WTIO30 FMEE 120030 RSMC / TROPICAL CYCLONE CENTER / LA REUNION TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN) 0.A WARNING NUMBER: 4/8/20152016 1.A MODERATE TROPICAL STORM 8 (FANTALA) 2.A POSITION 2016/04/12 AT 0000 UTC: WITHIN 20 NM RADIUS OF POINT 13.2 S / 70.3 E (THIRTEEN DECIMAL TWO DEGREES SOUTH AND SEVENTY DECIMAL THREE DEGREES EAST) MOVEMENT : WEST 8 KT 3.A DVORAK ANALYSIS: 3.0/3.0/D 0.5/12 H 4.A CENTRAL PRESSURE: 998 HPA 5.A MAX AVERAGE WIND SPEED (10 MN): 40 KT RADIUS OF MAXIMUM WINDS (RMW) :32 KM 6.A EXTENSION OF WIND BY QUADRANTS (KM): 28 KT NE: 40 SE: 170 SW: 190 NW: 70 34 KT NE: SE: 60 SW: 70 NW: 40 7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1008 HPA / 400 KM 8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP 1.B FORECASTS: 12H: 2016/04/12 12 UTC: 13.3 S / 69.3 E, MAX WIND=045 KT, MODERATE TROPICAL STORM 24H: 2016/04/13 00 UTC: 13.2 S / 68.2 E, MAX WIND=050 KT, SEVERE TROPICAL STORM 36H: 2016/04/13 12 UTC: 13.2 S / 66.8 E, MAX WIND=055 KT, SEVERE TROPICAL STORM 48H: 2016/04/14 00 UTC: 12.8 S / 65.4 E, MAX WIND=065 KT, TROPICAL CYCLONE 60H: 2016/04/14 12 UTC: 12.5 S / 63.7 E, MAX WIND=070 KT, TROPICAL CYCLONE 72H: 2016/04/15 00 UTC: 12.2 S / 62.0 E, MAX WIND=075 KT, TROPICAL CYCLONE 2.B LONGER-RANGE OUTLOOK : 96H: 2016/04/16 00 UTC: 12.0 S / 59.4 E, MAX WIND=075 KT, TROPICAL CYCLONE 120H: 2016/04/17 00 UTC: 11.4 S / 57.8 E, MAX WIND=075 KT, TROPICAL CYCLONE 2.C ADDITIONAL INFORMATION: T=CI=3.0- OVER THE LAST 6 HOURS, THE SYSTEM CONTINUED TO INTENSIFY. CLOUD PATTERN EVOLVED AGAIN, WITH THE BUILDING OF A CURVED BAND. UPPER LEVEL DIVERGENCE IS STILL EXCELLENT ESPECIALLY ON THE POLAR SIDE. LAST MICROWAVE DATA (AMSR2 2034Z) SHOW A SINGIIFCANT IMPROVEMENT OF THE LLCC. THANKS TO THE DECAY OF THE EASTERLY CONSTRAINT WITH FANTALA ACCELARATION, THE SYSTEM IS MORE SYMMETRIC. DEEP CONVECTION BEGIN TO WRAP ALL AROUND THE CENTER. THE SYSTEM IS MOVING OVER THE NORTHERN EDGE OF THE LOW TO MID LEVEL HIGHS LOCATED TO ITS SOUTH AND SOUTH-WEST. WITHIN THE NEXT DAYS, THIS HIGHS SHOULD MAINTAIN TO THE SOUTH-WEST OF THE SYSTEM AND A WEAKNESS IS EXPECTED TO BUILD BETWEEN 70E AND 80E. THEREFORE, THE TRACK SHOULD BEND TOWARDS THE WEST-NORTH-WEST OVER THE NORTHEASTERN EDGE OF THE SUBTROPICAL RIDGE. SATURDAY A DEEP MID-LAT HIGH TO MID LEVEL TROUGH SHOULD DEEP FURTHER THE WEAKNESS OF THE SUBTROPICAL RIDGE EVEN EXTENDING IT WESTWARDS UP TO 65E. IN RESPONSE, THE SOME MODEL PARTICULARLY GFS SLOW DOWN AND THEN STOP THE WESTWARDS MOTION THIS WEEK-END, AS THE SYSTEM BANG INTO A NORTHWARD STRETCHED SUBTROPICAL RIDGE TO ITS WEST. BUT, FOR NOW THIS TRAJECTORY CHANGE IS STILL UNCERTAIN, AS DESCRIBED BY THE LAST ECMWF EPS. SOME MEMBERS LIKE THE DETERMINISTIC DELAY THIS COMEBACK, WHILE THE MAJORITY (FASTER MEMBERS MOSTLY) SUGGEST THE CONTINUATION OF THE ZONAL TRACK. THE PRESENT FORECAST IS AN INTERMEDIATE SCENARIO IN TERMS OF SPEED, CLOSE TO THE ECMWF DETERMINISTIC. WHILE THE ENVIRONMENT IS EXPECTED TO REMAIN MORE OR LESS THE SAME DURING THE NEXT 24 HOURS, DEEPENING IS LIKELY TO BE LIMITED BY THE SLIGHT EASTERLY VWS, IN A DRYER SURROUNDING AIR MASS. THURSDAY, FANTALA SHOULD FOUND CONDUCIVE CONDITIONS FOR A STRONG DEEPENING UNDER THE RIDGE. SATURDAY, THE UPPER LEVEL DIVERGENCE SHOULD BECOME MARGINAL EQUATORWARDS (BUT STILL GOOD TO THE SOUTH) AND A NORTHWESTERLY CONSTRAINT IS EVEN POSSIBLE. COMBINED WITH A POTENTIAL SELF INDUCED COOLING OF THE SST DUE TO THE SLOW FORWARD MOTION, AT LEAST A TEMPORARY WEAKENING TREND IS POSSIBLE NEAR THE END OF THE FORECAST PERIOD.=