WDPN32 PGTW 171500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (CHAMPI) WARNING NR 18// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 25W (CHAMPI), LOCATED APPROXIMATELY 368 NM SOUTH OF IWO TO, JAPAN HAS TRACKED NORTHWESTWARD AT 17 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A DEVELOPING 13NM EYE FEATURE SURROUNDED BY A DEEP CONVECTIVE CORE. THE EYE FEATURE PROVIDES HIGH CONFIDENCE IN THE INITIAL POSITION. A 171153Z AMSU-B MICROWAVE IMAGE SHOWS DEEP CONVECTIVE BANDING WRAPPING AROUND THE WESTERN PERIPHERY OF A DISTINCT MICROWAVE EYE. THE CURRENT INTENSITY HAS BEEN HELD AT 90 KNOTS BASED ON CONCURRING DVORAK INTENSITY ESTIMATES OF T5.0 (90 KNOTS) FROM ALL AGENCIES. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS LOCATED IN A FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND SHEAR (VWS) AND GOOD EQUATORWARD OUTFLOW WITH A DEVELOPING POLEWARD OUTFLOW CHANNEL AS SEEN IN WATER VAPOR IMAGERY. TY 25W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH-NORTHEAST. 3. FORECAST REASONING. A. NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY CHAMPI WILL CONTINUE TO TRACK NORTHWESTWARD OVER THE NEXT 12 TO 24 HOURS UNDER THE INFLUENCE OF THE STR. BEYOND TAU 24, THE SYSTEM WILL TURN POLEWARD AND ROUND THE STR AXIS. AFTERWARDS, TY CHAMPI WILL TRACK TO THE NORTHEAST ALONG THE NORTHWESTERN PERIPHERY OF THE STR. AS THE TYPHOON GAINS LATITUDE, ENVIRONMENTAL CONDITIONS WILL BEGIN TO DETERIORATE AS VWS INCREASES AND SEA SURFACE TEMPERATURES (SSTS) DECREASE. C. IN THE EXTENDED FORECAST, TY CHAMPI WILL ACCELERATE NORTHEASTWARD AND CONTINUE TO WEAKEN DUE TO POOR ENVIRONMENTAL CONDITIONS. THE TYPHOON WILL START TO INTERACT WITH THE BAROCLINIC ZONE AND BEGIN EXTRA-TROPICAL TRANSITION BY TAU 96. DYNAMIC MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT THROUGHOUT THE FORECAST PERIOD, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK.// NNNN