Tropical Storm CHAMPI Advisory Cu, 23.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (CHAMPI) WARNING NR 39//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 25W (CHAMPI), LOCATED APPROXIMATELY 136 NM EAST OF
IWO TO, JAPAN, HAS TRACKED EAST-NORTHEASTWARD AT 13 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS A
MOSTLY UNCHANGED CONVECTIVE CORE STRUCTURE THAT IS SURROUNDING A 40NM
EYE WHICH SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. THE
SYSTEM CONTINUES TO BE ELONGATED TO THE NORTHEAST AS IT INTERACTS
WITH THE MID-LATITUDE WESTERLY FLOW. THE INITIAL INTENSITY IS BASED
ON CONGRUENT DVORAK ESTIMATES FROM PGTW AND RJTD. UPPER LEVEL ANALYSIS
INDICATES A MARGINAL ENVIRONMENT WITH MODERATE (20-25 KNOT) VERTICAL
WIND SHEAR (VWS) BEING OFFSET BY A STRONG POLEWARD OUTFLOW CHANNEL,
ENHANCED BY THE MID-LATITUDE ZONAL FLOW. 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 CONTINUE TO TRACK EAST-NORTHEASTWARD ALONG THE
NORTHERN PERIPHERY OF THE STR THROUGHOUT THE FORECAST PERIOD.
INCREASING VWS AND DECREASING SEA SURFACE TEMPERATURES WILL CONTINUE
TO ERODE THE TYPHOON AS IT GAINS LATITUDE. TY CHAMPI WILL BEGIN
EXTRA-TROPICAL TRANSITION (ETT) BY TAU 36 AS IT EMBEDS IN THE
BAROCLINIC ZONE AND COMPLETES ETT BY THE END OF THE FORECAST PERIOD
AS A STRONG COLD CORE LOW. DYNAMIC MODEL GUIDANCE REMAINS IN VERY
TIGHT AGREEMENT, LENDING HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
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