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Tropical Storm GUILLERMO


ZCZC MIATCDEP5 ALL
TTAA00 KNHC DDHHMM
TROPICAL STORM GUILLERMO DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP102009
800 PM PDT THU AUG 13 2009
 
EVEN THOUGH VISIBLE IMAGERY SHOWS THAT AN EYE-LIKE FEATURE DEVELOPED
EARLIER TODAY...INFRARED IMAGERY SHOWS A MORE RAGGED APPEARANCE
WITH ONE WELL-DEFINED CONVECTIVE BAND TO THE SOUTHWEST OF THE
LOW-LEVEL CENTER.  A RECENT PARTIAL SSMI PASS SUGGESTS THAT A
CONVECTIVE RING HAS ENCIRCLED THE CENTER...AND THIS COULD BE A SIGN
THAT GUILLERMO IS READY TO STRENGTHEN.  DVORAK FINAL T-NUMBERS ARE
T4.0 FROM TAFB AND T3.5 FROM SAB...SO THE INITIAL INTENSITY IS KEPT
JUST BELOW HURRICANE STATUS AT 60 KT.  VERTICAL SHEAR IS EXPECTED
TO REMAIN LOW FOR ANOTHER 48 HOURS OR SO...BUT SEA SURFACE
TEMPERATURES ALONG THE FORECAST TRACK ARE EXPECTED TO FALL FROM 27C
TO NEAR 24C OVER THE NEXT 3 DAYS.  THE OFFICIAL FORECAST STILL
SHOWS GUILLERMO BECOMING A HURRICANE SOON...BUT THEN SHOWS STEADY
WEAKENING AFTER 36 HOURS.  THIS SCENARIO IS VERY CLOSE TO THE
INTENSITY CONSENSUS.  

THE INITIAL MOTION IS 275/13.  GUILLERMO IS EXPECTED TO TURN TOWARD
THE WEST-NORTHWEST OVER THE NEXT DAY OR SO ONCE IT BECOMES
POSITIONED ON THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE
EXTENDING WESTWARD FROM NORTHERN MEXICO.  ALL OF THE NUMERICAL
MODELS...AS WELL AS BAM SHALLOW...INDICATE THAT THIS MOTION WILL
CONTINUE THROUGH THE FORECAST PERIOD EVEN AFTER GUILLERMO WEAKENS
AND BECOMES A SHALLOW SYSTEM.  THIS IS LIKELY THE RESULT OF A
WEAKNESS IN THE SUBTROPICAL RIDGE FORECAST TO DEVELOP JUST NORTH OF
THE HAWAIIAN ISLANDS BY DAY 4.  THE OFFICIAL TRACK FORECAST IS
THEREFORE SHIFTED A LITTLE NORTHWARD ON DAYS 4 AND 5 TOWARDS THE
TIGHT MODEL CLUSTERING.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/0300Z 17.2N 124.5W    60 KT
 12HR VT     14/1200Z 17.6N 126.5W    65 KT
 24HR VT     15/0000Z 18.2N 129.2W    65 KT
 36HR VT     15/1200Z 18.8N 131.9W    60 KT
 48HR VT     16/0000Z 19.3N 134.6W    55 KT
 72HR VT     17/0000Z 20.5N 140.0W    45 KT
 96HR VT     18/0000Z 21.5N 145.0W    35 KT
120HR VT     19/0000Z 22.0N 150.0W    30 KT
 
$$
FORECASTER BERG
 
NNNN


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