Tropical Storm GUILLERMO

ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM
TROPICAL DEPRESSION GUILLERMO DISCUSSION NUMBER  15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 PM PDT SUN AUG 10 2003
 
GUILLERMO HAS LOOKED LESS THAN IMPRESSIVE THE PAST 6 HOURS AND HAS
BEEN VIRTUALLY DEVOID OF ANY CENTRAL DEEP CONVECTION...UNTIL A
BURST OF CONVECTION DEVELOPED DURING THE PAST COUPLE OF HOURS TO
THE SOUTH OF THE BROAD LOW-LEVEL CENTER. OUTFLOW IS RESTRICTED TO
THE WEST...BUT IS FAIR AND IMPROVING ELSEWHERE. DVORAK SATELLITE
INTENSITY ESTIMATES FROM TAFB...SAB...AND AFWA AVERAGE OUT TO 30
KT...AND THAT IS WHAT WAS USED FOR THE INITIAL INTENSITY ESTIMATE.
THEREFORE...GUILLERMO HAS BEEN DOWNGRADED TO A TROPCIAL DEPRESSION. 
 
THE INITIAL MOTION ESTIMATE IS 270/14. THE RECENT INCREASE IN
FORWARD SPEED IS LIKELY DUE TO THE DECREASE IN THE CENTRAL
CONVECTION AND THE RESULTANT DECOUPLING OF THE LOW-LEVEL AND
MID-/UPPER-LEVEL CIRCULATIONS. THAT MAKES THE LOW-LEVEL EASTERLIES
THE DOMINANT STEERING FLOW...AT LEAST IN THE NEAR TERM. GUILLERMO
IS EXPECTED TO REMAIN SOUTH OF A STRONG SUBTROPICAL RIDGE THAT
SHOULD ENSURE A GENERAL WESTWARD MOTION THROUGHOUT THE FORECAST
PERIOD. THERE MAY BE FLUCTUATIONS IN THE FORWARD SPEED DEPENDING ON
HOW MUCH CONVECTION PERIODICALLY BURSTS NEAR THE CENTER...BUT THE
GENERAL MOTION SHOULD BE STEADY WESTWARD BETWEEN 10 TO 15 KT. THE
RECENT WEAKENING OF BOTH GUILLERMO AND TROPICAL STORM HILDA SHOULD
REDUCE THE LIKELIHOOD OF ANY INTERACTION BETWEEN THE TWO CYCLONES.
THE OFFICIAL FORECAST TRACK IS JUST AN EXTENSION OF THE PREVIOUS
TRACK AND IS CLOSE TO THE GFDL AND GFS ENSEMBLE MEAN MODELS.
 
GUILLERMO HAS BEEN INGESTING COLD AIR STRATOCUMULUS INTO THE WESTERN 
SEMICIRCLE AND THIS...ALONG WITH WESTERLY SHEAR INDUCED BY A
DEVELOPING DISTURBANCE LOCATED TO THE SOUTHWEST...HAS CONTRIBUTED
TO THE DECREASE IN CONVECTION. WHILE THE SHIPS INTENSITY MODEL
STRENGTHENS GUILLERMO BACK TO A 55-KT TROPICAL STORM BY 120
HOURS...SUCH STRENGTHENING IS UNLIKELY SINCE THERE MAY NOT BE MUCH
OF A CIRCULATION REMAINING AT THAT TIME. THE OFFICIAL INTENSITY
FORECAST IS SIMILAR TO THE PREVIOUS ONE AND CALLS FOR THE CYCLONE
INTENSITY TO REMAIN STEADY THROUGH 48 HOURS AND THEN SLOWLY WEAKEN
AFTER THAT. OF COURSE...ONLY MINOR BURSTS OF CONVECTION OVER THE
LOW-LEVEL CENTER COULD EASILY BRING GUILLERMO BACK TO MINIMAL
TROPICAL STORM STRENGTH AT ANY TIME.

FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/0300Z 15.5N 130.0W    30 KT
 12HR VT     11/1200Z 15.5N 131.5W    30 KT
 24HR VT     12/0000Z 15.6N 133.9W    30 KT
 36HR VT     12/1200Z 15.6N 136.5W    30 KT
 48HR VT     13/0000Z 15.6N 139.2W    30 KT
 72HR VT     14/0000Z 15.5N 144.5W    25 KT
 96HR VT     15/0000Z 15.5N 150.0W    25 KT
120HR VT     16/0000Z 15.5N 155.0W    25 KT
 
 
NNNN