WTXS51 PGTW 290900 WARNING ATCG MIL 17S SIO 160329071616 2016032906 17S SEVENTEEN 002 01 175 15 SATL 045 T000 178S 0783E 040 R034 040 NE QD 040 SE QD 025 SW QD 025 NW QD T012 203S 0791E 040 R034 040 NE QD 045 SE QD 025 SW QD 025 NW QD T024 232S 0805E 035 T036 258S 0822E 030 AMP 024HR DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER 036HR DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER SUBJ: TROPICAL CYCLONE 17S (SEVENTEEN) WARNING NR 002 1. TROPICAL CYCLONE 17S (SEVENTEEN) WARNING NR 002 01 ACTIVE TROPICAL CYCLONE IN SOUTHIO MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 290600Z --- NEAR 17.8S 78.3E MOVEMENT PAST SIX HOURS - 175 DEGREES AT 15 KTS POSITION ACCURATE TO WITHIN 045 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 040 NM NORTHEAST QUADRANT 040 NM SOUTHEAST QUADRANT 025 NM SOUTHWEST QUADRANT 025 NM NORTHWEST QUADRANT REPEAT POSIT: 17.8S 78.3E --- FORECASTS: 12 HRS, VALID AT: 291800Z --- 20.3S 79.1E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 040 NM NORTHEAST QUADRANT 045 NM SOUTHEAST QUADRANT 025 NM SOUTHWEST QUADRANT 025 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 155 DEG/ 16 KTS --- 24 HRS, VALID AT: 300600Z --- 23.2S 80.5E MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER VECTOR TO 36 HR POSIT: 150 DEG/ 15 KTS --- 36 HRS, VALID AT: 301800Z --- 25.8S 82.2E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 290900Z POSITION NEAR 18.4S 78.5E. TROPICAL CYCLONE 17S (SEVENTEEN), LOCATED APPROXIMATELY 726 NM SOUTH-SOUTHEAST OF DIEGO GARCIA, HAS TRACKED SOUTHWARD AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH THE FLARING CENTRAL CONVECTION BEING SHEARED AWAY TO THE SOUTH. RECENT MICROWAVE IMAGERY CONFIRMS THE LOW LEVEL STRUCTURE HAS IMPROVED OVER THE LAST SIX HOURS AS CONVECTIVE BANDING IS MORE DEFINED AND IS ROTATING INTO A WELL DEFINED LLCC WITH THE STRONGEST CONVECTION LOCATED IN THE SOUTHERN PERIPHERY. A 290424Z MHS 89GHZ IMAGE SHOWS A REGION OF DRY AIR APPROACHING TC 17S FROM THE WEST WHICH WILL HINDER FUTURE INTENSIFICATION. THE CURRENT INTENSITY IS ASSESSED AT 40 KNOTS AND IS BASED ON A 290337Z METOP-B ASCAT IMAGE SHOWING 35 TO 40 KNOT SURFACE WINDS ON THE EASTERN PERIPHERY. THIS IS IN CONTRAST TO DVORAK ESTIMATES FROM REPORTING AGENCIES SUGGESTING TC 17S HAS WEAKENED OVER THE LAST SIX HOURS. THIS IS ATTRIBUTED TO THE RELATIVELY SMALL SIZE AND WANING STRUCTURE OF THE TC IN WHICH DVORAK TECHNIQUES CAN BE UNREPRESENTATIVE OF TRUE INTENSITY. CURRENTLY, CONDITIONS ARE MARGINALLY FAVORABLE WITH WARM (29 CELSIUS) SEA SURFACE TEMPERATURES (SSTS) AND A STRONG POLEWARD OUTFLOW CHANNEL BEING OFFSET BY HIGH (20 TO 25 KNOTS) VERTICAL WIND SHEAR. TC 17S IS CURRENTLY POSITIONED BETWEEN A LONG WAVE TROUGH TO THE WEST AND A SUBTROPICAL RIDGE TO THE EAST STEERING IT ALONG A SOUTHWARD TRACK. AS THE TROUGH APPROACHES, VERTICAL WIND SHEAR IS EXPECTED TO INCREASE CONSIDERABLY OVER THE NEXT 12 TO 24 HOURS AND BY TAU 36 SSTS WILL BE NEAR 26 CELSIUS. DUE TO THE DETERIORATING ENVIRONMENT TC 17S IS EXPECTED TO FULLY DISSIPATE BY TAU 36 AS IT GETS FULLY ABSORBED IN THE PASSING TROUGH. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT GIVING HIGH CONFIDENCE TO THE FORECAST TRACK. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 290600Z IS 14 FEET. NEXT WARNINGS AT 292100Z AND 300900Z. // 1716032718 125S 737E 20 1716032800 129S 751E 25 1716032806 135S 761E 30 1716032812 145S 770E 30 1716032818 152S 775E 35 1716032900 163S 781E 35 1716032906 178S 783E 40 NNNN