WTPA42 PHFO 250250
TCDCP2

HURRICANE IOKE DISCUSSION NUMBER  21
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP012006
500 PM HST THU AUG 24 2006

IOKE HAS BEEN ABLE TO MAINTAIN A RATHER NICE EYE AND SYMMETRIC
STRUCTURE DURING THE DAY.  A 2016 UTC MICROWAVE PASS SHOWED A
CLOSED INNER EYEWALL SURROUNDED BY WHAT APPEARED TO BE AN
INCOMPLETE OUTER EYEWALL.  THIS MAY BE INDICATING THAT IOKE IS
GOING THROUGH AN EYEWALL REPLACEMENT CYCLE.  IT IS CERTAINLY A
STRONG ENOUGH SYSTEM TO MAKE THIS A POSSIBILITY.  DVORAK ESTIMATES
FROM CPHC...SAB AND JTWC INDICATE 127 KT WHILE AFWA SHOWS 115 KT. 
WILL MAINTAIN AN INITIAL INTENSITY OF 125 KT...OR CATEGORY 4 ON THE
SAFFIR-SIMPSON SCALE FOR THIS PACKAGE.  WINDSAT DATA ALSO INDICATE
THAT IOKE IS A LARGE SYSTEM SO THE INITIAL WIND RADII HAVE BEEN
INCREASED ESPECIALLY IN THE SOUTHWEST QUADRANT.

AN INITIAL MOTION OF 290 AT 6 KT IS BEING USED AGAIN AS IOKE
CONTINUES TO MOVE SOUTH OF A WEAK SUBTROPICAL RIDGE.  NO MAJOR
CHANGES HAVE BEEN MADE FROM THE PREVIOUS FORECAST PACKAGE WHICH
EXPECTS A NORTHEAST TO SOUTHWEST ORIENTED RIDGE TO BUILD IN WEST OF
THE HURRICANE.  THE RIDGE SHOULD IMPART A SOUTHWESTWARD MOTION ON
IOKE FROM DAYS 2 THROUGH 4.  A WEAKNESS IN THE RIDGE IS FORECAST TO
DEVELOP BY DAY 5 WHICH SHOULD PULL IOKE BACK TOWARD THE NORTHWEST. 
GLOBAL MODELS ARE IN GENERAL AGREEMENT WITH THIS SCENARIO WITH THE
MAIN DIFFERENCES BEING THE STRENGTH OF THE RIDGE AT THE END OF THE
FORECAST PERIOD.  THE ECMWF KEEPS A STRONGER RIDGE AND HAS THE
SOUTHERNMOST TRACK WHILE THE GFS WEAKENS THE RIDGE SUBSTANTIALLY TO
FORCE A NORTHWESTWARD TURN FARTHER EAST THAN THE OTHER MODELS.  THE
FORECAST TRACK FOLLOWS THE GUNS...GUNA AND CONU DYNAMIC CONSENSUS
AND CALLS FOR IOKE TO CROSS THE DATELINE AND BECOME A TYPHOON SOME
TIME BETWEEN DAYS 2 AND 3.
 
THE INTENSITY FORECAST IS ESSENTIALLY IDENTICAL TO THE PREVIOUS
PACKAGE AND MAINTAINS 125 KT THROUGH 36 HOURS FOLLOWED BY A MODEST
WEAKENING TO 115 KT AFTERWARD.  NOTE THAT A HURRICANE OF THIS
INTENSITY IS EXPECTED TO HAVE RAPID AND TOUGH TO FORECAST
FLUCTUATIONS.  SST VALUES ARE NEARLY 28C AND THE FORECAST TRACK
TAKES IOKE OVER 29C WATERS.  THIS FAVORS AT LEAST CURRENT INTENSITY
MAINTENANCE AND POSSIBLY FURTHER INTENSIFICATION.  THE CIMSS SHEAR
ANALYSIS FROM 0000 UTC SHOWS ONLY 2.8 M/S VERTICAL SHEAR WHICH IS A
VERY LOW VALUE.  INTENSITY GUIDANCE FROM THE DYNAMIC MODELS SHOW
STEADY VALUES THROUGH 36 HOURS THEN SOME DIVERGENCE IN THE
SOLUTIONS THEREAFTER.  BOTH THE GFDI AND GFS WANT TO EVENTUALLY
INTENSIFY IOKE TO A CATEGORY 5 SYSTEM WHILE THE OTHERS MAINTAIN A
CATEGORY 4 SYSTEM.  THE SHIPS MODEL IS NOT USED IN THIS PACKAGE DUE
TO PROBLEMS WITH THE COMPUTATIONS OVER THE WESTERN EXTREME OF THE
MODEL DOMAIN.  THE SLIGHT WEAKENING FORECAST AFTER 36 HOURS IS A
RESULT OF SOME NORTHERLY TO NORTHEASTERLY SHEAR THAT IS EXPECTED TO
AFFECT THE SYSTEM.  HOWEVER...THE SHEAR SHOULD NOT PREVENT IOKE
FROM BEING A MAJOR HURRICANE THROUGHOUT THE ENTIRE FORECAST PERIOD.
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      25/0300Z 19.1N 173.7W   125 KT
 12HR VT     25/1200Z 19.5N 174.5W   125 KT
 24HR VT     26/0000Z 19.9N 176.0W   125 KT
 36HR VT     26/1200Z 19.9N 177.4W   125 KT
 48HR VT     27/0000Z 19.5N 178.9W   120 KT
 72HR VT     28/0000Z 18.6N 178.6E   115 KT
 96HR VT     29/0000Z 19.0N 176.1E   115 KT
120HR VT     30/0000Z 20.4N 174.0E   115 KT
 
$$
FORECASTER KODAMA/BURKE