WTIO30 FMEE 201838 RSMC / TROPICAL CYCLONE CENTER / LA REUNION TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN) 0.A WARNING NUMBER: 39/8/20152016 1.A TROPICAL CYCLONE 8 (FANTALA) 2.A POSITION 2016/04/20 AT 1800 UTC: WITHIN 20 NM RADIUS OF POINT 11.6 S / 54.3 E (ELEVEN DECIMAL SIX DEGREES SOUTH AND FIFTY FOUR DECIMAL THREE DEGREES EAST) MOVEMENT : SOUTH-EAST 9 KT 3.A DVORAK ANALYSIS: 4.5/5.0/W 0.5/6 H 4.A CENTRAL PRESSURE: 968 HPA 5.A MAX AVERAGE WIND SPEED (10 MN): 80 KT RADIUS OF MAXIMUM WINDS (RMW) :30 KM 6.A EXTENSION OF WIND BY QUADRANTS (KM): 28 KT NE: 130 SE: 110 SW: 110 NW: 140 34 KT NE: 70 SE: 70 SW: 70 NW: 80 48 KT NE: 60 SE: 60 SW: 60 NW: 70 64 KT NE: 50 SE: 50 SW: 50 NW: 60 7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1007 HPA / 300 KM 8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP 1.B FORECASTS: 12H: 2016/04/21 06 UTC: 12.3 S / 55.1 E, MAX WIND=070 KT, TROPICAL CYCLONE 24H: 2016/04/21 18 UTC: 13.2 S / 55.6 E, MAX WIND=060 KT, SEVERE TROPICAL STORM 36H: 2016/04/22 06 UTC: 13.3 S / 55.4 E, MAX WIND=050 KT, SEVERE TROPICAL STORM 48H: 2016/04/22 18 UTC: 13.1 S / 54.9 E, MAX WIND=040 KT, MODERATE TROPICAL STORM 60H: 2016/04/23 06 UTC: 12.6 S / 53.5 E, MAX WIND=035 KT, MODERATE TROPICAL STORM 72H: 2016/04/23 18 UTC: 12.0 S / 52.2 E, MAX WIND=035 KT, MODERATE TROPICAL STORM 2.B LONGER-RANGE OUTLOOK : 96H: 2016/04/24 18 UTC: 10.4 S / 49.1 E, MAX WIND=030 KT, TROPICAL DEPRESSION 120H: 2016/04/25 18 UTC: 9.0 S / 45.2 E, MAX WIND=025 KT, LOW 2.C ADDITIONAL INFORMATION: T=4.5+ CI=5.0+ OVER THE PAST 6 HOURS, FANTALA'S WIDE EYE APPEARED MORE AND MORE RAGGED ON IR IMAGES. THIS LOSS OF ORGANISATION HAS BEEN COMPENSATED BY COLDER CLOUD TOPS. 1545Z SSMIS MW IMAGES SHOW THAT FANTALA'S GENERAL STRUCTURE HAS NOT MUCH EVOLVED, EXCEPT A LIGHT CONTRACTION OF THE MAX WINDS RADIUS. NO MAJOR CHANGE IN THE TRACK FORECAST : UNTIL THURSDAY EVENING, 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 SOUTH OF MADAGASCAR AND PROGRESSIVELY EXTEND NORTHWARD. FANTALA SHOULD SLOW AGAIN OR EVEN REMAINS STATIONARY ON FRIDAY BEFORE TRACKING NORTH-WESTWARDS, STEERED BY THIS WIDE RIDGE IN ITS SOUTH-WEST. THEN, UNTIL THE END OF THE FORECAST PERIOD, THE SYSTEM IS LIKELY TO REMAIN STEERED BY THIS HIGH SUBTROPICAL CELL IN THE LOW AND MID TROPOSPHERE, AND SHOULD KEEP ON A NORTH-WESTWARDS TRACK. ON THIS PART OF THE TRACK, THE AGREEMENT BETWEEN THE MODELS IS A BIT LOWER WITH THE GFS TRACK STILL MORE SOUTHWARD THAN THE ECMWF ONE. AS IT HEADS BACK ON ITS TRACK, FANTALA IS CURRENTLY PASSING OVER ITS POSITION OF 4 DAYS AGO. THE SYSTEM IS EXPECTED TO STAY WITHIN THE AREA PREVIOUSLY COOLED BY ITSELF UNTIL TOMORROW AFTERNOON. THIS LACK OF OCEANIC ENERGY SHOULD GRADUALLY WEAKEN THE SYSTEM THROUGHOUT THIS PERIOD. WITH A NEW SLOW TRACK TURN EXPECTED FRIDAY OVER A LOW OHC AREA AND SIGNIFICANTLY LESS FAVORABLE ATMOSPHERIC CONDITIONS (WEAKENING OF THE UPPER LEVEL DIVERGENCE ESPECIALLY EVEN ON THE POLAR SIDE, INCREASE OF THE NORTHERLY SHEAR MORE SIGNIFICANTLY AT THE END OF THE FORECAST PERIOD WHEN IT TURNS WESTERLY, VERY DRY MID-LEVEL AIR MASS SURROUNDING THE SYSTEM FROM FRIDAY AND BEYOND), FANTALA'S ENVIRONMENT SHOULD LEAD TO A SUSTAINED WEAKENING OVER THE WEEK-END AND FURTHER. THIS INTENSITY FORECAST IS CONSISTENT WITH THE DECREASE OF THE STORM SIGNAL IN THE ECMWF ENSEMBLE PREDICTION FROM SATURDAY EVENING.=