WDPN31 PGTW 180300
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 21W WARNING NR 32//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 180000Z TO 200000Z OCT 2005.
   A. TYPHOON (TY) 21W (KIROGI), LOCATED APPROXIMATELY 375 NM SOUTH-
SOUTHWEST OF TOKYO, JAPAN, HAS TRACKED NORTHEASTWARD AT 09 KNOTS
OVER THE PAST SIX HOURS.
   B. TY 21W IS TRACKING NORTHEASTWARD ALONG THE NORTHWESTERN PERI-
PHERY OF THE SUBTROPICAL RIDGE LOCATED TO THE EAST. RECENT SATELLITE
IMAGERY INDICATES THE SYSTEM IS IN THE EARLY STAGES OF BECOMING AN
EXTRATROPICAL SYSTEM. A SHORTWAVE TROUGH CURRENTLY EXTENDING FROM
SOUTH KOREA EXTENDING SOUTHWESTWARD INTO THE SOUTH CHINA SEA IS FORE-
CAST TO CONTINUE MOVING EASTWARD AND INTERACT WITH TY 21W BETWEEN
TAUS 12 AND 24 WHICH WILL FURTHER ENHANCE THE TRANSITION TO AN
EXTRATROPICAL SYSTEM. THE AVAILABLE DYNAMIC AIDS CONSISTING OF TCLAPS,
NOGAPS, EGRR, JGSM, JTYM, NCEP GFS, COAMPS, MM5, GFDN AND WBAR ARE IN
FAIR AGREEMENT WITH THIS FORECAST.
   C. TY 21W HAS REMAINED STEADY OVER THE PAST 12 HOURS IN AN ENVIRONMENT
OF HIGH VERTICAL WIND SHEAR AS THE EFFECTS OF THE SHEAR WAS OFFSET BY A
GOOD POLEWARD OUTFLOW CHANNEL. HOWEVER, THE SYSTEM WILL BEGIN TO RAPIDLY
WEAKEN AS IT TRACKS INTO AN ENVIRONMENT OF VERY HIGH VERTICAL WIND SHEAR
ASSOCIATED WITH THE BAROCLINIC ZONE AND COOLER SEA SURFACE TEMPERATURES.
THE SYSTEM IS FORECAST TO BEGIN TRANSITIONING TO AN EXTRATROPICAL SYSTEM
IN THE NEXT 12 TO 24 HOURS AND IS FORECAST TO COMPLETE THE TRANSITION
BETWEEN TAUS 36 AND 48.
   D. CURRENT WIND RADII ARE BASED ON A 172144Z SSM/I PASS. FORECAST
WIND RADII ARE BASED ON CLIMATOLOGY FOR AN AVERAGED-SIZED SYSTEM.
3. FORECAST TEAM: ALPHA//
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