WDPN31 PGTW 021500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (FOUR) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 26.2N 146.3E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 226 NM EAST-SOUTHEAST OF CHICHI JIMA MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY REVEALS A WELL-DEFINED AND FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH TROPICAL STORM (TS) 04W. THE UNAMBIGUOUS PRESENTATION OF THE LLCC ALLOWS FOR A HIGH-CONFIDENCE POSITION ASSESSMENT. ENVIRONMENTAL ANALYSIS INDICATES MARGINALLY CONDUCIVE ENVIRONMENT, AS WITNESSED BY A 15-20 KTS SOUTHERLY VERTICAL WIND SHEAR (VWS), WARM (27-28 C) SEA SURFACE TEMPERATURES (SST), ROBUST POLEWARD OUTFLOW, PARTIALLY NEGATED BY THE PROXIMITY OF A TUTT CELL SITUATED TO THE SOUTHWEST OF THE LLCC, AS WELL AS DRY AIR ENTRAINMENT AFFECTING THE CONVECTIVE STRUCTURE OF THE TS. BASED ON A SYNTHESIS OF SCATTEROMETRY, DVORAK ESTIMATES AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW, THE INITIAL INTENSITY IS ASSESSED AT 35 KTS WITH HIGH CONFIDENCE. INITIAL WIND RADII BASIS: 021057Z METOP-C ASCAT DATA CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T1.5 - 25 KTS KNES: T2.0 - 30 KTS CIMSS ADT: 34 KTS AT 021130Z CIMSS AIDT: 36 KTS AT 021130Z CIMSS D-MINT: 32 KTS AT 020823Z CIMSS D-PRINT: 31 KTS AT 021130Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 15-20 KTS SST: 27-28 CELSIUS OUTFLOW: STRONG POLEWARD OTHER FACTORS: DRY AIR ENTRAINMENT, AS WELL AS TUTT CELL ASSOCIATED SHEAR 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 PROJECTED TO TRACK NORTHWESTWARD INITIALLY UNDER THE STEERING INFLUENCE OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST. BY TAU 24, THIS RIDGE WILL REORIENT AND EXTEND ALONG A SOUTHWEST-NORTHEAST AXIS. THIS EVOLVING SYNOPTIC PATTERN WILL RESULT IN A POLEWARD ACCELERATION, WITH THE SYSTEM TRACKING NORTH TO NORTHEAST THROUGH TAU 96. BEYOND THIS, FURTHER RIDGE AMPLIFICATION EAST OF THE SYSTEM WILL INITIATE A SECONDARY POLEWARD TURN. THE INTENSITY FORECAST CALLS FOR STEADY INTENSIFICATION THROUGH TAU 72 AS VWS BECOMES MORE FAVORABLE AND THE SYSTEM CONTINUES TO DISTANCE ITSELF FROM THE SUPPRESSIVE INFLUENCE OF THE TUTT CELL. PEAK INTENSITY IS FORECAST TO REACH 65 KTS DURING THIS PERIOD. THEREAFTER, INCREASED DRY AIR ENTRAINMENT, IN CONJUNCTION WITH PROGRESSIVELY DECREASING SST ALONG THE POLEWARD TRACK, ARE EXPECTED TO INDUCE WEAKENING. INTERACTION WITH AN APPROACHING UPPER-LEVEL TROUGH IS ANTICIPATED LATE IN THE FORECAST PERIOD, LIKELY RESULTING IN A SHARP INCREASE IN VWS. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE EXHIBITS MODERATE CONSENSUS THROUGH TAU 96, WITH ALL MEMBERS SUGGESTING AN S-SHAPED TRAJECTORY. CROSS-TRACK SPREAD IS APPROXIMATELY 120 NM AT TAU 72. BEYOND THAT, MODEL DIVERGENCE INCREASES SIGNIFICANTLY DUE TO UNCERTAINTY REGARDING THE EVOLUTION AND ORIENTATION OF THE UPPER-LEVEL TROUGH ADVANCING FROM THE WEST AND ITS TIMING RELATIVE TO THE MOTION OF TS 04W. GALWEM AND DETERMINISTIC GFS FAVOR A NORTHWESTWARD DEFLECTION JUST PRIOR TO TAU 120, WHILE NAVGEM AND JGSM SUGGEST CONTINUED NORTHEASTWARD MOTION. THE REMAINDER OF GLOBAL MODELS TREND TOWARD A POLEWARD TRACK, AND THE JTWC OFFICIAL FORECAST REMAINS CLOSELY ALIGNED WITH THE MULTI-MODEL CONSENSUS ENVELOPE. INTENSITY GUIDANCE SHOWS FAIR AGREEMENT ON THE INTENSIFICATION PHASE, PEAKING AROUND TAU 72, FOLLOWED BY WEAKENING. PEAK WIND SPEED PROJECTIONS SPAN A RANGE OF 50 KTS, WITH COAMPS-TC AT THE HIGH END (95 KTS) AND STATISTICAL-DYNAMICAL MODELS OSCILLATING NEAR 45-50 KTS. THE JTWC INTENSITY FORECAST IS ANCHORED NEAR THE CONSENSUS MEAN AND IS PREDICTING PEAK OF 65 KTS REACHED AROUND TAU 72. ADDITIONALLY, RAPID INTENSIFICATION (RI) CONSENSUS MODEL (RICN), AS WELL AS THE COAMPS-TC ENSEMBLE RI AID (CTR1) INDICATE POTENTIAL FOR 30 KTS INTENSITY INCREASE WITHIN THE NEXT 24 HOURS. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN