WTIO30 FMEE 191237 RSMC / TROPICAL CYCLONE CENTER / LA REUNION TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN) 0.A WARNING NUMBER: 34/8/20152016 1.A TROPICAL CYCLONE 8 (FANTALA) 2.A POSITION 2016/04/19 AT 1200 UTC: WITHIN 15 NM RADIUS OF POINT 9.4 S / 50.4 E (NINE DECIMAL FOUR DEGREES SOUTH AND FIFTY DECIMAL FOUR DEGREES EAST) MOVEMENT : EAST-SOUTH-EAST 4 KT 3.A DVORAK ANALYSIS: 4.0/4.5/W 1.0/6 H 4.A CENTRAL PRESSURE: 973 HPA 5.A MAX AVERAGE WIND SPEED (10 MN): 70 KT RADIUS OF MAXIMUM WINDS (RMW) :41 KM 6.A EXTENSION OF WIND BY QUADRANTS (KM): 28 KT NE: 240 SE: 250 SW: 240 NW: 280 34 KT NE: 150 SE: 70 SW: 90 NW: 120 48 KT NE: 100 SE: 60 SW: 70 NW: 90 64 KT NE: 60 SE: 60 SW: 60 NW: 60 7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1009 HPA / 500 KM 8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP 1.B FORECASTS: 12H: 2016/04/20 00 UTC: 10.0 S / 51.3 E, MAX WIND=060 KT, SEVERE TROPICAL STORM 24H: 2016/04/20 12 UTC: 10.8 S / 52.5 E, MAX WIND=055 KT, SEVERE TROPICAL STORM 36H: 2016/04/21 00 UTC: 12.0 S / 53.6 E, MAX WIND=050 KT, SEVERE TROPICAL STORM 48H: 2016/04/21 12 UTC: 12.8 S / 54.2 E, MAX WIND=050 KT, SEVERE TROPICAL STORM 60H: 2016/04/22 00 UTC: 13.3 S / 54.5 E, MAX WIND=045 KT, MODERATE TROPICAL STORM 72H: 2016/04/22 12 UTC: 13.3 S / 54.2 E, MAX WIND=045 KT, MODERATE TROPICAL STORM 2.B LONGER-RANGE OUTLOOK : 96H: 2016/04/23 12 UTC: 12.6 S / 52.8 E, MAX WIND=040 KT, MODERATE TROPICAL STORM 120H: 2016/04/24 12 UTC: 12.0 S / 50.9 E, MAX WIND=040 KT, MODERATE TROPICAL STORM 2.C ADDITIONAL INFORMATION: T=4.0- CI=4.5 DURING THE PAST 6 HOURS, THE CONVECTION FELL APART NEAR THE CENTER OF THE SYSTEM, LEAVING A WIDE EYE PATTERN ON THE VIS IMAGES. LAST IR IMAGES LET AN OBVIOUS WEAKNESS APPEAR IN THE SOUTH-WESTERN QUADRANT, RATHER SUGGESTING AN EVOLUTION TOWARDS A CURVED BAND PATTERN. 1121Z SSMI MW DATA REVEAL THAT CONVECTION REMAINS STRONG AND RELATIVELY SYMMETRIC AROUND THE CENTER. THUS, AMONG NEUTRAL TO SLIGHTLY CONDUCIVE ATMOSPHERIC CONDITIONS, FANTALA'S CURRENT WEAKENING IS PROBABLY DUE TO A LACK OF OCEANIC ENERGY. FROM TODAY AND UNTIL THURSDAY, FANTALA'S TRACK WILL BE STEERED BY TWO ATMOSPHERIC PATTERNS : THE NEAR EQUATORIAL RIDGE BUILDING IN ITS NORTH-EAST AND A WIDE MID-LATITUDES TROUGH COMING FROM THE SOUTH-WEST. UNDER THIS DOUBLE INFLUENCE, THE PREDICTABILITY OF THE EAST-SOUTH-EASTWARD TRACK IS QUITE HIGH AND THE MODEL GUIDANCE IS THUS IN AGREEMENT. FROM THURSDAY EVENING, NONE OF THE AVAILABLE MODELS ALLOW FANTALA TO REACH THE TROUGH, WHICH IS AN EXIT DOOR TOWARDS THE MID-LATITUDES. A NEW HIGH GEOPOTENTIAL CELL FOLLOWING THE TROUGH IS FORECASTED TO SETTLE OVER THE SOUTHERN MOZAMBIQUE CHANNEL AND PROGRESSIVELY EXTEND NORTHWARD. FRIDAY, FANTALA SHOULD HEAD NORTH-WESTWARD AGAIN, STEERED BY THIS WIDE RIDGE IN ITS SOUTH-WEST. IN THE END OF THE FORECAST PERIOD, A HIGH GEOPOTENTIAL AREA IS STRENGHTENING AGAIN IN THE EAST. FANTALA IS THEN STUCK BETWEEN THE RIDGE IN ITS SOUTH-WEST WHICH DRIVES IT NORTH-WESTWARD (MAIN STEERING FLOW FOR ECMWF) AND THE HIGH IN ITS EAST WHICH TENDS TO PUSH IT MORE SOUTHWARD (WITH A STRONGER INFLUENCE FOR GFS). THUS, THE UNCERTAINTY BECOMES HIGH FROM FRIDAY. IF THE GFS SCENARIO IS CONFIRMED IN THE NEXT RUNS, THE RISK OF FANTALA MAKING LANDFALL (THOUGH WITH A LOWER INTENSITY THAN THE CURRENT ONE) IN THE NORTHERN REGION OF MADAGASCAR, ALREADY MODERATE, WOULD BECOME HIGH. THE OCEAN HEAT CONTENT IS BEGINNING TO LACK AND REMAINS LOW UNTIL FRIDAY, AS FANTALA IS TRACKING OVER WATERS IT HAS ALREADY COOLED. FROM THURSDAY, THE UPPER LEVEL CONDITIONS ARE LIKELY TO BECOME LESS FAVORABLE EQUATORWARD, WITH A POORER DIVERGENCE AND A WEAK TO MODERATE NORTHERLY TO NORTHEASTERLY CONSTRAINT. THUS, FANTALA INTENSITY IS LIKELY TO DECREASE SLOWLY AND NOT MUCH EVOLVE FROM FRIDAY, AS FANTALA TRACKS AGAIN OVER A LITTLE WARMER WATERS.=