WDXS32 PGTW 152100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (DINGANI) WARNING NR 014// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 28.9S 68.2E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 795 NM SOUTHEAST OF PORT LOUIS, MAURITIUS MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 12 KTS SIGNIFICANT WAVE HEIGHT: 21 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FULLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), WITH THE PRIMARY CONVECTIVE HOT TOWERS SOUTH AS THEY ARE EVACUATED EASTWARD BY THE SUBTROPICAL JET. A 151433Z SSMIS 91GHZ MICROWAVE IMAGE REVEALS DIMINISHED AND FRAGMENTING LOW LEVEL BANDING FEATURES AS THE SYSTEM PROGRESSES INTO AN INCREASINGLY HOSTILE ENVIRONMENT. A FORTUITOUS 151732Z ASCAT-B SCATTEROMETRY PASS REVEALS AN ASYMMETRIC WIND FIELD WITH THE HIGHER WINDS (35-40KTS) EXCLUSIVELY IN THE SOUTHERN SEMICIRCLE WHILE 25-30KT WINDS DOMINATE THE NORTHERN SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON EIR AND SSMIS IMAGERY AND SCATTEROMETRY DATA. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON SCATTEROMETRY DATA INDICATING 40KT WINDS STILL PERSIST TO THE SOUTH OF THE LLCC DESPITE AGENCY DVORAK INTENSITY ESTIMATES INDICATING BELOW 30KTS. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE EAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.5 - 25 KTS KNES: T1.0 - 25 KTS DEMS: T1.5 - 25 KTS CIMSS ADT: 25 KTS AT 151500Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE VWS: 30+ KTS SST: 24-25 CELSIUS OUTFLOW: MODERATE POLEWARD OTHER FACTORS: DRY AIR ENTRAINMENT 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: OVER THE NEXT 12 HOURS TC 13S (DINGANI) WILL CONTINUE TO ROUND THE STR AND MAKE AN ABRUPT SOUTH-SOUTHEASTWARD AND EVENTUALLY SOUTHEASTWARD COURSE CORRECTION. DURING THIS TIME, 11S WILL CONTINUE TO WEAKEN AS VERTICAL WIND SHEAR (VWS) AND DRY AIR ENTRAINMENT INCREASE AND SEA SURFACE TEMPERATURES CONTINUE TO FALL. BETWEEN TAU 12 AND TAU 24 13S WILL BEGINS TO ENTER THE SUBTROPICAL JET AND DRAMATICALLY INCREASED UPPER LEVEL OUTFLOW MAY TEMPORARILY DELAY THE SYSTEMS IMMINENT DEMISE, HOWEVER BY TAU 36 TC DINGANI WILL DISSIPATE. MODEL DISCUSSION: NUMERICAL MODELS ARE IN EXCELLENT AGREEMENT THAT 11S WILL CONTINUE ALONG THE WESTERN PERIPHERY OF THE STR AND EVENTUALLY ENTER THE SUBTROPICAL JET AND SWIFTLY PROCEED SOUTHEASTWARD. FOR THIS REASON THE JTWC INTENSITY FORECAST IS PLACED WITH HIGH CONFIDENCE. RELIABLE MODEL INTENSITY GUIDANCE IS IN GOOD AGREEMENT WITH A BULK OF THE GUIDANCE CLOSELY FOLLOWING THE MULTI MODEL CONSENSUS FORECAST, FOR THIS REASON THE JTWC INTENSITY FORECAST IS PLACED NEAR THE CONSENSUS WITH HIGH CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH INTENSITY 0 - 72 HR: HIGH// NNNN