WDPN31 PGTW 070900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 023// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 35.8N 148.3E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 385 NM EAST OF NARITA AIRPORT MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 16 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER OF TROPICAL STORM (TS) 04W (MUN) SURROUNDED BY SHALLOW BANDS OF CONVECTION. THE SYSTEM IS CURRENTLY TRACKING NORTH-NORTHWESTWARD UNDER THE INFLUENCE OF A SUBTROPICAL RIDGE TO THE EAST. TS 04W IS MAINTAINING STRUCTURAL VORTEX INTEGRITY DESPITE 35+ KTS VERTICAL WIND SHEAR (VWS), AS WELL AS SIGNIFICANT DRY AIR SURROUNDING THE VORTEX. ADDITIONAL ENVIRONMENTAL ANALYSIS REVEALS WEAK EQUATORWARD OUTFLOW CHANNEL AND COOLING (24-25 C) SEA SURFACE TEMPERATURES (SST) IN THE PATH OF TS MUN. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC PRESENT IN VISIBLE SATELLITE IMAGERY. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A COMBINATION OF DVORAK FIXES AND OBJECTIVE ESTIMATES LISTED BELOW. INITIAL WIND RADII BASIS: 062334Z METOP-C ASCAT UHR PASS CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T3.0 - 45 KTS RCTP: T2.5 - 35 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 43 KTS AT 070236Z CIMSS ADT: 33 KTS AT 070520Z CIMSS AIDT: 39 KTS AT 070520Z CIMSS D-MINT: 28 KTS AT 070708Z CIMSS D-PRINT: 30 KTS AT 070630Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE VWS: 30+ KTS SST: 24-25 CELSIUS OUTFLOW: WEAK EQUATORWARD OTHER FACTORS: SIGNIFICANT DRY AIR ENTRAINMENT ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM 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 04W IS FORECAST TO BEGIN ROUNDING THE AXIS OF A STR TO THE EAST WITHIN THE NEXT 6-12 HOURS, WHILE SIMULTANEOUSLY WEAKENING DUE TO INCREASINGLY HOSTILE ENVIRONMENT DISCUSSED EARLIER. SUBTROPICAL TRANSITION IS EXPECTED TO BEGIN AROUND TAU 24 AND IS FORECAST TO COMPLETE BY TAU 36, AT THE CONCLUSION OF THE CURRENT FORECAST PERIOD. AT THAT TIME, THE SYSTEM IS EXPECTED TO WEAKEN TO 25 KTS. MODEL DISCUSSION: NUMERICAL TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT AS INDICATED BY A 15 NM CROSS-TRACK SPREAD AT TAU 12, EXPANDING TO 95 NM BY TAU 24. BEYOND THAT, FORECAST DIVERGENCE INCREASES DUE TO DIFFERENCES IN REPRESENTATIONS OF THE SYSTEM INTERACTION WITH THE BAROCLINIC ZONE AND ASSOCIATED UPPER-LEVEL, WESTERLY FLOW. GFS DETERMINISTIC MODEL IS PROJECTING THE TIGHTEST AND QUICKEST TURN, WHILE ECMWF AND ECMWF ENSEMBLE PREDICT A SLOWER AND MORE GRADUAL TURN. JTWC TRACK FORECAST IS THEREFORE ASSESSED WITH OVERALL MEDIUM CONFIDENCE AND IS LAID CLOSE TO THE MULTI-MODEL CONSENSUS. INTENSITY GUIDANCE IS ASSESSED WITH GOOD CONFIDENCE, WITH ALL MODELS SUPPORTING A FORECAST OF PROGRESSIVE WEAKENING. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM INTENSITY 0 - 72 HR: HIGH// NNNN