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. __TOC__
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.
New crops planted in the aftermath of Cyclone Berguitta were largely destroyed by Cyclone Dumazile just a few weeks later. At that point, the island had experienced nearly three months of continuous rainfall, with only ten dry days. Several items, including salads, zucchini, paracress, carrots, and tomatoes, were expected to have shortages or be entirely unavailable. Three systems, mainly Fakir, caused significant damage to sugar canes. Estimates for the sugar harvest fell to , the lowest since Cyclone Gamede affected Réunion in 2007. These losses represent at least 20 percent of the sugar cane production. The actual sugar harvest was less than forecast, reaching , which was the worst harvest in over fifty years. Berguitta, Fakir, and other significant rainfall events caused €39.3 million (US$46.5 million) in agricultural losses. The Réunion prefecture government allocated €41.5 million (US$49.1 million in aid for farms that experiences losses due to the aforementioned weather events and the Yellow Vest protests that took place during November 2018. An additional €16 million (US$18.9 million) in aid was approved for investment projects, farmer income increases, the creation of employment opportunities, and the reduction of prices.
In March 2019, the General Confederation of Planters and Breeders of Réunion Island requested that the agricultural minister to increase the dispersal rate for the aid package to help with recovery efforts. Aid of €2,000 (US$2,350) per was also promised for some farms, however, the dispersal of the aid was slow. Following Fakir, vegetable prices were expected to increase once again. An additional €2.3 million (US$2.7 million) in aid was authorized by 2 May 2018 by the Réunion Departmental Council. At least 95 farmers had received at least €220,000 (US$258,800) in aid for damage sustained during the season by 11 July 2018. Agricultural experts anticipated that it would take months or years for farmers to recuperate the losses sustained during the cyclone season.
After Ava, Berguitta, Dumazile, and Fakir, the mayor of Sainte-Suzanne called for an emergency meeting of the Association of Mayors of Reunion Island in order to discuss potential solutions to the problems these storms caused. MP David Lorion requested that the Réunion Prefecture government and the Minister of Overseas establish a relief fund to help repair damage sustained by floods and mudslides during cyclones Berguitta and Fakir.
The season had a considerable impact on plans, weather alerts, construction standards, and infrastructure. The Communist Party of Réunion discussed implementing multiple improvements following the season, including redrawing risk areas and construction guidelines and adapting school schedules to the island's climate. Near Saint-Pierre, at least €6.1 million (US$7.3 million) in funds were provided to improve the Chemin Stéphane highway, a roadway used by over 8,500 people per day, by constructing better drainage networks, new sidewalks, and a new driving surface. The Réunion Prefecture government assembled a meeting of the mayors on 4 May 2018 to discuss implementing a new warning system for the next cyclone season. A new purple alert was created for cyclones affecting the island with winds in excess of 200 km/h (125 mph). The warning system was also modified to allow for warning declarations as a result of severe rainfall. Repair work at the Bras de Cilaos following Berguitta was halted following torrential rainfall during Cyclone Dumazile. Protests erupted in Cilaos because the postponement of work left 400 people isolated on the other side of the city and 100 more at Îlet Furçy.
Systems Tropical Cyclone Ava
An area of low pressure formed on 27 December 2017 and was classified as a tropical disturbance by Météo-France La Réunion (MFR) on 30 December. It became Moderate Tropical Storm Ava on 2 January 2018 and intensified to reach peak intensity with 10-minute sustained winds of , 1-minute sustained winds of , and a central pressure of on 5 January. Ava made landfall over Madagascar shortly after and reemerged over water as a weak tropical storm on 7 January. It became post-tropical on 8 January and dissipated the next day.
Ava severely impacted Madagascar, causing at least 73 fatalities. Ava combined with the seasonal monsoon to inflict US$195 million in losses across the country. At least 51,000 people were left homeless in Ava's wake. Over a dozen healthcare facilities were destroyed and nearly 150 schools were impacted. Several dozen classrooms were used as shelters for over 20 thousand people who were displaced by the storm, and over thirty thousand students were unable to go to school. Flooding and landslides forced thousands of people to evacuate across the capital city of Antananarivo, Brickaville, Toamasina, Mananjary, and Ifanadiana. The storm caused significant damage to infrastructure across the country, with floods washing away bridges and damaging roadways. Heavy rainfall also occurred in Mauritius, flooding roads and houses. The rainfall either damaged or destroyed thirty-to-fifty percent of crops across local plantations.
Tropical Cyclone Irving
Tropical Cyclone Irving was named by the Bureau of Meteorology of Australia on 6 January as it crossed over into the South-West Indian Ocean basin a few hours later. It strengthened to an equivalent of a Category 2 cyclone, before weakening as it turned southwestwards. It became post-tropical on 9 January as it dissipated to the west of Madagascar. It stayed well from land.
Intense Tropical Cyclone Berguitta
Berguitta formed on 11 January and dissipated on 19 January.
Berguitta brought damaging winds and torrential rainfall to Rodrigues. The island received nearly a quarter of its average annual rainfall during 13–15 January. As a result, severe, widescale flooding ensued, most notably in low-lying regions. Felled trees damaged powerlines and floodwaters blocked roads. On Mauritius Island, two days of nonstop rainfall from 17 to 18 January also resulted in severe flooding. The floodwaters damaged around 75–80 percent of the island's agriculture and damaged buildings. Water utilities in the capital of Port Louis were disrupted by the storm, and around 6,800 residences lost power as trees fell on electrical cables. Two people died on the island: one person fell off of a ladder and another was killed in a traffic accident. At least ₨ 2 billion (US$58 million) in economic losses occurred across the island nation. The Mauritian government allocated relief funds to at least 13,000 citizens. Protests erupted twice in the country: the first occurred as a result of delayed and small relief fund payments, and the second occurred several months later as a result of families being evicted from disaster evacuation centers.