WDPN31 PGTW 131500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 09W (MEARI) WARNING NR 010// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 35.7N 140.1E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 31 NM NORTHEAST OF YOKOSUKA, JAPAN MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 18 KTS SIGNIFICANT WAVE HEIGHT: N/A SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP CONVECTIVE BANDING OVER THE SOUTHERN SEMICIRCLE WRAPPING INTO THE NORTHEAST QUADRANT. ANIMATED RADAR IMAGERY AND A 131151Z AMSU-B 89GHZ MICROWAVE IMAGE REVEAL A BROAD LOW-LEVEL CIRCULATION CENTER WITH A LINE OF INTENSE CONVECTION EXTENDING SOUTH OF TOKYO. RECENT SURFACE OBSERVATIONS (131300-131500Z) ARE GENERALLY LESS THAN 15 KNOTS BUT DO SUGGEST THE BROAD CENTER MAY BE TRACKING OVER WATER. CHOSHI (35.7N 140.8E), HOWEVER, IS REPORTING MORE SIGNIFICANT SOUTH-SOUTHWESTERLY WINDS OF 30-35 KNOTS WITH SLP NEAR 1002.6 MB. THESE SURFACE OBSERVATIONS AS WELL AS THE RJTD DVORAK ESTIMATE SUPPORT THE INITIAL INTENSITY OF 30 KTS WITH MEDIUM CONFIDENCE. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON RADAR IMAGERY AND THE 1200Z RJTD RADAR FIX. ENVIRONMENTAL CONDITIONS ARE MARGINALLY-FAVORABLE AS THE SYSTEM BEGINS TO INTERACT WITH A BROAD UPPER-LEVEL TROUGH OVER CENTRAL JAPAN WITH STRONG DIFFLUENCE ALOFT SUSTAINING INTENSE CONVECTION OVER WATER. VERTICAL WIND SHEAR (VWS) REMAINS AT HIGH (25 KNOTS) LEVELS. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE SOUTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: NO CURRENT ESTIMATE RJTD: T2.0 - 30 KTS FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY UNFAVORABLE VWS: 20-25 KTS SST: 26-27 CELSIUS OUTFLOW: MODERATE POLEWARD AND EQUATORWARD OTHER FACTORS: INTERACTION WITH LAND ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM 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 09W HAS COMMENCED EXTRA-TROPICAL TRANSITION (ETT) AND IS FORECAST TO ACCELERATE NORTHEASTWARD WITHIN THE MIDLATITUDE SOUTHWESTERLIES ALONG THE NORTHWESTERN FLANK OF THE STR. TD 09W WILL GRADUALLY RE-INTENSIFY TO 35 KNOTS BY TAU 12 THEN 40 KNOTS BY TAU 24 AS IT COMPLETES ETT WITHIN THE STRONG MIDLATITUDE WESTERLY FLOW UNDER 40-50 KNOT VWS AND GAINS FRONTAL CHARACTERISTICS. MODEL DISCUSSION: DETERMINISTIC AND PROBABILISTIC MODEL GUIDANCE IS IN TIGHT AGREEMENT WITH A 20NM SPREAD IN SOLUTIONS AT TAU 12 DIVERGING TO A 43NM SPREAD IN SOLUTIONS AT TAU 24 LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. THERE IS MEDIUM CONFIDENCE IN THE JTWC INTENSITY FORECAST DUE TO THE DETRIMENTAL INTERACTION WITH LAND AND UNCERTAINTY IN THE TIMING OF THE REINTENSIFICATION PHASE AFTER TAU 06. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH INTENSITY 0 - 72 HR: MEDIUM// NNNN