MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (CHAMPI) WARNING NR 27// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 25W (CHAMPI), LOCATED APPROXIMATELY 232 NM SOUTH- SOUTHWEST OF IWO TO, HAS TRACKED NORTHWESTWARD AT 01 KNOT OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A SLIGHTLY WEAKENING ASYMMETRIC CONVECTIVE CORE SURROUNDING A 14NM EYE WHICH SUPPORTS THE CURRENT POSITION WITH HIGH CONFIDENCE. A 191652Z N-19 MICROWAVE IMAGE SHOWS THE DEEPEST CONVECTION ON THE SOUTHERN SIDE OF THE LLCC, WHICH IS INDICATIVE OF SUBSIDENCE ON THE NORTHERN SIDE OF THE SYSTEM. THIS CAN ALSO BE SEEN IN THE WATER VAPOR LOOP. THE TOTAL PRECIPITABLE WATER LOOP SHOWS DRY AIR WRAPPING INTO THE WESTERN PERIPHERY OF THE CIRCULATION WHICH, IN TURN, SLIGHTLY ELONGATES THE CLOUD SYSTEMS STRUCTURE. THE INTENSITY REMAINS AT 100 KNOTS BASED ON DVORAK INTENSITY ESTIMATES FROM ALL REPORTING AGENCIES. UPPER LEVEL ANALYSIS INDICATES GOOD EQUATORWARD OUTFLOW AND LOW VWS. TY CHAMPI IS TRACKING ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED STR EXTENSION 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 AXIS OF THE STR EXTENSION. WHILE THE INTENSITY WILL MAINTAIN FOR A LIMITED AMOUNT OF TIME, INCREASING VWS WILL SLOWLY ERODE THE SYSTEM THOUGH TAU 48. THIS IS IN SPITE OF THE SLIGHTLY INCREASED POLEWARD OUTFLOW AS THE SYSTEM ROUNDS THE STR AXIS THOUGH TAU 48. BY TAU 72 TY 25W WILL BE ALONG THE NORTHERN PERIPHERY OF THE STR. C. IN THE EXTENDED FORECAST PERIOD, TY CHAMPI WILL CONTINUE TO ACCELERATE NORTHEASTWARD AND WEAKEN DUE TO POOR ENVIRONMENTAL CONDITIONS WITH SSTS DROPPING BELOW 26 CELSIUS. ADDITIONALLY, THE CYCLONE WILL START TO INTERACT WITH THE ZONAL MID-LATITUDE FLOW AND BEGIN A WEAK EXTRA- TROPICAL TRANSITION (ETT). THE TYPHOON WILL COMPLETE ETT BY THE END OF THE FORECAST PERIOD. DYNAMIC MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT THROUGHOUT THE FORECAST PERIOD, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK.// NNNN NNNN