WDPN31 PGTW 290300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (HINNAMNOR) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 27.3N 145.3E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 937 NM EAST OF KADENA AB MOVEMENT PAST 6 HOURS: WESTWARD AT 14 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A COMPACT, SYMMETRICAL SYSTEM WITH SPIRAL BANDING FROM THE NORTHERN PERIPHERY THAT HAS WRAPPED TIGHTER INTO AN OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC). THE CENTRAL DENSE OVERCAST FEATURE, WHICH IS OBSCURING THE LLCC HAS A FORMATIVE EYE NEAR THE CENTER. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A DEFINED EYE FEATURE IN THE 2313Z GPM 37GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY OF 55KTS IS ALSO ASSESSED WITH HIGH CONFIDENCE BASED ON AGENCY AND AUTOMATED DVORAK ESTIMATES THAT REFLECT THE 6-HR STRUCTURAL IMPROVEMENT AND CONSISTENT WITH A FORMATIVE EYE. THE ENVIRONMENT REMAINS FAVORABLE WITH STRONG EQUATORWARD OUTFLOW, MODERATE VERTICAL WIND SHEAR, AND WARM SSTS. INITIAL WIND RADII BASIS: PERSISTENCE. CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) EXTENSION TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS RJTD: T3.0 - 45 KTS KNES: T3.5 - 55 KTS CIMSS SATCON: 53 KTS AT 282208Z CIMSS ADT: 53 KTS AT 282340Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 15-20 KTS SST: 30-31 CELSIUS OUTFLOW: STRONG EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM HINNAMNOR WILL TRACK GENERALLY WESTWARD TOWARD OKINAWA UNDER THE STEERING STR. AFTER TAU 72, A SECONDARY STR OVER CENTRAL CHINA, EMERGING BEHIND A TRANSITORY SHORTWAVE TROUGH, AND A NEAR EQUATORIAL RIDGE TO THE SOUTHEAST WILL COMPETE FOR STEERING, FORCING THE SYSTEM TO BECOME QUASI-STATIONARY (QS) IN A COL AREA. THE AFOREMENTIONED FAVORABLE CONDITIONS WILL PROMOTE GRADUAL THEN RAPID INTENSIFICATION TO A PEAK OF 130KTS BY TAU 72. AFTERWARD, COOLING SST DUE TO UPWELLING INDUCED BY THE SYSTEM BEING QS IN THE COL WILL WEAKEN THE SYSTEM TO 105KTS BY TAU 100. MODEL DISCUSSION: THE MAJORITY OF AVAILABLE NUMERICAL MODELS IS IN BROAD AGREEMENT UP TO TAU 72. AFTERWARD, TWO MODELS - NVGM AND UKMET - RECURVE THE VORTEX TOWARD JAPAN IN RESPONSE TO THE TRANSITORY SHORTWAVE TROUGH. THE MAIN PACK CONTINUES WESTWARD TOWARD THE COL AREA. IN VIEW OF THIS, AND GIVEN THE UNCERTAINTIES IN TRACK MOTION INHERENT IN A COL, THERE IS MEDIUM CONFIDENCE IN THE JTWC TRACK, LAID NEAR THE CONSENSUS OF THE MAIN PACK, AND INTENSITY FORECASTS UP TO TAU 72 THEN LOW CONFIDENCE AFTERWARD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN