WDPN31 PGTW 290900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (JANGMI) WARNING NR 009// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 15.9N 132.8E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 695 NM SOUTH-SOUTHEAST OF KADENA AB MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 22 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: THE INITIAL POSITION OF TROPICAL STORM (TS) 06W (JANGMI) IS ESTABLISHED WITH MEDIUM CONFIDENCE, CENTERING ON A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER IDENTIFIED IN THE MULTISPECTRAL SATELLITE IMAGERY (MSI). THE CENTER OF ROTATION REMAINS BROAD, HOWEVER, PREVIOUSLY VISIBLE MESOVORTICES APPEAR TO HAVE CONSOLIDATED, WITH STRONGEST TURNING AND ASSOCIATED CONVECTIVE ACTIVITY PRESENT THROUGHOUT THE SOUTHERN REGION. A 290456Z GCOMW1 AMSR2 PASS REVEALS A SLIGHTLY IMPROVED WIND FIELD SYMMETRY. ADDITIONALLY, THE MSI DEPICTS PERSISTENT NORTHEASTERLY VERTICAL WIND SHEAR, WITH DRIER AIR PRESENT THROUGHOUT THE NORTHEASTERN QUADRANT. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CERTAINTY, MATCHING THE SUPPORTING SUBJECTIVE DVORAK ASSESSMENTS AND OBJECTIVE AIDS LISTED BELOW. CURRENT MOVEMENT IS DRIVEN BY THE STRENGTHENING DEEP-LAYER SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST. THE CORRESPONDING SYNOPTIC OVERVIEW REMAINS LARGELY CONDUCIVE FOR CONTINUOUS TROPICAL DEVELOPMENT, BOLSTERED BY WARM (29-30 C) SEA SURFACE TEMPERATURES AND MODERATE EQUATORWARD OUTFLOW ALOFT. ADDITIONAL ANALYSIS REVEALS GENERALLY LOW (10-15 KTS) VERTICAL WIND SHEAR COMBINED WITH SOME DRIER AIR ENTRAINMENT FROM THE NORTHEAST, WHICH ARE SLIGHTLY OFFSETTING THE OTHERWISE HIGHLY FAVORABLE ENVIRONMENT. INITIAL WIND RADII BASIS: A 290456Z GCOMW1 AMRS2 PASS CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE CENTERED TO THE NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.0 - 30 KTS RCTP: T2.5 - 35 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 44 KTS AT 290600Z CIMSS ADT: 32 KTS AT 290600Z CIMSS AIDT: 38 KTS AT 290600Z CIMSS D-MINT: 41 KTS AT 290600Z CIMSS D-PRINT: 42 KTS AT 290600Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: A BROAD INNER CORE WIND FIELD, NORTHEASTERLY VERTICAL SHEAR, AND ENTRAINING DRY AIR WILL RESULT IN AN INITIALLY SLOW INTENSIFICATION OF TS 06W. THE SYSTEM IS FORECAST TO ATTAIN A PEAK INTENSITY OF 80 KTS AROUND TAUS 48 AND 72 AS IT CONSOLIDATES, WHILE TRAVELLING ALONG THE FLANK OF AN AMPLIFYING DEEP-LAYER STR. AS THIS RIDGE CONTINUES TO BUILD, TS JANGMI WILL ACCELERATE TOWARD THE RIDGE AXIS. SHORTLY AFTER TAU 48, RECURVATURE WILL COMMENCE, RE-DIRECTING THE SYSTEM ON A POLEWARD AND EASTWARD HEADING BY TAU 72. WHILE TRANSITING THE RYUKYU ARCHIPELAGO NEAR KADENA, DWINDLING OCEANIC HEAT CONTENT WILL EXPOSE THE VORTEX TO LOCALIZED UPWELLING FEEDBACK, ACCELERATING THE DECAY. AFTER TAU 96, AS THE CIRCULATION NEARS KYUSHU, ANY SEVERE POLEWARD VENTILATION GAINED FROM THE MID-LATITUDE JET STREAM WILL BE OFFSET BY COOL SEA SURFACE TEMPERATURES PLUMMETING TO 24-25 C, INDUCING A RAPID WEAKENING TREND. AT THE SAME TIME, INTERACTION WITH MID-LATITUDE WESTERLIES WILL LEAD TO AN EXPANSION OF THE WIND FIELD, RESULTING IN POTENTIAL IMPACTS TO MAINLAND JAPAN. MODEL DISCUSSION: WHILE THE RECURVATURE DRIVEN BY THE STR CENTERED TO THE NORTHEAST IS UNANIMOUSLY SIMULATED ACROSS ALL DYNAMICAL AND EXPERIMENTAL AI MODELS, OVERALL TRACK FORECAST CERTAINTY IS ASSESSED AS MODERATE. THIS MEDIUM CONFIDENCE STEMS FROM A CROSS-TRACK SPREAD OF 210 NM NEAR KADENA (BETWEEN TAU 72 AND TAU 96), INDUCED PRIMARILY BY THE WESTWARD OUTLIER TRACE OF NAVGEM. REMOVING NAVGEM REVEALS A TIGHT MODEL CONVERGENCE CONFINED TO A 115 NM CORRIDOR. CONSEQUENTLY, THE OFFICIAL JTWC TRACK IS POSITIONED SLIGHTLY EASTWARD OF THE MULTI-MODEL CONSENSUS TO PREFERENTIALLY WEIGHT THIS HIGHER DENSITY CLUSTER. ADDITIONALLY, ALONG-TRACK SPREAD INCREASES TOWARDS THE END OF THE FORECAST, WITH NAVGEM REMAINING THE PRIMARY OUTLIER, INCREASING THE ALONG-TRACK SPREAD TO 525 NM, FROM 215 NM MEASURING THE ENVELOPE EXCLUDING NAVGEM. REGARDING INTENSITY GUIDANCE, THE TIMELINE FOR A PEAK OCCURRING BETWEEN TAUS 48 AND 72 FOLLOWED BY ACCELERATED DECAY IS WELL-SUPPORTED ACROSS THE CONSENSUS MEMBERS SUITE. NEVERTHELESS, INTENSITY CONFIDENCE REMAINS MEDIUM DUE TO PERSISTENT AMPLITUDE DISPERSION. THE DETERMINISTIC GFS AND GFS-INITIALIZED COAMPS-TC REPRESENT THE AGGRESSIVE EDGE OF THE ENVELOPE AT 85-95 KTS MAXIMUM INTENSITY, CONTRASTING WITH MORE CONSERVATIVE PROJECTIONS OF STATISTICAL-DYNAMICAL MODELS PEAKING AT 60-65 KTS. THE STANDING JTWC OFFICIAL PROJECTION LIES SLIGHTLY ABOVE THE MULTI-MODEL MEAN, LEANING TOWARD THE REPRESENTATION DEPICTED BY HAFS GUIDANCE. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN