WDPN31 PGTW 250900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 02W (SEPAT) WARNING NR 012// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 32.7N 139.6E INITIAL INTENSITY: 25 KTS GEOGRAPHIC REFERENCE: 156 NM SOUTH OF YOKOSUKA, JAPAN MOVEMENT PAST 6 HOURS: NORTHWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY EXPOSED LOW-LEVEL CIRCULATION TRACKING WEAKLY NORTHWARD IN A COMPETING STEERING ENVIRONMENT BETWEEN TWO WEAK SUBTROPICAL RIDGES TO THE EAST AND WEST. TROPICAL DEPRESSION (TD) 02W IS IN A UNFAVORABLE UPPER-LEVEL ENVIRONMENT FOR DEVELOPMENT AS HIGHLIGHTED ON WATER VAPOR IMAGERY, PREVENTING OUTFLOW ALOFT. THE SHALLOW NATURE OF TD 02W IS IDENTIFIED IN A 250334Z GCOM W1 AMSR2 37GHZ MICROWAVE IMAGE WHICH REVEALS THE LOW-LEVEL CLOUD BANDING WRAPPING INTO THE CIRCULATION, BUT DEEP CONVECTION IS ABSENT IN THE 89GHZ IMAGE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED ANIMATED MSI REVEALING THE FULLY EXPOSED CIRCULATION CENTER. THE INITIAL INTENSITY OF 25 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON EARLIER 250334Z GCOM W1 AMSR2 WIND SPEED DATA REVEALING A SWATH OF 25KTS IN THE NORTHEASTERN PERIPHERY OF THE LLCC. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT BETWEEN TWO SUBTROPICAL RIDGES AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.5 - 25 KTS RJTD: T1.5 - 25 KTS CIMSS ADT: 25 KTS AT 250220Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE VWS: 5-10 KTS SST: 25-26 CELSIUS OUTFLOW: WEAK RADIAL 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 02W WILL CONTINUE TO TRACK NORTHWARD UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL RIDGE FOR THE NEXT 12 HOURS. AFTER TAU 12, THE SYSTEM WILL INCREASE TRACK SPEED AS IT BECOMES EMBEDDED IN AN UPPER-LEVEL TROUGH AND ASSUME A NORTHEASTWARD TRACK. THE SYSTEM WILL COMMENCE EXTRATROPICAL TRANSITION BETWEEN TAU 12-24 AFTER PASSING INTO COOL SEA SURFACE TEMPERATURES. THE SYSTEM WILL BECOME FULLY EXTRATROPICAL BY TAU 36 AS IT BECOMES FULLY BAROCLINIC AND COLD CORE. THE SYSTEM IS NOT ANTICIPATED TO INTENSIFY FOR THE REMAINDER OF THE FORECAST PERIOD AND IS EXPECTED TO MAINTAIN 25KTS AFTER BECOMING BAROCLINIC. MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN STRONG AGREEMENT THAT THE SYSTEM WILL TRACK NORTHEASTWARD FOR THE REMAINDER OF THE FORECAST PERIOD. THE CROSS-TRACK SPREAD BY TAU 36 IS 75NM, LENDING TO THE HIGH CONFIDENCE IN THE TRACK FORECAST. THE ONLY OUTLIER IS GALWEM, WHICH DEPICTS AN UNREALISTIC SOLUTION FAR WEST OF THE JTWC MULTI-MODEL CONSENSUS. THE INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT THAT THE SYSTEM WILL REMAIN 25-30KTS FOR THE NEXT 36 HOURS. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH INTENSITY 0 - 72 HR: HIGH// NNNN