Tropical Storm BLANCA

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TROPICAL STORM BLANCA DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 PM PDT WED JUN 18 2003
 
AS HAS BEEN THE CASE THE PAST 2 DAYS...CONVECTION HAS CONTINUED
TO FLUCTUATE QUITE DRAMATICALLY BETWEEN THE DAY AND NIGHTIME
PERIODS AND BLANCA IS CURRENTLY GOING THROUGH ANOTHER WANING PERIOD
IN THE CONVECTIVE PATTERN. EARLIER IMAGES DURING THE DAY SUGGEST
THAT AN EYE WAS TRYING TO APPEAR IN THE CIRRUS CANOPY...BUT
EASTERLY UPPER-LEVEL SHEAR HAS BEEN DISRUPTING THE DEVELOPMENT
PROCESS. HOWEVER...THE CURRENT INTENSITY IS INCREASED SLIGHTLY TO
55 KT BASED ON A BLEND OF SATELLITE INTENSITY ESTIMATES OF 65 KT
FROM TAFB AND 45 KT FROM BOTH SAB AND AFWA. IT IS POSSIBLE THAT
BLANCA COULD BE A LITTLE STRONGER GIVEN ITS RATHER COMPACT SIZE.
 
THE INITIAL MOTION IS 270/03.  THERE REMAINS LITTLE CHANGE IN THE
SYNOPTIC REASONING FROM THE PREVIOUS COUPLE OF ADVISORY PACKAGES.
BLANCA REMAINS EMBEDDED IN A WEAKNESS IN THE SUBTROPICAL RIDGE WITH
A SLIGHT WESTERLY NUDGE BEING INDUCED BY THE UPPER-LEVEL EASTERLY
FLOW. WHILE THERE IS CONSIDERABLE SPREAD IN THE NHC TRACK
GUIDANCE...THE MODELS ARE IN GENERAL AGREEMENT ON A SLOW WESTWARD
MOTION CONTINUING THROUGHOUT THE 5-DAY PERIOD. THIS APPEARS
REASONABLE GIVEN THE LARGE-SCALE RIDGE PATTERN...ALBEIT WEAK...THAT
IS FORECAST TO REMAIN NORTH OF BLANCA. THE OFFICIAL FORECAST TRACK
IS ONLY SLIGHTLY SOUTH OF AND SLOWER THAN THE PREVIOUS TRACK...AND
IS CLOSE TO A BLEND OF THE VARIOUS GLOBAL AND REGIONAL MODELS.
 
BLANCA MAY BE SMALL...BUT THE SYSTEM HAS BEEN QUITE TENACIOUS IN
FIGHTING OFF INTERMITTENT MODERATE UPPER-LEVEL EASTERLY SHEAR. THE
CYCLONE PROBABLY ONLY HAS ONE MORE 12-18 HOUR PERIOD REMAINING
TONIGHT WHEN DEEP CONVECTION MAY REDEVELOP AROUND THE CENTER AND
POSSIBLY ALLOW BLANCA TO REACH HURRICANE STRENGTH. AFTER THAT...ALL
OF THE GLOBAL MODELS INDICATE THAT UPPER-LEVEL WINDS WILL INCREASE
TO SOUTHEASTERLY AT 35-45 KT. THE COMBINATION OF COOLER SSTS AND
INCREASING UPPER-LEVEL SHEAR SHOULD BRING ABOUT A STEADY WEAKENING
TREND BY 36 HOURS...IF NOT SOONER.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/0300Z 16.7N 104.8W    55 KT
 12HR VT     19/1200Z 16.8N 105.3W    60 KT
 24HR VT     20/0000Z 16.9N 105.9W    65 KT
 36HR VT     20/1200Z 16.9N 106.5W    60 KT
 48HR VT     21/0000Z 16.9N 107.2W    55 KT
 72HR VT     22/0000Z 16.8N 108.3W    45 KT
 96HR VT     23/0000Z 16.8N 110.0W    35 KT
120HR VT     24/0000Z 16.8N 112.0W    25 KT...DISSIPATING
 
 
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