WDPN31 PGTW 230300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (TALAS) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 30.8N 134.8E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 250 NM SOUTHEAST OF IWAKUNI, JAPAN MOVEMENT PAST 6 HOURS: NORTHWARD AT 13 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN IMPROVED CONVECTIVE STRUCTURE, WITH A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) THAT HAS BECOME SLIGHTLY MORE TUCKED UNDER THE DEEP PERSISTENT CONVECTION. AN EARLIER 222121Z SSMIS 91GHZ MICROWAVE IMAGE REVEALS SHALLOW BANDING WRAPPING INTO A LOW LEVEL CIRCULATION CENTER POSITIONED ALONG THE SOUTHWESTERN EDGE OF A CURVED CONVECTIVE BAND. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON MSI IMAGERY AND THE SSMIS MICROWAVE IMAGERY. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE CURRENT CONVECTIVE STRUCTURE AS WELL AS A COMBINATION OF AGENCY DVORAK INTENSITY ESTIMATES, PGTW T2.0, RJTD T2.0 AND CIMSS ADT 34 KTS. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T2.0 - 30 KTS CIMSS SATCON: 46 KTS AT 222121Z CIMSS ADT: 34 KTS AT 222340Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 10-15 KTS SST: 27-28 CELSIUS OUTFLOW: STRONG POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: AFTER A BRIEF INTENSIFICATION PERIOD TO 35 KTS, TS 17W WILL LIKELY MAINTAIN ITS INTENSITY BASED ON THE OVERALL MARGINALLY FAVORABLE ENVIRONMENT, WHERE VERTICAL WIND SHEAR (VWS) IS AN INHIBITING FACTOR AND IS FORECAST TO INCREASE AS THE SYSTEM CONTINUES TO MOVES POLEWARD. OVER THE NEXT 12-24 HOURS THE JTWC OFFICIAL TRACK SHOWS THE SYSTEM TURNING SHARPLY TO THE NORTHEAST BEFORE MAKING LANDFALL INTO HONSHU. BY TAU 24, AFTER THE SYSTEM MAKES LANDFALL IT WILL BEGIN TO DECREASE IN INTENSITY DUE TO LAND INTERACTION WHILE ALSO INTERACTING WITH AN APPROACHING UPPER-LEVEL TROUGH TO THE NORTHWEST OF THE SYSTEM. THIS INTERACTION BETWEEN THE SYSTEM AND THE UPPER LEVEL FEATURE WILL INDUCE INCREASED VERTICAL WIND SHEAR (VWS) WHICH WILL FURTHER DISRUPT THE SYSTEMS TROPICAL CONVECTIVE STRUCTURE. AFTER TAU 36, 17W WILL CONTINUE TO WEAKEN FURTHER DUE TO CONTINUED LAND INTERACTION FROM THE RUGGED TERRAIN. THEREFORE, SIGNIFICANTLY IMPACTING THE SYSTEMS STRUCTURE, WITH DISSIPATING FORECAST BY TAU 48. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT WITH ONLY A 40NM SPREAD UP TO TAU 24. THEREAFTER, THE NUMERICAL MODEL GUIDANCE SPREADS ONCE THE SYSTEM MAKES LANDFALL, WITH INCREASES IN BOTH CROSS TRACK AND ALONG TRACK VARIABILITY. LIKELY DUE TO HOW MODELS ARE STRUGGLING TO RESOLVE THE WEAK STRUCTURE OF THE CIRCULATION INDUCED BY INCREASED VERTICAL WIND SHEAR AND TERRAIN INTERACTION. THUS, THE JTWC OFFICIAL TRACK FORECAST IS PLACED WITH MEDIUM CONFIDENCE. THE JTWC INITIAL INTENSITY IS CLOSE TO THE MULTI-MODEL CONSENSUS WITH MEDIUM CONFIDENCE THROUGHOUT THE FORECAST PERIOD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM// NNNN