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Tropical Storm GUILLERMO


ZCZC MIATCDEP5 ALL
TTAA00 KNHC DDHHMM
TROPICAL STORM GUILLERMO DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP102009
800 AM PDT THU AUG 13 2009
 
CONVENTIONAL SATELLITE IMAGERY INDICATES THE FORMATION OF A
TRANSIENT EYE-LIKE FEATURE WITHIN A DEVELOPING CENTRAL DENSE
OVERCAST...WITH A WELL-DEFINED BAND IN THE SOUTHERN SEMICIRCLE.
THESE INCREASES IN ORGANIZATION SUGGEST GUILLERMO IS LIKELY
APPROACHING HURRICANE STRENGTH.  DVORAK T-NUMBERS FROM TAFB AND SAB
ARE 3.5 AND 4.0...RESPECTIVELY...AND SUPPORT AN INCREASE IN THE
INITIAL INTENSITY TO 55 KT FOR THIS ADVISORY.
 
THE INITIAL MOTION IS ESTIMATED AT 285/12. NO MAJOR CHANGES HAVE
BEEN MADE TO THE PREVIOUS FORECAST TRACK...AS GUILLERMO CONTINUES
TO MOVE AROUND THE SOUTHWEST PERIPHERY OF A MID-LEVEL RIDGE
EXTENDING WESTWARD FROM THE SOUTH CENTRAL UNITED STATES TO AROUND
140W. MODEL SPREAD IS FAIRLY SMALL DURING THE NEXT 72 HOURS AND THE
OFFICIAL FORECAST TRACK IS IN THE MIDDLE OF THE GUIDANCE
ENVELOPE...CLOSE TO THE MODEL CONSENSUS.  THE MODEL SOLUTIONS
DIVERGE AFTER 72 HOURS...WITH THE GFS/UKMET/ECMWF FARTHER SOUTH
THAN THE HWRF AND GFDL.  THE LIKELY CAUSE FOR THIS IS AN
INTERACTION BETWEEN GUILLERMO AND TROPICAL DEPRESSION NINE-E.
WHILE THIS CANNOT BE RULED OUT...IT APPEARS AS A MORE REMOTE
POSSIBILITY AT THIS TIME.
 
GIVEN RECENT STRUCTURAL CHANGES...IT MIGHT NOT BE LONG TILL
GUILLERMO BECOMES A HURRICANE.  THE CYCLONE IS IN A LOW SHEAR
ENVIRONMENT AND IS CURRENTLY MOVING OVER MARGINAL SEA SURFACE
TEMPERATURES...WHICH ARE FORECAST TO DROP BELOW 26.5C IN ABOUT 24
HOURS.  SEA SURFACE TEMPERATURES CONTINUE TO GRADUALLY DECREASE
ALONG THE FORECAST TRACK THROUGH ABOUT 72 HOURS...AND SOUTHWESTERLY
FLOW ALOFT BEGINS TO INCREASE AROUND THIS TIME.  BASED UPON THESE
FACTORS...IT APPEARS THAT GUILLERMO WILL HAVE A NARROW WINDOW OF
OPPORTUNITY TO INTENSIFY.  THE OFFICIAL FORECAST CALLS FOR
GUILLERMO TO REACH HURRICANE STRENGTH IN 12 HOURS AND BEGIN TO
SLOWLY WEAKEN AFTER 36 HOURS.  THE INCREASING SOUTHWESTERLY SHEAR
LATER IN THE PERIOD SHOULD ACCELERATE THE WEAKENING TREND...AND IT
IS POSSIBLE THAT GUILLERMO COULD WEAKEN MORE THAN FORECAST BEYOND
72 HOURS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/1500Z 17.1N 121.6W    55 KT
 12HR VT     14/0000Z 17.5N 123.7W    65 KT
 24HR VT     14/1200Z 17.9N 126.4W    65 KT
 36HR VT     15/0000Z 18.3N 129.0W    65 KT
 48HR VT     15/1200Z 18.8N 131.8W    60 KT
 72HR VT     16/1200Z 19.5N 137.0W    50 KT
 96HR VT     17/1200Z 20.0N 143.0W    45 KT
120HR VT     18/1200Z 20.0N 148.5W    35 KT
 
$$
FORECASTER KIMBERLAIN
 
NNNN


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Page last modified: Thursday, 31-Dec-2009 12:09:22 UTC