MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (CHAN-HOM) WARNING NR 34// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 09W (CHAN-HOM), LOCATED APPROXIMATELY 326 NM SOUTH- SOUTHEAST OF KADENA AB, HAS TRACKED NORTHWESTWARD AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED EIR SATELLITE IMAGERY DEPICTS THE TYPHOON HAS SLIGHTLY EXPANDED IN SIZE AND A DISTINCT 24 NM DIAMETER EYE THAT SUPPORTS THE HIGH CONFIDENCE IN THE CURRENT POSITION. THE INITIAL INTENSITY OF 90 KNOTS IS BASED ON THE CURRENT STRUCTURE AND AN OVERALL ASSESSMENT OF DVORAK INTENSITY ESTIMATES FROM ALL REPORTING AGENCIES. UPPER-LEVEL ANALYSIS INDICATES TY 09W IS LOCATED IN AN AREA OF LOW TO MODERATE VWS BEING OFFSET BY THE EXCELLENT EQUATORWARD OUTFLOW AS EVIDENT ON THE WATER VAPOR IMAGERY. THE CYCLONE IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF AN EXTENSION OF THE STR TO THE NORTH. 3. FORECAST REASONING. A. 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 72. FAVORABLE CONDITIONS WILL PERSIST, ALLOW TY CHAN-HOM TO STEADILY INTENSIFY LEADING TO A PEAK INTENSITY OF 115 KNOTS BY TAU 48. AFTERWARD, TY CHAN-HOM IS EXPECTED TO BEGIN ITS WEAKENING TREND AS THE SYSTEM INTERACTS WITH THE EASTERN COAST OF CHINA. DYNAMIC GUIDANCE IS IN TIGHT AGREEMENT THROUGH THIS PERIOD, LENDING HIGH CONFIDENCE TO THIS PORTION OF THE TRACK FORECAST. C. IN THE EXTENDED TAUS, AN APPROACHING MID-LATITUDE TROUGH WILL PASS TO THE NORTH, CAUSING A BREAK IN THE STR AND ALLOWING TY 09W TO TURN NORTHEASTWARD. UNFAVORABLE ENVIRONMENTAL CONDITIONS ALONG WITH LAND INTERACTION WILL FURTHER DECAY THE SYSTEM. NUMERICAL MODEL GUIDANCE SHOWS A LARGE SPREAD AND SIGNIFICANT DIFFERENCES IN THE TRACK SPEEDS; THEREFORE, DUE TO SOME UNCERTAINTY IN TIMING AND SPEED OF THE SYSTEM IN THE EXTENDED FORECAST TRACK, THE JTWC TRACK FORECAST CONFIDENCE LEVEL REMAINS LOW.// NNNN NNNN