Tropical Storm BLANCA

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TROPICAL STORM BLANCA DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP032009
800 PM PDT MON JUL 06 2009
 
ALTHOUGH THE COVERAGE AND INTENSITY OF THE DEEP CONVECTION NEAR THE
CORE OF BLANCA HAS DIMINISHED SOMEWHAT OVER THE PAST FEW
HOURS...THE OVERALL CLOUD PATTERN APPEARS TO BE A LITTLE MORE
ORGANIZED WITH SLIGHTLY BETTER-DEFINED CURVED BANDING FEATURES. 
THE CURRENT INTENSITY ESTIMATE IS INCREASED TO 45 KT FOR THIS
ADVISORY IN AGREEMENT WITH THE LATEST DVORAK SATELLITE ESTIMATES
FROM TAFB AND SAB.  THE SYSTEM IS IN AN ENVIRONMENT OF MODEST
EASTERLY SHEAR AND CIRRUS MOTIONS SHOW FAIRLY STRONG UPPER-LEVEL
OUTFLOW EXCEPT OVER THE NORTHEAST QUADRANT OF THE STORM.  BLANCA
COULD STRENGTHEN A LITTLE MORE...BUT ITS WINDOW OF OPPORTUNITY FOR
INTENSIFICATION IS CLOSING QUICKLY AS THE CYCLONE SHOULD BEGIN TO
TRAVERSE SSTS COOLER THAN 26 DEGREES C IN 12 HOURS OR SO.  THUS THE
OFFICIAL FORECAST SHOWS A WEAKENING TREND COMMENCING BY 24 HOURS...
AND THE SYSTEM BEING REDUCED TO A REMNANT LOW IN 96 HOURS.  THIS IS
IN GOOD AGREEMENT WITH THE SHIPS GUIDANCE.  HOWEVER GIVEN THE
COOLER WATERS...AND A POSSIBLY MORE STABLE THAN EXPECTED AIR
MASS...BLANCA'S DEMISE COULD OCCUR SOONER THAN INDICATED HERE.

BASED ON A BLEND OF FIXES FROM GEOSTATIONARY AND MICROWAVE
IMAGERY...THE INITIAL MOTION IS ESTIMATED TO BE 295/9.  THERE IS
LITTLE CHANGE TO THE TRACK FORECAST OR THE REASONING BEHIND IT.  A
WEAKENING MID-LEVEL SUBTROPICAL RIDGE TO THE NORTH OF BLANCA SHOULD
PRODUCE A CONTINUED WEST-NORTHWESTWARD TRACK WITH A GRADUALLY
DECREASING FORWARD SPEED OVER THE NEXT FEW DAYS.  ONCE BLANCA
BECOMES A VERY WEAK CYCLONE...A GENERALLY WESTWARD MOTION IS
LIKELY.  THE OFFICIAL TRACK FORECAST IS FAIRLY CLOSE TO THE
DYNAMICAL MODEL CONSENSUS AND NOT TOO DISSIMILAR TO THE PREVIOUS
NHC TRACK.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0300Z 18.2N 113.8W    45 KT
 12HR VT     07/1200Z 18.8N 115.1W    50 KT
 24HR VT     08/0000Z 19.5N 116.9W    50 KT
 36HR VT     08/1200Z 20.0N 118.4W    45 KT
 48HR VT     09/0000Z 20.4N 119.8W    35 KT
 72HR VT     10/0000Z 20.8N 122.0W    25 KT
 96HR VT     11/0000Z 21.0N 124.0W    20 KT...REMNANT LOW
120HR VT     12/0000Z...DISSIPATED
 
$$
FORECASTER PASCH
 
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