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.// NNNN NNNN