WDPN32 PGTW 281500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (WUTIP) WARNING NR 08// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 20W (WUTIP), LOCATED APPROXIMATELY 326 NM EASTWARD OF DA NANG, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD AT 02 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) INDICATES THAT TY 20W HAS CONTINUED TO INCREASE IN CONVECTIVE ORGANIZATION AS THE CENTRAL DENSE OVERCAST FEATURE HAS PERSISTED AND DEEPENED OVER THE LOW-LEVEL CIRCULATION CENTER (LLCC) WHILE THE SYSTEM HAS SLOWLY DRIFTED TO THE WEST DISPLAYING QUASI-STATIONARY MOVEMENT. A 281004Z CORIOLIS 37GHZ MICROWAVE IMAGE DEPICTS A TIGHTLY WRAPPED SYSTEM WITH IMPROVED CONVECTIVE BANDING WRAPPING INTO A SMALL MICROWAVE EYE FEATURE. THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION AND RECENT MOTION BASED ON THE MICROWAVE IMAGE AND RADAR IMAGERY FROM PADDLE ISLAND, CHINA. THE INITIAL INTENSITY HAS BEEN INCREASED TO 65 KNOTS BASED ON THE IMPROVING STRUCTURE AND AN AVERAGE OF DVORAK INTENSITY ESTIMATES THAT RANGE FROM 55 TO 77 KNOTS. UPPER-LEVEL ANALYSIS AND ANIMATED WATER VAPOR IMAGERY SHOWS A FAVORABLE ENVIRONMENT WITH DUAL CHANNEL OUTFLOW AND LOW TO MODERATE (10 TO 20 KNOTS) VERTICAL WIND SHEAR. TY 20W CONTINUES TO MEANDER IN A WEAK STEERING ENVIRONMENT AS THE SUBTROPICAL STEERING RIDGE (STR) HAS BROKE DOWN IN RESPONSE TO THE DIGGING TROUGH THAT IS CURRENTLY OVER EASTERN CHINA. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 20W IS FORECAST TO TRACK SLOWLY WESTWARD TO WEST- SOUTHWESTWARD THROUGH TAU 24 UNDER THE WEAK STEERING INFLUENCE OF THE REBUILDING STR. AFTER TAU 24, THE SYSTEM IS EXPECTED TO GRADUALLY ACCELERATE WESTWARD AS THE STR BECOMES MORE ESTABLISHED AND THE SHORTWAVE TROUGH PROPAGATES TO THE EAST. TY 20W WILL CONTINUE TO INTENSIFY TO A PEAK INTENSITY OF 85 KNOTS PRIOR TO LANDFALL DUE TO FAVORABLE ENVIRONMENTAL CONDITIONS. TY 20W WILL THEN MAKE LANDFALL OVER VIETNAM SHORTLY AFTER TAU 48 AND WILL BEGIN TO DISSIPATE DUE TO THE LAND INTERACTION WITH COMPLETE DISSIPATION BY TAU 72. NUMERIC MODEL GUIDANCE CONTINUES TO REMAIN IN TIGHT AGREEMENT WITH ONLY A 90NM SPREAD BY TAU 48 ALTHOUGH THERE ARE SOME SLIGHT DIFFERENCES IN TRACK SPEED. DUE TO THIS CONTINUED TIGHT AGREEMENT, HIGH CONFIDENCE REMAINS IN THE JTWC FORECAST TRACK.// NNNN