WDPN32 PGTW 120300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (VAMCO) WARNING NR 012// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 25W (VAMCO), LOCATED APPROXIMATELY 89 NM WEST- NORTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 17 KNOTS OVER THE PAST SIX HOURS. TY 25W HAS WEAKENED OVER THE PAST SIX HOURS AND HAS JUST RE-EMERGED OVER THE SOUTH CHINA SEA. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY REVEALS TIGHTLY-CURVED BANDING WRAPPING INTO A DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC), HOWEVER, EIR INDICATES SIGNIFICANT WARMING OF CLOUD TOPS. A 120045Z GMI 89GHZ MICROWAVE IMAGE SHOWS MULTIPLE CONVECTIVE BANDS WRAPPING INTO A DEFINED LLCC, WHICH SUPPORTS THE INITIAL POSITION WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 80 KNOTS BASED ON SUBJECTIVE AND OBJECTIVE DVORAK CURRENT INTENSITY ESTIMATES OF 4.5- 4.6 (ABOUT 77 KNOTS). UPPER-LEVEL ANALYSIS DEPICTS A FAVORABLE ENVIRONMENT WITH RADIAL OUTFLOW AND ENHANCED POLEWARD OUTFLOW ASSOCIATED WITH THE WESTERLIES TO THE NORTH, AND LOW VERTICAL WIND SHEAR. TY 25W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP- LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 25W IS FORECAST TO TRACK WESTWARD THROUGH TAU 48 UNDER THE STEERING INFLUENCE OF THE STR POSITIONED TO THE NORTH. TRACK SPEEDS ARE EXPECTED TO DECREASE AS THE SYSTEM TRANSITS SOUTH OF A BREAK IN THE STR. AFTER TAU 48, TY 25W SHOULD TURN WEST-NORTHWESTWARD AS IT TRACKS ALONG THE SOUTHWEST PERIPHERY OF THE STR. AFTER TRACKING OVER WARM WATER (28-29C), TY 25W SHOULD RE-INTENSIFY TO A PEAK OF 80 KNOTS BY TAU 36. HOWEVER, SST VALUES ARE EXPECTED TO COOL TO 26-27C, WITH VERY LOW OCEAN HEAT CONTENT VALUES, WHICH SUPPORTS THE GRADUAL WEAKENING TREND THROUGH TAU 72. TY 25W WILL MAKE LANDFALL NEAR TAU 72. NUMERICAL MODEL GUIDANCE DIVERGES THROUGH THE FORECAST PERIOD WITH A 215NM SPREAD IN SOLUTIONS AT TAU 72. C. AFTER TAU 72, THE SYSTEM WILL RAPIDLY DISSIPATE AS IT TRACKS NORTHWESTWARD OVER THE MOUNTAINOUS TERRAIN OF VIETNAM AND CAMBODIA. NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT LENDING MODERATE CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN