WDPN31 PGTW 030900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 007// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 27.6N 145.4E INITIAL INTENSITY: 50 KTS GEOGRAPHIC REFERENCE: 173 NM EAST OF CHICHI JIMA MOVEMENT PAST 6 HOURS: NORTHWARD AT 06 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL STORM (TS) 04W HAS MAINTAINED A COMPLEX UPPER-LEVEL OUTFLOW PATTERN, WITH AN UPPER-LEVEL CYCLONE POSITIONED OVER THE CENTER AND STRONG EASTWARD, DIFFLUENT OUTFLOW ENHANCED BY A JET TO THE NORTHEAST. THE PRESENCE OF THE UPPER-LEVEL LOW AND DRY AIR ENTRAINMENT WITHIN THE CORE OF THE SYSTEM IS HINDERING CONVECTIVE DEVELOPMENT. DESPITE THIS LIMITATION, ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS TIGHTLY WRAPPED LOW-LEVEL BANDING AND A WELL-DEFINED LOW-LEVEL CIRCULATION CENTER SUPPORTING THE INITIAL POSITION WITH HIGH CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 50 KNOTS BASED ON THE PGTW AND KNES DVORAK ESTIMATES, WHICH ARE CONSISTENT WITH RECENT ASCAT UHR DATA SHOWING A PATCH OF 50-55 KNOT WINDS. CIMSS OBJECTIVE ESTIMATES REMAIN TOO LOW, RANGING FROM 33-39 KNOTS. AS INDICATED IN THE DYNAMIC MODELS, THE CORE IS EXPECTED TO MOISTEN AND CONSOLIDATE WITHIN THE NEXT 12 HOURS, WHICH IS EXPECTED TO LEAD TO A SHARPER INTENSIFICATION RATE. OVER THE PAST FEW HOURS, THERE APPEARS TO BE SOME EVIDENCE THAT THIS IS COMMENCING, WITH ANIMATED INFRARED SATELLITE IMAGERY REVEALING BETTER ORGANIZED CORE CONVECTION, WITH CLOUD TOP TEMPERATURES NEAR -59C. INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK CURRENT STEERING MECHANISM: EXTENSIVE DEEP-LAYERED SUBTROPICAL RIDGE (STR) PATTERN TO THE SOUTH, EXTENDING NORTHEASTWARD OVER THE EASTERN PERIPHERY OF THE SYSTEM, WITH A WEAK STR EXTENSION TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.0 - 30 KTS RCTP: T2.5 - 35 KTS KNES: T3.5 - 55 KTS CIMSS ADT: 33 KTS AT 030530Z CIMSS AIDT: 37 KTS AT 030530Z CIMSS D-MINT: 38 KTS AT 030348Z CIMSS D-PRINT: 39 KTS AT 030530Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 27-28 CELSIUS OUTFLOW: STRONG EASTWARD OTHER FACTORS: DRY AIR ENTRAINMENT OVER THE WESTERN SEMICIRCLE 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 TRACK NORTHWARD THROUGH TAU 24 ALONG THE WESTERN PERIPHERY OF THE STR. AFTER TAU 24, THE SYSTEM IS EXPECTED TO TURN SHARPLY NORTHEASTWARD AS THE STR REORIENTS IN RESPONSE TO AN APPROACHING SHORTWAVE TROUGH OVER NORTHERN JAPAN. THE SHORTWAVE TROUGH WILL RAPIDLY PROPAGATE EASTWARD ALLOWING THE STR TO REBUILD, WHICH WILL DRIVE THE SYSTEM ON A MORE POLEWARD TRAJECTORY THROUGH TAU 120. AS ALLUDED TO EARLIER, ENVIRONMENTAL CONDITIONS ARE EXPECTED TO IMPROVE, WHICH SHOULD SUPPORT A SHORT PERIOD OF INTENSIFICATION, DRIVEN LARGELY BY THE ROBUST EASTWARD OUTFLOW, WITH A PEAK INTENSITY OF 70 KNOTS FORECAST BY TAU 48. SST VALUES WILL COOL STEADILY FROM TAU 36 TO TAU 120, WITH VALUES DECREASING TO ABOUT 25C BY TAU 48 THEN STEADILY DOWN TO 20-21C BY TAU 120. THEREFORE, THE TIMING OF THE PEAK INTENSITY MAY OCCUR EARLIER. AFTER TAU 72, ENVIRONMENTAL CONDITIONS WILL DEGRADE QUICKLY, WITH INCREASING VERTICAL WIND SHEAR (VWS) OF 25-30 KNOTS AFTER TAU 96, WHICH WILL LEAD TO RAPID WEAKENING. THE SYSTEM IS EXPECTED TO TRANSITION TO A SUBTROPICAL SYSTEM NEAR TAU 120. MODEL DISCUSSION: DUE TO THE COMPLEX STEERING ENVIRONMENT AND RUN-TO- RUN INCONSISTENCIES, THERE IS MEDIUM CONFIDENCE IN THE JTWC TRACK FORECAST THROUGH TAU 72. THERE IS A 150NM CROSS-TRACK SPREAD IN THE GUIDANCE AT TAU 72, HOWEVER, THERE ARE SIGNIFICANT DIFFERENCES IN THE ALONG-TRACK SPEEDS. THE 030000Z GEFS RUN, IN PARTICULAR, INDICATES A WIDE SWATH OF SOLUTIONS FROM CENTRAL JAPAN TO 160E. THE GFS DETERMINISTIC MODEL HAS JUMPED AROUND ERRATICALLY THE PAST TWO RUNS, AND NOW SHOWS A DISSIPATING, WEAK SYSTEM TRACKING TOWARD MAINLAND JAPAN. ALTHOUGH THERE ARE ROUGHLY SIX ECENS SOLUTIONS TRACKING TOWARD MAINLAND JAPAN, THE BULK OF THE ECENS GUIDANCE SUPPORTS A MORE POLEWARD ORIENTED TRACK. RELIABLE INTENSITY GUIDANCE IS MORE COHESIVE, WITH THE BULK OF THE GUIDANCE SHOWING A BRIEF INTENSIFICATION PERIOD FROM TAU 24 TO TAU 60. HAFS-A INDICATES A PEAK INTENSITY OF 88 KNOTS BY TAU 60 WHILE COAMPS-TC (GFS) SHOWS A PEAK OF 80 KNOTS BY TAU 84. DUE TO HIGH UNCERTAINTY AFTER TAU 72, THERE IS LOW CONFIDENCE IN THE EXTENDED JTWC FORECAST TRACK. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN