WDPN31 PGTW 111500
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 111200Z5 SEP 02 TO 141200Z8 SEP 02.
   A. TROPICAL STORM (TS) 23W (HAGUPIT), APPROXIMATELY 100 NM 
SOUTHWEST OF HONG KONG, HAS TRACKED WEST-NORTHWESTWARD AT 09 KNOTS 
DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 111130Z7 
ENHANCED INFRARED SATELLITE IMAGERY AND SYNOPTIC DATA. THE WARNING 
INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 45 
AND 55 KNOTS AND SURFACE OBSERVATIONS. ANIMATED WATER VAPOR IMAGERY 
INDICATES THAT THE CONVECTION HAS WEAKENED OVER THE PAST SIX HOURS.
   B. THE MID-LEVEL SUBTROPICAL RIDGE OVER EASTERN CHINA IS 
EXPECTED TO BUILD WESTWARD THROUGH 72 HOURS. TS 23W IS FORECAST TO 
TRACK WESTWARD ALONG THIS RIDGE THROUGH THE PERIOD. A SOUTHWEST 
MONSOON SURGE IS EXPECTED INTERACT WITH THE SYSTEM BY MID-PERIOD, 
CAUSING THE SYSTEM TO SLOW DOWN AFTER 48 HOURS. THE AVAILABLE 
DYNAMIC AIDS, CONSISTING OF NOGAPS, GFDN, COAMPS, AFWA MM5, NCEP 
AVIATION, THE JAPANESE GLOBAL (JGSM) AND TYPHOON (JTYM), AND THE 
UKMET OFFICE GLOBAL MODELS ARE IN FAIR AGREEMENT. GFDN HAS THE 
FASTEST TRACK, KEEPING THE SYSTEM MORE INTENSE THROUGH THE PERIOD. 
COAMPS DOES NOT BUILD THE RIDGE AS MUCH AS THE OTHER AIDS, CAUSING 
THE TRACK TO BE MORE POLEWARD. OUR FORECAST IS BASED ON PERSISTENCE 
AND A BLEND OF ALL AVAILABLE DYNAMIC AIDS. 
   C. AN UPPER LEVEL RIDGE LOCATED OVER SOUTHERN CHINA IS IMPEDING 
POLEWARD OUTFLOW AND IS EXPECTED TO CONTINUE TO CREATE AN 
UNFAVORABLE ENVIRONMENT OVER THE NEXT 24 HOURS. TS 23W IS EXPECTED 
TO WEAKEN THROUGH THE FORECAST PERIOD AS IT ENCOUNTERS VERTICAL WIND 
SHEAR FROM THE UPPER LEVEL RIDGE AND THEN TRACKS OVER LAND.
   D. INITIAL AND FORECAST WIND RADII ARE BASED ON CLIMATOLOGY FOR 
AN AVERAGE-SIZED SYSTEM.   
FORECAST TEAM: WINGEART/LAM/KUMAGA/STATEN//
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