Tropical Storm BARBARA

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TROPICAL STORM BARBARA DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP022007
800 PM PDT WED MAY 30 2007
 
THE BANDING FEATURES EVIDENT EARLIER TODAY HAVE MOSTLY
DIMINISHED...RELEGATING THE DEEP CONVECTION TO ONE CLUSTER VERY
NEAR THE CIRCULATION CENTER.  DVORAK DATA-T NUMBERS FROM TAFB AND
SAB HAVE BOTH COME DOWN TO 2.5 BUT A BLEND OF THE CI VALUES
SUPPORTS MAINTAINING THE ADVISORY INTENSITY AT 40 KT.  BARBARA FELL
IN THE GAP BETWEEN QUIKSCAT SWATHS TONIGHT...SO THERE IS NOTHING TO
CONFIRM OR DENY THE INTENSITY ESTIMATE.
 
THE TRACK FORECAST REMAINS EXTREMELY LOW-CONFIDENCE.  NOT ONLY ARE
THERE SIGNIFICANT DISAGREEMENTS AMONG THE PRIMARY DYNAMICAL
MODELS...THE ENSEMBLES BASED ON INDIVIDUAL MODELS SUCH AS THE GFS
AND ECMWF ARE ALL OVER THE PLACE TOO.  FOR EXAMPLE...THE CONTROL
RUN OF THE 12Z ECMWF FORECASTS BARBARA TO BE PICKED UP BY THE TROUGH
OVER THE GULF OF MEXICO AND TO MOVE INLAND OVER GUATEMALA IN LESS
THAN 72 HOURS...WHILE ITS VARIOUS ENSEMBLE MEMBERS INCLUDE
NORTHWESTWARD TRACKS ALONG THE PACIFIC COAST OF MEXICO.  MEANWHILE
THE GFS...WHICH HAD BEEN ADAMANT ABOUT A NORTHEASTWARD TRACK...HAS
DRAMATICALLY SHIFTED AND NOW FORECASTS A RELATIVELY BRISK
NORTHWESTWARD MOTION TO THE SOUTH OF THE MEXICAN RIDGE ON DAYS 4
AND 5.  OTHER MODELS SUCH AS GFDL AND NOGAPS ARE IN BETWEEN...BUT
THEY LOSE THE CIRCULATION IN THREE OR FOUR DAYS NEAR THE GULF OF
TEHUANTEPEC.  ALL OF THE MODEL FLIP-FLOPPING GIVES ME LITTLE
JUSTIFICATION TO SHIFT THE OFFICIAL TRACK IN ANY DIRECTION...SO IT
IS VERY SIMILAR TO THE PREVIOUS ADVISORY.  THIS TRACK IS SLOW
SOUTHWARD FOR A DAY OR SO...THEN SLOW NORTHWARD TOWARD THE WEAKNESS
IN THE SUBTROPICAL RIDGE...WITH A SUBTLE WESTWARD BEND ON DAYS 4
AND 5 WHEN THE MODELS FORECAST THE RIDGE TO BUILD SLIGHTLY OVER THE
GULF OF MEXICO.
 
WATER VAPOR IMAGERY REVEALS THAT THE MID-LEVEL NORTHERLY FLOW BEHIND
THE GULF OF MEXICO TROUGH HAS REACHED THE CENTER OF BARBARA...WITH
THE ANTICIPATED INHIBITING EFFECTS ON THE INTENSITY.  THAT PATTERN
SHOULD GRADUALLY ABATE DURING THE NEXT COUPLE OF DAYS...AND BARBARA
WILL STILL BE OVER VERY WARM WATERS AND IN AN ENVIRONMENT OF WEAK
VERTICAL WIND SHEAR.  THEREFORE...GRADUAL STRENGTHENING IS FORECAST
IN ACCORDANCE WITH MOST OF THE INTENSITY GUIDANCE.  IN GENERAL...
THE NEW OFFICIAL FORECAST IS ONLY ADJUSTED VERY SLIGHTLY DOWNWARD
AS COMPARED TO THE PREVIOUS ADVISORY.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      31/0300Z 13.0N  96.9W    40 KT
 12HR VT     31/1200Z 12.6N  96.8W    45 KT
 24HR VT     01/0000Z 12.4N  96.7W    50 KT
 36HR VT     01/1200Z 12.7N  96.5W    55 KT
 48HR VT     02/0000Z 13.1N  96.3W    60 KT
 72HR VT     03/0000Z 14.0N  96.0W    65 KT
 96HR VT     04/0000Z 15.0N  96.5W    70 KT
120HR VT     05/0000Z 15.5N  97.5W    70 KT
 
$$
FORECASTER KNABB
 
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