WDPN32 PGTW 211500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 10W (CEMPAKA) WARNING NR 013// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 22.5N 110.5E INITIAL INTENSITY: 25 KTS GEOGRAPHIC REFERENCE: 206 NM WEST OF HONG KONG MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 05 KTS SIGNIFICANT WAVE HEIGHT: 0 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THAT A COHERENT LOW-LEVEL CIRCULATION CENTER (LLCC) IS TRACKING NORTHWESTWARD ABOUT 60 NM INLAND OVER SOUTHERN CHINA. CONVECTIVE BANDING HAS BECOME LESS DISTINCT DURING THE PAST SIX HOURS, AND SATELLITE IMAGERY SUGGESTS THAT THE MID-LEVEL CENTER MAY BE OFFSET WEST-SOUTHWEST FROM THE LLCC. WATER VAPOR SATELLITE IMAGERY INDICATES THAT THE SYSTEM IS LOCATED IN A POCKET OF LOW VERTICAL SHEAR BETWEEN AN UPPER-LEVEL TROUGH TO THE NORTHWEST AND UPPER-LEVEL NORTHEASTERLIES TO THE SOUTH, WITH HEALTHY DIFFLUENT OUTFLOW EVIDENT TOWARD THE SOUTH. THE INITIAL INTENSITY IS HELD AT 25 KT. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: WEAK RIDGE OVER EASTERN CHINA AGENCY DVORAK AND AUTOMATED FIXES: PGTW: NO CURRENT ESTIMATE RJTD: T2.0 - 30 KTS RCTP: T1.5 - 25 KTS FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: OVER LAND OUTFLOW: MODERATE EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM 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: TROPICAL DEPRESSION (TD) 10W (CEMPAKA) IS EXPECTED TO TRACK WESTWARD FOR THE NEXT 12 HOURS OVER SOUTHERN CHINA, THEN TURN SOUTHWARD INTO THE GULF OF TONKIN BY 36 HOURS AS NORTHERLY FLOW ON THE WESTERN SIDE OF TYPHOON 09W BEGINS TO ALTER THE DEEP-LAYER STEERING FLOW. A LOOPING TRACK SOUTHEASTWARD AND THEN EASTWARD NEAR HAINAN IS EXPECTED DURING THE 48-96 HOUR PERIOD AS CEMPAKA BECOMES EMBEDDED IN THE MONSOONAL WESTERLIES ACROSS THE SOUTH CHINA SEA. SOME NUMERICAL MODEL GUIDANCE, SUCH AS HWRF AND NEARLY HALF OF ECMWF ENSEMBLE MEMBERS, SUGGESTS THAT TD 10W WILL RETAIN A COHERENT CIRCULATION OVER THE GULF OF TONKIN AND REGAIN SOME STRENGTH. THE JTWC INTENSITY FORECAST RETAINS THIS SCENARIO AND FORECASTS REINTENSIFICATION TO 35 KT BY 48 HOURS. THEREAFTER, AS CEMPAKA BECOMES EMBEDDED IN THE BRISK MONSOONAL WESTERLIES, HIGH VERTICAL SHEAR IS EXPECTED TO QUICKLY CAUSE DISSIPATION AS THE CIRCULATION OPENS UP IN MOST MODEL GUIDANCE. IT IS EQUALLY POSSIBLE THAT TD 10W DISSIPATES MUCH EARLIER IF IT IS UNABLE TO REINTENSIFY OVER THE GULF OF TONKIN, A SCENARIO SHOWN BY THE GFS AND ECMWF. THE INTENSITY FORECAST IS THUS OF ONLY MEDIUM CONFIDENCE. THE JTWC TRACK FORECAST IS A LITTLE SLOWER THAN THE PREVIOUS FORECAST, AND OF LOWER CONFIDENCE AFTER 48 HOURS. MODEL DISCUSSION: THE JTWC TRACK FORECAST IS A LITTLE SLOWER THAN THE MULTI-MODEL CONSENSUS DUE TO THE ERRANTLY FAST NAVGEM, AND THE INTENSITY FORECAST IS SLIGHTLY ABOVE CONENSUS, BUT BELOW HWRF. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN