[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 030300
TCDAT3
TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT TUE AUG 02 2005

THE UPPER LEVEL LOW TO THE SOUTHWEST OF THE DEPRESSION CONTINUES TO
IMPOSE SOUTHERLY SHEAR... LEAVING MUCH OF THE LOW LEVEL CIRCULATION
EXPOSED.  THE PRIMARY CONCENTRATION OF CONVECTION HAS BEEN
PERSISTING NORTH OF THE CENTER... WITH A DISJOINTED BAND OF
CONVECTION EXTENDING TO THE SOUTHEAST.  LACKING ANY OTHER SOURCE OF
RELEVANT DATA THIS EVENING... THE CURRENT INTENSITY HINGES ON
SUBJECTIVE INTERPRETATION OF GOES INFRARED IMAGERY.  THE LATEST
DVORAK INTENSITY ESTIMATES ARE 25 KT FROM TAFB BASED ON THE CURVED
BANDING... AND 25 KT FROM SAB AND AFWA BASED ON THE SUBTROPICAL
APPEARANCE OF THE CLOUD PATTERN.  IT IS POSSIBLE THAT THE MAXIMUM
WINDS ARE ACTUALLY NEAR TROPICAL STORM STRENGTH SINCE THE LOW LEVEL
CENTER APPEARS TO BE JUST A SHORT DISTANCE SOUTH OF THE
CONCENTRATED CONVECTION... PERHAPS WORTHY OF A T2.5/35 KT DVORAK
CLASSIFICATION USING A SHEAR PATTERN.  HOWEVER... THERE IS
SUFFICIENT UNCERTAINTY IN THE LOCATION OF THE LOW LEVEL CENTER TO
COMPROMISE BETWEEN ALL OF THESE POSSIBILITIES AND MAINTAIN THE
INTENSITY AT 30 KT.

THE INITIAL MOTION ESTIMATE IS 015/8... CONSTRUCTED WITH THE HELP OF
A 01Z SSMI OVERPASS... WHICH A LITTLE SLOWER THAN THE PREVIOUS
ADVISORY AND WITH A SLIGHTLY GREATER NORTHEASTERLY COMPONENT.  THIS
APPEARS TO BE THE START OF THE TURN TOWARD THE NORTHEAST AHEAD OF A
MIDLATITUDE SHORTWAVE TROUGH EMERGING OFF THE UNITED STATES EAST
COAST.  EVEN AFTER THAT TROUGH PASSES BY THE TROPICAL CYCLONE...
PERSISTENT WESTERLIES SHOULD CONTINUE TO INDUCE AN EASTWARD MOTION
LATER IN THE FORECAST PERIOD.  THE DYNAMICAL MODELS INITIALIZE AND
FORECAST THE CIRCULATION OF THE DEPRESSION IN A VARIETY OF WAYS...
NONE OF WHICH APPEAR TO BE COMPLETELY CONSISTENT WITH RECENT MOTION
TRENDS.  THE NEW OFFICIAL FORECAST IS A LITTLE SLOWER THAN AND TO
THE RIGHT OF THE PREVIOUS ADVISORY... MAINLY TO BLEND WITH THE
SLOWER GFDL AND NOGAPS SOLUTIONS.

THE UPPER LEVEL LOW TO THE SOUTHWEST OF THE DEPRESSION IS EXPECTED
TO ALSO MOVE EAST BUT SHEAR OUT DURING THE NEXT 2-3 DAYS... BUT
THIS WILL LEAVE THE TROPICAL CYCLONE IN A WESTERLY SHEAR
ENVIRONMENT SOMEWHAT PROHIBITIVE FOR TOO MUCH STRENGTHENING.
HOWEVER...THE SHEAR COULD BE JUST WEAK ENOUGH... AND THE OCEAN WARM
ENOUGH... TO ALLOW THE SYSTEM TO REMAIN A TROPICAL STORM THROUGH
ABOUT DAY THREE.  THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS
ADVISORY AND IS A COMPROMISE BETWEEN THE GFDL AND SHIPS GUIDANCE.


FORECASTER KNABB

FORECAST POSITIONS AND MAX WINDS

INITIAL      03/0300Z 29.4N  68.5W    30 KT
 12HR VT     03/1200Z 30.4N  67.9W    40 KT
 24HR VT     04/0000Z 31.7N  66.2W    45 KT
 36HR VT     04/1200Z 32.8N  63.9W    40 KT
 48HR VT     05/0000Z 33.6N  61.1W    35 KT
 72HR VT     06/0000Z 34.0N  57.0W    35 KT
 96HR VT     07/0000Z 34.5N  54.0W    30 KT
120HR VT     08/0000Z 35.0N  51.0W    30 KT


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