MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (CHAN-HOM) WARNING NR 02// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 16W (CHAN-HOM), LOCATED APPROXIMATELY 799 NM SOUTHEAST OF SASEBO, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 02 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A CONSOLIDATING LOW LEVEL CIRCULATION CENTER (LLCC) WITH FLARING CONVECTION OVER THE SOUTHERN SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH GOOD CONFIDENCE BASED ON THE BROAD CIRCULATION PRESENT IN A 050045Z METOP-B ASCAT PASS AND THE ASSOCIATED AMSU 89GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY IS BASED ON THE AFOREMENTIONED ASCAT-B PASS SHOWING 25-30 KT BARBS CONTAINED WITHIN THE SOUTHEAST QUADRANT. TS 16W IS SLOWLY TRACKING ALONG THE PERIPHERY OF A SUBTROPICAL RIDGE POSITIONED TO THE NORTHEAST THROUGH A FAVORABLE ENVIRONMENT FOR FURTHER DEVELOPMENT, WITH LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS) AND WARM (30-31 CELSIUS) SEA SURFACE TEMPERATURES (SST). THE SYSTEM IS UNDER SUPPORTIVE UPPER LEVEL EQUATORWARD OUTFLOW. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 16W IS FORECAST TO CONTINUE TRACKING GENERALLY NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE STR THROUGH TAU 72. DURING THIS TIME, THE SYSTEM IS FORECAST TO REACH AN INTENSITY OF 85 KTS BY TAU 72 DUE TO THE CONTINUED LOW VWS AND WARM SSTS. MODEL GUIDANCE HAS IMPROVED SIGNIFICANTLY, WITH A CROSS TRACK SPREAD OF 220NM BY TAU 72. AFUM AND JGSM HAVE TS 16W TRACKING TOWARDS KADENA, WHEREAS ECMWF, NAVGEM AND GFS SHOW A TIGHTER RECURVE SOUTH OF HONSHU. THE JTWC FORECAST IS LAID NEAR THIS SECOND GROUP OF MEMBERS, INSTEAD OF DRIVING TS 16W INTO THE RIDGE SITUATED OVER CHINA. C. AFTER TAU 72, THE SYSTEM WILL BEGIN TO ROUND THE STR AXIS WITH A NORTHWARD TRACK TOWARDS KYUSHU. TS 16W WILL GRADUALLY WEAKEN DURING THIS PERIOD AS THE VWS BEGINS TO INCREASE TO 20 KNOTS BY TAU 96 AND THEN TO OVER 30 KNOTS OF VWS BY TAU 120. NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT WITH A CROSS TRACK SPREAD OF 250 NM AT TAU 96, LENDING FAIR CONFIDENCE TO THE JTWC FORECAST TRACK. THERE IS OVERALL FAIR CONFIDENCE IN THE JTWC INTENSITY GIVEN THE SIGNIFICANT SPREAD IN MEMBERS AND THE DYNAMIC ENVIRONMENT.// NNNN NNNN