WDPN31 PGTW 040900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (AERE) WARNING NR 016// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 30.8N 127.8E INITIAL INTENSITY: 25 KTS GEOGRAPHIC REFERENCE: 169 NM SOUTHWEST OF SASEBO, JAPAN MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 08 KTS SIGNIFICANT WAVE HEIGHT: 10 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TD 05W CONTINUES TO STRUGGLE AS THE LOW LEVEL CIRCULATION (LLC) IS PARTLY EXPOSED AS THE MAIN CONVECTION IS SHEARED SOUTHEASTWARD. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE LLC FEATURE IN THE MSI LOOP. THE INITIAL INTENSITY IS ALSO PLACED WITH HIGH CONFIDENCE BASED ON THE PGTW DVORAK ESTIMATE OF T1.5 AND CONSISTENT WITH PERIPHERAL SURFACE WIND AND MSLP OBSERVATIONS. ANIMATED WATER VAPOR IMAGERY INDICATES THAT AN UPPER-LEVEL TROUGH REMAINS ENTRENCHED OVER THE SYSTEM, INDUCING SUBSIDENCE AND STRONG NORTHWESTERLY VERTICAL WIND SHEAR. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE TO THE EAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.5 - 25 KTS CIMSS SATCON: 39 KTS AT 040102Z CIMSS ADT: 33 KTS AT 040230Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY UNFAVORABLE VWS: 20-25 KTS SST: 26-27 CELSIUS OUTFLOW: MODERATE POLEWARD OTHER FACTORS: UPPER-LEVEL TROUGH OVER THE LOW-LEVEL CIRCULATION. ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH 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 05W WILL TURN EAST-NORTHEASTWARD THEN EASTWARD AS IT ROUNDS THE NORTHWESTERN PERIPHERY OF THE STEERING STR. AFTER TAU 72, TD 05W IS EXPECTED TO MERGE WITH A DEVELOPING SHORTWAVE TROUGH AND SLOW DOWN SIGNIFICANTLY OFF THE EAST COAST OF HONSHU. BY TAU 96, A SECONDARY STR TO THE NORTHEAST WILL ASSUME STEERING AND DRIVE THE CYCLONE NORTHWESTWARD. THE SYSTEM WILL, AT BEST, MAINTAIN ITS CURRENT INTENSITY UP TO TAU 12 BEFORE MAKING LANDFALL INTO HONSHU NEAR SASEBO. AFTERWARD, LAND INTERACTION WITH THE JAPANESE ISLANDS WILL REDUCE IT TO 20KTS. BY TAU 48, IT WILL EXIT BACK OVER WATER JUST SOUTH OF OKAZAKI AND REGAIN INTENSITY OF 25KTS. ONWARD, WEAKENING VERTICAL WIND SHEAR AND FAVORABLE DIFFLUENCE ALOFT AS BAROCLINIC INTERACTION BEGINS WILL GRADUALLY TRANSFORM THE CYCLONE INTO A SUBTROPICAL LOW WITH EXPANSIVE GALE FORCE WINDS AT TAUS 72 AND 96. MODEL DISCUSSION: NUMERICAL MODELS REMAIN IN OVERALL GOOD AGREEMENT WITH THE CURRENT FORECAST SCENARIO THROUGH TAU 120. SOME SPREAD REMAINS IN THE ORIENTATION AND SPEED OF THE TRACK AS THE SYSTEM ROUNDS THE RIDGE AXIS, AND THE NAVGEM AND ECMWF DETERMINISTIC MODEL TRACKERS LOSE THE VORTEX BY TAU 36 DUE TO THE DISSIPATION OVER LAND. OVERALL, CONFIDENCE IN THE TRACK FORECAST IS MEDIUM FOR THE WHOLE DURATION. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN