Tropical Storm CHAMPI Advisory Fri Oct 23

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (CHAMPI) WARNING NR 40//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 25W (CHAMPI), LOCATED APPROXIMATELY 207 NM EAST OF
IWO TO, HAS TRACKED EAST-NORTHEASTWARD AT 12 KNOTS OVER THE PAST SIX
HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A CONVECTIVE
CORE SURROUNDING A 40 NM EYE FEATURE, HOWEVER MORE RECENT IMAGERY
INDICATES THIS CORE IS BEGINNING TO WEAKEN IN THE NORTHWEST
QUADRANT. THE INITIAL POSITION IS BASED ON THE EYE FEATURE 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 DVORAK FINAL-T ESTIMATES FROM PGTW, KNES,  AND
RJTD RANGING FROM 90 TO 102 KNOTS. 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. SEA SURFACE TEMPERATURES REMAIN
FAVORABLE UP TO 30 DEGREES NORTH LATITUDE. 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 SHORTLY AFTER TAU 48. DYNAMIC
MODEL GUIDANCE REMAINS IN VERY TIGHT AGREEMENT, LENDING HIGH
CONFIDENCE IN THE JTWC FORECAST TRACK.//
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