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TROPICAL STORM BARBARA DISCUSSION NUMBER   9
NATIONAL WEATHER SERVICE MIAMI FL
8 PM PDT THU JUN 21 2001
 
DEEP CONVECTION HAS REDEVELOPED NEAR THE LOW-LEVEL CENTER AND DVORAK
SATELLITE CURRENT INTENSITY ESTIMATES REMAIN AT 3.0...OR 45 KT...
FROM TAFB...SAB...AND KGWC.  AS A RESULT...THE INITIAL INTENSITY IS
HELD AT 45 KT.  SHIP V2FA2 LOCATED 105 NM NORTHWEST OF THE CENTER
REPORTED A NORTHEAST WIND OF 47 KT AND 26 FT SEAS AT 22/00Z.
HOWEVER...THE WINDS SEEM RATHER HIGH AND REMOVING THE 15 KT
NORTHEAST SHIP MOTION YIELDS 32 KT WINDS...WHICH BETTER FITS THE
SATELLITE PATTERN AND EARLIER SYNOPTIC DATA.  WIND RADII REMAIN
UNCHANGED...BUT THE 12 FT SEAS RADII WERE INCREASED BASED ON THAT
SHIP REPORT.

INITIAL MOTION ESTIMATE IS 290/12.  BARBARA HAS REMAINED ON TRACK
AND THE OFFICIAL FORECAST TRACK IS VERY CLOSE TO THE PREVIOUS
FORECAST.  THE MAIN QUESTION IS WHEN WILL THE LOW-LEVEL AND
UPPER-LEVEL CIRCULATIONS DECOUPLE?  BY 36 HOURS...BARBARA IS
EXPECTED TO WEAKEN BELOW TROPICAL STORM STRENGTH AND BE STEERED MORE
WESTWARD BY THE PREVAILING EASTERLY LOW-LEVEL FLOW SOUTH OF THE
SUBTROPICAL RIDGE.  THIS SCENARIO IS IN CLOSE AGREEMENT WITH THE
AVN...GFDL...UKMET...  AND NOGAPS MODELS THROUGH 48 HOURS... AND 
THEN SIMILAR TO THE SHALLOW BAM MODEL AFTER THAT.

WHILE OCCASIONAL BURSTS OF CONVECTION NEAR THE CENTER MAY OCCUR...
THE GENERAL TREND SHOULD BE FOR STEADY OR POSSIBLY RAPID WEAKENING
AS BARBARA MOVES OVER INCREASINGLY COOLER WATER AND ENCOUNTERS
STRONG WESTERLY SHEAR OWING TO A 50 TO 75 KT SUBTROPICAL JET THAT IS
FORECAST TO DEVELOP ACROSS THE HAWAIIAN ISLANDS BY 48 HOURS.  THE
OFFICIAL INTENSITY FORECAST IS CLOSE TO THE SHIPS INTENSITY MODEL.

FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     22/0300Z 15.8N 137.0W    45 KTS
12HR VT     22/1200Z 16.5N 138.7W    40 KTS
24HR VT     23/0000Z 17.4N 141.2W    35 KTS
36HR VT     23/1200Z 17.9N 143.7W    30 KTS
48HR VT     24/0000Z 18.3N 146.1W    25 KTS...DISSIPATING
72HR VT     25/0000Z 19.0N 151.0W    20 KTS...DISSIPATING
 
 
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