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TROPICAL STORM DEAN DISCUSSION NUMBER 8
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT MON AUG 27 2001
DEAN HAS CONTINUED TO BECOME BETTER ORGANIZED AND IS STILL TRYING TO
CLOSE OFF AN EYE. THE INITIAL INTENSITY OF 60 KT IS BASED ON DVORAK
SATELLITE INTENSITY ESTIMATES OF 55 KT...T3.5... FROM TAFB...AND 45
KT...T3.0...FROM BOTH SAB AND AFWA. HOWEVER...THE INTENSITY WAS
INCREASED SLIGHTLY OVER THE SATELLITE ESTIMATES BASED ON THE
APPEARANCE OF AN INTERMITTENT TIGHT BANDED EYE FEATURE.
INITIAL MOTION ESTIMATE IS 035/20. EXCELLENT AGREEMENT IN THE
NHC MODEL GUIDANCE CONTINUES WITH DEAN FORECAST TO MOVE
NORTHEASTWARD THROUGHOUT THE PERIOD. THE ONLY DIFFERENCES ARE IN THE
FORWARD SPEED. THE CURRENT MOTION IS LEFT OF THE PREVIOUS FORECAST
TRACK...WHICH IS MAINLY DUE TO THE NEGATIVELY-TILTED SHORTWAVE
TROUGH UNDERCUTTING DEAN AND LIFTING IT MORE POLEWARD. HOWEVER...
12Z UPPER-AIR DATA AND SATELLITE ANIMATION INDICATE THAT A STRONG
SOUTHWESTERLY UPPER-LEVEL JET LIES ACROSS THE NORTHEAST U.S. AND
SOUTHEAST CANADA...WHICH SHOULD ACT TO TURN DEAN BACK TO THE RIGHT
OF ITS CURRENT MOTION BY 12 HOURS. THE OFFICIAL TRACK IS CLOSE TO
THE UKMET-AVN-GFDL CONSENSUS.
DEAN HAS LIKELY PEAKED IN INTENSITY...ALTHOUGH I CAN NOT RULE OUT A
POSSIBLE EYE APPEARING AND DEAN BECOMING A HURRICANE IN THE NEXT 6
HOURS. HOWEVER...TIME IS RAPIDLY RUNNING OUT FOR DEAN TO INTENSIFY
SINCE THE CYCLONE WILL BE OVER 22C SST WATER IN ABOUT 12 HOURS. BY
24 HOURS...DEAN IS EXPECTED TO UNDERGO EXTRATROPICAL TRANSITION AS
IT MERGES WITH OR IS ABSORBED BY AN APPROACHING MID-LATITUDE LOW
PRESSURE SYSTEM.
FORECASTER STEWART
FORECAST POSITIONS AND MAX WINDS
INITIAL 27/2100Z 41.3N 58.6W 60 KTS
12HR VT 28/0600Z 43.5N 56.0W 60 KTS...BECOMING EXTRATROPICAL
24HR VT 28/1800Z 45.7N 51.7W 55 KTS...EXTRATROPICAL
36HR VT 29/0600Z 47.4N 46.9W 50 KTS...EXTRATROPICAL
48HR VT 29/1800Z 50.1N 42.9W 40 KTS...EXTRATROPICAL
72HR VT 30/1800Z 54.0N 36.5W 35 KTS...EXTRATROPICAL
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