WDXS31 PGTW 230900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05S (DARIAN) WARNING NR 012// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 12.4S 84.3E INITIAL INTENSITY: 105 KTS GEOGRAPHIC REFERENCE: 767 NM EAST-SOUTHEAST OF DIEGO GARCIA MOVEMENT PAST 6 HOURS: WESTWARD AT 08 KTS SIGNIFICANT WAVE HEIGHT: 37 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A WARMING EYE OVER THE PAST SIX HOURS, SURROUNDED BY -73 TO -78 DEGREE CELSIUS CLOUD TOPS. OCCASIONAL HINTS OF CONCENTRIC CONVECTIVE RINGS ARE EVIDENT, BUT NO RECENT MICROWAVE IMAGERY IS AVAILABLE TO CONFIRM WHETHER CONCENTRIC EYEWALLS ARE PRESENT. A 222350Z PARTIAL SAR PASS SHOWED MAXIMUM WINDS OF AROUND 95 KT, AND THE STORM'S SATELLITE PRESENTATION HAS SUBSTANTIALLY IMPROVED SINCE THAT TIME. THE INITIAL INTENSITY IS THUS SET AT 105 KT, SUPPORTED BY THE PGTW AND KNES DVORAK ESTIMATES OF T6.0 (115 KT) AND RISING ADT ESTIMATES OF 95-102 KT. VISUAL SIGNS OF MID-LEVEL VERTICAL SHEAR HAVE MARKEDLY DECREASED COMPARED TO 24 HOURS AGO, AND RADIAL OUTFLOW IS EVIDENT IN ALL QUADRANTS. THE CYCLONE IS ALSO APPROACHING A PATCH OF WARMER SEA SURFACE TEMPERATURES OF 28-29 DEGREES CELSIUS JUST TO THE WEST, LIKELY CONTRIBUTING TO THE ONGOING REORGANIZATION TREND. INITIAL WIND RADII BASIS: SAR DATA CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE SOUTH AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T6.0 - 115 KTS KNES: T6.0 - 115 KTS CIMSS ADT: 77 KTS AT 230315Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 27-28 CELSIUS OUTFLOW: MODERATE 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: TROPICAL CYCLONE 05S (DARIAN) CONTINUES TO TRACK WESTWARD AT A MODEST PACE ALONG THE NORTHERN FLANK OF A SUBTROPICAL RIDGE TO THE SOUTH. THE PAST 24 HOURS HAD CONSISTED OF A WEAKENING TREND, LIKELY DUE TO A COMBINATION OF OCEANIC UPWELLING AND MID-LEVEL VERTICAL SHEAR OF 20-25 KT. HOWEVER, A RESTRENGTHENING TREND IS IN PROGRESS AS THE CYCLONE MOVES OVER SLIGHTLY WARMER WATERS AND VERTICAL SHEAR ABATES SOMEWHAT. THIS COULD CONTINUE BRIEFLY UNTIL DARIAN BEGINS TO TURN SOUTH OR SOUTH-SOUTHEASTWARD DURING THE 12-36 HOUR PERIOD DUE TO A DIGGING UPPER-LEVEL TROUGH WEST OF AUSTRALIA AND A STRENGTHENING WESTERLY WIND BURST SOUTH OF THE EQUATOR. DURING THIS TURN, THE CYCLONE'S FORWARD MOTION WILL SLOW. THE RESULTING INCREASE IN OCEANIC UPWELLING WILL LIKELY INDUCE WEAKENING ONCE MORE, WHICH HAS BEEN CONSISTENTLY FORECAST BY THE COUPLED HWRF MODEL. A GRADUAL DECREASE IN INTENSITY IS FORECAST FROM 36 THROUGH 72 HOURS, THEN MORE RAPIDLY THEREAFTER AS DARIAN MOVES SOUTH AND SOUTHWESTWARD OVER SUBTROPICAL WATERS COOLER THAN 26 DEGREES CELSIUS. MODEL DISCUSSION: THE JTWC TRACK FORECAST IS CLOSE TO THE MULTI-MODEL CONSENSUS THROUGHOUT THE FORECAST PERIOD. THE JTWC INTENSITY FORECAST IS CLOSE TO THE MULTI-MODEL CONSENSUS THROUGH 48 HOURS, THEN SLIGHTLY ABOVE CONSENSUS THEREAFTER DUE TO A DISCOUNTING OF THE WEAK OUTLIER COAMPS-TC, WHICH SEEMS TO SHOW AN UNREALISTIC AMOUNT OF OCEANIC COOLING DURING THIS PERIOD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: HIGH INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN