WDPN31 PGTW 051500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 016// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 31.3N 148.0E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 395 NM NORTHEAST OF CHICHI JIMA MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 08 KTS SIGNIFICANT WAVE HEIGHT: 21 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY REVEALS TIGHTLY CURVED BANDS OF CONVECTION WRAPPING AROUND THE LOW-LEVEL CIRCULATION CENTER (LLCC) OF TROPICAL STORM (TS) 04W (MUN). THE SYSTEM EXHIBITS A COMPACT STRUCTURE, WITH THE DEEP CONVECTIVE ACTIVITY PRIMARILY CONFINED TO THE SOUTHERN SEMICIRCLE, AND MORE SHALLOW BANDING ALONG THE NORTHERN PERIPHERY. INFRARED SATELLITE DATA INDICATES CLOUD-TOP TEMPERATURES AROUND -65 DEGREES C. ENVIRONMENTAL CONDITIONS REMAIN CONDUCIVE TO FURTHER INTENSIFICATION, CHARACTERIZED BY WARM (27-28 C) SEA SURFACE TEMPERATURES (SST), LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS), AND MODERATE UPPER-LEVEL OUTFLOW. DRY AIR SURROUNDING THE SYSTEM IS BEING ENTRAINED INTO THE CORE OF THE VORTEX AND HINDERS FURTHER DEVELOPMENT OF ITS STRUCTURE AT THE MOMENT. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON A 051136Z METOP-C ASCAT PASS, IN CONJUNCTION WITH AN EXTRAPOLATION FROM A BULLSEYE 050819Z RCM-1 SAR PASS. THE INITIAL INTENSITY IS ESTIMATED AT 55 KTS WITH HIGH CONFIDENCE, UTILIZING AGENCY DVORAK CLASSIFICATIONS, OBJECTIVE SATELLITE-BASED ESTIMATES, AND CONSIDERING THE COMPACT STRUCTURE OF THE SYSTEM. INITIAL WIND RADII BASIS: 050819Z RCM-1 SAR PASS CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE SOUTH AND SOUTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.5 - 35 KTS RCTP: T2.5 - 35 KTS KNES: T3.5 - 55 KTS CIMSS SATCON: 46 KTS AT 051200Z CIMSS ADT: 33 KTS AT 051130Z CIMSS AIDT: 52 KTS AT 051130Z CIMSS D-PRINT: 45 KTS AT 051200Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 27-28 CELSIUS OUTFLOW: STRONG POLEWARD AND EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH 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 04W IS EXPECTED TO TRACK GENERALLY EAST-NORTHEASTWARD OVER THE NEXT 24 HOURS, STEERED BY A STR POSITIONED TO THE SOUTH. SUBSEQUENTLY, RIDGING IS FORECAST TO EXTEND AND BUILD TO THE EAST OF THE STORM, INDUCING A NORTHWARD AND NORTHWESTWARD TURN. TS 04W IS EXPECTED TO ROUND THE RIDGE AXIS BETWEEN TAUS 48 AND 72, AFTER WHICH IT WILL BEGIN ITS SUBTROPICAL TRANSITION. THE SYSTEM IS PROJECTED TO REACH PEAK INTENSITY OF 60 KTS WITHIN THE NEXT 12-24 HOURS, DURING A BRIEF PHASE OF LESS INTENSE DRY AIR ENTRAINMENT. BEYOND THIS PERIOD, A COMBINATION OF DECREASING SST AND PROGRESSIVE DRY AIR INTRUSION WILL INITIATE WEAKENING. ADDITIONALLY, BY APPROXIMATELY TAU 72, TS 04W IS ANTICIPATED TO BEGIN SUBTROPICAL TRANSITION, LIKELY COMPLETING THIS PROCESS BY THE END OF THE FORECAST PERIOD. MODEL DISCUSSION: TRACK GUIDANCE FROM NUMERICAL MODELS IS IN GOOD AGREEMENT THROUGH TAU 36, WITH A CROSS-TRACK SPREAD OF APPROXIMATELY 50 NM. HOWEVER, THIS DIVERGENCE INCREASES TO OVER 275 NM BY TAU 72, REFLECTING VARIABILITY IN HOW MODELS RESOLVE THE INTERACTION BETWEEN TS O4W AND THE EVOLVING RIDGE TO THE EAST. ALONG-TRACK SPREAD BECOMES SIGNIFICANT BY TAU 96, EXCEEDING 950 NM. INTENSITY GUIDANCE SHOWS GOOD CONSENSUS THROUGHOUT THE FORECAST PERIOD, WITH ALL MEMBERS INDICATING MODEST STRENGTHENING OVER THE NEXT 12-24 HOURS, FOLLOWED BY GRADUAL WEAKENING THEREAFTER. BY TAU 72 ALL AVAILABLE GUIDANCE INDICATES WEAKENING BELOW 30 KTS. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: HIGH INTENSITY 72-120 HR: HIGH// NNNN