WDPN31 PGTW 020900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 04W (FOUR) WARNING NR 003// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 25.7N 146.8E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 261 NM EAST-SOUTHEAST OF CHICHI JIMA MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 08 KTS SIGNIFICANT WAVE HEIGHT: 14 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH TROPICAL DEPRESSION (TD) 04W. THE INITIAL POSITION IS THEREFORE PLACED WITH HIGH CONFIDENCE. RECENT FLARE UP OF CENTRAL CONVECTION WAS QUICKLY SHEARED OFF TO THE NORTH BY A 15-20 KTS PREDOMINANTLY SOUTHERLY VERTICAL WIND SHEAR (VWS). ADDITIONAL ENVIRONMENTAL ANALYSIS REVEALS MARGINALLY FAVORABLE ENVIRONMENT, CHARACTERIZED BY WARM (28-29 C) SEA SURFACE TEMPERATURES (SST), DEEP MOISTURE ACROSS THE ATMOSPHERIC COLUMN, STRONG POLEWARD OUTFLOW ALOFT, OFFSET BY THE IMPACTS OF THE TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL LOCATED TO THE SOUTHWEST OF THE LLCC, AS WELL AS DRY AIR ENTERING THE CORE OF THE VORTEX. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON COMBINATION OF AGENCY FIXES AND OBJECTIVE ESTIMATES LISTED BELOW. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). 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: 32 KTS AT 020530Z CIMSS AIDT: 35 KTS AT 020530Z CIMSS D-PRINT: 32 KTS AT 020530Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 15-20 KTS SST: 28-29 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: 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 INITIALLY TRACK NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF A STR TO THE NORTHEAST. AROUND TAU 48 THE RIDGE WILL BEGIN TO REORIENT, RESULTING IN STRENGTHENING OF TWO RIDGING AREAS THAT ARE SOUTH AND EAST OF THE SYSTEM. THIS WILL LEAD TO TD 04W TRACKING NORTH AND EVENTUALLY NORTHEAST THROUGHOUT TAU 96. AFTER THAT, FURTHER STRENGTHENING OF THE RIDGE TO THE EAST WILL CAUSE THE SYSTEM TO BEGIN TURNING NORTHWARD AGAIN. INTENSITY IS FORECAST TO STEADILY INCREASE THROUGHOUT TAU 72, WHILE THE SYSTEM DISTANCES ITSELF FROM THE TUTT CELL. PEAK INTENSITY IS EXPECTED TO REACH 60 KTS AROUND THAT TIME. AFTERWARD HOWEVER, IMPACTS FROM CONTINUOUS DRY AIR ENTRAINMENT, AS WELL AS COOLING SST WILL RESULT IN WEAKENING, AS THE SYSTEM TRACKS POLEWARD. FINALLY, MODELS SUGGEST AN UPPER-LEVEL TROUGH INTERACTION TOWARD THE END OF THE FORECAST PERIOD, RESULTING IN A DRASTIC INCREASE IN VWS. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN FAIR AGREEMENT THROUGH TAU 96 WITH ALL MODELS SUGGESTING AN S-SHAPED TRACK PATTERN, AS WITNESSED BY A CROSS-TRACK SPREAD OF 110 NM AT TAU 72. AFTER THAT, UNCERTAINTY INCREASES, AS MODELS DO NOT AGREE ON THE DOMINANT STEERING PATTERN AND THEREFORE TIMELINE AND EXTENT OF THE INTERACTION WITH THE UPPER-LEVEL TROUGH PASSING FROM THE WEST. DETERMINISTIC GFS SUGGESTS A NORTHWESTWARD TURN BY TAU 120, WHILE NAVGEM AND ECWMF ENSEMBLE ARE PLACING THE TRACK TURNING NORTHEASTWARD. MAJORITY OF THE MODELS ARE LEANING TOWARD THE NORTH OR NORTHEASTWARD TRACK AND JTWC FORECAST IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS. INTENSITY GUIDANCE IS IN FAIR AGREEMENT THROUGHOUT THE FORECAST PERIOD, WITH NEARLY ALL CONSENSUS MEMBERS AGREEING ON THE TIMELINE OF INTENSIFICATION AND WEAKENING. PEAK INTENSITY SPREAD HOWEVER IS ASSESSED AT 30 KTS, WITH COAMPS-TC GOING AS HIGH AS 75 KTS AND STATISTICAL-DYNAMICAL MODELS ON THE LOWER END OF THE SPECTRUM, PREDICTING PEAK INTENSITY OF 45-50 KTS. ONCE AGAIN, JTWC FORECAST IS PLACED CLOSE TO THE MULTI-MODEL AVERAGE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN