Tropical Storm GUILLERMO

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TROPICAL STORM GUILLERMO DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2 PM PDT FRI AUG 08 2003
 
GUILLERMO HAS SHOWN MIXED SIGNALS DURING THE DAY.  ON ONE SIDE...
SSM/I DATA RECEIVED SINCE THE LAST ADVISORY SHOWS TIGHTLY CURVED
CONVECTIVE BANDS AND A POSSIBLE EYE.  ON THE OTHER HAND...THE CLOUD
PATTERN IN VISIBLE IMAGERY HAS DECAYED SOMEWHAT THIS AFTERNOON...
POSSIBLY DUE TO SOME WEAK SOUTHERLY SHEAR CAUSED BY AN UPPER-LEVEL
LOW NEAR 17N125W.  SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM
TAFB...45 KT FROM SAB...AND 35 KT FROM AFWA.  BASED ON THESE AND
THE POSSIBLE EYE...THE MAXIMUM WINDS ARE INCREASED TO 50 KT.

THE MICROWAVE DATA INDICATES THAT THE CENTER IS ABOUT A HALF DEGREE
SOUTH OF THE PREVIOUS ADVISORY POSITION.  IT IS UNCLEAR WHETHER
THIS COMES FROM MOTION OR REFORMATION OF THE CENTER...SO THE
INITIAL MOTION IS AN UNCERTAIN 250/7.  OTHER THAN THIS...THERE IS
LITTLE CHANGE IN EITHER THE SYNOPTIC PATTERN OF THE FORECAST
PHILOSOPHY FROM THE PREVIOUS PACKAGE.  GUILLERMO IS ON THE SOUTH
SIDE OF A LOW/MID-LEVEL RIDGE...WHICH SHOULD PERSIST DURING THE
FORECAST PERIOD.  THIS SHOULD KEEP THE STORM ON A GENERAL WESTWARD
COURSE THROUGH THE FORECAST PERIOD.  NHC TRACK GUIDANCE STILL
AGREES WITH THIS SCENARIO...ALTHOUGH A FAIR AMOUNT OF SPREAD IN THE
SPEED REMAINS.  THE OFFICIAL FORECAST IS ALMOST PARALLEL TO THE
PREVIOUS TRACK...BUT IS SHIFTED ABOUT A DEGREE SOUTHWARD BASED ON
CURRENT TRENDS.  THE FORECAST IS IN BEST AGREEMENT WITH THE NOGAPS.

THE ABOVE BEING SAID...THERE IS AN ALTERNATIVE TRACK FORECAST
POSSIBILITY.  AN AREA OF DISTURBED WEATHER CENTERED NEAR 13N107W IS
WEAKER...BUT LARGER THAN GUILLERMO.  THERE IS A SLIGHT CHANCE THAT
THE TWO SYSTEMS COULD INTERACT...AND SUCH AN INTERACTION COULD
CAUSE A DIFFERENT TRACK FOR GUILLERMO THAN CURRENTLY FORECAST. 
THERE ARE NO SIGNS OF THIS YET.

LARGE-SCALE MODELS NOW SUGGEST THAT THE CURRENTLY SOUTHERLY SHEAR
COULD PERSIST FOR 24 HR OR MORE AS THE UPPER-LEVEL LOW NORTHWEST OF
GUILLERMO MOVES WESTWARD ALONG WITH THE STORM.  HOWEVER...THE SHIPS
MODEL DOES NOT FORECAST ENOUGH SHEAR TO KEEP THE SYSTEM FROM
STRENGTHENING...AND THE GFDL STRENGTHENS IT AS WELL.  THE INTENSITY
FORECAST WILL BE BASED ON THE PREMISE THAT THE SHEAR WILL ONLY SLOW
THE DEVELOPMENT AND FORECASTS THE STORM TO REACH 60 KT IN 36-48 HR.  
WHILE THE MORE SOUTHERLY TRACK KEEPS THE STORM IN WARMER WATER THAN
THE PREVIOUS TRACK...AFTER 72 HR GUILLERMO SHOULD COME CLOSE ENOUGH
TO COOLER WATER TO SLOWLY WEAKEN.

FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/2100Z 16.0N 119.6W    50 KT
 12HR VT     09/0600Z 15.9N 120.7W    50 KT
 24HR VT     09/1800Z 15.9N 122.8W    55 KT
 36HR VT     10/0600Z 15.9N 125.1W    60 KT
 48HR VT     10/1800Z 16.0N 127.4W    60 KT
 72HR VT     11/1800Z 16.0N 131.5W    55 KT
 96HR VT     12/1800Z 16.0N 135.5W    55 KT
120HR VT     13/1800Z 16.0N 139.5W    50 KT
 
 
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