MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (CHAN-HOM) WARNING NR 42// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 09W (CHAN-HOM), LOCATED APPROXIMATELY 268 NM SOUTH- SOUTHEAST OF SHANGHAI, CHINA, HAS TRACKED NORTHWESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED IR SATELLITE IMAGERY DEPICTS A DECAYING SYSTEM WITH DEEP SPIRAL BANDING WRAPPING INTO AN 18-NM EYE, WHICH LENDS HIGH CONFIDENCE TO THE INITIAL POSITION. HOWEVER, THE IR LOOP HIGHLIGHTS A GRADUAL WEAKENING TREND WITH WARMING CONVECTIVE TOPS AND DIMINISHING DEEP CONVECTIVE BANDING ESPECIALLY OVER THE NORTHERN SEMI-CIRCLE. THE INITIAL INTENSITY OF 90 KTS IS BASED ON AN OVERALL ASSESSMENT OF DVORAK ESTIMATES FROM ALL REPORTING AGENCIES. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM IS IN AN AREA OF INCREASING VWS (20-30 KNOTS). HOWEVER, EXCELLENT EQUATORWARD OUTFLOW IS PARTIALLY OFFSETTING THE VWS AND PROVIDING VENTILATION TO THE ASSOCIATED CONVECTION. THE CYCLONE IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF THE DEEP-LAYERED STR TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 09W IS FORECAST TO CONTINUE TRACKING NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE STR THROUGH TAU 12. AFTERWARDS, IT WILL RECURVE NORTHWESTWARD INTO THE YELLOW SEA TOWARDS THE KOREAN DMZ AS IT ROUNDS THE WESTERN EDGE OF THE STR. TY 09W IS EXPECTED TO RAPIDLY WEAKEN DUE TO INCREASING VWS, LAND INTERACTION, AND COOLING SSTS. TY 09W WILL LIKELY REDUCE TO MINIMAL TROPICAL STORM STRENGTH BY TAU 48, WHICH SHOULD PRODUCE GALE-FORCE WINDS ALONG THE WEST COAST OF SOUTH KOREA. AVAILABLE DYNAMIC GUIDANCE IS IN FAIR AGREEMENT ON THE GENERAL TRACK BUT POOR AGREEMENT ON THE TRACK SPEEDS. IN VIEW OF THIS, THERE IS LOW CONFIDENCE IN THE JTWC TRACK FORECAST, WHICH IS POSITIONED CLOSE TO BUT SLIGHTLY FASTER THAN THE MULTI-MODEL CONSENSUS.// NNNN NNNN