In the south-west Indian Ocean, tropical cyclones form south of the equator and west of 90° E to the coast of Africa.
Warnings and nomenclature In 1946, Réunion's first airstrip opened, then called Gillot, and now called Roland Garros Airport. In 1950, the first meteorological station on the island opened at the airport, operated by Météo-France (MFR). The agency began publishing annual reviews in the 1962–63 season. Each year, the Météo-France office (MFR) based on Réunion island issues warnings on tropical cyclones within the basin, which is defined as the waters of the Indian Ocean from the coast of Africa to 90° E, south of the equator. The agency issues the warnings as part of its role as a Regional Specialized Meteorological Center, designated as such in 1993 by the World Meteorological Organization. Intensities are estimated through the Dvorak technique, which utilizes images from satellites by the American National Oceanic and Atmospheric Administration.
The Joint Typhoon Warning Center – a joint United States Navy – United States Air Force task force – also issues tropical cyclone warnings for the region. Wind estimates from Météo-France and most other basins throughout the world are sustained over 10 minutes, while estimates from the United States–based Joint Typhoon Warning Center are sustained over 1 minute. 1-minute winds are about 1.12 times the amount of 10-minute winds.
If a tropical storm in the basin strengthens to attain 10 minute sustained winds of at least , the MFR classifies it as a tropical cyclone, equivalent to a hurricane or typhoon (a use of "tropical cyclone" which is more restrictive than the usual definition).
History of the basin The first storm in the MFR database of the basin originated on January 11, 1848. In January 1960, the first named storm was Alix, and each subsequent year had a list of storm names. Beginning in 1967, satellites helped locate cyclones in the basin, and in the following year, the MFR began estimating storm intensities from the satellite images. By 1977, the agency was using the Dvorak technique on an unofficial basis, but officially adopted it in 1981. Originally, the basin only extended to 80° E, and while it was extended eastward to the current 90° E, a lack of satellite imagery initially made data uncertain east of 80° E. The World Meteorological Organization designated the MFR as a Regional Tropical Cyclones Advisory Centre in 1988, and upgraded it to a Regional Specialized Meteorological Center in 1993. In May 1998, two Europe-based Meteosat satellites began providing complete coverage of the basin. On July 1, 2002, the MFR shifted the cyclone year to begin on this date and end on June 30 of the following year; previously, the cyclone year began on August 1 and ended on the subsequent July 31. In 2003, the MFR extended their area of warning responsibility to 40°S, having previously been limited to 30°S. During 2011, MFR started a reanalysis project of all tropical systems between 1978 and 1998, with methods such as a Dvorak technique reanalysis and use of microwave imagery. Preliminary results from this reanalysis project include correcting an increasing trend in the number of very intense tropical cyclones in the basin since 1978. This also revealed a seemingly systematic underestimation of tropical cyclone intensities in the past.
Statistics From the 1980–81 to the 2010–11 season, there was an average of 9.3 tropical storms each year in the basin. A tropical storm has 10-minute winds of at least . There are an average of five storms that become tropical cyclones, which have 10-minute winds of at least . As of 2002, there was an average of 54 days when tropical systems were active in the basin, of which 20 had tropical cyclones active, or a system with winds of over . The median start date for the season was November 17, and the median end date was April 20.
Climatology
Generally, the monsoon does not cross into the Mozambique Channel until December; as a result, storms rarely form there before that time. From 1948 to 2010, 94 tropical systems developed in the small body of water, of which about half made landfall. Occasionally, small storms form in the Mozambique Channel that resemble Mediterranean cyclones or storms in the northeastern Atlantic Ocean; these systems are well-organised but have weaker convection than typical tropical cyclones, and originate over sea surface temperatures cooler than . A survey in 2004 conducted by weather expert Gary Padgett found meteorologists divided over whether these storms should be classified as tropical or subtropical.
In an average year, ten tropical depressions or storms strike Madagascar, and most generally do not cause much damage. Occasionally, storms or their remnants move inland over southeastern Africa, bringing heavy rainfall to Zimbabwe.
Seasons +Historical storm formation by month between 1990 and 2026
Before 1900
1900–1950
1950–1959
1959 Season Strongeststorm Deaths DamageUSD Notes andReferences 1959–1960 6 8 Carol 48 Features the first officially named tropical cyclone 'Alix'Included Carol which remains one of the most powerful storms in Mauritian history, with a central pressure of 942 hPa. It destroyed over 70,000 homes and led to the "Carol villages" housing reconstruction projects.
1960s Season Strongeststorm Deaths DamageUSD Notes andReferences 1960–1961 6 1 Doris Featured Cyclone Jenny, which is infamous for its rapid forward speed and no warning in advance for Mauritius. 1961–1962 14 5 DaisyMaud 1962–1963 10 4 Delia 1963–1964 12 4 Giselle Notable for Cyclone Danielle, which reached Very Intense status. It struck Madagascar’s east coast, causing significant loss of life and destroying substantial portions of the vanilla and coffee crops. 1964–1965 14 1 Freda 1965–1966 17 5 Ivy 3 1966–1967 13 2 Gilberte 1967–1968 8 4 Georgette Janine 38 1968–1969 8 4 Dany Helene 82 1969–1970 13 8 Jane 30
1970s Season Strongeststorm Deaths DamageUSD Notes andReferences 1970–1971 16 11 8 4 0 Maggie-Muriel 32 1971–1972 9 7 2 1 0 Fabienne 7 Featured Fabienne, which struck Rodrigues and Mauritius. It was particularly destructive in Rodrigues, where it destroyed nearly 70% of the housing and caused severe agricultural losses. 1972–1973 13 11 4 2 1 Lydie 11 1973–1974 8 7 1 0 0 Deidre-Delinda 1974–1975 10 6 2 0 0 Gervaise 9 Marked by Cyclone Gervaise, one of the most famous storms in Mauritian history. It produced a record wind gust of 280 km/h at Mon Désert and led to a complete overhaul of building codes on the island. 1975–1976 8 6 1 1 0 Terry-Danae 1976–1977 9 8 3 1 0 Jack-Io 301 1977–1978 14 12 2 1 0 Aurore 2 1978–1979 10 6 4 2 0 Celine 74 1979–1980 11 11 4 2 0 Viola-Claudette 30 Featured, Hyacinthe, which holds the world record for the most rainfall from a single tropical system (over 6,000 mm on Réunion).
1980s Season Strongeststorm Deaths DamageUSD Notes andReferences 1980–81 12 10 3 2 Florine Featured Cyclone Florine, which passed just north of Réunion. It produced immense rainfall, including a record-breaking 1,161 mm in 24 hours at Foc-Foc. 1981–82 14 10 5 2 Chris-Damia 100 $250 million 1982–83 6 3 0 0 Bemany and Elinah 33 $23 million Least active season on record, tied with the 2010–11 season. Featured, Cyclone Elinah which made a rare and devastating landfall on the Comoro Islands (Comoros), causing significant damage to infrastructure. 1983–84 14 11 4 4 Andry, Bakoly, Annette-Jaminy, and Kamisy 356 $496 million Included Domoina caused 100-year floods in South Africa and record rainfall in Swaziland (now Eswatini). 1984–85 9 9 1 0 Helisaonina 0 Unknown Helisaonina holds the record for the longest single name assigned in the basin at 11 characters. 1985–86 13 13 5 1 Erinesta 99 $150 million 1986–87 10 8 1 0 Daodo 10 $2 million 1987–88 11 11 4 1 Gasitao 100 $10 million 1988–89 12 11 6 0 Leon-Hanitra and Krissy 11 $217 million Notable for Cyclone Firinga, which struck Réunion in January 1989. It caused immense damage due to wind gusts exceeding 200 km/h and remains one of the "benchmark" storms for disaster preparedness on the island. 1989–90 9 9 5 1 Walter-Gregoara 46 $1.5 million Totals 110 95 34 11 Chris-Damia 755 ≥
