Subject: Pacific-EN: Tropical Storm Guillermo Discussion Number 3 [310829]

From: SIU Weather Processor <[email-masked]>
Date: Thu, 31 Jul 1997 03:29:01 -0500

262
WTPZ44 KNHC 310829
TCDEP4
TROPICAL STORM GUILLERMO DISCUSSION NUMBER   3
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT THU JUL 31 1997

WHILE POSITION ESTIMATES BASED ON IR IMAGERY SHOW UNCERTAINTY
...THEY SUGGEST THAT THE CYCLONE HAS EITHER NOT MOVED MUCH DURING
THE PAST 6 TO 12 HOURS OR IS STILL IN THE PROCESS OF DEVELOPING A
CONSOLIDATED CENTER.  THE CLASSIFICATIONS FROM BOTH TAFB AND SAB
HAVE REACHED 2.5 AND SUPPORT UPGRADING THE SYSTEM TO TROPICAL STORM
GUILLERMO WITH 35 KNOT WINDS.  THE STORM HAS A LARGE CIRCULATION OF
CLOUDS...WITH DEEPEST CONVECTION OCCURRING IN A BAND JUST EAST OF
THE ESTIMATED CENTER POSITION AND IN ANOTHER BAND ABOUT 100-150 N MI
TO THE WEST OF THE CENTER.

THE 00Z AVN AND GFDL SHOW A 500 MB ANTICYCLONE CENTERED OVER THE
SOUTHERN PLAINS...AS IN SEEN IN WATER VAPOR IMAGERY.  THE FLOW
AROUND THE SOUTH SIDE OF THE HIGH IS FORECAST TO DRIVE GUILLERMO
TOWARD THE WEST TO WEST-NORTHWEST AT ABOUT 10 TO 15 KNOTS.  THIS IS
SIMILAR TO WHAT THE TRACK MODELS SHOWED PREVIOUSLY BUT WHICH HAS YET
TO BE OBSERVED.  ONLY THE STATISTICAL-DYNAMICAL MODEL AND CLIPER ARE
MUCH DIFFERENT THROUGH 48 HOURS...APPROACHING THE COAST NEAR
ACAPULCO.  THE OFFICIAL TRACK SHOWS A W TO WNW HEADING BUT AT
A SLOWER INITIAL SPEED THAN INDICATED BY THE GUIDANCE.

THE AVN AND GFDL SHOW WEAKENING OF THE UPPER-LEVEL LOW TO THE NW OF
GUILLERMO AND KEEP THE LOW AT SOME DISTANCE FROM THE STORM.  THE
CURRENTLY ANALYZED WEAK ANTICYCLONE OVER GUILLERMO IS FORECAST BY
THOSE MODELS TO GIVE WAY TO A LIGHT...GENERALLY DIFFLUENT
ENVIRONMENTAL FLOW ALOFT.  ALL THREE INTENSITY FORECAST SCHEMES
PREDICT THAT GUILLERMO WILL BECOME A HURRICANE WITHIN THREE DAYS.
WITH LIGHT SHEAR AND EVEN WARMER THAN NORMAL WATERS ALONG THE
FORECAST TRACK...THE NHC FORECAST DOES AS WELL.

RAPPAPORT

FORECAST POSITIONS AND MAX WINDS

INITIAL     31/0900Z 11.5N  95.7W    35 KTS
12HR VT     31/1800Z 12.0N  96.7W    40 KTS
24HR VT     01/0600Z 12.6N  98.1W    45 KTS
36HR VT     01/1800Z 13.2N  99.8W    55 KTS
48HR VT     02/0600Z 13.9N 101.8W    65 KTS
72HR VT     03/0600Z 15.5N 106.5W    70 KTS

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