Tropical Storm HECTOR

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TROPICAL STORM HECTOR DISCUSSION NUMBER  20
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP092006
800 AM PDT SUN AUG 20 2006

A HELPFUL TRMM MICROWAVE PASS AT 1020 UTC SHOWED THAT THE LOW-LEVEL
CENTER OF HECTOR HAS DECOUPLED FROM THE MIDDLE-LEVEL CENTER
PREVIOUSLY SEEN ON THE NIGHT-VIS IMAGERY... REQUIRING A SMALL
SOUTHWARD ADJUSTMENT TO THE INITIAL POSITION.  RECENT SATELLITE
PICTURES SHOW THAT THE EYE FEATURE HAS DISSIPATED AND CONVECTION
HAS SHIFTED EXCLUSIVELY TO THE EASTERN SEMICIRCLE OF THE STORM...
CONSISTENT WITH THE IMPACTS OF WESTERLY SHEAR.  DVORAK ESTIMATES
FROM SAB/TAFB ARE DROPPING AS QUICKLY AS THE RULES ALLOW AND THE
INITIAL INTENSITY IS LOWERED TO 60 KT.  A FAST WEAKENING IS LIKELY
DUE TO INCREASING WESTERLY SHEAR... COLD SSTS DROPPING BELOW 24C...
AND PLENTY OF STABLE AIR AS DIAGNOSED BY SHIPS.  THE INTENSITY
FORECAST IS IN GOOD AGREEMENT WITH SHIPS AND THE FSU
SUPERENSEMBLE... CALLING FOR THE TROPICAL CYCLONE TO DISSIPATE
TOMORROW.  

THE MOTION FOR THE PAST 12 HOURS IS ABOUT 300/9.  THIS GENERAL
MOTION SHOULD CONTINUE FOR ABOUT A DAY UNTIL THE CYCLONE LOSES MOST
OF ITS DEEP CONVECTION.  THEREAFTER A WEST-NORTHWEST TURN IS
ANTICIPATED AS HECTOR BECOMES A SHALLOW SYSTEM STEERED BY THE
LOWER-LEVEL FLOW.  MOST MODEL GUIDANCE SEEMS TO BE HOLDING ONTO A
STRONG VERTICALLY-STACKED SYSTEM FOR TOO LONG... LEADING TO A
NORTHWESTWARD OR EVEN NORTHWARD MOTION.  THE OFFICIAL FORECAST WILL
STAY ON THE SOUTHERN EDGE OF THE GUIDANCE ENVELOPE... CLOSE TO A
COMPOSITE OF THE GFS ENSEMBLE... BAM SHALLOW... AND THE UKMET.  THE
WEST-NORTHWEST TURN COULD OCCUR SOONER THAN FORECAST IF THE CYCLONE
WEAKENS FASTER THAN SHOWN BELOW. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/1500Z 19.8N 133.5W    60 KT
 12HR VT     21/0000Z 20.5N 134.7W    45 KT
 24HR VT     21/1200Z 21.3N 136.1W    30 KT
 36HR VT     22/0000Z 22.0N 137.5W    25 KT...REMNANT LOW
 48HR VT     22/1200Z 22.5N 139.0W    20 KT...REMNANT LOW
 72HR VT     23/1200Z 23.0N 142.5W    20 KT...REMNANT LOW
 96HR VT     24/1200Z...DISSIPATED
 
$$
FORECASTER BLAKE/FRANKLIN
 
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