Tropical Storm BLANCA

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TROPICAL STORM BLANCA DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 AM PDT THU JUN 19 2003
 
A NEW BURST OF CONVECTION HAS FORMED NEAR AND SOUTHWEST OF THE
LOW-LEVEL CENTER OF BLANCA DURING THE PAST FEW HR. SATELLITE
INTENSITY ESTIMATES ARE 45 KT FROM TAFB...SAB...AND AFWA.  SHIP
9VID2 REPORTED 28 KT AND 1004.5 MB ABOUT 40 N MI SOUTHWEST OF THE
CENTER AS 12Z...SUGGESTING THE CENTRAL PRESSURE IS NEAR 1000 MB.
BASED ON THIS...THE INITIAL INTENSITY REMAINS 45 KT.

BLANCA REMAINS ESSENTIALLY STATIONARY IN A WEAKNESS IN THE
SUBTROPICAL RIDGE.  IF ANYTHING...IT HAS DRIFTED A LITTLE SOUTHWARD
SINCE YESTERDAY.  LARGE SCALE-MODELS INDICATE WEAK STEERING
CURRENTS WILL PERSIST NEAR THE CYCLONE THROUGH THE FORECAST
PERIOD...WITH SOME RIDGING DEVELOPING NORTH OF BLANCA GIVING IT A
GENERAL WESTWARD NUDGE.  THE DYNAMICAL MODELS ARE SPREAD BETWEEN A
NORTHWESTWARD AND SOUTHWESTWARD MOTION...BUT ARE UNANIMOUSLY SLOW.
THE BAMS AND NHC 91 CALL FOR A WESTWARD TO WEST-NORTHWESTWARD MOTION
AND ARE MUCH FASTER.  THE OFFICIAL FORECAST WILL LEAN ON THE SLOW
MOTION OF THE DYNAMICAL MODELS AND IS NUDGED A LITTLE SOUTH OF THE
PREVIOUS FORECAST TRACK.

BLANCA CONTINUES IN EASTERLY SHEAR...AND TENDENCY ANALYSES FROM
CIMSS AT THE UNIVERSITY OF WISCONSIN INDICATE THE SHEAR HAS
INCREASED OVER THE PAST 24 HR.  ADDTIONALLY...SATELLITE IMAGERY
SHOWS MID/UPPER LEVEL DRY AIR AND LOW-LEVEL STRATOCUMULUS NEAR THE
CYCLONE.  THIS COMBINATION SUGGESTS THAT THE WINDOW IS CLOSING ON
CHANCES FOR INTENSIFICATION.  LARGE-SCALE MODELS ALL SHOW INCREASED
SHEAR AFTER 24 HR...AND EVEN THOUGH THE FORECAST TRACK NOW KEEPS
BLANCA OVER WARM SEAS SURFACE TEMPERATURES THE SHEAR SHOULD BE
STRONG ENOUGH TO KILL IT.  THE INTENSITY FORECAST CALLS FOR LITTLE
CHANGE IN STRENGTH FOR THE FIRST 24 HR...FOLLOWED BY WEAKENING TO
EVENTUAL DISSIPATION IN 96-120 HR.

THE 34 KT WIND RADII HAVE BEEN REVISED DOWNWARD BASED ON THE SHIP
REPORT.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/1500Z 16.4N 104.6W    45 KT
 12HR VT     20/0000Z 16.2N 105.0W    45 KT
 24HR VT     20/1200Z 16.0N 105.6W    45 KT
 36HR VT     21/0000Z 16.0N 106.3W    40 KT
 48HR VT     21/1200Z 16.0N 107.0W    35 KT
 72HR VT     22/1200Z 16.0N 108.5W    30 KT
 96HR VT     23/1200Z 16.0N 110.0W    25 KT...DISSIPATING
120HR VT     24/1200Z 16.0N 112.0W    20 KT...REMNANT LOW
 
 
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