000
WTPZ45 KNHC 150835
TCDEP5
HURRICANE GUILLERMO DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP102009
200 AM PDT SAT AUG 15 2009
 
THE SATELLITE APPEARANCE OF GUILLERMO REMAINS IMPRESSIVE...ALTHOUGH
THE CLARITY OF THE EYE IN INFRARED IMAGERY HAS VARIED OVER THE PAST
FEW HOURS. DVORAK T-NUMBERS WERE 5.5 FROM TAFB AND 5.0 FROM SAB
AT 0600 UTC...WHILE THE 3-HOUR AVERAGE UW-CIMSS ADT VALUES REMAIN
AROUND 6.0. THE INITIAL INTENSITY IS KEPT AT 100 KT AS A BLEND OF
THESE ESTIMATES.

ACCORDING TO THE SHIPS MODEL THE CYCLONE IS NOW OVER SSTS OF LESS
THAN 26C...AND WILL CROSS THE 25C ISOTHERM IN ABOUT 12 HOURS. THE
INTENSITY FORECAST CALLS FOR A GRADUAL WEAKENING BEGINNING LATER
TODAY...AND MORE RAPID WEAKENING BEYOND 24 HOURS AS THE SHIPS MODEL
SHOWS VERTICAL WIND SHEAR INCREASING ABOVE 20 KT AFTER THAT
TIME. THE OFFICIAL FORECAST IS CLOSE TO THE ICON INTENSITY
CONSENSUS THROUGH 48 HOURS...AND IS A BLEND OF SHIPS AND LGEM AT
DAY 3 AND BEYOND...AS THE HWRF AND GFDL ARE UNREALISTICALLY
INTENSE WITH THE CYCLONE AT THAT TIME RANGE.

THE INITIAL MOTION ESTIMATE IS 285/14 AND THE TRACK FORECAST
REASONING REMAINS UNCHANGED. GUILLERMO WILL CONTINUE MOVING TOWARD
THE WEST-NORTHWEST AROUND THE EDGE OF THE SUBTROPICAL RIDGE AND
INTO A WEAKNESS IN THE RIDGE THAT FORMS NORTHEAST OF THE HAWAIIAN
ISLANDS IN A COUPLE OF DAYS. THE OFFICIAL FORECAST HAS BEEN
ADJUSTED SLIGHTLY TO THE NORTH OF THE PREVIOUS PACKAGE...TOWARD THE
TVCN MULTI-MODEL CONSENSUS.

THE INITIAL 34-KT WIND RADII WERE ADJUSTED BASED ON A 0230 UTC
QUIKSCAT PASS AND A 0545 UTC ASCAT PASS.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/0900Z 18.7N 131.9W   100 KT
 12HR VT     15/1800Z 19.2N 134.0W    95 KT
 24HR VT     16/0600Z 19.8N 136.5W    85 KT
 36HR VT     16/1800Z 20.4N 139.0W    70 KT
 48HR VT     17/0600Z 21.2N 141.5W    60 KT
 72HR VT     18/0600Z 23.0N 146.5W    40 KT
 96HR VT     19/0600Z 25.0N 151.5W    30 KT
120HR VT     20/0600Z 27.5N 157.5W    25 KT...REMNANT LOW
 
$$
FORECASTER BRENNAN