WDPN31 PGTW 301500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 028// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 29.0N 143.2E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 126 NM NORTH-NORTHEAST OF CHICHI JIMA MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 01 KTS SIGNIFICANT WAVE HEIGHT: 14 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS WARMING CLOUD TOPS AND FRAGMENTED CONVECTIVE BANDING OVER TROPICAL STORM (TS) 12W. TROPICAL STORM (TS) 12W IS EMBEDDED WITHIN DRY AIR AND IS FIGHTING TO MAINTAIN MOISTURE IN AN OTHERWISE MARGINAL ENVIRONMENT FOR DEVELOPMENT. VERTICAL WIND SHEAR IS LOW AND FAVORABLE, AND AN UPPER-LEVEL TROUGH TO THE NORTH IS ALLOWING MODERATE POLEWARD OUTFLOW. SIGNIFICANT UPWELLING DUE TO THE QUASI-STATIONARY STATE WHICH TS 12W HAS REMAINED IN IS ANOTHER NEGATIVE FACTOR WEIGHING INTO THE DEGRADING STRUCTURE OF THE SYSTEM. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE AFOREMENTIONED RAGGED CIRCULATION IDENTIFIED IN ANIMATED EIR. THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE FIXES LISTED BELOW. INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK CURRENT STEERING MECHANISM: COMPETING AND WEAK STEERING ENVIRONMENT AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T3.0 - 45 KTS RCTP: T3.0 - 45 KTS KNES: T3.5 - 55 KTS CIMSS SATCON: 44 KTS AT 301130Z CIMSS ADT: 34 KTS AT 301130Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL VWS: 5-10 KTS SST: 27-28 CELSIUS OUTFLOW: MODERATE POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: LOW INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 12W HAS REMAINED QUASI-STATIONARY OVER THE LAST SIX HOURS, AND THE TRACK WILL REMAIN AND THE TRACK WILL REMAIN IRREGULAR AND SLOW WHILE IN A COMPETING STEERING ENVIRONMENT BETWEEN THE SUBTROPICAL RIDGE OVER JAPAN AND MONSOONAL FLOW TO THE SOUTH. THE TRACK WILL REMAIN SLOW AND IRREGULAR OVER THE NEXT 24 HOURS IN THE NORTHWESTWARD DIRECTION. A VORTICITY MAXIMUM EMBEDDED WITHIN THE MONSOON TROUGH TO THE SOUTHWEST WILL ENHANCE THE CURVE AS A RESULT OF BINARY INTERACTION. AFTER TAU 48, THE SUBTROPICAL RIDGE INFLUENCING THE SYSTEM WILL WEAKEN, AND TS 12W WILL CURVE NORTHEASTWARD WITH THE MONSOONAL FLOW ON THE NORTHWESTERN PERIPHERY OF THE NEAR EQUATORIAL RIDGE TO THE SOUTHWEST. TS 12W WILL STRUGGLE TO INTENSIFY WHILE REMAINING QUASI STATIONARY AND SLOW FOR THE NEXT 24 HOURS DUE TO SIGNIFICANT UPWELLING. AS THE SYSTEM TRACKS NORTHWESTWARD AFTER TAU 24, THE SYSTEM WILL BE MET WITH WARMER SEA SURFACE TEMPERATURES, ALLOWING FOR GRADUAL INTENSIFICATION. HOWEVER, THE UPPER-LEVEL ENVIRONMENT WILL BECOME UNFAVORABLE, AND DRY AIR WILL CONTINUE TO INTRUDE INTO CYCLONE. VERTICAL WIND SHEAR WILL INCREASE AFTER TAU 48, AND THE SYSTEM WILL CONTINUOUSLY WEAKEN THROUGH THE END OF THE FORECAST. MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE LEADS TO SIGNIFICANT UNCERTAINTY IN THE TRACK FORECAST. THE JTWC MULTI-MODEL CONSENSUS MEMBERS FAN OUT WITH A LARGE SPREAD AND VARYING ANGLES WHICH THE SYSTEM WILL TRACK BETWEEN WEST-NORTHWEST AND NORTH-NORTHWEST. THE ENSEMBLE GUIDANCE FOLLOWS SUIT WITH SIGNIFICANT SPREAD OF ENSEMBLE MEMBERS FANNING OUT BETWEEN BOTH GEFS AND ECENS. THE CURVE WEST-NORTHWESTWARD IS LIKELY ASSOCIATED WITH VARYING STRENGTH OF BINARY INTERACTION WITH THE VORTICITY MAXIMUM EMBEDDED WITHIN THE MONSOONAL FLOW. OF NOTE, SEVERAL DETERMINISTIC AND ENSEMBLE SOLUTIONS MAKE LANDFALL ON HONSHU, AND IF THE TRACK DEVIATES SLIGHTLY THERE MAY BE IMPACTS TO THE MAINLAND OF JAPAN. THE INTENSITY FORECAST IS MADE WITH LOW CONFIDENCE DUE TO THE SIGNIFICANT TRACK VARIATION. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN