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Tropical Storm BLAS (Text)

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TROPICAL STORM BLAS DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 AM PDT TUE JUL 13 2004
 
BLAS IS A HEALTHY TROPICAL STORM THIS MORNING...SHOWING A LARGE
CONVECTIVE OVERCAST WITH TOPS COLDER THAN -80C AND GOOD OUTFLOW
OVER THE SOUTHEASTERN QUADRANT.  SATELLITE INTENSITY ESTIMATES ARE
55 KT FROM TAFB...AND 45 KT FROM SAB AND AFWA.  THE INITIAL
INTENSITY REMAINS 50 KT.  FIRST-LIGHT VISIBLE IMAGES SUGGEST THAT
CENTER MAY BE BETTER INVOLVED WITH THE CONVECTIVE OVERCAST THAN AT
THE TIME OF THE INTENSITY ESTIMATES...SO 50 KT MAY BE A LITTLE
CONSERVATIVE.

THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 305/14...AS THE VISIBLE
IMAGES HINT THAT THE STORM MAY BE MOVING FASTER.  BLAS IS ON THE
SOUTHWEST SIDE OF A STRONG MID-LEVEL RIDGE OVER THE WESTERN UNITED
STATES...AND IS MOVING TOWARD A DEEP-LAYER TROUGH OVER THE
NORTHEASTERN PACIFIC.  LARGE-SCALE MODELS SUGGEST THE TROUGH SHOULD
WEAKEN DURING THE FORECAST PERIOD...WHILE BLAS MOVES OVER COLDER
SEA SURFACE TEMPERATURES AND WEAKENS.  THIS COMBINATION SHOULD TURN
THE CYCLONE WESTWARD AS LOW-LEVEL STEERING BECOME MORE PREDOMINANT
DURING THE WEAKENING.  THE GFS AND NOGAPS MODELS CONTINUE TO BACK
OFF ON A FORECAST OF A SECOND TROPICAL CYCLONE FORMING SOUTHWEST OF
BLAS...AND THOSE MODEL FORECASTS ARE NOW SIMILAR TO THE PREVIOUS
OFFICIAL FORECAST.  THE UKMET CONTINUES TO CALL FOR DEVELOPMENT TO
THE SOUTHWEST OF BLAS...AND THUS MOVES THE STORM MORE NORTHWARD AND
SLOWER.  THE CURRENT OFFICIAL FORECAST IS AN UPDATE OF THE PREVIOUS
PACKAGE...WHICH IS MORE OF LESS DOWN THE MIDDLE OF THE GFS...
NOGAPS...AND GFDL.

BLAS HAS AT THE MOST ABOUT 12-18 HR BEFORE IT REACHES SEA SURFACE
TEMPERATURES OF LESS THAN 26C.  EVEN THOUGH THE CYCLONE IS IN A
FAVORABLE UPPER-LEVEL WIND ENVIRONMENT...IT SHOULD REACH PEAK
INTENSITY IN ABOUT 12 HR THEN SLOWLY WEAKEN THEREAFTER.  BLAS IS
FORECAST TO BECOME A DEPRESSION BY 72 HR AND A REMNANT LOW BY 120
HR.  THERE IS A CHANCE THAT BLAS COULD BECOME A HURRICANE BEFORE IT
REACHES THE COLDER WATER...AS INDICATED BY THE GFDL.

WHILE THE CENTER OF BLAS IS EXPECTED TO REMAIN WELL OFFSHORE...
RAINBANDS AND GUSTY WINDS TO THE NORTH OF THE CENTER COULD AFFECT
PORTIONS OF SOUTHERN BAJA CALIFORNIA STARTING LATER TODAY.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/1500Z 18.4N 111.0W    50 KT
 12HR VT     14/0000Z 19.5N 112.7W    60 KT
 24HR VT     14/1200Z 20.9N 115.1W    60 KT
 36HR VT     15/0000Z 21.8N 117.1W    50 KT
 48HR VT     15/1200Z 22.4N 118.9W    40 KT
 72HR VT     16/1200Z 23.0N 122.5W    30 KT
 96HR VT     17/1200Z 23.5N 126.0W    25 KT...DISSIPATING
120HR VT     18/1200Z 23.5N 129.5W    20 KT...REMNANT LOW
 
 
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