WDPN31 PGTW 202100 AMD MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 28W (RAI) WARNING NR 031 AMENDED// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 18.8N 112.5E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 231 NM SOUTH-SOUTHWEST OF HONG KONG MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 08 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE SYSTEM CONTINUED TO RAPIDLY DETERIORATE AS THE CENTRAL CONVECTION HAS FURTHER COLLAPSED AND DISINTEGRATED AS IT IS NOW SHEARED 100+ NM NORTHEASTWARD OF A FULLY EXPOSED AND RAGGED LOW LEVEL CIRCULATION (LLC). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLC. THE INITIAL INTENSITY OF 35KTS IS EXTRAPOLATED WITH MEDIUM CONFIDENCE BASED ON A SERIES OF SCATTEROMETER DATA AND REFLECTS THE RAPID DETERIORATION. TS RAI IS IN A HIGHLY UNFAVORABLE ENVIRONMENT WITH STRONG (25+ KTS) RELATIVE VWS, COOL (24-25C) SSTS IN THE SOUTH CHINA SEA (SCS), AND COLD DRY AIR INTRUSION IN THE LOW LEVELS ASSOCIATED WITH THE NORTHEAST COLD SURGE IN THE SCS. INITIAL WIND RADII BASIS: SCATTEROMETER DATA. CURRENT STEERING MECHANISM: GRADIENT FLOW BETWEEN MID-LATITUDE TROUGH TO THE WEST AND WESTERN PERIPHERY OF A LOW REFLECTION OF THE SUBTROPICAL RIDGE (STR) TO THE EAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: NO CURRENT ESTIMATE RJTD: T4.5 - 77 KTS CIMSS ADT: 41 KTS AT 201140Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE VWS: 25-30 KTS SST: 24-25 CELSIUS OUTFLOW: STRONG POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS RAI WILL CONTINUE ON ITS CURRENT TRACK AND RAPIDLY DECAY DUE TO THE HIGHLY UNFAVORABLE ENVIRONMENT, LEADING TO DISSIPATION BY TAU 24, POSSIBLY SOONER. MODEL DISCUSSION: NUMERICAL MODELS REMAIN IN TIGHT AGREEMENT LENDING HIGH CONFIDENCE IN THE JTWC TRACK FORECAST. THERE IS ONLY MEDIUM CONFIDENCE IN THE INTENSITY FORECAST DUE TO THE POSSIBILITY OF AN EARLIER DISSIPATION. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH INTENSITY 0 - 72 HR: MEDIUM 4. JUSTIFICATION FOR AMENDMENT: AMENDED INITIAL INTENSITY TO 35KTS.// NNNN