Very Intense Tropical Cyclone Fantala was the most intense tropical cyclone recorded in the South-West Indian Ocean in terms of sustained winds. Part of the 2015–16 cyclone season, Fantala formed on 11 April to the south of Diego Garcia, an island in the central Indian Ocean. With a ridge to the south, the storm moved westward for several days while gaining strength, aided by warm waters and decreasing wind shear. Late on 17 April, the Météo-France office on Réunion (MFR) estimated peak 10-minute winds of , making Fantala the strongest tropical cyclone of the basin in terms of 10-minute sustained winds. The Joint Typhoon Warning Center (JTWC) estimated peak 1-minute winds of , equivalent to Category 5 intensity on the Saffir-Simpson scale, also the strongest on record in the South-West Indian Ocean, in terms of maximum sustained wind speed. Early on 18 April, Fantala reached its peak intensity, with a minimum central pressure of .
While near peak intensity, Fantala passed near the Farquhar Group of the Seychelles, damaging most of the buildings in the small archipelago. Later on 18 April, Fantala had weakened to an intense tropical cyclone and slowed its forward motion, eventually reversing its direction of movement. After fluctuating in strength, the disorganized system reversed direction again, making its closest approach to Madagascar. Fantala degenerated into a remnant low on 24 April, and the remnants continued toward Tanzania. There, heavy rainfall resulted in flooding that washed away roads and houses, killing 13 people. Rains extended further into Kenya, with similar effects.
Meteorological history
On 9 April, an area of disturbed weather persisted to the southeast of Diego Garcia. The system moved generally westward, steered by a ridge, and a low-level circulation gradually became more defined. Limiting factors to faster development included poor inflow and moderate wind shear, although associated convection became more organized. At 06:00 UTC on 11 April, the Regional Specialized Meteorological Center Météo-France in La Réunion (MFR) classified the system as Tropical Disturbance 8 about south of Diego Garcia. Six hours later, the agency upgraded the system to a tropical depression. At 13:00 UTC on 11 April, the American-based Joint Typhoon Warning Center (JTWC) issued a tropical cyclone formation alert, noting the increased organization of the convection, circulation, and outflow. Later that day, the MFR upgraded the depression to Moderate Tropical Storm Fantala, and the JTWC classified it as Tropical Cyclone 19S. By that time, the convection was quickly consolidating around the center, organizing into a circular central dense overcast.
On 12 April, the previously detrimental wind shear began easing, allowing the structure to become more symmetric. On that day, an eye feature began developing in the center of Fantala, indicative of strengthening. At 12:00 UTC on 12 April, the MFR upgraded Fantala to severe tropical storm status, and six hours later, the JTWC upgraded it to the equivalent of a minimal hurricane, with 1 minute maximum sustained winds of ; rapid strengthening was prevented by the entrainment of nearby dry air, although the core of convection continued to contract. At 06:00 UTC on 13 April, the MFR upgraded Fantala to tropical cyclone status, with 10 minute winds of . By that time, the eye feature persisted, consisting of a warm area within the deepest convection, although the dry air in the region prevented quicker strengthening.
By early on 14 April, the eye became better defined after an eyewall replacement cycle. The intensity fluctuated after outflow decreased to the north, although increasingly warm waters favored further intensification. Early on 15 April, the MFR upgraded Fantala to an intense tropical cyclone, as the storm rapidly deepened. The outflow was enhanced by a large upper-level low well to the southeast, and shear had decreased to a minimum. After reaching an initial peak intensity with 10-minute sustained winds of at 12:00 UTC that day, Fantala's intensity leveled off for the following 48 hours, with its 10-minute sustained winds fluctuating between .