The 2017–18 South-West Indian Ocean cyclone season was a below-average season that produced only 8 tropical storms, of which 6 became tropical cyclones. It was an event in the annual cycle of a tropical cyclone and subtropical cyclone formation. It officially began on 15 November 2017, and officially ended on 15 May 2018, in Mauritius and the Seychelles. For the rest of the basin, the season ended on 30 April 2018. 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 La Réunion.
Seasonal Summary
Despite the season officially beginning on 15 November 2017, the basin featured no tropical systems in November and December, owing to below-average sea surface temperatures and a period of enhanced trade winds causing conditions across the basin to be unfavorable for tropical cyclogenesis. This made the 2017–18 season the third in a row to not feature a tropical system before 1 January. The first system, Tropical Cyclone Ava, became a tropical disturbance only on 1 January 2018, placing 2017–18 in the five latest-starting seasons since the satellite era began in 1967. January, however, was very active with four named systems developing (including Irving which entered the basin from the Australian region); Berguitta and Cebile in particular would become intense tropical cyclones on Météo-France La Réunion's scale. This tied with 1968 for the most active January, and ranked just behind February 1971 for the most named storms forming in a month.
Following the dissipation of Cebile on 7 February, no cyclone activity occurred in the basin for three weeks. March featured two systems: Dumazile in the first week of the month, and Eliakim in the third. Inactivity settled in again after Eliakim dissipated on 20 March and lasted for a month. The last week of April saw two systems, Fakir and Flamboyan (which entered the basin from the Australian region). The season ended on 1 May—about two weeks later than normal—with the dissipation of Flamboyan. Overall, the season featured near-normal activity with eight named storms (compared to the average of nine). However, a larger-than-normal fraction of these named storms reached tropical cyclone status. The season also featured greater than usual impact on land areas, as most of the systems formed in the western part of the basin and were thus in closer proximity to land. The Mascarene Islands were especially hard-hit, particularly Réunion which suffered the effects of five cyclones.
Effects on Réunion
The season had a large-scale impact across Réunion, with five cyclones: Ava, Berguitta, Dumazile, Eliakim, and Fakir, affecting the island. Accumulating rainfall from the cyclones generated ravines which prevented employees from getting to work and caused significant damage to small-scale fishing operations, agriculture, roads, houses, and public infrastructure. Preliminary assessments of damage totaled at least €15 million (US$17.6 million), however, the final total was expected to be significantly greater. In May 2018, electrical and water companies were conducting repairs on a daily basis. Repairs were also taking place to cliffs. Berguitta and Fakir damaged the Wolmar and Tamarin beaches by displacing sand.
Fakir furthered the losses of Berguitta in the towns of Tampon, Saint-Louis, Petite-Ile, and Saint-Joseph. The rising Saint-Etienne river completely destroyed the Ouaki bridge and over of roadway near Saint-Louis. The torrential rainfall from Fakir stalled reconstruction efforts for the third time that year. A trail linking Bois Court and Grand Bassin was scheduled to reopen in April 2018 after having been closed since 12 February 2018. Work to stabilize cliffs, following heavy rainfall from Berguitta and Dumazile, took place in March. The Dos d'Ane-Deux Bras trail, which was damaged by Ava, Berguitta, Dumazile, and Fakir, reopened on 17 July 2018. Several landslides occurred on the RN5 highway, the only major road to Cilaos, after Ava, Berguitta, and Dumazile, resulting in the road being closed for over four months. Work to repair two bridges was halted as a result of a ban on large machinery in the river and threats of criminal prosecution against the workers. Protests erupted on 7 March 2018 as a result of the halted work.