WDPN31 PGTW 120900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (MEARI) WARNING NR 005// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 30.8N 136.5E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 314 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 05 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THAT THE EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) THAT HAS BEEN TRACKED OVER THE PAST DAY, HAS STOPPED MOVING NORTHWARD AND HAS INSTEAD TAKEN A HARD TURN TO THE EAST OVER THE PAST FOUR HOURS OR SO. NET TRACK MOTION SINCE THE PREVIOUS BEST TRACK HAS THUS SLOWED TO ROUGHLY FIVE KNOTS. TS 09W CONTINUES TO STRUGGLE TO CONSOLIDATE AN ORGANIZED CONVECTIVE CORE ABOUT THE LLCC IN THE FACE OF PERSISTENT NORTH-NORTHWESTERLY SHEAR. HOWEVER, THE BULK SHEAR, WHILE STILL MODERATE, HAS SLACKED OFF QUITE A BIT SINCE THE PREVIOUS ANALYSIS, NOW ESTIMATED AT 15-20 KNOTS. ATMOSPHERIC MOTION VECTORS (AMVS) REVEAL AN UPPER-LEVEL COL REGION JUST NORTH OF TD 09W AND AS THE SYSTEM MOVES INTO THIS REGION, SHEAR IS EXPECTED TO SLACKEN EVEN MORE. JTWC HAND ANALYSIS INDICATES A MINISCULE POINT SOURCE LOCATED ABOVE TS 09W, PROVIDING MODERATE TO STRONG EQUATORWARD OUTFLOW AND SUPPORTING THE FLARING CONVECTION IN THE SOUTHERN HEMISPHERE OF THE SYSTEM. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC. THE INITIAL INTENSITY REMAINS ASSESSED AT 35 KNOTS WITH HIGH CONFIDENCE BASED ON AN OVERALL AVERAGE OF AGENCY SUBJECTIVE AND OBJECTIVE DVORAK FIX INTENSITIES. REGARDLESS OF THE RECENT RIGHTWARD JOG OF THE LLCC, THE OVERALL MOTION CONTINUES NORTHWARD ALONG THE WESTERN PERIPHERY OF A DEEP SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE EAST. INITIAL WIND RADII BASIS: PERSISTENCE AND SCATTEROMETER DATA. CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE EAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.0 - 30 KTS KNES: T2.0 - 30 KTS CIMSS SATCON: 40 KTS AT 120348Z CIMSS ADT: 35 KTS AT 120540Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 15-20 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE 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: TS 09W IS FORECAST TO CONTINUE TO TRACK NORTH-NORTHEASTWARD ALONG THE WESTERN PERIPHERY OF THE STEERING RIDGE THROUGH THE NEXT 12 HOURS. THEN AS THE RIDGE RAPIDLY SLIDES SOUTHWESTWARD AFTER TAU 24, TS 09W WILL TURN ONTO A NORTHEASTWARD TRACK THROUGH THE REMAINDER OF THE FORECAST PERIOD. THE SYSTEM IS FORECAST TO MAKE LANDFALL ALONG THE SOUTHERN TIP OF THE IZU PENINSULA AROUND TAU 24, THEN MOVE THROUGH THE SOUTHERN PORTION OF THE TOKYO WAN, THEN BACK OUT TO SEA EAST OF NARITA BY AROUND TAU 30, THEN CONTINUE TO ACCELERATE NORTHEAST TO NEAR THE CENTRAL KURIL ISLANDS BY THE END OF THE FORECAST PERIOD. AS DISCUSSED ABOVE, TS 09W CONTINUES TO STRUGGLE TO CONSOLIDATE A VERTICALLY STACKED CONVECTIVE CORE IN THE FACE OF PERSISTENT NORTHERLY FLOW. AS THE SYSTEM CONTINUES TRACKING NORTHWARD AND ENTERS A COL REGION OF RELATIVELY LIGHT WINDS, SHEAR IS FORECAST TO BACK OFF TO LOW LEVELS. AT THE SAME TIME THE SYSTEM WILL MOVE INTO AN AREA OF STRONGLY DIFFLUENT WESTERLY FLOW ALOFT, ENHANCING THE POLEWARD AND EASTWARD OUTFLOW. THE COMBINATION OF THESE TWO FACTORS SHOULD BE ENOUGH TO ALLOW THE CONVECTIVE CORE TO CONSOLIDATE AND INITIATE A SHORT BURST OF INTENSIFICATION. DUE TO THE LIMITED TIME REMAINING OVER OPEN WATERS AND THE VERY SHORT WINDOW DURING WHICH THE ABOVE FACTORS MUST CONGEAL, THE FORECAST PEAK IS ONLY 50 KNOTS BY TAU 24 AS THE SYSTEM APPROACHES LANDFALL. AFTER RETURNING TO OPEN WATERS EAST OF HONSHU, THE SYSTEM WILL BEGIN EXTRATROPICAL TRANSITION (ETT) AS IT MOVES AHEAD OF A NEGATIVELY TILTED 200MB TROUGH, AND CROSSES INTO MUCH COOLER WATERS (LESS THAN 24C). THE SYSTEM WILL ALSO BE RAPIDLY WEAKENING AS IT UNDERGOES ETT AND IT WILL BE A RACE TO SEE WHICH OCCURS FIRST, DISSIPATION OR ETT. AT THIS POINT, THE FORECAST FAVORS TRANSITION TO A COLD CORE BAROTROPIC EXTRATROPICAL SYSTEM PRIOR TO DISSIPATION BELOW WARNING CRITERIA, WITH TRANSITION OCCURRING NO LATER THAN TAU 72, AND LIKELY BY TAU 60. MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN EXTREMELY GOOD AGREEMENT THROUGH THE BULK OF THE FORECAST, WITH A MINIMAL 40NM SPREAD AT TAU 24, INCREASING TO ABOUT 200NM AT THE END OF THE FORECAST PERIOD. THE JGSM MODEL IS THE SOLE BLACK SHEEP OF THE FAMILY, HANGING OUT ABOUT 50NM WEST OF THE REMAINDER OF THE GUIDANCE PACKAGE THROUGH THE DURATION OF THE FORECAST. THE JTWC TRACK FORECAST LIES ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE THROUGH TAU 24, THEN CLOSELY FOLLOWS THE CONSENSUS MEAN THEREAFTER WITH HIGH CONFIDENCE. INTENSITY GUIDANCE SHOWS MORE VARIABILITY WITH THIS RUN, WITH THE CTCX AND CTR1 BACK TO THEIR OLD TRICKS, INDICATING A PEAK NEAR 70 KNOTS, SIGNIFICANTLY ABOVE THE REMAINDER OF THE GUIDANCE WHICH LIES IN A TIGHT 10 KNOT ENVELOPE BETWEEN 40-50 KNOTS. THE DECAY-SHIPS IS ALSO A SIGNIFICANT OUTLIER ON THE LOW SIDE, WITH BOTH THE GFS AND NAVGEM VERSION INDICATING WEAKENING FROM THE START. THE JTWC FORECAST REMAINS CONSISTENT WITH THE PREVIOUS FORECAST AND PEAKS AT 50 KNOTS, ON THE HIGH END OF THE TIGHTEST MODEL PACKING. CONFIDENCE IN THE FORECAST IS MEDIUM HOWEVER, DUE TO THE UNCERTAINTIES BROUGHT ON BY THE VERY TIGHT WINDOW OF OPPORTUNITY FOR ALL THE POSITIVE ENVIRONMENTAL FACTORS TO ALIGN AND TS 09W TO INTENSIFY. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH INTENSITY 0 - 72 HR: MEDIUM// NNNN