WDPN32 PGTW 040300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (BAILU) WARNING NR 009// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 37.2N 149.6E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 437 NM EAST-SOUTHEAST OF MISAWA, JAPAN MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 20 KTS SIGNIFICANT WAVE HEIGHT: 19 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS LOW-LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH TROPICAL STORM (TS) 13W (BAILU). THE SYSTEM CONTINUES TO EXHIBIT SIGNIFICANT STRUCTURAL ASYMMETRY, WITH A HIGHLY ANISOTROPIC WIND FIELD. ADDITIONALLY, SIGNIFICANT DRY AIR ENTRAINMENT CAN BE IDENTIFIED WITH CONVECTIVE BANDING STRUCTURE ASSESSMENT. DEEP CONVECTION NEAR THE CENTER IS FLARING AND SHALLOW. THE INITIAL POSITION IS DETERMINED WITH HIGH CONFIDENCE, BASED ON LOW-LEVEL CLOUD AND CONVECTIVE BANDING TRACKING INTO A RELATIVELY WELL-DEFINED LLCC. A 032307Z METOP-B ASCAT PASS ASSISTED IN THIS ASSESSMENT AS WELL, SHOWING A BEGINNING OF LLCC ELONGATION TOWARD THE NORTHEAST. INITIAL INTENSITY IS ASSESSED AT 35 KTS WITH HIGH CONFIDENCE, SUPPORTED BY THE AFOREMENTIONED ASCAT PASS SHOWING A BAND OF 30 KTS WIND BARBS TO THE SOUTH OF THE LLCC. AGENCY DVORAK INTENSITY ESTIMATES AND OBJECTIVE GUIDANCE LISTED BELOW WERE ALSO UTILIZED. THE SYSTEM IS CURRENTLY EMBEDDED WITHIN A MARGINAL SYNOPTIC-SCALE ENVIRONMENT, CHARACTERIZED BY LOW (5-10 KTS) DEEP-LAYER VERTICAL WIND SHEAR (VWS), AND MODERATE THERMODYNAMIC SUPPORT FROM SEA SURFACE TEMPERATURES (SST) NEAR 25-26 C. HOWEVER, DRY AIR ENTRAINMENT FROM THE WESTERN SECTOR IS INHIBITING CONVECTIVE CONSOLIDATION. INITIAL WIND RADII BASIS: A 032307Z METOP-B ASCAT PASS CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE SOUTH AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.0 - 30 KTS RCTP: T2.0 - 30 KTS KNES: T1.0 - 25 KTS CIMSS SATCON: 44 KTS AT 032108Z CIMSS ADT: 34 KTS AT 032030Z CIMSS AIDT: 41 KTS AT 032030Z CIMSS D-PRINT: 27 KTS AT 040110Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL VWS: 5-10 KTS SST: 25-26 CELSIUS OUTFLOW: MODERATE POLEWARD OTHER FACTORS: DRY AIR ENTRAINING FROM THE WEST ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH 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: TS 13W IS EXPECTED TO TRACK GENERALLY EASTWARD ALONG THE NORTHERN PERIPHERY OF A STR CENTERED TO THE SOUTH THROUGH THE NEXT 24 HOURS. DURING THIS PERIOD, THE ENVIRONMENT IS ANTICIPATED TO REMAIN MARGINAL RESULTING IN TS 13W STRUGGLING TO DEVELOP PERSISTENT CONVECTION. BY TAU 36, TS BAILU IS FORECAST TO DECELERATE AS THE STEERING GRADIENT WEAKENS. BEYOND TAU 48, A GRADUAL RECURVATURE TOWARD THE NORTH-NORTHEAST IS EXPECTED UNDER THE INFLUENCE OF A SECONDARY BUILDING STR LOCATED TO THE SOUTHEAST. DETERIORATING OCEAN HEAT CONTENT, SUSTAINED DRY AIR ENTRAINMENT, INCREASING VWS AND A GRADUAL DECOUPLING OF THE CONVECTIVE CORE WILL INDUCE A WEAKENING TREND. SIMULTANEOUSLY, EXTRATROPICAL TRANSITION (ETT) IS FORECAST TO INITIATE SHORTLY AFTER TAU 48, WITH COMPLETION EXPECTED AROUND TAU 72. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN TIGHT AGREEMENT THROUGHOUT THE FORECAST PERIOD, REFLECTING CONSENSUS IN THE SYNOPTIC-SCALE STEERING PATTERN. CROSS-TRACK SPREAD AT TAU 24 IS APPROXIMATELY 30 NM. AT TAU 72, MODEL DIVERGENCE INCREASES TO NEAR 90 NM, HIGHLIGHTING UNCERTAINTY IN THE LATER-STAGE STEERING ENVIRONMENT. THE JTWC INTENSITY FORECAST IS ISSUED WITH MEDIUM CONFIDENCE DUE TO MODEL DISPARITY. THE OFFICIAL JTWC INTENSITY FORECAST IS ANCHORED NEAR THE MULTI-MODEL CONSENSUS MEAN AND SLIGHTLY ABOVE MOST DETERMINISTIC GUIDANCE ENVELOPES WITH HIGH CONFIDENCE, AS A RESULT OF STRONG MODEL AGREEMENT. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM INTENSITY 00-72 HR: HIGH// NNNN