WDPN31 PGTW 122100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (MEARI) WARNING NR 007// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 33.0N 136.7E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 203 NM SOUTHWEST OF YOKOSUKA, JAPAN MOVEMENT PAST 6 HOURS: NORTHWARD AT 11 KTS SIGNIFICANT WAVE HEIGHT: 13 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE LOW LEVEL CIRCULATION (LLC) OF TS 09W REMAINS DECOUPLED AND FULLY EXPOSED, WITH THE MAIN CONVECTION SHEARED SOUTH- TO SOUTHWESTWARD OF THE LLC. THE EIR LOOP ALSO INDICATES SUBSIDENCE AND CONVERGENCE ALONG THE NORTHERN HALF OF THE SYSTEM, INHIBITING CONVECTIVE DEVELOPMENT AND INTENSIFICATION. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLC THAT LINED UP PERFECTLY WITH A 121802Z GPM 89GHZ MICROWAVE LLC FEATURE. THE INITIAL INTENSITY OF 35KTS IS HEDGED SLIGHTLY HIGHER THAN THE AGENCY AND OBJECTIVE DVORAK CURRENT INTENSITY ESTIMATES AND EXTRAPOLATED FROM RECENT SCATTEROMETRY PASSES TO REFLECT THE SUSTAINED 6-HR EIR SIGNATURE. INITIAL WIND RADII BASIS: SCATTEROMETER DATA. CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF THE LOW- TO MID-LAYER REFLECTION OF THE SUBTROPICAL RIDGE (STR) TO THE EAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T2.0 - 30 KTS CIMSS SATCON: 42 KTS AT 121701Z CIMSS ADT: 35 KTS AT 121740Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL VWS: 20-25 KTS SST: 28-29 CELSIUS OUTFLOW: STRONG EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS MEARI WILL BEGIN TO TRACK MORE NORTHEASTWARD AS IT ROUNDS THE NORTHWESTERN EDGE OF THE STEERING STR, DRAG ACROSS THE SOUTHERN COAST OF HONSHU THROUGH TOKYO THEN EXIT BACK INTO THE PACIFIC OCEAN JUST AFTER TAU 12. THE VWS IS EXPECTED TO RELAX AND ALLOW A SLIGHT INTENSIFICATION TO A PEAK OF 40KTS AT TAUS 12 TO 24. AFTERWARD, COOLING SST AND ENTRY INTO THE BAROCLINIC ZONE WILL GRADUALLY WEAKEN THE CYCLONE. BY TAU 36, THE SYSTEM WILL BEGIN EXTRA-TROPICAL TRANSITION AND BY TAU 48, WILL TRANSFORM INTO A 30-KT COLD CORE LOW. THERE IS A DISTINCT POSSIBILITY THAT TS MEARI WILL DISSIPATE OR FALL BELOW JTWC WARNING CRITERIA AFTER ITS PASSAGE OVER LAND. MODEL DISCUSSION: NUMERICAL MODELS ARE IN VERY RIGHT AGREEMENT WITH GRADUAL AND EVEN SPREAD TO 100NM BY TAU 48, LENDING HIGH CONFIDENCE IN THE JTWC TRACK FORECAST. THERE IS, HOWEVER, LOW CONFIDENCE IN THE INTENSITY FORECAST DUE TO THE POTENTIAL EARLY DISSIPATION. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH INTENSITY 0 - 72 HR: LOW// NNNN