WDPN31 PGTW 240300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 25W (TWENTYFIVE) WARNING NR 001// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 12.4N 139.4E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 150 NM NORTH OF ULITHI MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 11 KTS SIGNIFICANT WAVE HEIGHT: 10 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP CONVECTION WRAPPING INTO A LOW LEVEL CIRCULATION CENTER (LLCC) WEST OF GUAM. A TIMELY 240004Z ASCAT METOP-B PASS INDICATES A MODEST REGION WITH MOSTLY 20 KNOT WINDS NEAR THE LLCC. OVERALL, THERE IS MODERATE CONFIDENCE IN THE INITIAL POSITION AND INTENSITY BASED ON THE MSI, ASCAT IMAGE, AND MULTIPLE AGENCY DVORAK ESTIMATES FIXES OF 30 KNOTS FROM PGTW, RJTD. ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE WITH MODERATE RADIAL OUTFLOW, LOW VERTICAL WIND SHEAR AND WARM (29-30C) SEA SURFACE TEMPERATURES (SST). INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: TD 25W IS TRACKING ALONG THE WESTERN PERIPHERY OF A LOW TO MID-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED 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: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY. FORECAST DISCUSSION: TD 25W WILL TRACK TO THE NORTH OVER THE NEXT 72 HOURS AS THE MAIN STEERING FROM THE STR REMAINS TO THE EAST. AT TAU 48 A LOW PRESSURE SYSTEM WILL FORM JUST SOUTH OF HONSHU AND BEGIN TRACKING TO THE EAST WITH A WEAK FRONTAL BOUNDARY DRAWING 25W IN ITS WAKE. BY TAU 72 TD 25W WILL SPEED UP AND INTENSIFY TO 60 KNOTS AS IT BEGINS TO ROUND THE STR AXIS. SHORTLY BEFORE TAU 96 THE SYSTEM WILL CONTINUE TO INTENSIFY TO TYPHOON STRENGTH AS IT REACHES A PEAK INTENSITY OF 70 KNOTS. THEREAFTER, THE SYSTEM WILL CONTINUE TRACKING ALONG THE WESTERN SIDE OF THE STR AND APPROACH THE BAROCLINIC ZONE WELL TO THE EAST OF MAINLAND JAPAN AND BEGIN EXPERIENCING GREATER SHEAR AND COOLER SSTS. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT WITH A GRADUAL SPREAD FROM 45NM AT TAU 12 TO A MAXIMUM OF 150NM BY TAU 72, LENDING TO MEDIUM CONFIDENCE THROUGH TAU 72 AND LOW THEREAFTER. THE JTWC FORECAST TRACK IS POSITIONED NEAR THE MULTI-MODEL CONSENSUS (CONW) WITH UKMET AS THE LEFT OUTLIER AND NAVGEM THE OUTERMOST RIGHT OUTLIER. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN