WDPN32 PGTW 231500
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 19W
/WARNING NR 20//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 230000Z5 TO 280000Z0 AUG 2004.
    A. SUPER TYPHOON (TY) 19W (CHABA), LOCATED APPROXIMATELY
500 NM SOUTH OF IWO JIMA, HAS TRACKED NORTHWESTWARD AT 10 KNOTS
OVER THE PAST 06 HOURS. THE WARNING POSITION IS BASED ON 231130Z0
INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON
SATELLITE CURRENT INTENSITY ESTIMATES OF 140 AND 155 KNOTS.
    B. STY 19W IS FORECAST TO TRACK AROUND THE SOUTHWESTERN
PERIPHERY OF THE SUBTROPICAL STEERING RIDGE ANCHORED TO THE
NORTH. THE RIDGE WILL WEAKEN AS A MAJOR SHORTWAVE TROUGH PASSES
OVER THE TOP ALLOWING FOR STY 19W TO TRANSITION TO A MORE
POLEWARD TRACK. FURTHER WEAKENING OF THE STEERING RIDGE
FOLLOWED BY SUBSEQUENT BUILDING OF A PERIPHERAL RIDGE TO THE
EAST WILL SEND STY 19W FURTHER POLEWARD. THE AVAILABLE DYNAMIC
AIDS CONSISTING OF UKMET EGRR, JGSM, JTYM, NOGAPS, COAMPS, NCEP
GFS, GFDN, TCLAPS, AND WBAR ARE IN GOOD AGREEMENT WITH THIS
SCENARIO AND HAVE FINALLY ZEROED IN ON A CONSISTENT SOLUTION
GIVING HIGH CONFIDENCE TO THE FORECAST FOR THE FIRST 72 HOURS.
THIS FORECAST IS BASED ON A CONSENSUS OF ALL AVAILABLE DYNAMIC
AIDS.
    C. STY 19W CONTINUES TO EXPERIENCE GOOD OUTFLOW IN THE
EQUATORWARD DIRECTION SO THE SYSTEM IS EXPECTED TO MAINTAIN
INTENSITY OR WEAKEN SLIGHTLY FOR THE NEXT 12 TO 24 HOURS.
THE LATEST STATISTICAL GUIDANCE SHOWS THAT STY 19W WILL CONTINUE
TO SLOWLY WEAKEN WITH TIME, ESPECIALLY AFTER THE 48 HOUR TAU
WHEN IT MOVES INTO AN ENVIRONMENT OF LOWER RELATIVE HUMIDITY.
    D. CURRENT WIND RADII ARE BASED ON A RECENT 230823Z8 QUIKSCAT
PASS. FORECAST WIND RADII ARE BASED ON CLIMATOLOGY FOR A LARGE
SIZED SYSTEM.
    E. THE EXTENDED FORECAST CALLS FOR STY TO APPROACH SOUTHERN
JAPAN AND CONTINUE TO WEAKEN IN A MUCH DRIER ENVIRONMENT. 
3. FORECAST TEAM: GRUBER/KLINZMAN/HEILER//