WTPA42 PHFO 220304
TCDCP2

HURRICANE IOKE DISCUSSION NUMBER   9
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP012006
500 PM HST MON AUG 21 2006

HURRICANE IOKE CONTINUES TO INTENSIFY FEATURING A WELL DEFINED 
EYE/EYEWALL STRUCTURE AND GOOD OVERALL SYMMETRY IN VISIBLE AND IR 
IMAGERY. INTENSITY ESTIMATES FROM THE VARIOUS SATELLITE AGENCIES 
RANGE FROM T5.5 TO T6.0. GIVEN THE RAPID DEVELOPMENT OF IOKE OVER 
THE PAST 24 HOURS...WILL CONTINUE TO HEDGE TOWARD THE HIGHER DVORAK 
ESTIMATES. THUS...HAVE UPGRADED IOKE TO A CATEGORY 4 HURRICANE WITH 
MAXIMUM WINDS OF 115 KT.
 
IOKE IS CURRENTLY MOVING NORTHWEST AT 11 KT...REPRESENTING A FAIRLY 
CLIMATOLOGICAL TRACK GIVEN ITS POSITION IN THE CENTRAL PACIFIC. THE 
MOST RECENT MODEL GUIDANCE SHIFTED SLIGHTLY TOWARD THE EAST AND 
SLOWED DOWN THROUGH 48 HOURS. THE OFFICIAL FORECAST THROUGH 48 
HOURS FOLLOWED THIS TREND...PLACING IOKE WITHIN 30 MILES OF JOHNSTON 
ISLAND AT 24 HOURS. AT 72 HOURS AND BEYOND...ALL THE DYNAMIC AIDS 
SHIFTED MARKEDLY TO THE WEST. THIS SHIFT IS IN RESPONSE TO A 
STRONGER THAN PREVIOUSLY FORECAST LOW AND MID LEVEL RIDGING NORTH 
OF IOKE...THAT WILL CURTAIL ITS NORTHWARD MOTION AND FAVOR A MORE 
WEST NORTHWEST TRACK. A RESULT...AT 72 HOURS HAVE BEGUN A SHIFT OF 
THE OFFICIAL FORECAST TO THE WEST. AT 96 AND 120 HOURS...THE 
OFFICIAL FORECAST IS TO THE WEST OR SOUTH OF THE PREVIOUS 
TRACK...THOUGH STILL RIGHT OR NORTH OF THE DYNAMIC AIDS. THE DYNAMIC 
AIDS AT 96 AND 120 HOURS ARE ALSO SLOWER THAN THE PREVIOUS...AND 
HAVE ACCORDINGLY ADJUSTED THE LONG TERM SPEED DOWNWARD. THERE IS 
STILL CONSIDERABLE UNCERTAINTY IN THE LONG TERM PORTION OF THE 
FORECAST...GIVEN THE RECENT SHIFT IN MODEL GUIDANCE.
 
THE INTENSITY FORECAST CALLS FOR AN INCREASE IN INTENSITY TO 120 KT 
AT 24 AND 36 HOURS...IN AGREEMENT WITH THE DYNAMIC GUIDANCE. 
THEREAFTER...THE 18Z GFDL AND GFS INDICATE ADDITIONAL 
INTENSIFICATION THROUGH 120 HOURS...WHILE THE 12Z UKMET SUGGESTS A 
GRADUAL WEAKENING THROUGH 72 HOURS AND THEN LEVELING OUT. WILL 
FOLLOW THE UKMET TREND...KEEPING IOKE AT CATEGORY 4 STRENGTH THROUGH 
36 HOURS...THEN AT CATEGORY 3 STRENGTH THEREAFTER. THIS CHANGE 
REPRESENTS A RATHER SIGNIFICANT DEVIATION TO THE PREVIOUS INTENSITY 
FORECAST CALLING FOR WEAKENING FROM 48 HOURS AND BEYOND. THE SHIPS 
INTENSITY GUIDANCE SUGGESTED MORE RAPID WEAKENING BEYOND 48 
HOURS...BUT IS BASED UPON A FORECAST TRACK TAKING IOKE NORTH OF 23N. 
AS THE OFFICIAL FORECAST TRACK MAINTAINS IOKE AT 21N AND 
SOUTH...HAVE DISREGARDED THE SHIPS GUIDANCE.
 
ALL INTERESTS IN THE VICINITY OF JOHNSTON ISLAND SHOULD IMMEDIATELY
PREPARE FOR HURRICANE FORCE WINDS WITHIN THE NEXT 24 HOURS.
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/0300Z 13.9N 167.4W   115 KT
 12HR VT     22/1200Z 15.2N 168.6W   120 KT
 24HR VT     23/0000Z 16.6N 170.0W   120 KT
 36HR VT     23/1200Z 17.7N 171.3W   115 KT
 48HR VT     24/0000Z 18.4N 172.2W   110 KT
 72HR VT     25/0000Z 19.9N 174.2W   105 KT
 96HR VT     26/0000Z 21.0N 176.4W   105 KT
120HR VT     27/0000Z 21.9N 179.0W   105 KT
 
$$
FORECASTER TANABE/NASH