[Tropical] Tropical Cyclone Discussion

[Nashville EMWIN]

WTNT41 KNHC 251432
TCDAT1
TROPICAL DEPRESSION SIX DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT WED AUG 25 2004

TROPICAL DEPRESSION SIX IS LOOKING A LITTLE RAGGED THIS MORNING.
WHILE STILL ORGANIZED INTO BANDS...THE ASSOCIATED CONVECTION HAS
DECREASED SIGNIFICANTLY IN DEPTH AND COVERAGE SINCE SUNRISE.  THE
REASON FOR THIS IS NOT CLEAR...ALTHOUGH THE SYSTEM MAY BE INGESTING
SOME OF THE DRY AIR SEEN NEARBY IN WATER VAPOR IMAGERY.  SATELLITE
INTENSITY ESTIMATES ARE 35 KT FROM SAB...30 KT FROM TAFB...AND 25
KT FROM AFWA.  THE INITIAL INTENSITY REMAINS 30 KT.

THE INITIAL MOTION IS NOW 275/15.  THE CYCLONE IS CURRENTLY SOUTH OF
A SUBTROPICAL RIDGE.  LARGE-SCALE MODELS INDICATE THAT A MID/
UPPER-LEVEL LEVEL LOW CURRENTLY SEEN IN WATER VAPOR IMAGERY JUST
SOUTHEAST OF NOVA SCOTIA WILL DIVE SOUTHEASTWARD AND WEAKEN THE
RIDGE FROM 48-96 HR AND THEN LIFT OUT TO THE NORTHEAST.  IF THIS
VERIFIES...IT WOULD ALLOW THE TROPICAL DEPRESSION TO TURN
NORTHWESTWARD AFTER 24-36 HR...AND THEN POSSIBLY TURNING MORE
WESTWARD BY 120 HR AS THE RIDGE REBUILDS TO THE NORTH.  THE
DYNAMICAL MODELS GENERALLY AGREE WITH THIS SCENARIO.  HOWEVER...THE
GFS HAS SHIFTED ITS TRACK CONSIDERABLY TO THE SOUTH AND WEST OF THE
GFDL...UKMET...AND NOGAPS.  THE OFFICIAL FORECAST TRACK ALSO SHIFTS
TO THE LEFT OF THE PREVIOUS TRACK...BUT NOT AS FAR AS THE GFS.  THE
NEW TRACK IS ALONG THE WESTERN EDGE OF THE OTHER DYNAMICAL MODELS
IN BEST AGREEMENT WITH THE GFDL AND THE CONSENSUS MODELS.

OTHER THAN THE CURRENT RAGGED APPEARANCE...CONDITIONS GENERALLY
APEPAR FAVORABLE FOR THE CYCLONE TO INTENSIFY FOR THE FIRST 72-96
HR.  THE INTENSITY FORECAST WILL CALL FOR SLOW STRENGTHENING FOR
THE FIRST 48 HR OR SO IN AGREEMENT WITH THE CURRENT ORGANIZATION
AND TRENDS...THEN CALL FOR FASTER DEVELOPMENT AS THE SYSTEM NEARS
HURRICANE STRENGTH.  AFTER 72-96 HR...IF THE CYCLONE TRACKS AS FAR
NORTH AS FORECAST...IT MAY ENCOUNTER WESTERLY SHEAR TO THE NORTH OF
THE UPPER-LEVEL RIDGE FORECAST TO LIE EAST-WEST ALONG 18-19N.  THAT
WOULD LIMIT STRENGTHENING AS INDICATED IN THE FORECAST.  AN
ALTERNATE SCENARIO WOULD BE IF THE CYCLONE STAYS SOUTH OF THE RIDGE
AXIS...WHICH WOULD ALLOW GREATER STRENGTHENING THAN CURRENTLY
FORECAST.

FORECASTER BEVEN

FORECAST POSITIONS AND MAX WINDS

INITIAL      25/1500Z 11.4N  39.1W    30 KT
 12HR VT     26/0000Z 11.8N  41.3W    35 KT
 24HR VT     26/1200Z 12.6N  43.7W    40 KT
 36HR VT     27/0000Z 13.5N  45.6W    45 KT
 48HR VT     27/1200Z 14.5N  47.2W    50 KT
 72HR VT     28/1200Z 16.5N  49.5W    65 KT
 96HR VT     29/1200Z 18.5N  52.0W    75 KT
120HR VT     30/1200Z 20.5N  55.0W    75 KT


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