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Tropical Storm BLANCA (Text)

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TROPICAL STORM BLANCA DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP032009
200 AM PDT TUE JUL 07 2009

THE STRUCTURE OF BLANCA HAS NOT CHANGED MUCH OVER THE PAST SEVERAL
HOURS...AS DEEP CONVECTION REMAINS CONFINED TO A SMALL AREA NEAR
THE CENTER AND IN A BAND TO THE SOUTHEAST. THE INITIAL INTENSITY IS
HELD AT 45 KT BASED ON DVORAK T-NUMBERS OF 3.0 FROM TAFB AND SAB AT
0600 UTC. WHILE BLANCA'S CIRCULATION REMAINS ROBUST...THE
OPPORTUNITY FOR SIGNIFICANT INTENSIFICATION HAS LIKELY PASSED. THE
SHIPS MODEL SHOWS THAT THE CYCLONE IS NOW LOCATED OVER SSTS LESS
THAN 27C...AND IS HEADED FOR SSTS BELOW 25C IN THE NEXT 12 TO 24
HOURS. THE COMBINATION OF COOL WATERS...A MORE STABLE LOWER
TROPOSPHERE AND MODERATE EASTERLY WIND SHEAR SHOULD CAUSE BLANCA TO
WEAKEN STEADILY AFTER 24 HOURS. THE OFFICIAL INTENSITY FORECAST HAS
BEEN ADJUSTED DOWNWARD IN CLOSE AGREEMENT WITH THE ICON
CONSENSUS...AND THE CYCLONE IS FORECAST TO BECOME A REMNANT LOW IN
ABOUT 3 DAYS. THE SHIPS MODEL AND SEVERAL OF THE GLOBAL MODELS SHOW
BLANCA DISSIPATING BY 96 HOURS...AND SO DOES THE OFFICIAL FORECAST.

THE INITIAL MOTION IS ESTIMATED TO BE 295/08 BASED ON RECENT
SATELLITE IMAGERY. THE TRACK FORECAST REASONING REMAINS UNCHANGED. 
BLANCA WILL BE STEERED WEST-NORTHWESTWARD SOUTH OF THE MID-LEVEL
RIDGE...WITH A REDUCTION IN FORWARD SPEED AFTER 36 HOURS AS BOTH
THE CYCLONE AND THE RIDGE WEAKEN. THE OFFICIAL TRACK FORECAST IS
VERY CLOSE TO THE PREVIOUS FORECAST THROUGH 24 HOURS.
THEREAFTER...THE OFFICIAL FORECAST IS NUDGED TO THE RIGHT OF THE
PREVIOUS FORECAST TOWARD THE NEW MULTI-MODEL CONSENSUS...WHICH SHOWS
LESS OF A TURN TOWARD THE WEST PRIOR TO DISSIPATION.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0900Z 18.5N 114.5W    45 KT
 12HR VT     07/1800Z 19.0N 115.8W    45 KT
 24HR VT     08/0600Z 19.7N 117.4W    40 KT
 36HR VT     08/1800Z 20.3N 118.9W    35 KT
 48HR VT     09/0600Z 20.7N 120.2W    30 KT
 72HR VT     10/0600Z 21.5N 122.5W    20 KT...REMNANT LOW
 96HR VT     11/0600Z...DISSIPATED
 
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FORECASTER BRENNAN
 
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