WDPN31 PGTW 071500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 04W (MUN) WARNING NR 024// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 36.7N 148.0E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 373 NM EAST OF NARITA AIRPORT MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ENHANCED INFRARED (EIR) SATELLITE IMAGERY REVEALS A FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH TROPICAL DEPRESSION (TD) 04W (MUN), ENCIRCLED BY FRAGMENTED, SHALLOW CONVECTIVE BANDING. THE SYSTEM IS CURRENTLY ROUNDING THE AXIS OF A STR LOCATED TO THE EAST AND THEREFORE BEGINNING TO TURN NORTH-NORTHEASTWARD. DESPITE EXPERIENCING STRONG VERTICAL WIND SHEAR (VWS) EXCEEDING 35 KTS AND BEING EMBEDDED IN AN INCREASINGLY DRY ENVIRONMENT, THE SYSTEM CONTINUES TO MAINTAIN SHALLOW CORE VORTEX STRUCTURE. ENVIRONMENTAL DIAGNOSTICS INDICATE A LIMITED EQUATORWARD OUTFLOW CHANNEL AND COOLING (24-25 C) SEA SURFACE TEMPERATURES (SST). THE INITIAL POSITION IS DETERMINED WITH HIGH CONFIDENCE BASED ON THE CLEARLY DEFINED LLCC OBSERVED IN THE SATELLITE IMAGERY. INITIAL INTENSITY IS ESTIMATED AT 30 KTS WITH HIGH CONFIDENCE AS WELL, AND IS DERIVED FROM A COMPOSITE ASSESSMENT OF SUBJECTIVE DVORAK TECHNIQUE FIXES, OBJECTIVE INTENSITY ESTIMATES OUTLINED BELOW, AS WELL AS A 071030Z METOP-B AND METOP-C ASCAT PASSES. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T2.5 - 35 KTS RCTP: T2.0 - 30 KTS KNES: T2.0 - 30 KTS CIMSS SATCON: 39 KTS AT 070858Z CIMSS ADT: 25 KTS AT 071130Z CIMSS AIDT: 37 KTS AT 071130Z CIMSS D-MINT: 28 KTS AT 070710Z CIMSS D-PRINT: 27 KTS AT 071230Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE VWS: 30+ KTS SST: 24-25 CELSIUS OUTFLOW: WEAK EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TD 04W IS EXPECTED TO BEGIN RAPIDLY ACCELERATING AND CONTINUING ON WITH THE RECURVATURE PHASE ALONG THE NORTHWESTERN PERIPHERY OF A STR TO THE EAST. CONCURRENTLY, IT IS FORECAST TO UNDERGO GRADUAL WEAKENING DUE TO ESCALATING ENVIRONMENTAL HOSTILITY. INITIATION OF SUBTROPICAL TRANSITION IS ANTICIPATED BY TAU 24 AND IS PROJECTED TO CONCLUDE BY TAU 36, MARKING THE TERMINUS OF THE CURRENT FORECAST PERIOD. AT THAT TIME, THE SYSTEM IS FORECAST TO DEGRADE TO A 25 KT SUBTROPICAL DEPRESSION AND BECOME COMPLETELY EMBEDDED IN A DEEP-LAYER WESTERLY FLOW. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE EXHIBITS TIGHT INITIAL CONSENSUS WITH A CROSS-TRACK SPREAD OF 40 NM AT TAU 12, GRADUALLY INCREASING TO 160 NM BY THE END OF FORECAST PERIOD. BEYOND TAU 12, TRACK SPREAD WIDENS DUE TO DIFFERING ASSESSMENT OF THE INTERACTION WITH THE BAROCLINIC ZONE AND ASSOCIATED WESTERLY UPPER-LEVEL FLOW REGIME. THE GFS DETERMINISTIC MODEL SUGGESTS A SHARPER AND MORE RAPID TURN, WHEREAS THE ECMWF DETERMINISTIC AND ECMWF ENSEMBLE SOLUTIONS INDICATE A SLOWER AND MORE GRADUAL RECURVATURE, WHILE SIMULTANEOUSLY DISSIPATING THE VORTEX BEYOND TAU 12. ACCORDINGLY, THE JTWC FORECAST TRACK IS POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS AND IS ASSESSED WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE EXHIBITS POOR AGREEMENT AS A RESULT OF BAROCLINIC FORCING IMPACTS PICKED UP BY GFS AND HWRF, WHICH INDICATE POTENTIAL FOR SLIGHT INTENSIFICATION. MEANWHILE COAMPS-TC AND HAFS SUGGEST IMMEDIATE WEAKENING AND EVENTUAL DISSIPATION. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM INTENSITY 0 - 72 HR: LOW// NNNN