WDPN31 PGTW 250900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (IN-FA) WARNING NR 037// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 30.0N 122.4E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 86 NM SOUTH-SOUTHEAST OF SHANGHAI, CHINA MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 05 KTS SIGNIFICANT WAVE HEIGHT: 25 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP CONVECTION ERUPTING CLOSE TO THE CENTER OF TROPICAL STORM 09W (IN-FA) DURING THE PAST SIX HOURS, AND BETTER RESEMBLES A CENTRAL DENSE OVERCAST THAN AN EYE STRUCTURE ON EIR IMAGERY. SURFACE OBSERVATIONS FROM DINGHAI, CHINA SHOW MEAN SEA-LEVEL PRESSURE FALLING TO 972 MB AND NORTHERLY WINDS DECREASING TO 6 KT, INDICATING THAT THE CENTER OF IN-FA IS JUST EAST OF THE STATION, AND WILL MAKE LANDFALL IMMINENTLY. THE INITIAL INTENSITY IS LOWERED TO 55 KT BASED ON SCATTEROMETER DATA FROM A 250123Z ASCAT-B PASS AND AGENCY DVORAK ESTIMATES. A SUSTAINED WIND OF 51 KT WAS OBSERVED IN THE NORTHERN EYEWALL AT SHENGSI, CHINA AT A SITE ELEVATION OF 81 METERS AT 250300Z. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: DEEP-LAYER RIDGE OVER THE SEA OF JAPAN AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS RJTD: T4.0 - 65 KTS RCTP: T4.0 - 65 KTS KNES: T3.5 - 55 KTS CIMSS SATCON: 53 KTS AT 250420Z CIMSS ADT: 37 KTS AT 250540Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 27-28 CELSIUS OUTFLOW: MODERATE RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM 09W (IN-FA) WILL SLOWLY TRACK INLAND OVER EASTERN CHINA DURING THE NEXT 72 HOURS AS STEERING CURRENTS WEAKEN. BROAD UPPER-LEVEL TROUGHING OVER MONGOLIA IS EXPECTED TO INDUCE A GRADUAL TURN TOWARD THE NORTH OR NORTHEAST AFTER 72 HOURS, POTENTIALLY BRINGING THE CIRCULATION OUT OVER THE WESTERN SIDE OF THE YELLOW SEA. THE JTWC FORECAST REMAINS JUST INLAND THROUGH 120 HOURS, CLOSE TO THE MULTI-MODEL CONSENSUS. THE CYCLONE WILL BE MOVING OVER MOSTLY FLAT TERRAIN, AND WITHOUT SIGNIFICANT BAROCLINIC INTERACTION DURING THE FORECAST PERIOD, A COHERENT CIRCULATION IS FORECAST TO PERSIST FOR SEVERAL DAYS OVER EASTERN CHINA BY MOST DYNAMICAL MODEL GUIDANCE. THE JTWC FORECAST THUS MAINTAINS IN-FA AS A TROPICAL CYCLONE FOR THE FULL 120-HOUR FORECAST PERIOD. IF THE CIRCULATION MOVES OUT OVER THE YELLOW SEA, SOME RESTRENGTHENING WOULD BE POSSIBLE. THE CURRENT JTWC INTENSITY FORECAST ASSUMES THAT THE CIRCULATION WILL REMAIN OVER LAND THROUGH 120 HOURS. MODEL DISCUSSION: THE MULTI-MODEL CONSENSUS HAS SHIFTED SLIGHTLY NORTHEASTWARD COMPARED TO THE PREVIOUS CYCLE, AND THE JTWC TRACK FORECAST HAS ALSO BEEN SHIFTED NORTHEASTWARD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: HIGH INTENSITY 72-120 HR: MEDIUM// NNNN