WDPN32 PGTW 281500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W (JEBI) WARNING NR 009// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 21.4N 142.7E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 849 NM SOUTH-SOUTHEAST OF YOKOSUKA, JAPAN MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: AS INDICATED IN ANIMATED ENHANCED INFRARED SATELLITE IMAGERY, TROPICAL DEPRESSION (TD) 19W CONTINUES TO STRUGGLE, WITH DEEP CONVECTION FLARING OVER THE EASTERN SEMICIRCLE OF A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION. A 281210Z MHS 89GHZ MICROWAVE IMAGE REVEALS A WEAKLY DEFINED LOW-LEVEL CIRCULATION CENTER, WITH DISORGANIZED DEEP CONVECTION OVER THE EASTERN SEMICIRCLE. A 281125Z ASCAT-C IMAGE SHOWS AN ELONGATED, WEAK CIRCULATION, WITH A SWATH OF 25-30 KNOT WINDS OVER THE EASTERN SEMICIRCLE WRAPPING INTO THE NORTHEAST QUADRANT. UPPER- LEVEL CONDITIONS REMAIN MARGINALLY FAVORABLE DUE TO THE PRESENCE OF AN UPPER-LOW OVER AND TO THE WEST OF THE SYSTEM, WHICH IS PRODUCING UPPER-LEVEL CONVERGENCE AND SUBSIDENCE OVER THE WESTERN SEMICIRCLE THUS INHIBITING CONVECTIVE DEVELOPMENT. UPPER-LEVEL DIFFLUENCE IS CONFINED TO THE EASTWARD AND EQUATORWARD REGIONS OF THE SYSTEM, AIDING IN SUSTAINMENT OF DEEP CONVECTION OVER THOSE REGIONS. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE ASCAT-C IMAGE. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE AGENCY DVORAK ESTIMATES, CIMSS ADT ESTIMATE, AND ASCAT DATA. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: LOW-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T2.5 - 35 KTS KNES: T2.0 - 30 KTS CIMSS SATCON: 36 KTS AT 280945Z CIMSS ADT: 32 KTS AT 281150Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE EASTWARD OTHER FACTORS: EXTENSIVE DRY AIR ASSOCIATED WITH THE UPPER-LEVEL LOW 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 19W IS FORECAST TO TRACK POLEWARD ALONG THE SOUTHWESTERN AND WESTERN PERIPHERY OF THE STR THROUGH TAU 48, WITH STEADY DEVELOPMENT AS THE UPPER-LOW GRADUALLY WEAKENS. AFTER TAU 48, THE SYSTEM WILL ROUND THE STR AND INTENSIFY TO TYPHOON STRENGTH DUE TO IMPROVING POLEWARD OUTFLOW ASSOCIATED WITH A DEEPENING MAJOR SHORTWAVE TROUGH EXPECTED TO DIG OVER WESTERN JAPAN. BY TAU 72, THE SYSTEM WILL EVENTUALLY TRACK INTO THE MIDLATITUDE WESTERLIES NORTH OF THE STR AND COMMENCE EXTRA-TROPICAL TRANSITION (ETT). TD 19W WILL COMPLETE ETT BY TAU 96 AS IT ACCELERATES POLEWARD AND GAINS FRONTAL CHARACTERISTICS. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT THROUGH THE FORECAST PERIOD, WITH GUIDANCE DIVERGING SIGNIFICANTLY AFTER TAU 72 AS THE SYSTEM UNDERGOES EXTRA-TROPICAL TRANSITION. THE 280000Z ECMWF (EPS) ENSEMBLE AND 280600Z GFS (GEFS) ENSEMBLE SHOW A SIMILAR SPREAD AND MEDIUM UNCERTAINTY AS THE SYSTEM TRACKS EAST OF THE KANTO PLAIN, WITH SOME POTENTIAL FOR THE SYSTEM TO TRACK CLOSER TO HONSHU AS IT ROUNDS THE STR. GEFS SUPPORTS THE JTWC INTENSITY FORECAST, SHOWING A STRONG TROPICAL STORM STRENGTH TO MINIMAL TYPHOON STRENGTH SYSTEM IN THE MAJORITY OF ITS SOLUTIONS AFTER TAU 48. ADDITIONALLY, THE 271200Z COAMPS-TC (GFS) ENSEMBLE SHOWS A HIGH PROBABILITY (80-90 PERCENT) OF A WEAK TYPHOON DEVELOPING IN THE TAU 48 TO TAU 72 PERIOD AS REFLECTED IN THE JTWC INTENSITY FORECAST. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN