WDPN31 PGTW 020300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 04W (FOUR) WARNING NR 002// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 25.0N 147.4E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 735 NM SOUTHEAST OF YOKOSUKA, JAPAN MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 08 KTS SIGNIFICANT WAVE HEIGHT: 14 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL DEPRESSION (TD) 04W WITH A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) AND WEAKENED CENTRAL CONVECTION. THE LARGE BAND OF FLARING CONVECTION ALONG THE EASTERN PERIPHERY PERSISTS. A 012315Z GMI 89 GHZ MICROWAVE IMAGE REVEALS THE DEFINED LOW-LEVEL CLOUDS WRAPPING INTO THE LLCC. THE SYSTEM CONTINUES TO FEEL THE EFFECTS OF THE TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL CENTERED TO THE SOUTHWEST, APPARENT BY THE CONVECTION STRUGGLING TO FORM OVER THE CIRCULATION CENTER. ENVIRONMENTAL ANALYSIS INDICATES THAT 04W IS IN A MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD OUTFLOW ALOFT, MODERATE (15-20 KTS) SOUTHERLY VERTICAL WIND SHEAR, DRY AIR WITHIN THE SOUTHERN SEMICIRCLE, AND WARM (28-29 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC IN THE ANIMATED MSI AND SHORT EXTRAPOLATION FROM THE MENTIONED GMI MICROWAVE IMAGE. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE AGENCY DVORAK AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF AN ELONGATED SUBTROPICAL RIDGE (STR) CENTERED 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: 32 KTS AT 020010Z CIMSS AIDT: 34 KTS AT 020010Z CIMSS DPRINT: 31 KTS AT 020010Z CIMSS DMINT: 29 KTS AT 012313Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 15-20 KTS SST: 28-29 CELSIUS OUTFLOW: STRONG POLEWARD OTHER FACTORS: PRESSURE FROM THE TUTT CELL AND DRY AIR ENTRAINMENT 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 FORECAST TO CONTINUE TRACKING NORTH-NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE THROUGH TAU 48. NEAR TAU 48, RIDGING TO THE WEST WILL BUILD AND PULL THE VORTEX TOWARD THE NORTHEAST THROUGH THE REMAINDER OF THE FORECAST PERIOD. REGARDING INTENSITY, 04W IS FORECAST TO MARGINALLY INTENSIFY OVER THE NEXT 24 HOURS AS THE TUTT CELL CONTINUES TO AFFECT THE VORTEX, HINDERING DEVELOPMENT. AFTER TAU 24, THE SYSTEM WILL HAVE SUFFICIENTLY DISTANCED ITSELF FROM THE TUTT CELL WHICH WILL ALLOW FOR FURTHER INTENSIFICATION AS SHEAR DROPS TO AROUND 5-10 KTS. A PEAK INTENSITY OF 55 KTS IS FORECAST TO OCCUR NEAR TAU 72-96. AFTER TAU 96, SEA SURFACE TEMPERATURES WILL BEGIN TO COOL, HALTING ANY FURTHER INTENSIFICATION. BY TAU 120, SEA TEMPERATURES ARE EXPECTED TO DROP TO AROUND 25 C, WHICH WILL INITIATE A WEAKENING TREND. ADDITIONALLY, AN UPPER-LEVEL TROUGH WILL PROPAGATE EASTWARD AND BEGIN INTERACTING WITH THE SYSTEM AROUND TAU 120, CAUSING SHEAR TO DRAMATICALLY INCREASE IN THE EXTENDED FORECAST. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 WITH A 120 NM CROSS-TRACK SPREAD AT TAU 72. AFTERWARD, MODELS SIGNIFICANTLY DIVERGE DUE TO DIFFERING INTERACTIONS WITH THE UPPER-LEVEL TROUGH. GFS DETERMINISTIC HAS THE SYSTEM TURN NORTHWESTWARD VICE NORTHEASTWARD AFTER TAU 96 AS THE VORTEX GETS CAUGHT UNDERNEATH RIDGING TO THE NORTH. HOWEVER, THE MAJORITY OF ENSEMBLE MEMBERS SHOW THE NORTHEASTWARD TRACK. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS THROUGH TAU 96 AND THEN SLIGHTLY TO THE EAST THROUGH TAU 120. INTENSITY GUIDANCE IS IN MODERATE AGREEMENT WITH HAFS-A AND GFS BEING THE LEAST AGGRESSIVE WHILE COAMPS-TC (GFS BASED) IS THE MOST AGGRESSIVE MODEL WITH A PEAK INTENSITY OF 80 KTS AT TAU 84. THE JTWC INTENSITY FORECAST IS PLACED IN LINE WITH THE CONSENSUS THROUGHOUT THE FORECAST PERIOD WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN