Cyclone Dumazile

South-West Indian cyclone in 2018

Intense Tropical Cyclone Dumazile
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Part of the 2017–18 South-West Indian Ocean cyclone season

Intense Tropical Cyclone Dumazile was a strong tropical cyclone that brought flooding to Madagascar and Réunion in early March 2018. Dumazile originated from an area of low pressure that formed in the South-West Indian Ocean near Agaléga on 27 February. The system concentrated into a tropical disturbance on 2 March and was named the next day, as it intensified into a tropical storm. Amid conditions conducive for intensification, Dumazile strengthened over the next two days and reached peak intensity on 5 March as an intense tropical cyclone, with 10-minute sustained winds of 165 km/h (105 mph), 1-minute sustained winds of 205 km/h (125 mph), and a central pressure of 945 hPa (27.91 inHg). The system weakened steadily over the next couple days because of increasing wind shear as it tracked to the southeast. Dumazile became post-tropical on 7 March and eventually dissipated completely on 10 March near the Kerguelen Islands.

Cyclone Dumazile affected Réunion less than two months after Cyclone Berguitta, halting ongoing repairs to bridges and reconstruction efforts. Torrential rainfall, reaching 1,600 mm (63 in) in Salazie, caused significant flooding across the island. Floodwaters, landslides, and downed trees caused significant damage and disruption to the road network on Réunion, particularly in coastal and mountainous areas. Repairs to the highway between Îlet Furçy and Cilaos were set back significantly. Large waves along the coast caused erosion, leading to collapses of beachfront infrastructure and beach closures. Ports were also damaged by the waves, and the Port of Saint-Gilles was clogged by debris. The agricultural sector incurred about €3 million (US$3.73 million; equivalent to $4.53 million in 2023) of damage, as crops were destroyed by floods and gusty winds. Recovery in Réunion was later hampered further by Cyclone Fakir in April.

The northern and eastern coasts of Madagascar experienced about 210 mm (8.3 in) of rain. Flooding occurred in Toamasina as a result of malfunctioning drainage systems which had been damaged by Cyclone Ava in January. Parts of the city lost power during the storm. Severe flooding in the Diana Region blocked roadways, inundated homes, and damaged crops. The RN6 highway in particular experienced several accidents and breakdowns, and a 18 m (59 ft) section of the road collapsed. Strong winds in coastal towns resulted in fallen trees, beach erosion, and damage to property and infrastructure. The Ambalavola District was left underwater, with sewage flowing through neighborhoods. Two people died in Madagascar during the storm: one in Ankorondrano and the other in Ambatoroka.

Meteorological history

A large region of unsettled weather along the Intertropical Convergence Zone spawned a broad area of low pressure in the South-West Indian Ocean near Agaléga on 27 February 2018.[1][2] The system became more concentrated and well-defined as it drifted between Agaléga and Tromelin Island,[3] leading Météo-France La Réunion (MFR) to classify it as a Zone of Disturbed Weather at 00:00 UTC on 1 March.[4][nb 1] That night increased thunderstorm activity in conjunction with an easterly wind burst furthered development,[6] and the MFR reported that the system became Tropical Disturbance 06 at 06:00 UTC on 2 March.[4] At the same time, the Joint Typhoon Warning Center (JTWC) classified the system as a tropical depression.[7][nb 2] The incipient disturbance underwent a small clockwise loop over the rest of 2 March, amid opposing steering flows from the north and south.[9] During that time the disturbance's organisation increased, with the development of a curved rainband. The MFR noted the surrounding atmospheric environment to be quite conducive to strengthening, with low wind shear, high relative humidity values, and pronounced outflow channels.[10] The JTWC stated that the system had become a tropical storm at 12:00 UTC on 2 March, as it began producing 1-minute sustained winds of 65 km/h (40 mph).[7] The MFR also upgraded the system to a tropical storm at 00:00 UTC on 3 March, based on scatterometer data, upon which it received the name Dumazile.[11]

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Map plotting the storm's track and intensity, according to the Saffir–Simpson scale
  Tropical depression (≤38 mph, ≤62 km/h)
  Tropical storm (39–73 mph, 63–118 km/h)
  Category 1 (74–95 mph, 119–153 km/h)
  Category 2 (96–110 mph, 154–177 km/h)
  Category 3 (111–129 mph, 178–208 km/h)
  Category 4 (130–156 mph, 209–251 km/h)
  Category 5 (≥157 mph, ≥252 km/h)
  Unknown
Storm type
circle Tropical cyclone
square Subtropical cyclone
triangle Extratropical cyclone, remnant low, tropical disturbance, or monsoon depression