
INITIAL INTENSITY OF 90 KT IS BASED ON A FLIGHT-LEVEL WIND OF 105
KT...OR A SURFACE WIND ESTIMATE OF 95 KT...AND A 92 KT DROPSONDE
SURFACE WIND. A SMALL EYE HAS BECOME QUITE DISTINCT IN SATELLITE
IMAGERY AND UPPER-LEVEL OUTFLOW CONTINUES TO IMPROVE AND EXPAND IN
ALL QUADRANTS AS THE VERTICAL SHEAR HAS DECREASED SIGNIFICANTLY.

THE INITIAL MOTION IS NOW 335/15. CHARLEY BASICALLY REMAINS ON
TRACK. UNFORTUNATELY...THERE IS SOMETHING OF A QUANDARY WITH THE
LATEST NHC MODEL GUIDANCE. THE NEW GFDL AND UKMET RUNS HAVE MADE A
WIDE TURN 75 TO 150 NMI LEFT OF THE PREVIOUS FORECAST TRACK...AND
MOST OF THE OTHER GLOBAL MODELS AND NHC MODELS HAVE ALSO MADE A
WESTWARD SHIFT. HOWEVER...THE 6- AND 12-HOUR GFDL AND UKMET
FORECAST POSITIONS ARE ALREADY 30 TO 60 NMI WEST OR LEFT OF THE
CURRENT POSITION AND MOTION. A STRONG UPSTREAM TROUGH NOTED DIGGING
SOUTHEASTWARD OVER THE NORTHWESTERN GULF OF MEXICO IN WATER VAPOR
IMAGERY SHOULD HELP TO BLOCK ANY SIGNIFICANT WESTWARD MOTION. BASED
ON THE DEVELOPING WESTERLY TO SOUTHWESTERLY SYNOPTIC FLOW PATTERN
OVER THE GULF...AND AN APPARENT LEFT BIAS BY MOST OF THE MODEL
GUIDANCE...THE OFFICIAL TRACK IS JUST AN UPDATE AND EXTENSION OF
THE PREVIOUS TWO FORECAST TRACKS.

THE UPPER-LOW TO THE WEST OF CHARLEY IS NO LONGER AN INHIBITING
FACTOR. IN CONTRAST...CHARLEY HAS DEVELOPED WELL-DEFINED
UPPER-LEVEL ANTICYCLONIC OUTFLOW THAT SHOWS SIGNS OF ONLY GETTING
BETTER FOR THE NEXT 24 HOURS. GIVEN THE SMALL EYE FEATURE AND AN
ABUNDANCE OF WARM WATER AHEAD OF THE HURRICANE...CHARLEY IS
EXPECTED TO CONTINUE STRENGTHENING...POSSIBLY EVEN RAPIDLY
INTENSIFYING...AND BECOME A MAJOR HURRICANE BEFORE MAKING LANDFALL
OVER WESTERN CUBA THIS EVENING. THE TERRAIN OVER WESTERN CUBA IS
NOT PARTICULARLY HIGH AND LITTLE...IF ANY...DISRUPTION OF THE
CIRCULATION IS EXPECTED. GIVEN THE IMPRESSIVE OUTFLOW REGIME THAT
IS FORECAST TO DEVELOP OVER THE FLORIDA PENINSULA AND EASTERN GULF
BY ALL OF THE GLOBAL AND REGIONAL MODELS...MAJOR HURRICANE STRENGTH
SEEMS QUITE PROBABLE OVER THE SOUTHEASTERN GULF OF MEXICO ON FRIDAY.
CHARLEY COULD STRENGTHEN A LITTLE MORE BETWEEN THE 12 AND 24 HOURS
TIME PERIODS...AND THEN WEAKEN SLIGHTLY BEFORE MAKING LANDFALL DUE
TO INCREASING VERTICAL SHEAR AND COOLER COASTAL WATERS AROUND THE
TAMPA BAY AREA. THE OFFICIAL FORECAST IS CONSISTENT WITH THE SHIPS
AND GFDL INTENSITY MODELS.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL      12/2100Z 21.2N  81.9W    90 KT
 12HR VT     13/0600Z 23.1N  82.7W   100 KT
 24HR VT     13/1800Z 26.5N  83.0W   105 KT
 36HR VT     14/0600Z 30.5N  82.3W    65 KT...INLAND
 48HR VT     14/1800Z 34.2N  80.0W    45 KT...INLAND
 72HR VT     15/1800Z 42.0N  75.0W    35 KT...INLAND EXTRATROPICAL
 96HR VT     16/1800Z 48.5N  65.0W    30 KT...INLAND EXTRATROPICAL
120HR VT     17/1800Z...ABSORBED BY FRONTAL SYSTEM


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