WTPA42 PHFO 222105
TCDCP2

HURRICANE IOKE DISCUSSION NUMBER  12
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP012006
1100 AM HST TUE AUG 22 2006

SUBJECTIVE DVORAK INTENSITY ESTIMATES INDICATE THAT IOKE HAS
WEAKENED OVER THE LAST 12 HOURS...AND THE FORMERLY WELL DEFINED EYE
HAS BECOME ILL-DEFINED. WATER VAPOR LOOP SHOWS MOISTURE FIELD ON
THE WEST SIDE OF THE HURRICANE HAS ERODED SOME FROM WEST TO
EAST...INDICATING WEAK SOUTHWESTERLY WIND SHEAR. 1800Z CIMSS
VERTICAL SHEAR PRODUCT SHOWS 9M/S SHEAR FROM 236 DEGREES...WHICH
MATCHES THE SATELLITE DEPICTION WELL. NO MICROWAVE IMAGERY OF
LATE...BUT VISIBLE AND IR IMAGERY SHOW A REMNANT NORTHERN EYEWALL
STILL LIKELY INTACT ABOUT 10 MILES SOUTH OF JOHNSTON ISLAND. 

IOKE CONTINUES TO MOVE NORTHWESTWARD AND GUIDANCE IS TIGHTLY
CLUSTERED AROUND A CONTINUED NORTHWEST MOVEMENT THROUGH 72 HOURS.
THE FORECAST TRACK IS AN EXTENSION OF THE PREVIOUS FORECAST TRACK
WHICH LIES WITHIN THE AFOREMENTIONED TIGHTLY CLUSTERED GUIDANCE.
BEYOND 72 HOURS...MOST OF THE OBJECTIVE AIDS BEND THE STORM
WESTWARD...THEN WEST...SOUTHWESTWARD. THE OFFICIAL FORECAST
TRACK...WHICH IS SOUTH OF THE PREVIOUS FORECAST TRACK...FOLLOWS A
BLEND OF THESE MODELS...WHICH SEEM TO BE RESPONDING TO A DEVELOPING
ANTICYCLONE NORTH OF IOKE. 

WITH REGARD TO INTENSITY...THE SHIPS GUIDANCE STEADILY WEAKENS THE
HURRICANE TO TROPICAL STORM FORCE BY AROUND 72 HOURS...HOWEVER THE
MAJORITY OF INTENSITY MODEL OUTPUT SUGGESTS THAT IOKE WILL MAINTAIN
ITS CURRENT INTENSITY.  SHEAR ALONG THE TRAJECTORY LOOKS TO BE
RELATIVELY WEAK...AS IOKE BECOMES WEDGED BETWEEN 2 LARGE UPPER
LEVEL LOWS...ONE TO THE NORTHWEST...AND ONE TO THE NORTHEAST. THIS
RESULTS IN A LARGE AREA OF ANTICYCLONIC FLOW ALOFT SURROUNDING
IOKE...SO WITH SST REMAINING NEAR 28 C ALONG THE PATH AND NEUTRAL
TO SOMEWHAT FAVORABLE UPPER LEVEL FLOW...IT APPEARS LIKELY THAT
IOKE WILL CONTINUE AS A HURRICANE THROUGH 72 HOURS. BEYOND
THAT...INCREASING SHEAR MAY BEGIN TO WEAKEN THE HURRICANE...AND
THIS IS REFLECTED IN THE OFFICIAL FORECAST.             
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/2100Z 16.2N 169.7W    90 KT
 12HR VT     23/0600Z 17.1N 170.6W    85 KT
 24HR VT     23/1800Z 18.1N 171.7W    85 KT
 36HR VT     24/0600Z 18.9N 172.7W    85 KT
 48HR VT     24/1800Z 19.6N 173.8W    85 KT
 72HR VT     25/1800Z 20.7N 175.9W    85 KT
 96HR VT     26/1800Z 21.0N 177.7W    80 KT
120HR VT     27/1800Z 20.9N 179.6W    75 KT
 
$$
FORECASTER BROWNING