WDPN31 PGTW 191500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (ONE) WARNING NR 001// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 4.8N 158.4E INITIAL INTENSITY: 25 KTS GEOGRAPHIC REFERENCE: 127 NM SOUTH OF POHNPEI MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 10 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A MEDIUM-SIZED SYSTEM WITH SHALLOW, FRAGMENTED FORMATIVE BANDING FEEDING IN FROM ALL QUADRANTS INTO THE DEEP CENTRAL CONVECTION THAT IS OBSCURING THE LOW LEVEL CIRCULATION. THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON LOW-CLOUD TRACING IN THE EIR LOOP AND EXTRAPOLATION FROM THE CURRENT STORM MOTION. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON OVERALL ASSESSMENT OF AGENCY DVORAK ESTIMATES AND REFLECTS THE IMPROVED 6-HR CONVECTIVE SIGNATURE. ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH LOW VWS, MODERATE RADIAL OUTFLOW, AND WARM SST. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: LOW- TO MID-LAYER SUBTROPICAL RIDGE (STR) TO THE NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T1.5 - 25 KTS KNES: T1.5 - 25 KTS FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 0-5 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: LOW INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY. FORECAST DISCUSSION: TD 01W WILL TRACK GENERALLY NORTHWESTWARD UNDER THE STEERING STR TOWARD THE DIRECTION OF GUAM. THE FAVORABLE CONDITIONS WILL FUEL A MODEST INTENSIFICATION TO A PEAK OF 35KTS AT TAUS 24-36. AFTERWARD, AS THE CYCLONE APPROACHES 10 DEG NORTH LATITUDE, INCREASING VWS ASSOCIATED WITH STRONG UPPER LEVEL SOUTHWESTERLY WINDS AND NEAR-SURFACE NORTHEASTERLY DRY AIR INTRUSION WILL GRADUALLY ERODE THE SYSTEM TOWARD DISSIPATION BY TAU 72. MODEL DISCUSSION: AVAILABLE NUMERICAL MODELS ARE IN LOOSE AGREEMENT WITH THE NORTHWESTWARD TRACK WITH GFS THE NOTABLE SLOW RIGHT-OF-TRACK OUTLIER. OTHERWISE, THE MAIN ENVELOPE GRADUALLY SPREADS OUT TO 128NM BY TAU 72. HOWEVER, GIVEN THE FORMATIVE NATURE OF THE SYSTEM AND THE HIGH VARIABILITY IN THE INTENSIFICATION, THERE IS LOW CONFIDENCE IN BOTH THE TRACK AND INTENSITY FORECASTS. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW INTENSITY 0 - 72 HR: LOW// NNNN