WTIO30 FMEE 171818 RSMC / TROPICAL CYCLONE CENTER / LA REUNION TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN) 0.A WARNING NUMBER: 20/3/20172018 1.A SEVERE TROPICAL STORM 3 (BERGUITTA) 2.A POSITION 2018/01/17 AT 1800 UTC: WITHIN 30 NM RADIUS OF POINT 19.0 S / 59.3 E (NINETEEN DECIMAL ZERO DEGREES SOUTH AND FIFTY NINE DECIMAL THREE DEGREES EAST) MOVEMENT : SOUTH-WEST 6 KT 3.A DVORAK ANALYSIS: 3.5/4.0/W 0.5/18 H 4.A CENTRAL PRESSURE: 972 HPA 5.A MAX AVERAGE WIND SPEED (10 MN): 60 KT RADIUS OF MAXIMUM WINDS (RMW) :46 KM 6.A EXTENSION OF WIND BY QUADRANTS (KM): 28 KT NE: 200 SE: 480 SW: 560 NW: 240 34 KT NE: 150 SE: 200 SW: 150 NW: 120 48 KT NE: 60 SE: 70 SW: 70 NW: 60 7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1004 HPA / 1200 KM 8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP 1.B FORECASTS: 12H: 2018/01/18 06 UTC: 20.6 S / 57.5 E, MAX WIND=060 KT, SEVERE TROPICAL STORM 24H: 2018/01/18 18 UTC: 22.0 S / 55.1 E, MAX WIND=055 KT, SEVERE TROPICAL STORM 36H: 2018/01/19 06 UTC: 23.5 S / 52.8 E, MAX WIND=055 KT, SEVERE TROPICAL STORM 48H: 2018/01/19 18 UTC: 25.3 S / 51.0 E, MAX WIND=050 KT, SEVERE TROPICAL STORM 60H: 2018/01/20 06 UTC: 27.8 S / 50.1 E, MAX WIND=045 KT, MODERATE TROPICAL STORM 72H: 2018/01/20 18 UTC: 31.5 S / 49.8 E, MAX WIND=045 KT, MODERATE TROPICAL STORM 2.B LONGER-RANGE OUTLOOK : 96H: 2018/01/21 18 UTC: 33.6 S / 51.9 E, MAX WIND=035 KT, POST-TROPICAL DEPRESSION 120H: 2018/01/22 18 UTC: 34.1 S / 56.3 E, MAX WIND=035 KT, POST-TROPICAL DEPRESSION 2.C ADDITIONAL INFORMATION: T=3.5+ CI=4.0+ OVER THE PAST SIX HOURS, THE STRUCTURE OF THE SYSTEM HAS REMAINED QUITE SIMILAR AND THE WEAKNESS INTO DEEP CONVECTION SEEMS TO BE NOW IN THE SOUTH-EASTERN QUADRANT OF THE CIRCULATION. ANIMATED IMAGERY SHOWS THAT BERGUITTA BEGINS TO EXPERIENCE A NORTHEASTERN VERTICAL WINDSHEAR, BUT KEEP A VERY GOOD DIVERGENCE IN WESTERN PART. LAST SATELLITE IMAGERIES CONFIRM THAT BERGUITTA HAS BENT SOUTHWESTWARD UNDER THE STEERING FLOW OF A BUILDING MID-TROPOSPHERIC RIDGE LOCATED EAST. THIS NIGHT, BERGUITTA IS FORECASTED TO GOING ON ACCELERATING TOWARD MAURITIUS AND THEN REUNION ISLAND. AFTER ITS PASSING BY THE REUNION ISLAND, BERGUITTA WILL CONTINUE TRACKING SOUTHWESTWARD BEFORE TRACKING SOUTHWARDS. LATER, HIGH PRESSURE FURTHER SOUTH SHOULD SLOW DOWN THE MOVING OF BERGUITTA, AND NEXT THE SYSTEM BERGUITTA SHOULD FOLLOW THE MID-LATITUDE CIRCULATION. THE SYSTEM IS EXPERIENCING A MODERATE NORTHEASTERN VERICAL WINDSHEAR OVER THE NORTHEASTERN EDGE OF THE AFOREMENTIONED RIDGE. BUT THE EFFECTS OF THIS CONSTRAINT SHOULD BE ATTENUED AS THE SYSTEM ACCELERATES TOWARD THE SAME DIRECTION. AT THE SAME TIME, THE UPPER LEVEL DIVERGENCE IS FORECASTED TO REMAIN GOOD WITH AN EFFICIENT POLERWARD CHANNEL. SO THE SYSTEM SHOULD KEEP THE SEVERE TROPICAL STATUS WHEN IT WILL TRANSIT NEAR THE MAURITIUS AND REUNION ISLAND. FROM SATURDAY, NORTHWESTWARD VERTICAL WINDSHEAR IS FORECASTED TO INCREASE AHEAD AN UPPER LEVEL TROUGH AND WEAKEN SIGNIFICANTLY BERGUITTA. HOWEVER THE WEAKENING OF THE LAST 24 HOURS BERGUITTA REMAINS A VERY DANGEROUS SYSTEM WHICH IS FORECAST TO MOVE CLOSER MAURICE AND REUNION ISLANDS AT A SIGNIFICANT INTENSITY. INHABITANTS ARE INVITED TO MONITOR CLOSELY THE EVOLUTION OF THIS SYSTEM IN THE NEXT DAYS.=