Tropical Storm BLANCA

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TROPICAL STORM BLANCA DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 PM PDT THU JUN 19 2003
 
BLANCA LIKELY PEAKED AROUND 15Z-16Z WHEN SSMI AND AMSU MICROWAVE
DATA INDICATED A LOW- AND MID-LEVEL EYE FEATURE. SINCE THEN...IT
HAS BEEN ALL DOWN HILL. SATELLITE IMAGERY INDICATES VIRTUALLY NO
CENTRAL DEEP CONVECTION...ALTHOUGH SOME CONVECTION HAS RE-DEVELOPED
WELL SOUTH OF THE CENTER. THE INITIAL INTENSITY HAS BEEN DECREASED
TO 40 KT BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 35 KT
FROM TAFB AND 45 KT FROM BOTH SAB AND AFWA.
 
THE INITIAL MOTION ESTIMATE CONTINUES TO BE 225/03. NOW THAT BLANCA
HAS LOST ITS CENTRAL DEEP CONVETCION...THE VERTICAL CIRCULATION HAS
LIKELY DECREASED AND THE SYSTEM IS NOW BEING STEERED MORE BY THE
NORTHEASTERLY LOW- TO MID-LEVEL FLOW ON THE SOUTH SIDE OF THE WEAK
SUBTROPICAL RIDGE LOCATED OVER MEXICO. A SLOW SOUTHWEST TO WESTWARD
DRIFT IS FORECAST BY ALL OF THE NHC MODEL GUIDANCE FOR THE NEXT
48-72 HOURS...AND THEN THE MODELS DIVERGE SIGNIFICANTLY AFTER THAT.
BLANCA IS EXPECTED TO DRIFT SOUTHWESTWARD FOR THE NEXT 24 HOURS AND
THEN TURN MORE WESTWARD...WHICH IS SIMILAR TO THE GLOBAL AND
REGIONAL TRACK MODELS AND THE PREVIOUS OFFICIAL FORECAST TRACK.

SOUTHEASTERLY UPPER-LEVEL FLOW HAS BEEN INCREASING OVER BLANCA...BUT
AS THE CYCLONE DRIFTS FARTHER SOUTHWEST...THE SHEAR COULD ACTUALLY
WEAKEN SLIGHTLY FOR THE NEXT 12-24 HOURS. AFTER THAT...HOWEVER...
BLANCA SHOULD BEGIN EXPERIENCING 30-40 KT UPPER-LEVEL SOUTHEASTERLY
SHEAR AS INDICATED BY ALL OF THE GLOBAL MODELS. THERE MAY BE BRIEF
PERIODS OF CONVECTIVE DEVELOPMENT OR BURSTING...ESPECIALLY AT
NIGHT...FOR THE NEXT 36-48 HOURS. HOWEVER...THE GENERAL TREND
SHOULD BE FOR CONTINUED WEAKENING TO OCCUR DUE TO INCREASING
SHEAR...DRY AIR ENTRAINMENT...AND THE CYCLONE MOVING INTO A FIELD
OF STABLE STRATOCUMULUS CLOUDS. IF CENTRAL DEEP CONVECTION DOES NOT
RE-DEVELOP...THEN A FASTER RATE OF WEAKENING WILL OCCUR.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0300Z 15.8N 105.2W    40 KT
 12HR VT     20/1200Z 15.7N 105.6W    35 KT
 24HR VT     21/0000Z 15.6N 106.2W    35 KT
 36HR VT     21/1200Z 15.6N 106.9W    30 KT
 48HR VT     22/0000Z 15.8N 107.6W    30 KT
 72HR VT     23/0000Z 15.9N 108.9W    25 KT...DISSIPATING
 96HR VT     24/0000Z 15.9N 110.5W    20 KT...REMNANT LOW
120HR VT     25/0000Z 15.9N 112.0W    20 KT...REMNANT LOW
 
 
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