WDPN31 PGTW 012100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (HINNAMNOR) WARNING NR 019// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 21.4N 125.5E INITIAL INTENSITY: 115 KTS GEOGRAPHIC REFERENCE: 331 NM SOUTH-SOUTHWEST OF KADENA AB MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 01 KTS SIGNIFICANT WAVE HEIGHT: 47 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS ERODING DEEP CONVECTION OVER THE NORTHERN SEMICIRCLE DUE TO INCREASING NORTHEASTERLY VERTICAL WIND SHEAR (VWS) CAUSED BY A RIDGE TO THE NORTHWEST AND A TROUGH TO THE NORTHEAST. MOREOVER, THE CENTRAL CONVECTION IS SHOWING SIGNS OF DECAY LIKELY DUE TO THE SEA SURFACE TEMPERATURES (SSTS) SLIGHTLY COOLING AS THE RESULT OF UPWELLING CREATED BY THE WAKE OF TY 12W AS IT TRANSITED TO ITS CURRENT LOCATION. IN ADDITION, TY 12W HAS BEEN QUASI-STATIONARY OVER THE PAST 6 HOURS DUE TO BEING NESTED BETWEEN THE AFOREMENTIONED RIDGE TO THE NORTHWEST, THE SUBTROPICAL RIDGE TO THE EAST-NORTHEAST, AND THE NEAR EQUATORIAL RIDGE TO THE SOUTH. THE SYSTEM STILL HAS THE PRESENCE OF A CLOUD-FILLED EYE, AND FRAGMENTED SPIRAL BANDING IN THE WESTERN AND EASTERN SEMICIRCLES. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: QUASI-STATIONARY DUE TO BEING NESTED BETWEEN THE AFOREMENTIONED RIDGE TO THE NORTHWEST, THE SUBTROPICAL RIDGE TO THE EAST-NORTHEAST, AND THE NEAR EQUATORIAL RIDGE TO THE SOUTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T6.0 - 115 KTS RJTD: T6.0 - 115 KTS RCTP: T5.5 - 102 KTS KNES: T5.0 - 90 KTS CIMSS SATCON: 130 KTS AT 011322Z CIMSS ADT: 102 KTS AT 011740Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 20-25 KTS SST: 30-31 CELSIUS OUTFLOW: STRONG EQUATORWARD OTHER FACTORS: UPWELLING COOLER WATER 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: TY HINNAMNOR WILL REMAIN SOMEWHAT QUASI- STATIONARY OVER THE NEXT 12-24 HOURS. AS A RESULT, THE SEA SURFACES TEMPERATURES WILL CONTINUE TO COOL DUE TO IMMENSE UPWELLING AND DECREASE THE OVERALL INTENSITY OF THE SYSTEM TO 95 KTS BAT TAU 24. BY TAU 36, TY 12W WILL BEGIN TO TRANSIT NORTHWARD DUE TO THE WEAKENING OF THE SUBTROPICAL RIDGE, AT THE SAME TIME IT WILL CONTINUE TO DECREASE IN INTENSITY TO 90 KTS AS A RESULT OF THE SURROUNDING ONGOING UPWELLING. BY TAUS 48-72, TY HINNAMNOR WILL CONTINUE TO TRACK NORTHWARD AND STEADILY INTENSIFY TO ITS MAX PEAK OF 115 KTS DUE TO THE FAVORABLE ENVIRONMENT CHARACTERIZED BY GOOD OUTFLOW ALOFT AND VERY WARM (29-30 C) SSTS. AFTER TAU 72, TY 12W WILL ROUND THE RIDGE AXIS AND MAKE THE A NORTHEASTWARD TURN. BY TAU 96, TY 12W WILL BEGIN ITS EXTRA-TROPICAL TRANSITION APPROX 67 NM SOUTH OF JEJU, KOREA AND DECREASE IN INTENSITY TO 105 KTS DUE TO SURROUNDING COOLER SSTS. BY TAU 120, TY 12W WILL BECOME FULLY EXTRA-TROPICAL OVER THE SEA OF JAPAN WITH AN OVERALL INTENSITY OF 75 KTS. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT WITH AN 110NM SPREAD AT TAU 72. THIS SPREAD GRADUALLY INCREASES TO 170NM BY TAU 120 WHICH IS TIGHTER THAN THE PREVIOUS MODEL RUN. HOWEVER, THERE IS STILL UNCERTAINTY AMONG THE MODEL MEMBERS WITH TRACK SPEED AFTER TAU 72. THUS, THE CONFIDENCE AFTER TAU 72 REMAINS LOW. THERE IS MEDIUM CONFIDENCE IN THE JTWC INTENSITY FORECAST THROUGH TAU 72 AS THE LARGE SPREAD IN INTENSITY GUIDANCE REMAINS AS IT DID ON THE PREVIOUS MODEL RUN. AFTER TAU 72, THE INTENSITY FORECAST IS MORE UNCERTAIN DUE TO THE EXTRA-TROPICAL TRANSITION AND INTERACTION WITH LAND. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN