WDXS31 PGTW 212100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05S (DARIAN) WARNING NR 009// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 13.2S 89.0E INITIAL INTENSITY: 130 KTS GEOGRAPHIC REFERENCE: 1040 NM EAST-SOUTHEAST OF DIEGO GARCIA MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 50 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE SYSTEM HAS MAINTAINED A MEDIUM-SIZED, HIGHLY-SYMMETRICAL STRUCTURE WITH A DEFINED PINHOLE EYE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A MICROWAVE EYE FEATURE IN THE 211822Z GPM IMAGE AND LINED UP WITH A DEFINED LOW LEVEL CIRCULATION CENTER IN THE 211603Z ASCAT BULLSEYE PASS. THE INITIAL INTENSITY IS BASED ON OVERALL ASSESSMENT OF AGENCY AND AUTOMATED DVORAK ESTIMATES AND REFLECTS THE SUSTAINED CONVECTIVE SIGNATURE. TC DARIAN HAS TRACKED MORE POLEWARD OVER THE LAST SIX HOURS. LIKELY DUE TO STRONGER STEERING STR THAN ANTICIPATED. ALSO, ANALYSIS OF RECENT MICROWAVE SATELLITE IMAGES, INCLUDING THE 211822Z GPM PASS, SHOWS THE SYSTEM MAY BE UNDERGOING A SLOW EYEWALL REPLACEMENT CYCLE. INITIAL WIND RADII BASIS: SCATTEROMETER DATA. CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE SOUTH AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T7.0 - 140 KTS KNES: T7.0 - 140 KTS CIMSS ADT: 137 KTS AT 211515Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 26-27 CELSIUS OUTFLOW: STRONG RADIAL 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: TC DARIAN WILL TRACK MORE WESTWARD UNDER THE STEERING INFLUENCE OF THE STR TO THE SOUTH THAT IS RECEDING EASTWARD. BY TAU 72, THE CYCLONE WILL BEGIN TO ROUND THE STR AXIS AND TRACK MORE SOUTHWARD. THE UPPER LEVEL ENVIRONMENT WILL REMAIN FAVORABLE WITH LOW VWS AND STRONG RADIAL OUTFLOW; HOWEVER, THE ALONG-TRACK SST IS PROJECTED TO SLOWLY COOL LEADING TO A GRADUAL WEAKENING UP TO TAU 72. 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 60 KTS. MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH A GRADUAL AND EVEN SPREADING TO 84NM AT TAU 72. AFTERWARD, THE MEMBERS SPREAD OUT SIGNIFICANTLY ALONG-TRACK AND UP TO 286NM ACROSS-TRACK BY TAU 120 WITH NVGM ON THE RIGHT AND EEMN ON THE LEFT MARGIN OF THE MODEL ENVELOPE. IN VIEW OF THIS, THERE IS HIGH CONFIDENCE IN THE JTWC TRACK FORECAST UP TO TAU 72, THEN LOW CONFIDENCE AFTERWARD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN