Tropical Storm BLAS

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TROPICAL STORM BLAS DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP032010
800 AM PDT FRI JUN 18 2010

FIRST-LIGHT VISIBLE IMAGERY SHOWS BLAS HAS BECOME A LITTLE BETTER
ORGANIZED...WITH THE LOW-LEVEL CENTER NEAR OR EMBEDDED IN THE
NORTHERN SIDE OF THE CENTRAL CONVECTION.  SATELLITE INTENSITY
ESTIMATES ARE 45 KT FROM TAFB AND 35 KT FROM SAB.  BASED ON
THIS...THE INITIAL INTENSITY IS INCREASED TO 40 KT.  THE STORM
CONTINUES TO EXPERIENCE MODERATE NORTHEASTERLY VERTICAL WIND
SHEAR...WITH POOR TO FAIR CIRRUS OUTFLOW IN THE SOUTHWESTERN
SEMICIRCLE AND NONE ELSEWHERE.

WHILE THE LARGE-SCALE MODELS FORECAST THE SHEAR TO DECREASE DURING
THE NEXT 48-72 HR...THE FORECAST TRACK TAKES BLAS OVER STEADILY
DECREASING SEA SURFACE TEMPERATURES.  THIS SHOULD CAUSE THE STORM
TO SLOWLY WEAKEN...WITH THE INTENSITY FORECAST CALLING FOR IT TO
BECOME A TROPICAL DEPRESSION IN ABOUT 48 HR AND A REMNANT LOW IN
ABOUT 96 HR.  THE NEW INTENSITY FORECAST IS IN BEST AGREEMENT WITH
THE INTENSITY CONSENSUS.

THE INITIAL MOTION IS 300/5.  BLAS IS ON THE SOUTH SIDE OF A
MID-LEVEL RIDGE EXTENDING WESTWARD FROM MEXICO...AND THE
LARGE-SCALE MODELS FORECAST THIS FEATURE TO PERSIST WITH LITTLE
CHANGE IN STRENGTH THROUGH THE FORECAST PERIOD...WITH A LOW-LEVEL
RIDGE BUILDING NORTH AND WEST OF THE CYCLONE AFTER 72 HR.  THE
TRACK GUIDANCE RESPONDS TO THIS BY SHOWING THE CURRENT WEST-
NORTHWESTWARD MOTION BECOMING WESTWARD DURING THE NEXT COUPLE OF
DAYS...AND WEST-SOUTHWESTWARD AFTER 72 HR.  THE NEW FORECAST TRACK
IS A LITTLE SOUTH OF AND FASTER THAN THE PREVIOUS TRACK...AND IT
LIES A LITTLE TO THE NORTH OF THE MODEL CONSENSUS AND THE GLOBAL
MODEL FORECASTS.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/1500Z 16.0N 107.4W    40 KT
 12HR VT     19/0000Z 16.3N 108.3W    40 KT
 24HR VT     19/1200Z 16.6N 109.7W    35 KT
 36HR VT     20/0000Z 16.8N 111.1W    35 KT
 48HR VT     20/1200Z 16.9N 112.8W    30 KT
 72HR VT     21/1200Z 17.0N 116.0W    25 KT
 96HR VT     22/1200Z 16.5N 119.0W    25 KT...POST-TROP/REMNT LOW
120HR VT     23/1200Z 16.0N 122.0W    20 KT...POST-TROP/REMNT LOW
 
$$
FORECASTER BEVEN
 
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