MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (CHAN-HOM) WARNING NR 39// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 09W (CHAN-HOM), LOCATED APPROXIMATELY 135 NM WEST- SOUTHWEST OF KADENA AB, HAS TRACKED WEST-NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. RECENT ANIMATED MSI CONTINUES TO DEPICT VIGOROUS FEEDER BANDS WRAPPING INTO A WELL-DEFINED 15 NM DIAMETER EYE. THE CURRENT POSITION IS BASED ON THE EYE FEATURE WITH HIGH CONFIDENCE. THE CURRENT INTENSITY OF 120 KNOTS IS BASED ON THE CURRENT STRUCTURE AND IS HEDGED SLIGHTLY HIGHER THAN THE CORRESPONDING DVORAK INTENSITY ESTIMATES OF T6.0 (115 KNOTS) FROM ALL REPORTING AGENCIES. UPPER-LEVEL ANALYSIS INDICATES THE TYPHOON IS LOCATED IN AN AREA OF FAVORABLE VWS AND GOOD DIFFLUENCE ALOFT. TY 09W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF THE DEEP-LAYERED 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 24. FAVORABLE CONDITIONS WILL PERSIST, MAINTAINING THE CURRENT INTENSITY IN THE SHORT TERM. AFTERWARD, UNFAVORABLE ENVIRONMENTAL CONDITIONS WILL START THE WEAKENING TREND. BY TAU 36, TY 09W WILL FURTHER WEAKEN AS IT TRACKS OVER EASTERN CHINA. CONCURRENTLY, AN APPROACHING MID- LATITUDE TROUGH WILL PASS TO THE NORTH, WEAKENING THE STR AND ALLOWING TY 09W TO TURN POLEWARD. BY TAU 72, THE STR IS EXPECTED TO REORIENT AND WILL DRIVE THE SYSTEM NORTHEASTWARD. C. TYPHOON CHAN-HOM WILL MAINTAIN A NORTHEASTWARD TRAJECTORY THROUGH THE END OF THE FORECAST PERIOD. WITH THE EXCEPTION OF NAVGEM TAKING THE TYPHOON FURTHER INLAND, MAJORITY OF THE MODEL GUIDANCE IS OVERALL IN GOOD AGREEMENT EMERGING THE SYSTEM INTO THE SOUTHERN YELLOW SEA. DUE TO THE SPREAD IN DYNAMIC GUIDANCE IN THE EXTENDED TAUS, THE JTWC FORECAST TRACK CONFIDENCE LEVEL REMAINS LOW.// NNNN NNNN