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Tropical Storm BLAS


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TROPICAL STORM BLAS DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 PM PDT MON JUL 12 2004

SATELLITE IMAGES SHOW THAT THE BANDING FEATURES HAVE BECOME MORE
WELL-DEFINED AND THE SYSTEM HAS BECOME BETTER ORGANIZED OVERALL.
DVORAK T-NUMBERS FROM TAFB...SAB AND AFWA ARE 2.5 WHICH SUPPORTS 35
KT FOR THE CURRENT INTENSITY.  THEREFORE THE CYCLONE IS UPGRADED TO
THE SECOND TROPICAL STORM OF THE EAST PACIFIC SEASON.  CONTINUED
GRADUAL STRENGTHENING IS PREDICTED OVER THE NEXT DAY OR SO...A LA
THE SHIPS GUIDANCE.  SINCE THE STORM IS EXPECTED TO HAVE LITTLE
TIME OVER WARM WATERS...WEAKENING SHOULD COMMENCE WITHIN A COUPLE
OF DAYS.  BLAS IS LIKELY TO SPIN DOWN TO A REMNANT LOW BY THE END
OF THE FORECAST PERIOD.

THE INITIAL MOTION ESTIMATE...310/13...IS A LITTLE FASTER THAN
BEFORE.  THE MAIN ISSUE REGARDING THE TRACK FORECAST IS THE GLOBAL
MODELS' DEPICTION OF ANOTHER VORTEX TO THE WEST-SOUTHWEST OF BLAS. 
THIS SECONDARY VORTEX...IF IT EXISTS...APPEARS TO BE OVERDONE IN
THE MODELS' INITIALIZATION.  IF THAT IS TRUE THEN THE TRACK
GUIDANCE MAY BE INFLUENCED BY AN ARTIFICIAL FUJIWHARA-TYPE
INTERACTION WITH THE SECONDARY VORTEX.  THE OFFICIAL FORECAST LEANS
ON THE LEFT SIDE OF THE GUIDANCE SUITE...CLOSER TO THE
CLIMATOLOGICAL EXPECTATION.

SATELLITE IMAGES AND SHIP OBSERVATIONS SUGGEST THAT BLAS IS A
LARGER-THAN AVERAGE TROPICAL CYCLONE.  THE 120 N MI WIND RADII MAY
BE CONSERVATIVE.
 
FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/0300Z 16.8N 108.4W    35 KT
 12HR VT     13/1200Z 18.0N 110.0W    45 KT
 24HR VT     14/0000Z 19.6N 112.2W    50 KT
 36HR VT     14/1200Z 21.0N 114.5W    55 KT
 48HR VT     15/0000Z 22.0N 116.5W    45 KT
 72HR VT     16/0000Z 23.0N 120.0W    35 KT
 96HR VT     17/0000Z 24.0N 123.5W    25 KT...DISSIPATING
120HR VT     18/0000Z 24.0N 127.0W    20 KT...REMNANT LOW
 
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