WDPN32 PGTW 231500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (CHAMPI) WARNING NR 42//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 25W (CHAMPI), LOCATED APPROXIMATELY 643 NM NORTH OF 
SAIPAN, HAS TRACKED EASTWARD AT 15 KNOTS OVER THE PAST SIX 
HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A RAGGED 
EYE FEATURE WITH CONTINUED DETERIORATION OF THE CONVECTIVE STRUCTURE 
AS IT BECOMES FURTHER ELONGATED TO THE NORTHEAST. A 231046Z GPM 
89GHZ MICROWAVE IMAGE SHOWS ALL CONVECTION SHEARED TO THE NORTHEAST 
WITH AN ELONGATED LOW LEVEL CIRCULATION CENTER. WATER VAPOR IMAGERY 
SHOWS THE TYPHOON EMBEDDED WITHIN THE BOUNDARY LAYER AND BEGINNING 
TO SHOW FRONTAL CHARACTERISTICS; INDICATING THE BEGINNING OF EXTRA-
TROPICAL TRANSITION (ETT). UPPER LEVEL ANALYSIS INDICATES A POOR 
ENVIRONMENT WITH VERTICAL WIND SHEAR IN EXCESS OF 30 KNOTS WITH A 
POLEWARD OUTFLOW ENHANCED BY THE MID-LATITUDE ZONAL FLOW. SEA 
SURFACE TEMPERATURES (SSTS) REMAIN FAVORABLE AT 28 CELSIUS. TY 25W 
IS TRACKING ALONG THE POLEWARD SIDE OF THE SUB-TROPICAL RIDGE (STR) 
TO THE SOUTHEAST.
3. FORECAST REASONING.
   A. NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY SINCE THE 
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 25W WILL TRACK EAST-NORTHEASTWARD ALONG THE NORTHERN 
PERIPHERY OF THE STR THROUGHOUT THE FORECAST PERIOD. INCREASING VWS 
AND DECREASING SSTS WILL CONTINUE TO ERODE THE TYPHOON AS IT GAINS 
LATITUDE. TY CHAMPI WILL CONTINUE EXTRA-TROPICAL TRANSITION (ETT) AS 
IT EMBEDS IN THE BAROCLINIC ZONE AND WILL COMPLETE ETT BY THE END OF 
THE FORECAST PERIOD. DYNAMIC MODEL GUIDANCE REMAINS IN VERY TIGHT 
AGREEMENT, LENDING HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
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