WDPN32 PGTW 122100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (MAN-YI) WARNING NR 016// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 13.0N 145.0E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 33 NM SOUTHEAST OF NAVSTA GUAM MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 16 KTS SIGNIFICANT WAVE HEIGHT: 22 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL STORM 25W (MAN-YI) WITH A BROAD AREA OF CONVECTION NOW OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC). ANIMATED RADAR IMAGERY FROM GUAM REVEALS THAT 25W HAS MADE A SOMEWHAT UNEXPECTED JOG TO THE SOUTHWEST OVER THE PAST 6 HOURS. ENVIRONMENTAL ANALYSIS INDICATES THAT 25W IS IN A MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE RADIAL OUTFLOW ALOFT, LOW (5-10 KTS) VERTICAL WIND SHEAR, DRY AIR OVER THE NORTHWESTERN PORTION OF THE SYSTEM, AND WARM (29-30 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE MENTIONED ANIMATED RADAR IMAGERY. THE INITIAL INTENSITY OF 45 KTS IS ALSO ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK AND OBJECTIVE INTENSITY ESTIMATES. ADDITIONALLY, PERSISTENCE FROM A 121137Z ASCAT-B IMAGE WHICH SHOWS A SWATH OF 40 KNOT WINDS IN THE NORTHERN PERIPHERY. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.0 - 30 KTS RCTP: T3.0 - 45 KTS KNES: T2.0 - 30 KTS CIMSS ADT: 43 KTS AT 121800Z CIMSS AIDT: 37 KTS AT 121800Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE RADIAL OTHER FACTORS: DRY AIR TO THE NORTHWEST OF THE LLCC. ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: 25W IS FORECAST TO TRACK GENERALLY WESTWARD THROUGH TAU 48 ALONG THE SOUTHERN PERIPHERY OF THE STR TO THE NORTH. NEAR TAU 72, THE SYSTEM IS FORECAST TO BEGIN TRACKING NORTHWESTWARD AS IT ROUNDS THE SOUTHWESTERN PERIPHERY OF THE STR AND HEADS TOWARD NORTHERN LUZON. REGARDING INTENSITY, 25W IS FORECAST TO STEADILY INTENSIFY TO AROUND 60 KTS AT TAU 24. AFTERWARDS THE SYSTEM IS FORECAST TO BEGIN A RAPID INTENSIFICATION PHASE THROUGH TAU 48 DUE TO THE HIGHLY CONDUCIVE ENVIRONMENT. A PEAK INTENSITY OF 115 KTS IS PLACED NEAR TAU 72. AFTER TAU 72, THE SYSTEM IS EXPECTED TO BEGIN INTERACTING WITH THE COOLER WATERS LEFT BEHIND FROM THE UPWELLING OF 26W AND 27W WHICH WILL INITIATE A WEAKENING TREND THROUGH THE REMAINDER OF THE FORECAST PERIOD. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT ON THE TRACK OF 25W THROUGH TAU 72 WITH A 150 NM CROSS-TRACK SPREAD AT THAT TIME. AFTER TAU 72, MODELS BEGIN TO DIVERGE WITH SOME MODELS (UKMET AND GALWEM) TRACKING THE VORTEX INTO THE CENTRAL PHILIPPINES WHILE THE MAIN GROUPING HAS THE VORTEX MAKE A SHARPER TURN TOWARD NORTHERN LUZON. THE JTWC TRACK FORECAST IS PLACED CLOSER TO THE MAIN GROUPING WITH HIGH CONFIDENCE THROUGH TAU 72 AND MEDIUM CONFIDENCE THEREAFTER. INTENSITY GUIDANCE IS IN MODERATE AGREEMENT WITH CLOSE AGREEMENT THROUGH TAU 36. PEAK INTENSITIES RANGE FROM 95 KTS (GFS) TO 130 KTS (COAMPS-TC) AROUND TAU 72. MODELS AGREE OVERALL ON WEAKENING AFTER TAU 72. THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO CONSENSUS THROUGHOUT THE FORECAST PERIOD WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN