WDPN31 PGTW 031500
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 031200Z6 TO 061200Z9 DEC 02.
   A. TROPICAL STORM (TS) 31W (PONGSONA), LOCATED APPROXIMATELY 40 
NM SOUTH-SOUTHEAST OF UJELANG ATOLL, HAS TRACKED WESTWARD AT 09 
KNOTS OVER THE PAST SIX HOURS. THE WARNING POSITION IS BASED ON 
031130Z8 ENHANCED INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY 
IS BASED ON A 030722Z4 QUIKSCAT PASS AND SATELLITE CURRENT INTENSITY 
ESTIMATES OF 35 AND 45 KNOTS. ANIMATED WATER VAPOR SATELLITE IMAGERY 
INDICATES INCREASING POLEWARD OUTFLOW OVER THE PAST SIX HOURS.
   B. AN APPROACHING SHORTWAVE TROUGH IS EXPECTED TO WEAKEN THE LOW 
TO MID-LEVEL SUBTROPICAL RIDGE NORTH OF THE SYSTEM BY THE END OF THE 
PERIOD. TS 31W IS FORECAST TO TRACK WESTWARD THROUGH 48 HOURS AND 
THEN WEST-NORTHWESTWARD BY 72 HOURS ALONG THIS SUBTROPICAL RIDGE. 
THE AVAILABLE DYNAMIC AIDS, CONSISTING OF NOGAPS, GFDN, GFS, UKMET 
OFFICE GLOBAL (EGRR), AND JAPANESE GLOBAL (JGSM) AND TYPHOON (JTYM) 
MODELS, ARE IN GOOD AGREEMENT WITH THIS SCENARIO. OUR FORECAST IS 
BASED ON A BLEND OF ALL AVAILABLE DYNAMIC AIDS.
   C. TS 31W IS EXPECTED TO REMAIN SOUTH OF THE UPPER LEVEL RIDGE 
AXIS THROUGH THE PERIOD. THE SYSTEM IS EXPECTED TO INTENSIFY AT A 
CLIMATOLOGICAL RATE THROUGH THE PERIOD IN A FAVORABLE ENVIRONMENT. 
   D. INITIAL WIND RADII ARE BASED ON A 030722Z4 QUIKSCAT PASS. 
FORECAST WIND RADII ARE BASED ON CLIMATOLOGY FOR AN AVERAGE-SIZED 
SYSTEM.
FORECAST TEAM: WINGEART/LAM/STATEN/KUMAGA//
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