WDPN32 PGTW 181500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 10W (TEN) WARNING NR 001// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 20.6N 113.7E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 106 NM SOUTH-SOUTHWEST OF HONG KONG MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 8 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A CONSOLIDATING, COMPACT SYSTEM WITH CONVECTIVE BANDING WRAPPING INTO A DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC). AN 181058Z SSMIS 91GHZ MICROWAVE IMAGE ALSO SHOWS IMPROVED CONVECTIVE STRUCTURE AND A DEFINED LLCC, WHICH SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. AN 181321Z ASCAT-B BULLSEYE IMAGE REVEALS ASYMMETRIC CIRCULATION WITH 25-30 KNOT WINDS OVER THE NORTHERN SEMICIRCLE AND 15-25 KNOT WINDS ELSEWHERE. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE ASCAT DATA. ENVIRONMENTAL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH FAIR OUTFLOW ALOFT, LOW VERTICAL WIND SHEAR AND WARM SST VALUES. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.0 - 25 KTS RJTD: T1.0 - 25 KTS FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 0-5 KTS SST: 30-31 CELSIUS OUTFLOW: MODERATE EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY. FORECAST DISCUSSION: TD 10W IS FORECAST TO TRACK SLOWLY WEST-NORTHWESTWARD TO WESTWARD THROUGH TAU 72 UNDER THE STEERING INFLUENCE OF THE WEAK STR TO THE NORTH. AFTER TAU 72, THE SYSTEM WILL SLOW UNDER COMPETING STEERING INFLUENCES AND TURN GRADUALLY BACK TO THE SOUTHEAST UNDER THE STEERING INFLUENCE OF THE LOW-LEVEL WESTERLY FLOW. IN GENERAL, THE NUMERICAL MODEL GUIDANCE SUPPORTS THE FORECAST TRACK, HOWEVER, THERE IS A LARGE DEGREE OF SPREAD DUE TO THE COMPLEX, EVOLVING SYNOPTIC STEERING ENVIRONMENT. TD 10W SHOULD INTENSIFY QUICKLY TO A PEAK OF 55 KNOTS AT TAU 36 JUST PRIOR TO LANDFALL WITH STEADY WEAKENING AS THE SYSTEM TRACKS OVER LAND. TD 10W WILL LIKELY RE-INTENSIFY NEAR TAU 120 OR SHORTLY AFTER REEMERGING BACK OVER WATER. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE SUPPORTS THE JTWC TRACK FORECAST WITH LOW CONFIDENCE. CONFIDENCE IN THE JTWC INTENSITY FORECAST IS MEDIUM WITH SOME UNCERTAINTY IN THE PEAK INTENSITY, WHICH COULD BE SLIGHTLY HIGHER CONSIDERING THE COMPACT NATURE OF THE SYSTEM AND THE TENDENCY FOR THESE TYPES OF SYSTEMS TO RAPIDLY INTENSIFY. ADDITIONALLY, THERE IS ENOUGH UNCERTAINTY IN THE TRACK AND THE POTENTIAL FOR A MORE PROLONGED TRACK OVER THE VERY WARM WATER. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN