South-West Indian Ocean tropical cyclone

In the south-west Indian Ocean, tropical cyclones form south of the equator and west of 90° E to the coast of Africa.

Satellite image of Cyclone Gafilo, the strongest storm on record in the basin by minimum central pressure

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.[1][2][3][4]

The Joint Typhoon Warning Center – a joint United States Navy – United States Air Force task force – also issues tropical cyclone warnings for the region.[5] 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.[6]

If a tropical storm in the basin strengthens to attain 10 minute sustained winds of at least 118 km/h (74 mph), 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).[7]

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 Alex, 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 at 30° S.[2] 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.[8] Preliminary results from this reanalysis project include correcting an increasing trend in the number of very intense tropical cyclones in the basin since 1978.[8] This also revealed a seemingly systematic underestimation of tropical cyclone intensities in the past.[8]

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 65 km/h (40 mph). There are an average of five storms that become tropical cyclones, which have 10  minute winds of at least 120 km/h (75 mph).[9] 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 120 km/h (75 mph). The median start date for the season was November 17, and the median end date was April 20.[1]

Climatology
Tracks of storms in the basin from 1980 to 2005

Generally, the monsoon does not cross into the Mozambique Channel until December; as a result, storms rarely form there before that time.[1] From 1948 to 2010, 94 tropical systems developed in the small body of water, of which about half made landfall.[10] Occasionally, small storms form in the Mozambique Channel that resemble Mediterranean tropical cyclones or storms in the northeastern Atlantic Ocean; these systems are well-organized but have weaker convection than typical tropical cyclones, and originate over cooler than normal water temperatures of less than 26 °C (79 °F). A survey in 2004 conducted by weather expert Gary Padgett found meteorologists split whether these storms should be classified as tropical or subtropical.[11]

In an average year, ten tropical depressions or storms strike Madagascar, and most generally do not cause much damage.[12] Occasionally, storms or their remnants enter the interior of southeastern Africa, bringing heavy rainfall to Zimbabwe.[13]

Seasons
Historical storm formation by month between 1990 and 2020
10
20
30
40
50
60
70
80
90
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
  •   Very intense tropical cyclone
  •   Intense tropical cyclone
  •   Tropical cyclone
  •   Severe tropical storm
  •   Moderate tropical storm
  •   Tropical depression
  •   Tropical disturbance

Before 1959
Main article: List of South-West Indian Ocean cyclones before 1959

1959
SeasonTDTCStrongest
storm		DeathsDamage
USD		Notes and
References
1959–196068Carol48

1960s
SeasonTDTCStrongest
storm		DeathsDamage
USD		Notes and
References
1960–196161Doris
1961–1962145Daisy/Maud
1962–1963104Delia
1963–1964124Giselle
1964–1965141Freda
1965–1966175Ivy
1966–1967132Gilberte
1967–196884Georgette/Janine38
1968–196984Dany/Helene
1969–1970138Jane

1970s
SeasonTDMTSTCITCVITCStrongest
storm		DeathsDamage
USD		Notes and
References
1970–19711611840Maggie-Muriel32
1971–197297210Fabienne7
1972–19731311421Lydie11
1973–197487100Deidre-Delinda
1974–1975106200Gervaise9
1975–197686110Terry-Danae
1976–197798310Jack-Io301
1977–19781412210Aurore2
1978–1979106420Celine74
1979–19801111420Viola-Claudette30

1980s
SeasonTDMTSTCITCStrongest
storm		DeathsDamage
USD		Notes and
References
1980–81121032Alice-Adelaide/Florine
1981–82141052Chris-Damia100$250 million
1982–836300Bemany/Elinah33$23 million
1983–84141144Andry/Annette-Jaminy/Kamisy356$496 million
1984–859910Helisaonina0Unknown
1985–86131351Erinesta99$150 million
1986–8710810Daodo10$2 million
1987–88111141Gasitao100$10 million
1988–89121160Leon-Hanitra/Krissy11$217 million
1989–909951Walter-Gregoara46$1.5 million

1990s
SeasonTDMTSTCITCVITCStrongest
storm		DeathsDamage
USD		Notes and
References
1990–91117300Bella88
1991–921411310Harriet-Heather2
1992–931811420Edwina20[A 1][14]
1993–941814840Geralda558
1994–952011530Marlene[15]
1995–962111630Bonita11[16]
1996–972112530Daniella311$50 million
1997–98165100Anacelle88
1998–99146220Evrina2
1999–00149431Hudah1,073$800 million[17]

2000s
SeasonTDMTSTCITCVITCStrongest
storm		DeathsDamage
USD		Notes and
References
2000–01116420Ando4[A 1][18]
2001–021511951Hary52$287 million[19]
2002–031412730Kalunde169$6.7 million[A 1]
2003–041510531Gafilo396$250 million[20][21]
2004–051810431Juliet253[21]
2005–06136320Carina75[22][23]
2006–071510760Dora/Favio188$337 million[A 1][23]
2007–081513640Hondo123$38.1 million[23]
2008–091210220Fanele/Gael30[24]
2009–10169541Edzani40[A 1][24][25]
1449752344Gafilo1,339≥$919 million

2010s
SeasonTDMTSTCITCVITCStrongest
storm		DeathsDamage
USD		Notes and
References
2010–1193200Bingiza34[A 1][26]
2011–121410320Funso164[A 1][26]
2012–131110730Felleng35$46 million
2013–141511552Hellen11$89.2 million
2014–151411432Bansi111$46.4 million
2015–1688331Fantala13$4.5 million[27]
2016–1775310Enawo341$137 million
2017–1898630Berguitta108$38.2 million
2018–19151511100Kenneth1,382≥$2.31 billionMost active, costliest, and deadliest season on record
2019–201210631Ambali45$25 million
1128949326Fantala2,244≥$2.7 billion

2020s
SeasonTDMTSTCITCVITCStrongest
storm		DeathsDamage
USD		Notes and
References
2020–21107310Faraji21None
107310Faraji21None

See also

Notes
  1. Number of tropical storms includes one subtropical depression that had winds above 65 km/h (40 mph).

References
  1. "Cyclone Season 2001–2002". RSMC La Reunion. Meteo-France. Retrieved April 28, 2013.
  2. Philippe Caroff; et al. (June 2011). Operational procedures of TC satellite analysis at RSMC La Reunion (PDF) (Report). World Meteorological Organization. Archived from the original (PDF) on 2014-10-06. Retrieved 2014-01-11.
  3. https://habiter-la-reunion.re/aeroport-reunion-roland-garros/
  4. Isabelle Mayer Jouanjean (2011). Lîle de La Réunion sous l’œil du cyclone au XXéme siécle (PDF) (Report) (in French). Université de la Réunion.
  5. Annual Tropical Cyclone Report (PDF) (Report). Joint Typhoon Warning Center. p. iii, 218, 240. Retrieved 2014-01-11.
  6. Chris Landsea (2006-04-21). "Subject: D4) What does "maximum sustained wind" mean? How does it relate to gusts in tropical cyclones?". Frequently Asked Questions. Hurricane Research Division. Retrieved 2017-08-06.
  7. Chris Landsea (2001-07-15). "Subject: A1) What is a hurricane, typhoon, or tropical cyclone?". Frequently Asked Questions. Hurricane Research Division. Retrieved 2015-02-20.
  8. Philippe Caroff (October 23, 2015). Review of recent (2012-2015) main activities and achievements at RSMC La Reunion (docx). Eighth tropical cyclone technical coordination meeting (TCM-8). World Meteorological Organization. Retrieved November 1, 2015.
  9. Chris Landsea; Sandy Delgado (2014-05-01). "Subject: E10) What are the average, most, and least tropical cyclones occurring in each basin?". Frequently Asked Questions. Hurricane Research Division. Retrieved 2014-10-13.
  10. Corene J. Matyas (2014-04-07). "Tropical cyclone formation and motion in the Mozambique Channel". International Journal of Climatology. 35 (3): 375–390. Bibcode:2015IJCli..35..375M. doi:10.1002/joc.3985.
  11. "June 2004 Monthly Global Tropical Cyclone Summary". Gary Padgett. Retrieved 2015-02-20.
  12. Cyclone Rehabilitation Project (PDF) (Report). World Bank. 1992-05-11. Retrieved 2015-02-20.
  13. A. Mhizha; M. Musariri; E. Madamombe; Tererai (2012-01-23). Preliminary Water Resources Assessment for the Limpopo River Basin (PDF) (Report). University of Zimbabwe. Archived from the original (PDF) on 2015-04-02. Retrieved 2015-03-05.
  14. RSMC La Reunion Tropical Cyclone Centre. Cyclone Season 1992–1993 (Report). Meteo-France. Retrieved December 20, 2012.
  15. RSMC La Reunion Tropical Cyclone Centre. Cyclone Season 1994–1995 (Report). MeteoFrance. Retrieved December 20, 2012.
  16. RSMC La Reunion Tropical Cyclone Centre. Cyclone Season 1995–1996 (Report). Meteo-France. Retrieved December 20, 2012.
  17. RSMC La Reunion Tropical Cyclone Centre. Cyclone Season 1999–2000 (Report). Meteo-France. Retrieved December 20, 2012.
  18. RSMC La Reunion Tropical Cyclone Centre. Cyclone Season 2000–2001 (Report). Meteo-France. Retrieved November 26, 2012.
  19. RSMC La Reunion Tropical Cyclone Centre. Cyclone Season 2001–2002 (Report). Meteo-France. Retrieved November 26, 2012.
  20. RSMC La Reunion Tropical Cyclone Centre. Cyclone Season 2003–2004 (Report). Meteo-France. Retrieved December 20, 2012.
  21. RA I Tropical Cyclone Committee for the South-West Indian Ocean (2006-06-16). RA I Tropical Cyclone Committee for the South-West Indian Ocean Seventeenth Session (PDF) (Final Report). World Meteorological Organisation. pp. 30–32. Retrieved December 20, 2012.
  22. RSMC La Reunion Tropical Cyclone Centre. Cyclone Season 2005–2006 (Report). Meteo-France. Retrieved December 20, 2012.
  23. RA I Tropical Cyclone Committee for the South-West Indian Ocean (2010-09-15). RA I Tropical Cyclone Committee for the South-West Indian Ocean Eighteenth Session (PDF) (Final Report). World Meteorological Organisation. p. 31. Retrieved December 20, 2012.
  24. RA I Tropical Cyclone Committee for the South-West Indian Ocean (August 3, 2011). RA I Tropical Cyclone Committee for the South-West Indian Ocean Nineteenth Session (PDF) (Final Report). World Meteorological Organisation. pp. 5–8. Retrieved December 20, 2012.
  25. Padgett, Gary (1997–2011). "Monthly Global Tropical Cyclone Summaries". Archived from the original on February 18, 2020. Retrieved July 25, 2012. Alt URL
  26. RA I Tropical Cyclone Committee for the South-West Indian Ocean (December 3, 2012). RA I Tropical Cyclone Committee for the South-West Indian Ocean Twentieth Session (PDF) (Final Report). World Meteorological Organisation. pp. 2, 7, 8. Archived (PDF) from the original on December 20, 2012. Retrieved December 20, 2012.
  27. $4.5 million in damages from cyclone that hit remote Seychellois island, World Bank says (Seychelles News Agency, May 17, 2016)
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