WDXS32 PGTW 142100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (DINGANI) WARNING NR 012// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 24.3S 71.4E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 822 NM EAST-SOUTHEAST OF PORT LOUIS, MAURITIUS MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 11 KTS SIGNIFICANT WAVE HEIGHT: 22 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FULLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), WITH ALL UPPER LEVEL FEATURES BEING SHEARED TO THE SOUTHEAST. A 141703Z AMSU-B 89GHZ MICROWAVE IMAGE REVEALS THE NORTHERN SEMICIRCLE OF 13S HAS MOSTLY ERODED, LEAVING A SINGLE PRIMARY BANDING FEATURE TO THE SOUTH AND AN OPEN CORE STRUCTURE. A FORTUITOUS 141347Z SENTINEL-1 SYNTHETIC APERTURE RADAR (SAR) BULLSEYE PASS REVEALED A ROBUST ALBEIT ASYMMETRIC WIND FIELD WITH LARGE 65-68KT REGIONS IN THE SOUTHERN SEMICIRCLE, WHILE THE NORTHERN SEMICIRCLE INDICATED MOSTLY 35-45KTS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON EIR AND AMSUB IMAGERY. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE SAR PASS AS WELL AS THE BULK OF AGENCY DVORAK INTENSITY ESTIMATES INDICATING T3.5, WHILE ADT AND OTHER AUTOMATED ESTIMATES INDICATE AN UNREALISTIC DROP BELOW 40KTS. INITIAL WIND RADII BASIS: SAR DATA CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE EAST-SOUTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS DEMS: T2.5 - 35 KTS FMEE: T3.5 - 55 KTS CIMSS ADT: 37 KTS AT 141500Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE VWS: 30+ KTS SST: 26-27 CELSIUS OUTFLOW: MODERATE 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: TC 13S (DINGANI) IS FORECAST TO CONTINUE ON ITS GENERALLY SOUTHWESTWARD TRACK THROUGH TAU 36 AS THE SYSTEM CONTINUES POLEWARD OF THE STR AXIS. DURING THIS TIME, SEA SURFACE TEMPERATURES WILL GRADUALLY FALL, VERTICAL WIND SHEAR REMAINS HIGH, AND DRY AIR ENTRAINMENT INCREASES. ALL OF THESE FACTORS WILL RESULT IN A PERSISTENT AND TERMINAL WEAKENING TREND THROUGH THE FORECAST PERIOD. AFTER TAU 36, THE SYSTEM WILL MAKE A SHARP SOUTHEASTERLY TURN, PLACING IT AT THE MERCY OF THE SUBTROPICAL JET, CONSEQUENTLY 13S WILL DRAMATICALLY INCREASE SPEED AND BY TAU 72 THE SYSTEM WILL DISSIPATE. MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT THAT 13S WILL CONTINUE ALONG THE WESTERN PERIPHERY OF THE STR THROUGH TAU 36, EVENTUALLY EXECUTING A SOUTHEASTERLY TURN AND INCREASING SPEED. FOR THIS REASON THE JTWC FORECAST TRACK IS PLACED WITH MEDIUM CONFIDENCE. RELIABLE MODEL INTENSITY GUIDANCE INDICATES A MODERATE SPREAD IN SOLUTIONS, WITH HWRF AND DECAY-SHIPS TAKING A SHARP WEAKENING TREND WHILE THE BULK OF THE GUIDANCE INDICATES A MORE GRADUAL DECLINE. BASED ON THIS INITIAL DISCREPANCY IN SOLUTIONS, THE JTWC INTENSITY GUIDANCE IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM// NNNN