WDPN32 PGTW 262100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (HIGOS) WARNING NR 018// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 34.0N 137.5E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 134 NM SOUTHWEST OF YOKOSUKA, JAPAN MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 28 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN EXTREMELY COMPACT LOW LEVEL CIRCULATION CENTER (LLCC) OBSCURED BY FLARING CONVECTION OVER AND NORTHEAST OF THE CENTER AS THE SYSTEM RACES OFF TO THE NORTHEAST. RADAR IMAGERY FROM THE JAPAN METEOROLOGICAL AGENCY SHOWS HEAVY CONVECTIVE RAINBANDS ALONG THE NORTHEAST PERIPHERY OF TROPICAL STORM 08W. AS THE NORTHERN SEMICIRCLE OF THE CIRCULATION CLIPS THE SOUTHERN COAST OF HONSHU, THE ASSOCIATED CONVECTION IS BECOMING ENHANCED BY STRONG POLEWARD DIVERGENCE ALOFT, EVIDENCED BY EXPANDING POLEWARD OUTFLOW ALOFT. 10-MINUTE SUSTAINED WINDS FROM THE ISLANDS OF KOZUSHIMA, MIYAKE, AND MIKURAJIMA, WHICH ARE UPSTREAM OF THE LLCC, HAVE INCREASED TO 30-35 KTS. ENVIRONMENTAL CONDITIONS ARE HOSTILE FOR TROPICAL CYCLONE DEVELOPMENT, CHARACTERIZED BY VERY HIGH VERTICAL WIND SHEAR OF 50-70 KTS AND SUB-26 DEGREE CELSIUS WATERS. HOWEVER, THE SYSTEM IS MAINTAINING INTENSITY DUE TO INCREASING BAROCLINICITY AND UPPER LEVEL DIVERGENCE. THE INITIAL POSITION IS ASSESSED WITH LOW CONFIDENCE DUE TO THE OBSCURATION OF THE CENTER BY DISORGANIZED CONVECTION. THE INITIAL INTENSITY IS SET AT 45 KTS WITH MEDIUM CONFIDENCE BASED ON 260930Z AND 261030Z SCATTEROMETER PASSES DEPICTING 45 KT WINDS IN THE EASTERN SEMICIRCLE. THE SUBJECTIVE DVORAK AND CIMSS OBJECTIVE ESTIMATES ARE DEEMED TO BE UNDERESTIMATING THE INTENSITY GIVEN THE HIGH TRANSLATION SPEED, THE DISORGANIZED NATURE OF THE CONVECTION, AND THE SIZE OF THE SYSTEM. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: THE NORTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE AND DEEP-LAYER WESTERLY FLOW AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T3.0 - 45 KTS CIMSS SATCON: 38 KTS AT 261700Z CIMSS ADT: 35 KTS AT 261830Z CIMSS AIDT: 42 KTS AT 261830Z CIMSS D-MINT: 33 KTS AT 261715Z CIMSS D-PRINT: 32 KTS AT 261800Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE VWS: 50-70 KTS SST: 24-25 CELSIUS OUTFLOW: STRONG POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: LOW INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE INTENSITY FORECAST HAS BEEN INCREASED AS A RESULT OF THE HIGHER ASSESSED INITIAL INTENSITY. FORECAST DISCUSSION: LOCATED ON THE NORTHWESTERN SIDE OF A STR, TROPICAL STORM 08W IS ACCELERATING TO THE NORTHEAST UNDER THE INFLUENCE OF DEEP-LAYER SOUTHWESTERLY FLOW. THIS NORTHEAST MOTION WILL CONTINUE THROUGH TAU 36, AFTER WHICH TIME HIGOS WILL BE ABSORBED BY A FRONTAL SYSTEM. THE SYSTEM IS PRESENTLY UNDERGOING EXTRATROPICAL TRANSITION WITH THERMAL ADVECTION WELL UNDERWAY. HIGOS IS PHASING WITH A 125-KT JET STREAK, WHICH WILL PROVIDE IMMENSE UPPER LEVEL DIVERGENCE AND HELP 08W MAINTAIN INTENSITY THROUGH TAU 12 EVEN UNDER VERY STRONG VWS AND COOL SST. IT IS POSSIBLE THAT IT COULD ACHIEVE 50 KTS WITHIN THE NEXT 12 HOURS. THE FORECAST CALLS FOR WEAKENING AT TAU 24 AND 36 AS THE SYSTEM LOSES THE POLEWARD OUTFLOW CHANNEL. DISSIPATION WILL OCCUR AT TAU 36. MODEL DISCUSSION: GUIDANCE IS LIMITED AS MODELS BEGIN TO LOSE TRACK OF THE CIRCULATION. THE JTWC FORECAST TRACK IS LARGELY LAID ON THE GFS AND THE GEFS ENSEMBLE MEAN TRACKERS WITH HIGH CONFIDENCE. THE JTWC INTENSITY FORECAST ALIGNS WITH THE HAFS-A AND EXPERIMENTAL GOOGLE DEEPMIND MODELS, WHICH IS SLIGHTLY BELOW THE 50 KTS DEPICTED BY THE GFS MODEL AT TAU 12 HOURS. THE FORECAST THEN LEANS CLOSER TO THE GFS SOLUTION, WHICH DEPICTS A SLOWER RATE OF WEAKENING AT TAU 24 AND 36 THAN HAFS-A. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: --- INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: ---// NNNN