WTPA44 PHFO 190251
TCDCP4

TROPICAL STORM GUILLERMO DISCUSSION NUMBER  28
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP102009
500 PM HST TUE AUG 18 2009

THE SATELLITE SIGNATURE OF GUILLERMO HAS DEGRADED THIS AFTERNOON AS
THE COVERAGE OF DEEP CONVECTION WITHIN THE NORTHERN QUADRANT
DIMINISHED. ONLY A NARROW BAND OF THUNDERSTORMS PERSISTS ABOUT 100
MILES NORTHWEST OF THE CENTER. WHAT IS LEFT OF THE CONVECTION IS
BEING DRIVEN BY LOW LEVEL CONVERGENCE BETWEEN GUILLERMO AND A
STRONG HIGH TO THE NORTHEAST. MEANWHILE...GUILLERMO REMAINS DEVOID
OF DEEP CONVECTION TO THE SOUTH. AS A RESULT...CI NUMBERS FROM JTWC
AND HFO HAVE DROPPED TO 1.5...AND THE ADT CI FROM UW-CIMSS DROPPED
TO 1.2. AN ASCAT PASS AT 2032Z JUST MISSED GUILLERMO TO THE WEST
BUT DETECTED SOME 35 TO 40 KT WINDS TO THE NORTHWEST OF THE CENTER. 
GIVEN THE TRENDS IN CONVECTION AND THE DVORAK NUMBERS BASED ON
SATELLITE SIGNATURE...THE INITIAL INTENSITY IS DROPPED TO 35 KT.

STEADY WEAKENING IS FORECAST AS STRONG SOUTHWESTERLY TO SOUTHERLY
WIND SHEAR PERSISTS OVER THE NEXT 36 HOURS. THE SOUTHWESTERLY
WIND SHEAR...IN EXCESS OF 40 KT ACCORDING TO THE LATEST UW-CIMSS
ANALYSIS...IS BEING PRODUCED BY AN UPPER LOW CENTERED ABOUT 625
MILES TO THE SOUTHWEST OF GUILLERMO. THE SHEAR MAY BRIEFLY RELAX
BEYOND 36 HOURS...BUT THE FORECAST CALLS FOR GUILLERMO TO BE A WEAK
TROPICAL DEPRESSION BY THAT TIME WITH MUCH...IF NOT ALL...OF ITS
WARM CORE DESTROYED. BEYOND THAT TIME...GUILLERMO IS FORECAST TO
ENCOUNTER NORTHERLY WIND SHEAR WHICH IS EXPECTED TO INDUCE FURTHER
WEAKENING TO A REMNANT LOW BY 72 HOURS. IT IS IMPORTANT TO NOTE THAT
THE FORECAST WEAKENING TREND IS FASTER THAN ALL THE INTENSITY
GUIDANCE...WHICH KEEP A STRONGER SYSTEM DESPITE THE VERY HIGH
AMOUNT OF VERTICAL WIND SHEAR.

GUILLERMO IS FORECAST MOVE TO THE NORTHWEST OVER THE NEXT 36 HOURS
INTO A WEAKNESS IN THE LOW TO MID LEVEL RIDGE TO THE NORTH CREATED
BY THE ABOVE MENTIONED UPPER LOW. THE FORECAST HAS BEEN SHIFTED TO
THE NORTH SLIGHTLY TO FOLLOW RECENT TRENDS IN MOTION AND TO BE
ROUGHLY DOWN THE MIDDLE OF THE DYNAMIC GUIDANCE. BEYOND 36 HOURS...
THE TRACK OF GUILLERMO HAS BEEN SLOWED AND SHIFTED NORTHWARD TOWARD 
A WEAKNESS IN THE LOW LEVEL RIDGE. IT IS WORTH NOTING THAT MOST OF 
THE CONSENSUS AND DYNAMIC MODELS HAVE ALSO SLOWED BEYOND 48 HOURS 
AND SHIFTED NORTHWARD...WHILE THE BAM MODELS AND THE NOGAPS SHOW 
GUILLERMO RECURVING AND BEING CAUGHT UP IN THE WESTERLIES. THE 
FORECAST CALLS FOR GUILLERMO TO DISSIPATE BEFORE THIS COULD OCCUR.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/0300Z 28.1N 152.2W    35 KT
 12HR VT     19/1200Z 29.4N 154.5W    30 KT
 24HR VT     20/0000Z 30.6N 157.7W    25 KT
 36HR VT     20/1200Z 31.5N 161.0W    25 KT
 48HR VT     21/0000Z 32.1N 163.8W    20 KT
 72HR VT     22/0000Z 32.7N 167.8W    20 KT...DISSIPATING
 96HR VT     23/0000Z...DISSIPATED
 
$$
FORECASTER WROE