Tropical Storm BLANCA

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TROPICAL STORM BLANCA DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 PM PDT TUE JUN 17 2003
 
THE INNER CORE CONVECTION OF TROPICAL STORM BLANCA HAS WAXED AND
WANED DURING THE PAST 12 HOURS...WITH ANOTHER CONVECTIVE BURST
HAVING OCCURRED NEAR THE CENTER DURING THE PAST COUPLE OF HOURS. A
17/1948Z TRMM OVERPASS INDICATED AN 80 PERCENT LOW-LEVEL EYEWALL
HAD FORMED AT THAT TIME. THE CURRENT INTENSITY OF 45 KT IS BASED ON
CONSENSUS T3.0 OR 45 KT INTENSITY FROM ALL 3 SATELLITE AGENCIES.
 
THE INITIAL MOTION IS A HIGHLY UNCERTAIN 290/2. THE TREND IN
MICROWAVE POSITIONS THE PAST 18 HOURS ACTUALLY SUGGESTS A SLOW
WESTWARD DRIFT HAS OCCURRED. IT ALSO APPEARS THAT THE EASTERLY
UPPER-LEVEL FLOW ACROSS THE CYCLONE IS ACTING TO NUDGE THE SYSTEM
SLOWLY WESTWARD. HOWEVER...THE GLOBAL MODELS ARE IN FAIR AGREEMENT
THAT THE WEAKNESS IN THE SUBTROPICAL RIDGE IN WHICH BLANCA IS
CURRENTLY EMBEDDED WILL WEAKEN A LITTLE MORE AS THE MID-LEVEL
TROUGH OVER BAJA CALIFORNIA DIGS A LITTLE FARTHER SOUTH DURING THE
NEXT 24 HOURS AND ALLOW BLANCA TO MOVE SLIGHTLY POLEWARD. BY 36
HOURS...THE TROUGH IS FORECAST TO LIFT OUT AND ALLOW THE RIDGE TO
BUILD WESTWARD TO THE NORTH OF BLANCA...WHICH SHOULD ACT TO KEEP
THE CYCLONE MOVING IN A MORE WESTWARD DIRECTION TOWARD COOLER
WATER. THE OFFICIAL FORECAST TRACK IS A LITTLE SLOWER AND SLIGHTLY
TO THE LEFT OF THE PREVIOUS TRACK AND IS CLOSE TO A BLEND OF THE
MEDIUM BAM...NOGAPS...GFDN...AND GFS ENSEMBLE MODELS.
 
EARLIER CIRRUS OUTFLOW FROM A DYING CONVECTIVE COMPLEX ALONG THE
MEXICAN COAST EAST OF BLANCA HAS BEEN ACTING TO ENHANCE THE
UPPER-LEVEL SHEAR ACROSS THE CYCLONE. HOWEVER...WATER VAPOR IMAGERY
INDICATES THE SHEAR HAS ABATED SLIGHTLY AND THIS HAS ALLOWED DEEP
CONVECTION TO REFORM NEAR THE CYCLONE CENTER. SINCE BLANCA IS
EXPECTED TO REMAIN OVER WARM SSTS AND IN A RELATIVELY LOW SHEAR
ENVIRONMENT... ADDITIONAL STRENGTHENING IS FORECAST WITH MOST OF
THAT OCCURRING DURING THE NEXT 12 HOURS OR SO. THE OFFICIAL
FORECAST IS CLOSE TO THE SHIPS MODEL WHICH BRINGS BLANCA UP TO
HURRICANE STRENGTH IN 36 HOURS...BEFORE WEAKENING ENSUES AFTERWARDS
AS THE CYCLONE BEGINS MOVING OVER COOLER WATER.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/0300Z 16.6N 103.8W    45 KT
 12HR VT     18/1200Z 16.8N 104.2W    55 KT
 24HR VT     19/0000Z 17.0N 104.7W    60 KT
 36HR VT     19/1200Z 17.3N 105.2W    65 KT
 48HR VT     20/0000Z 17.5N 105.8W    65 KT
 72HR VT     21/0000Z 17.8N 106.8W    60 KT
 96HR VT     22/0000Z 18.0N 108.0W    45 KT
120HR VT     23/0000Z 18.0N 109.5W    30 KT
 
 
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