WTPA44 PHFO 182054
TCDCP4

TROPICAL STORM GUILLERMO DISCUSSION NUMBER  27
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP102009
1100 AM HST TUE AUG 18 2009

TROPICAL STORM GUILLERMO HAS MANAGED TO MAINTAIN ITS INTENSITY THIS
MORNING DESPITE ITS RAGGED APPEARANCE ON SATELLITE AND BEING IN
AN ENVIRONMENT OF STRONG VERTICAL WIND SHEAR. THE SOUTHWESTERLY
WIND SHEAR...IN EXCESS OF 40 KT ACCORDING TO THE RECENT UW-CIMSS
ANALYSIS...IS BEING CREATED BY AN UPPER LOW CENTERED ABOUT 650
MILES TO THE SOUTHWEST OF GUILLERMO. THIS UPPER LOW IS ALSO
CREATING OUTFLOW ALOFT THAT HAS HELPED TO MAINTAIN DEEP CONVECTION
WITHIN THE NORTH QUADRANT OF GUILLERMO. THIS...TOGETHER WITH A
TIGHT PRESSURE GRADIENT BETWEEN THE SYSTEM AND A 1030 MB SURFACE
HIGH TO THE NORTH...HAS ALLOWED GUILLERMO TO MAINTAIN ITS
INTENSITY.

A MORNING QUIKSCAT PASS INDICATES AN ASYMMETRIC WIND FIELD...WITH A
BROAD AREA OF TROPICAL STORM FORCE WINDS WITHIN THE NORTHERN
QUADRANT AND MUCH WEAKER WINDS TO THE SOUTH. AN AMBIGUITY ANALYSIS
ON THESE DATA CONFIRMED THE PRESENCE OF A CLOSED CIRCULATION...
DESPITE THE RAGGED AND ELONGATED APPEARANCE OF THE LOW LEVEL CENTER
ON VISIBLE SATELLITE. CURRENT INTENSITY VALUES FROM ALL THE FIX
AGENCIES CAME IN AT 2.0...SUGGESTING A WEAKER SYSTEM...BUT THE
UW-CIMSS SATCON ESTIMATE ESTIMATED 39 KT...MAINLY DUE TO AMSU
DETECTING A PERSISTENT WARM CORE ALOFT. THUS...THE INITIAL
INTENSITY IS HELD AT 40 KT.

THE FORECAST CONTINUES TO MOVE GUILLERMO TO THE NORTHWEST OVER THE
NEXT 36 TO 48 HOURS INTO A WEAKNESS IN THE LOW TO MID LEVEL RIDGE
TO THE NORTH CREATED BY THE ABOVE MENTIONED UPPER LOW. DURING THIS
TIME...SOUTHERLY VERTICAL WIND SHEAR SHOULD TAKE ITS TOLL ON
GUILLERMO...WEAKENING THE SYSTEM TO A DEPRESSION BY 24 HOURS AND
NOT ALLOWING IT TO TAKE ADVANTAGE OF WARMING SST ALONG THE TRACK.
AROUND 48 HOURS THE SHEAR WILL SHIFT FROM THE NORTHEAST AND REMOVE
THE DIFLUENT FLOW ALOFT CURRENTLY SUPPORTING CONVECTION. THE
DISSIPATING SYSTEM IS THEN FORECAST TO TURN ON A WESTERLY THEN WEST
SOUTHWEST TRACK AS IT WEAKENS INTO A REMNANT LOW BY 96 HOURS AND 
BECOMES STEERED BY THE LOW LEVEL FLOW. THE TRACK SCENARIO FALLS 
ROUGHLY IN THE MIDDLE OF THE DYNAMICAL GUIDANCE ENVELOPE AND CLOSE 
TO THE HWRF...WHILE THE INTENSITY FORECAST WEAKENS THE SYSTEM 
SLIGHTLY FASTER THAN GUIDANCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/2100Z 27.0N 151.2W    40 KT
 12HR VT     19/0600Z 28.6N 153.7W    35 KT
 24HR VT     19/1800Z 30.0N 157.1W    30 KT
 36HR VT     20/0600Z 30.9N 160.5W    30 KT
 48HR VT     20/1800Z 31.4N 163.4W    25 KT
 72HR VT     21/1800Z 31.2N 169.1W    25 KT...DISSIPATING
 96HR VT     22/1800Z 30.4N 174.6W    20 KT...REMNANT LOW
120HR VT     23/1800Z 28.8N 179.9E    20 KT...REMNANT LOW
 
$$
FORECASTER WROE