Tropical Storm CHAMPI Advisory lun, 19.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (CHAMPI) WARNING NR 24//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 25W (CHAMPI), LOCATED APPROXIMATELY 300 NM SOUTH-
SOUTHWEST OF IWO TO, JAPAN, HAS TRACKED NORTH-NORTHEASTWARD AT 04
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) SHOWS THE SYSTEM HAS SLIGHTLY WEAKENED EVEN AS IT
MAINTAINED A 16-NM EYE SURROUNDED BY AN INTENSE CONVECTIVE CORE. THE
INITIAL POSITION IS BASED ON THE EYE IN THE MSI ANIMATION WITH HIGH
CONFIDENCE. THE INITIAL INTENSITY OF 115 KNOTS IS BASED ON AN OVERALL
ASSESSMENT OF DVORAK ESTIMATES FROM REPORTING AGENCIES AND REFLECTS
THE SLIGHT WEAKENING. THE UPPER LEVEL ENVIRONMENT REMAINS MOSTLY
FAVORABLE WITH LOW VERTICAL WIND SHEAR (VWS) AND DUAL OUTFLOW;
HOWEVER, THE POLEWARD CHANNEL HAS DIMINISHED WITH THE SUBSIDENT
EFFECT OF A MID-LATITUDE TROUGH TO THE NORTHWEST. THE CYCLONE IS
TRACKING ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED SUB-TROPICAL
RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
   A. NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 25W WILL CONTINUE TO TRACK SLOWLY NORTH TO
NORTH-NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF THE STR THAT IS
BUILDING. AFTER TAU 48, THE SYSTEM WILL ACCELERATE NORTHEASTWARD
WHERE ENVIRONMENTAL CONDITIONS WILL 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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