Tropical Storm GUILLERMO

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TROPICAL STORM GUILLERMO DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 AM PDT FRI AUG 08 2003
 
GUILLERMO HAD DEVELOPED A COLD AND PERSISTENT CONVECTIVE OVERCAST
THIS MORNING WITH CLOUD TOPS TO -80C NEAR THE CENTER.  THE CYCLONE
SHOWS GOOD CIRRUS OUTFLOW OVER THE WESTERN SEMICIRCLE AND POOR
ELSEWHERE.  SATELLITE INTENSITY ESTIMATES ARE 45 KT FROM TAFB AND
SAB...AND 35 KT FROM AFWA.  THE INITIAL INTENSITY IS INCREASED TO
45 KT.

THE INITIAL MOTION IS 270/6.  GUILLERMO IS ON THE SOUTH SIDE OF A
LOW/MID-LEVEL RIDGE...WHICH LARGE SCALE MODELS FORECAST TO PERSIST
AND PERHAPS STRENGTHEN SLIGHTLY DURING THE FORECAST PERIOD.  THIS
SHOULD KEEP THE STORM ON A GENERAL WESTWARD COURSE FOR THE NEXT
SEVERAL DAYS.  NHC TRACK GUIDANCE AGREES WITH THIS SCENARIO...
ALTHOUGH THERE IS A FAIR AMOUNT OF SPREAD IN THE SPEED.  THE
OFFICIAL FORECAST IS AN UPDATE OF THE PREVIOUS FORECAST...AND
SOMEWHAT FASTER AFTER 48 HR.  IT SHOULD BE NOTED THAT WHILE THIS
FORECAST IS FASTER THAN THE PREVIOUS FORECAST...IT IS STILL SLOWER
THAN THE UKMET...BAM MODELS...AND LBAR.
 
LARGE-SCALE MODELS SUGGEST THAT GUILLERMO SHOULD REMAIN IN A
LIGHT/MODERATE VERTICAL SHEAR ENVIRONMENT DURING THE FORECAST
PERIOD.  THUS...THE MAIN PART OF THE INTENSITY FORECAST PROBLEM IS
WHAT WILL THE SEA SURFACE TEMPERATURE UNDER THE STORM BE.   THE
FORECAST TRACK TAKES GUILLERMO OVER 26C SSTS ROUGHLY PARALLEL TO
THE ISOTHERMS.  IF IT MOVES NORTH OF THE TRACK...IT WILL MOVE INTO
COOLER WATER AND WEAKEN.  IF IT MOVES SOUTH OF THE TRACK...IT COULD
FIND WARMER WATER.  THE LOW-CONFIDENCE INTENSITY FORECAST CALLS FOR
SLOW STRENGTHENING TO 55 KT FOLLOWED BY AN EVEN SLOWER WEAKENING ON
THE PREMISE THAT GUILLERMO WILL MOVE CLOSE ENOUGH TO THE COLD WATER
FOR IT TO HAVE AN EFFECT.  THIS FORECAST IS IN GOOD AGREEMENT WITH
THE SHIPS MODEL.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/1500Z 16.6N 118.7W    45 KT
 12HR VT     09/0000Z 16.6N 120.0W    50 KT
 24HR VT     09/1200Z 16.7N 122.0W    55 KT
 36HR VT     10/0000Z 16.8N 124.2W    55 KT
 48HR VT     10/1200Z 16.9N 126.7W    55 KT
 72HR VT     11/1200Z 17.0N 130.5W    50 KT
 96HR VT     12/1200Z 17.0N 134.5W    50 KT
120HR VT     13/1200Z 17.0N 138.5W    45 KT
 
 
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