2018–19 South-West Indian Ocean cyclone season
The 2018–19 South-West Indian Ocean cyclone season was a record breaking and devastating season that was the most active season ever recorded in the basin. It was the deadliest cyclone season recorded in the South-West Indian Ocean, surpassing the 1891–92 season in which the 1892 Mauritius cyclone devastated the island of Mauritius, and was the costliest South-West Indian Ocean season at the time until it was surpassed by the 2024-25 season. Most of the fatalities and damage came from Cyclone Idai. The season was an event of the annual cycle of tropical cyclone and subtropical cyclone formation in the South-West Indian Ocean basin. It officially began on 15 November 2018, and ended on 30 April 2019, except for Mauritius and the Seychelles, which it ended on 15 May 2019. These dates conventionally delimit the period of each year when most tropical and subtropical cyclones form in the basin, which is west of 90°E and south of the Equator. Tropical and subtropical cyclones in this basin are monitored by the Regional Specialised Meteorological Centre in Réunion.
The season set a new record of nine intense tropical cyclones, the largest number since the start of reliable satellite coverage in 1967, surpassing the 2006–07 season. Beginning the season early, Moderate Tropical Storm 01 formed during September 2018. Two other systems formed prior to the official start of the season during November—the first intense tropical cyclone and the first named storm, Alcide, and Severe Tropical Storm Bouchra. A pair of intense tropical cyclones—Cilida and Kenanga—persisted in December. In January 2019, Desmond caused damages in Mozambique, and shortly thereafter, Eketsang passed by Madagascar, producing heavy rain and landslides that killed 27. Onto the next month, Funani and Gelena threatened Rodrigues, with the latter disrupting its electricity and causing US$1 million in damages.
The most active and destructive month was March. Haleh remained near the centre of the basin, bringing no impact. Cyclone Idai made two landfalls in Mozambique as a tropical depression and intense tropical cyclone, causing at least 1,593 deaths and leaving at least 2,262 people missing, and causing US$3.3 billion in damages in Mozambique, Zimbabwe, Malawi, and Madagascar. Savannah entered the basin in the middle of the month. Joaninha became the second cyclone of 2019 to strike Rodrigues, destroying the island's power grid. In April, Kenneth became the strongest storm of the season, with maximum sustained winds of ; the storm killed at least 7 people in Comoros and made landfall in Mozambique, causing at least 45 deaths and overall damage of US$345 million. Lorna remained over the eastern portion of the basin, concluding the season after it dissipated on 29 April.
Seasonal forecasts
On 24 October 2018, the Mauritius Meteorological Services released their summer 2018–19 outlook. The agency expected a slightly below to near-average season, predicting that 7 to 9 tropical cyclones would form. In addition, the MMS indicated that conditions in the central tropical Indian Ocean and between Diego Garcia and Agaléga, or west of the 70th meridian east, would be more conducive for tropical cyclogenesis. Also in October, the Indian Ocean Commission and the European Centre for Medium-Range Weather Forecasts forecasted a near-average season. ECMWF gave an index of 8.1 systems before revising it the next month to 7.3.Météo-France announced their seasonal forecast of tropical cyclone activity on 15 November, after the formation of 01, Alcide, and Bouchra, comparing the sudden start to the 1996–97 season. Despite this, the MFR forecasted a nearly-average season, citing the conditions of an El Niño event. Compared to an average of ten moderate tropical storms that usually form in the South-West Indian Ocean, MFR expected that 8 to 11 systems would form, with 4 to 6 of them reaching the tropical cyclone stage. A 20% chance was given to the probability of below-average activity, a 60% chance was given to near-average activity, and a 20% chance was given to above-average activity. The agency indicated that cyclogenesis would mainly occur over the central Indian Ocean and western portion of the basin. MFR also predicted that the motion of cyclones during the season would have a stronger meridional component than normal, having a tendency to track south quickly.
The forecasts from the MFR failed to predict enhanced activity over the Mozambique Channel and hypothesised that most of the energy for cyclone formation was caused by strong equatorial waves activity. For future operations, MFR planned to target inhabited areas.
Seasonal summary
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The 2018–19 South-West Indian Ocean cyclone season officially ran from 15 November 2018 to 30 April 2019, with the exception for the island nations of Mauritius and Seychelles, which ended on 15 May 2019. Collectively, the systems caused 1,675 deaths and about $3.65 billion in damage, and is mainly attributed to Cyclone Idai, which caused 1,593 deaths and $3.3 billion in damages. Throughout the season, 15 tropical disturbances formed, all of which reached the moderate tropical storm stage. Eleven of these storms attained tropical cyclone status, and all but two—Savannah and Lorna—reached the intense tropical cyclone stage, breaking the previous record of having the most intense tropical cyclones held by the 2006–07 season, which had six. Regardless of the activity, there were no systems in this season that acquired the strength of a very intense tropical cyclone—the highest classification in MFR's intensity scale.
Météo-France's meteorological office in Réunion – the official Regional Specialised Meteorological Centre for the South-West Indian Ocean – tracked all tropical cyclones from the east coast of Africa to 90° E, and south of the equator. Regional warning centres in Mauritius and Madagascar formally named the individual storms. The Joint Typhoon Warning Center, which is a joint United States Navy – United States Air Force task force that issues tropical cyclone warnings for the region, also issued advisories for storms during the season.
Pre/early season activity
The season abruptly began with the formation of Moderate Tropical Storm 01 on 14 September 2018. After two months of inactivity, a tropical disturbance formed. This system developed into a tropical depression and then to a tropical cyclone on 7 November, receiving the name Alcide. After affecting the dependency of Agaléga, the storm steered northwestward, and concurrently, a tropical disturbance at the eastern border of the basin formed on 9 November. As Alcide dissipated on 11 November, with its remnants last noted on 14 November, the embryonic system oscillated around the 90th meridian east for several days. The disturbance intensified into Severe Tropical Storm Bouchra during the period, and eventually stayed within the basin on 17 November, before dissipating on 20 November.Two storms emerged in the month of December: Kenanga and Cilida. The former entered the basin from the Australian region on 16 December, whereas the latter developed from the monsoon trough to a tropical depression two days later. Kenanga attained intense tropical cyclone status on 18 December, as Cilida headed towards Mauritius. Simultaneously on 20 December, both storms were tropical cyclones within the basin, the first such case since the 2013–14 season. Also peaking as an intense tropical cyclone, Cilida brought slight impact towards Mauritius. Both storms then weaken and had dissipated by 24 December.