1990s Season Strongeststorm Deaths DamageUSD Notes andReferences 1990–91 11 7 3 0 0 Bella 88 1991–92 14 11 3 1 0 Harriet-Heather 2 1992–93 18 11 4 2 0 Edwina 20 Features, Cyclone Colina, which made a direct hit on Réunion. It was the first cyclone for the eye to track over the island since 1962Number of tropical storms includes one subtropical depression that had winds above . 1993–94 18 14 8 4 0 Geralda 558 Includes, Geralda which struck the island as a Category 5-equivalent storm. It is often called the "Cyclone of the Century" for Madagascar, killing over 200 people and destroying the homes of 500,000. 1994–95 20 11 5 3 0 Marlene 1995–96 21 11 6 3 0 Bonita 11 1996–97 21 12 5 3 0 Daniella 311 1997–98 16 5 1 0 0 Anacelle 88 1998–99 14 6 2 2 0 Evrina 2 1999–00 14 9 4 3 1 Hudah 1,073 The fourth deadliest season on record.Cyclone Hudah, one of the deadliest, with over 1,000 fatalities across Mozambique and Madagascar. Totals 167 97 41 21 1 Hudah 2,153 ≥
2000s Season Strongeststorm Deaths DamageUSD Notes andReferences 2000–01 11 6 4 2 0 Ando 4 2001–02 15 11 9 5 1 Hary 52 2002–03 14 12 7 3 0 Kalunde 169 Notable for Dina, which caused significant damage to Mauritius and Réunion. 2003–04 15 10 5 3 1 Gafilo 396 This season featured the most intense storm on record in the basin, Gafilo. 2004–05 18 10 4 3 1 Juliet 253 2005–06 13 6 3 2 0 Carina 75 2006–07 15 10 7 6 0 Dora and Favio 188 2007–08 15 13 6 4 0 Hondo 123 Notable for Ivan, which made a catastrophic landfall on Sainte-Marie Island and mainland Madagascar as an Intense Tropical Cyclone, killing nearly 100 people and leaving 190,000 homeless. 2008–09 12 10 2 2 0 Fanele and Gael 30 2009–10 16 9 5 4 1 Edzani 40 Alt URL Totals 144 97 52 34 4 Gafilo 1,339 ≥
2010s Season Strongeststorm Deaths DamageUSD Notes andReferences 2010–11 9 3 2 0 0 Bingiza 34 Least active season on record, tied with the 1982–83 season. 2011–12 14 10 3 2 0 Funso 164 2012–13 11 10 7 3 0 Felleng 35 2013–14 15 11 5 5 2 Hellen 11 One of the fastest intensifying storms in the Mozambique Channel, Hellen. 2014–15 14 11 4 3 2 Bansi 111 2015–16 8 8 3 3 1 Fantala 13 Features the strongest storm by windspeed recorded in the basin, Fantala.$4.5 million in damages from cyclone that hit remote Seychellois island, World Bank says (Seychelles News Agency, May 17, 2016) 2016–17 7 5 3 1 0 Enawo 341 2017–18 9 8 6 3 0 Cebile 108 2018–19 15 15 11 9 0 Kenneth 1,672 ≥ Most active, second costliest, and deadliest season on recordFeatures Idai, deadliest cyclone on record and second costliest in basin history. Includes Kenneth, the strongest tropical cyclone to make landfall in Mozambique since modern records began. 2019–20 12 10 6 3 1 Ambali 45 Includes Ambali, the fastest intensification in the Southern Hemisphere, strengthening from a Tropical Depression to a Very Intense Tropical Cyclone in just 24 hours. Totals 112 89 49 32 6 Fantala 2,244 ≥
2020s Season Strongeststorm Deaths DamageUSD Notes andReferences 2020–21 16 12 7 2 2 Faraji Habana 56 $90.1 million Features two very intense tropical cyclones named in the basin.Record third consecutive season for a storm to develop before the official start (Alicia). 2021–22 13 12 5 5 0 Batsirai 376 $380 million Latest start to an SWIO season. 2022–23 10 9 5 3 2 Darian 1,483 >$1.55 billion