WTPA42 PHFO 142105
TCDCP2

HURRICANE FLOSSIE DISCUSSION NUMBER  25
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP092007
1100 AM HST TUE AUG 14 2007

AT 1800 UTC...UW-CIMMS ESTIMATED HURRICANE FLOSSIE WAS UNDERGOING 
ABOUT 25 KT OF SOUTHWEST SHEAR. GOOD OUTFLOW TO THE NORTH IS 
COUNTERED BY HAMPERED OUTFLOW ELSEWHERE AS THIS SHEAR REALLY BEGINS 
TO TAKE ITS TOLL. AIRCRAFT OBSERVATIONS SHOW FLOSSIE HAS AN OPEN 
EYEWALL TO THE SOUTHEAST...WITH AN EXTRAPOLATED SURFACE WIND OF 90 
KT AS OF 1600 UTC. AN 1800 UTC VORTEX MESSAGE LIMITS THIS SPEED TO 
THE NORTHEAST EYEWALL...WITH WEAKER WINDS ELSEWHERE. CI VALUES OF 
4.5 FROM CPHC AND SAB AS WELL AS 5.0 FROM JTWC...77 KT AND 90 
KT...SHOW THIS SYSTEM HAS WEAKENED OVER THE PAST SIX HOURS. WE GIVE 
FLOSSIE AN INITIAL STRENGTH OF 90 KT FOR THIS RUN. 

TRACK GUIDANCE DIVERGES SHARPLY BEYOND 24 HOURS AS EACH MODEL 
HANDLES THE DECLINE OF FLOSSIE DIFFERENTLY...BUT THE GUIDANCE MEAN 
HAS CHANGED LITTLE. THE FORECAST TRACK CLOSELY FOLLOWS THE ARC OF 
THE OLD TRACK...BUT AN INITIAL SLIGHT DEVIATION TO THE RIGHT WAS 
NEEDED GIVEN RADAR-DERIVED INITIAL MOTION OF 299 DEGREES. THIS WILL 
TAKE FLOSSIE A BIT CLOSER TO THE BIG ISLAND AT POINT OF CLOSEST 
APPROACH...BUT CONTINUED WEAKENING WILL MITIGATE THE EFFECT THIS 
CHANGE WILL HAVE ON THE BIG ISLAND. WE HAVE DECREASED THE TROPICAL 
STORM WIND RADIUS TO 90 NM WITHIN THE NORTHWEST AND NORTHEAST 
QUADRANTS BASED ON AIRCRAFT OBSERVATIONS AND SCATTEROMETER DATA. 
THIS RADIUS IS STILL LARGE ENOUGH TO AFFECT THE BIG 
ISLAND...PROMPTING CONTINUANCE OF THE TROPICAL STORM WARNING AND 
HURRICANE WATCH FOR THAT ISLAND. WE DO NOT ANTICIPATE THE NEED FOR 
WATCHES OR WARNINGS FOR THE SMALLER ISLANDS AT THIS TIME. RADAR 
SHOWS FLOSSIE FORWARD SPEED HAS SLOWED TO 9 KT AND THIS IS REFLECTED 
IN THE TRACK FORECAST AS WELL. HURRICANE FLOSSIE WILL PASS SOUTH OF 
THE MAIN HAWAIIAN ISLANDS...WEAKENING BELOW HURRICANE STRENGTH 
WITHIN 48 HOURS.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/2100Z 17.3N 154.9W    90 KT
 12HR VT     15/0600Z 18.0N 156.3W    80 KT
 24HR VT     15/1800Z 18.9N 158.2W    75 KT
 36HR VT     16/0600Z 19.8N 160.2W    65 KT
 48HR VT     16/1800Z 20.6N 162.4W    55 KT
 72HR VT     17/1800Z 22.0N 166.9W    40 KT
 96HR VT     18/1800Z 23.3N 171.2W    35 KT
120HR VT     19/1800Z 24.4N 175.4W    25 KT
 
$$
FORECASTER POWELL