WDXS32 PGTW 132100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (DINGANI) WARNING NR 010// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 20.7S 73.4E INITIAL INTENSITY: 75 KTS GEOGRAPHIC REFERENCE: 818 NM SOUTH OF DIEGO GARCIA MOVEMENT PAST 6 HOURS: SOUTHWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 25 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS RAGGED CONVECTION WRAPPING AROUND A LOW-LEVEL CIRCULATION CENTER (LLCC). THE AFOREMENTIONED EYE FEATURE IS NO LONGER EVIDENT IN SATELLITE IMAGERY. FURTHERMORE, CLOUD TOPS ARE GRADUALLY WARMING, INDICATING THAT THE SYSTEM IS WEAKENING. THE INITIAL INTENSITY IS ASSESSED AT 75 KNOTS BASED ON A BLEND OF SATCON AND DVORAK ANALYSES. A 131635Z METOP-B ASCAT IMAGE WAS USED TO ADJUST THE INITIAL WIND RADII. THE SYSTEM IS BEING IMPACTED BY NORTHWESTERLY VERTICAL WIND SHEAR OF 20 TO 25 KNOTS. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE SOUTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.0 - 90 KTS KNES: T5.0 - 90 KTS FMEE: T5.0 - 90 KTS CIMSS SATCON: 72 KTS AT 131549Z CIMSS ADT: 72 KTS AT 131800Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE VWS: 20-25 KTS SST: 26-27 CELSIUS OUTFLOW: MODERATE POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 13S HAS TAKEN A JOG TOWARD THE SOUTH-SOUTHEAST BUT IS FORECAST TO CONTINUE TRACKING GENERALLY SOUTH-SOUTHWESTWARD THROUGH TAU 72 ALONG THE WESTERN PERIPHERY OF THE STR TO THE SOUTHEAST. ENVIRONMENTAL CONDITIONS ARE DETERIORATING, WITH VERTICAL WIND SHEAR INCREASING FROM 20 KNOTS TO OVER 30 KNOTS IN THE COMING DAYS. SIMULTANEOUSLY, SEA SURFACE TEMPERATURES ARE FORECAST TO COOL BELOW THE NECESSARY 26C, SO DISSIPATION OVER WATER IS EXPECTED AS THE SYSTEM INTERACTS WITH THE SUBTROPICAL JET AROUND TAU 72. MODEL DISCUSSION: DETERMINISTIC AND PROBABILISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72. AFTERWARDS, THERE IS INCREASING UNCERTAINTY IN THE FORECAST TRACK AS THE SYSTEM IS FORECAST TO RECURVE SHARPLY TOWARD THE SOUTHEAST. DISSIPATION IS EXPECTED SHORTLY AFTER THE TURN OCCURS AS THE SYSTEMS BECOMES EMBEDDED IN THE MID-LATITUDE WESTERLIES. INTENSITY GUIDANCE IS IN GENERAL AGREEMENT, SUGGESTING GRADUAL WEAKENING THROUGH DISSIPATION. GIVEN THE INITIAL JOG TOWARD THE SOUTH-SOUTHEAST AND THE UNCERTAINTY ASSOCIATED WITH THE SHARP RECURVE AROUND TAU 72, THE OVERALL JTWC TRACK AND INTENSITY FORECAST CONFIDENCE IS MEDIUM. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN