Tropical Storm CHAMPI Advisory dom, 18.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (CHAMPI) WARNING NR 20//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 25W (CHAMPI), LOCATED APPROXIMATELY 343 NM SOUTH OF
IWO TO, JAPAN, HAS TRACKED NORTH-NORTHWESTWARD AT 04 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS THE
SYSTEM HAS MAINTAINED A 7-NM EYE FEATURE SURROUNDED BY DEEP
CONVECTIVE BANDS THAT HAVE WRAPPED TIGHTER INTO THE EYE. THE INITIAL
POSITION IS BASED ON THE EYE FEATURE WITH HIGH CONFIDENCE. THE
INITIAL INTENSITY OF 100 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF
DVORAK ESTIMATES FROM ALL REPORTING AGENCIES AND REFLECTS THE
IMPROVED STATE OF THE SYSTEM. UPPER LEVEL ANALYSIS INDICATES TY 25W
IS LOCATED IN A FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND SHEAR
(VWS) AND GOOD EQUATORWARD OUTFLOW WITH INCREASED POLEWARD OUTFLOW AS
SEEN IN WATER VAPOR IMAGERY. THE CYCLONE IS TRACKING ALONG THE
WESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE
EAST-NORTHEAST.
3. FORECAST REASONING.
   A. NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 25W IS NOW ROUNDING THE WESTERN EDGE OF THE STR AXIS. IT
WILL TRACK NORTHWARD UP TO TAU 36 THEN ACCELERATE NORTHEASTWARD ON
THE POLEWARD SIDE OF THE STR. AS TY 25W GAINS LATITUDE, ENVIRONMENTAL
CONDITIONS WILL BEGIN TO DETERIORATE AS VWS INCREASES AND SEA SURFACE
TEMPERATURES DECREASE.
   C. IN THE EXTENDED FORECAST, TY CHAMPI WILL CONTINUE TO ACCELERATE
NORTHEASTWARD AND WEAKEN DUE TO POOR ENVIRONMENTAL CONDITIONS.
CONCURRENTLY, THE CYCLONE WILL START TO INTERACT WITH THE BAROCLINIC
ZONE AND BEGIN EXTRA-TROPICAL TRANSITION. DYNAMIC MODEL GUIDANCE
REMAINS IN TIGHT AGREEMENT THROUGHOUT THE FORECAST PERIOD, LENDING
HIGH CONFIDENCE TO THE JTWC FORECAST TRACK.//
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