WDXS31 PGTW 222100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05S (DARIAN) WARNING NR 011// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 12.8S 85.8E INITIAL INTENSITY: 100 KTS GEOGRAPHIC REFERENCE: 857 NM EAST-SOUTHEAST OF DIEGO GARCIA MOVEMENT PAST 6 HOURS: WESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 45 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE SYSTEM HAS SLIGHTLY WEAKENED AS EVIDENCED BY WARMED CLOUD TOPS. OTHERWISE, THE CONVECTIVE STRUCTURE HAS REMAINED VIRTUALLY THE SAME. THE EYE FEATURE HAS SINCE BEEN OBSCURED BY HIGH CLOUD COVER. THE INITIAL POSITION IS EXTRAPOLATED WITH MEDIUM CONFIDENCE FROM A PIXELATED BUT DEFINED LOW LEVEL CIRCULATION FEATURE IN THE 221439Z AMSUB MICROWAVE IMAGE. THE INITIAL INTENSITY IS AVERAGED FROM AGENCY AND AUTOMATED DVORAK ESTIMATED AND REFLECTS THE SLIGHT WEAKENING. THE ENVIRONMENT REMAINS OVERALL FAVORABLE; THE SLIGHT WEAKENING IS LIKELY DUE TO SLIGHTLY ELEVATED VWS AND RELATIVELY COOLER ALONG-TRACK SST, BROUGHT ON BY UPWELLING. INITIAL WIND RADII BASIS: PERSISTENCE. CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE SOUTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.5 - 102 KTS KNES: T5.0 - 90 KTS CIMSS SATCON: 98 KTS AT 221353Z CIMSS ADT: 104 KTS AT 221515Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 27-28 CELSIUS OUTFLOW: STRONG RADIAL 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: TC DARIAN WILL TRACK MORE WESTWARD UNDER THE STEERING INFLUENCE OF THE WEAKENING STR TO THE SOUTH. AFTER TAU 24, THE CYCLONE WILL BEGIN TO ROUND THE STR AXIS AND TRACK MORE SOUTHWARD, THEN BY TAU 96, WILL REVERSE TO A SOUTHWESTWARD TRAJECTORY AS THE STR REBUILDS. THE UPPER LEVEL ENVIRONMENT WILL REMAIN FAVORABLE WITH LOW VWS AND STRONG RADIAL OUTFLOW OFFSET BY THE ALONG-TRACK SST IS PROJECTED TO REMAIN COOLER THAN ITS SURROUNDING. THIS EQUILIBRIUM WILL MAINTAIN AN INTENSITY NEAR 100KTS UP TO TAU 36. AFTERWARD, AS THE SYSTEM TRACKS MORE POLEWARD, SST IS EXPECTED TO COOL MORE RAPIDLY, RESULTING IN A MORE ACCELERATED WEAKENING. BY TAU 120, TC 05S WILL BE REDUCED TO 50 KTS. MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH A GRADUAL AND EVEN SPREADING TO 50NM AT TAU 72. AFTERWARD, THE MEMBERS SPREAD OUT MORE ALONG-TRACK AND UP TO 127NM ACROSS-TRACK BY TAU 120 WITH NVGM THE WEST-OF-TRACK OUTLIER. IN VIEW OF THIS, THERE IS HIGH CONFIDENCE UP TO TAU 72, THEN MEDIUM CONFIDENCE AFTERWARD, IN THE JTWC TRACK FORECAST THAT IS LAID SLIGHTLY EAST OF CONSENSUS TO OFFSET NVGM. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN