TROPICAL STORM GUILLERMO ADVISORY NUMBER 22
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP102009
500 AM HST MON AUG 17 2009

…GUILLERMO CONTINUES TO HEAD WEST-NORTHWEST AND WEAKEN…

AT 500 AM HST…1500 UTC…THE CENTER OF TROPICAL STORM GUILLERMO WAS LOCATED NEAR LATITUDE 21.5 NORTH…LONGITUDE 144.5 WEST OR ABOUT 695 MILES EAST-NORTHEAST OF HILO HAWAII AND ABOUT 860 MILES EAST OF HONOLULU HAWAII.

GUILLERMO IS MOVING TOWARD THE WEST-NORTHWEST NEAR 18 MPH. THE STORM WILL MAKE A GRADUAL TURN TO THE NORTHWEST OVER THE NEXT 48 HOURS.

MAXIMUM SUSTAINED WINDS ARE NEAR 60 MPH WITH HIGHER GUSTS. GUILLERMO WILL CONTINUE WEAKENING OVER THE NEXT 48 HOURS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 85 MILES FROM THE CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB…29.53 INCHES.

…SUMMARY OF 500 AM HST INFORMATION…
LOCATION…21.5N 144.5W
MAXIMUM SUSTAINED WINDS…60 MPH
PRESENT MOVEMENT…WEST-NORTHWEST OR 290 DEGREES AT 18 MPH
MINIMUM CENTRAL PRESSURE…1000 MB

THE NEXT ADVISORY WILL BE ISSUED BY THE CENTRAL PACIFIC HURRICANE CENTER AT 1100 AM HST.

TROPICAL STORM GUILLERMO DISCUSSION NUMBER 22
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP102009
500 AM HST MON AUG 17 2009

TROPICAL STORM GUILLERMO CONTINUES TO WEAKEN. MOST OF THE COLDER CLOUD TOPS HAVE NOW BEEN SHEARED OFF AND THE DEEP CONVECTION HAS COMPLETELY DISSIPATED. THE LOW LEVEL CENTER IS NOW COMPLETELY EXPOSED ON THE SOUTHWEST SIDE OF THE SYSTEM. GUILLERMO IS CLEARLY CONTINUING TO WEAKEN RATHER QUICKLY DUE TO STRONG WEST-SOUTHWEST SHEAR. RECENT MICROWAVE PASSES HAVE STILL SHOWN HEAVY RAIN WRAPPING AROUND THE NORTH SIDE OF GUILLERMO SO THE SYSTEM STILL HAS SOME PUNCH LEFT. I PUT THE INITIAL INTENSITY AT 50 KT…A BIT LOWER THAN THE SUBJECTIVE DVORAK ANALYSES. THE DVORAK CONSTRAINTS MAY BE MAKING THE INTENSITY ESTIMATES A BIT TOO HIGH IN THIS RAPIDLY SHEARING SYSTEM.

NOW THAT THE LOW LEVEL CENTER IS COMPLETELY EXPOSED…WE HAVE HIGH CONFIDENCE IN THE CENTER LOCATION. IT APPEARS THAT THE FORWARD SPEED HAS INCREASED AND THAT GUILLERMO HAS STARTED TO CURVE TOWARD THE NORTHWEST. I HAVE SHIFTED THE TRACK A BIT TO THE LEFT OF THE PREVIOUS TRACK. AS GUILLERMO CONTINUES TO WEAKEN AND BECOME SHALLOWER THE TRACK IS LIKELY TO BE MORE STRONGLY INFLUENCED BY THE LOW LEVEL EASTERLY FLOW.

GUILLERMO REMAINS OVER COOL…24.5 DEGREES CELSIUS…WATER AND STRONG…30 KT…WEST-NORTHWEST SHEAR. WITH SUCH AN UNFAVORABLE ENVIRONMENT…GUILLERMO CAN BE EXPECTED TO CONTINUE WEAKENING RATHER RAPIDLY. GUILLERMO WILL MOVE OVER WARMER WATER AFTER ABOUT 36 HOURS…BUT IT MAY NOT MATTER SINCE THE SHEAR WILL BECOME EVEN STRONGER. ONCE GUILLERMO HAS BEEN REDUCED TO A SHALLOW LOW…WARMER WATER IS UNLIKELY TO BE ENOUGH TO ALLOW THE SYSTEM TO REGENERATE.

Ray Tanabe, Central Pacific Hurricane Center warning coordination meteorologist, talks about how to track a storm via the NOAA website.

Central Pacific Hurricane Center: www.prh.noaa.gov/hnl/cphc

Weather forecasts of all the islands: www.prh.noaa.gov/pr/hnl