South-West Indian Ocean tropical cyclone

Satellite image of Cyclone Batsirai, the strongest tropical cyclone to strike Madagascar since Cyclone Enawo in 2017.

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.^[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 (73 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 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.^[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 sea surface temperatures cooler 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 1900

Main article: List of South-West Indian Ocean cyclones before 1900

1900–1950

Main article: 1900–1950 South-West Indian Ocean cyclone seasons

1950–1959

Main article: 1950s South-West Indian Ocean cyclone seasons

1959

Season	TD	TC	Strongest storm	Deaths	Damage USD	Notes and References
1959–1960	6	8	Carol	48

1960s

Season	TD	TC	Strongest storm	Deaths	Damage USD	Notes and References
1960–1961	6	1	Doris
1961–1962	14	5	Daisy Maud
1962–1963	10	4	TC  Delia
1963–1964	12	4	ITC  Giselle
1964–1965	14	1	TC  Freda
1965–1966	17	5	ITC  Ivy	3
1966–1967	13	2	TC  Gilberte
1967–1968	8	4	ITC  Georgette  ITC  Janine	38
1968–1969	8	4	TC  Dany  TC  Helene	82
1969–1970	13	8	VITC  Jane	30

1970s

Season	TD	MTS	TC	ITC	VITC	Strongest storm	Deaths	Damage USD	Notes and References
1970–1971	16	11	8	4	0	ITC  Maggie-Muriel	32
1971–1972	9	7	2	1	0	ITC  Fabienne	7
1972–1973	13	11	4	2	1	VITC  Lydie	11
1973–1974	8	7	1	0	0	TC  Deidre-Delinda
1974–1975	10	6	2	0	0	TC  Gervaise	9
1975–1976	8	6	1	1	0	ITC  Terry-Danae
1976–1977	9	8	3	1	0	ITC  Jack-Io	301
1977–1978	14	12	2	1	0	ITC  Aurore	2
1978–1979	10	6	4	2	0	ITC  Celine	74
1979–1980	11	11	4	2	0	ITC  Viola-Claudette	30

1980s

Season	TD	MTS	TC	ITC	Strongest storm	Deaths	Damage USD	Notes and References
1980–81	12	10	3	2	VITC  Florine
1981–82	14	10	5	2	ITC  Chris-Damia	100	$250 million
1982–83	6	3	0	0	STS  Bemany and Elinah	33	$23 million
1983–84	14	11	4	4	ITC  Andry, Bakoly, Annette-Jaminy, and Kamisy	356	$496 million
1984–85	9	9	1	0	TC  Helisaonina	0	Unknown
1985–86	13	13	5	1	ITC  Erinesta	99	$150 million
1986–87	10	8	1	0	TC  Daodo	10	$2 million
1987–88	11	11	4	1	ITC  Gasitao	100	$10 million
1988–89	12	11	6	0	TC  Leon-Hanitra and Krissy	11	$217 million
1989–90	9	9	5	1	ITC  Walter-Gregoara	46	$1.5 million

1990s

Season	TD	MTS	TC	ITC	VITC	Strongest storm	Deaths	Damage USD	Notes and References
1990–91	11	7	3	0	0	TC  Bella	88
1991–92	14	11	3	1	0	ITC  Harriet-Heather	2
1992–93	18	11	4	2	0	ITC  Edwina	20		[A 1][14]
1993–94	18	14	8	4	0	ITC  Geralda	558
1994–95	20	11	5	3	0	ITC  Marlene			[15]
1995–96	21	11	6	3	0	ITC  Bonita	11		[16]
1996–97	21	12	5	3	0	ITC  Daniella	311	$50 million
1997–98	16	5	1	0	0	TC  Anacelle	88
1998–99	14	6	2	2	0	ITC  Evrina	2
1999–00	14	9	4	3	1	VITC  Hudah	1,073	$800 million	The second deadliest season on record.[17]
	167	97	41	21	1	Hudah	2,153	≥$850 million

2000s

Season	TD	MTS	TC	ITC	VITC	Strongest storm	Deaths	Damage USD	Notes and References
2000–01	11	6	4	2	0	ITC  Ando	4		[A 1][18]
2001–02	15	11	9	5	1	VITC  Hary	52	$287 million	[19]
2002–03	14	12	7	3	0	ITC  Kalunde	169	$6.7 million	[A 1]
2003–04	15	10	5	3	1	VITC  Gafilo	396	$250 million	Fourth deadliest season on record, also features the most intense storm in the basin, Gafilo.[20][21]
2004–05	18	10	4	3	1	VITC  Juliet	253		[21]
2005–06	13	6	3	2	0	ITC  Carina	75		[22][23]
2006–07	15	10	7	6	0	ITC  Dora and Favio	188	$337 million	[A 1][23]
2007–08	15	13	6	4	0	ITC  Hondo	123	$38.1 million	[23]
2008–09	12	10	2	2	0	ITC  Fanele and Gael	30		[24]
2009–10	16	9	5	4	1	VITC  Edzani	40		[A 1][24][25]
	144	97	52	34	4	Gafilo	1,339	≥$919 million

2010s

Season	TD	MTS	TC	ITC	VITC	Strongest storm	Deaths	Damage USD	Notes and References
2010–11	9	3	2	0	0	TC  Bingiza	34		[A 1][26]
2011–12	14	10	3	2	0	ITC  Funso	164		[A 1][26]
2012–13	11	10	7	3	0	ITC  Felleng	35	$46 million
2013–14	15	11	5	5	2	VITC  Hellen	11	$89.2 million
2014–15	14	11	4	3	2	VITC  Bansi	111	$46.4 million
2015–16	8	8	3	3	1	VITC  Fantala	13	$4.5 million	Features the strongest storm by windspeed recorded in the basin, Fantala.[27]
2016–17	7	5	3	1	0	ITC  Enawo	341	$137 million
2017–18	9	8	6	3	0	ITC  Cebile	108	$38.2 million
2018–19	15	15	11	10	0	ITC  Kenneth	1,672	≥$3.65 billion	Most active, costliest, and deadliest season on record
2019–20	12	10	6	3	1	VITC  Ambali	45	$25 million
	112	89	49	32	6	Fantala	2,244	≥$2.7 billion

2020s

Season	TD	MTS	TC	ITC	VITC	Strongest storm	Deaths	Damage USD	Notes and References
2020–21	16	12	7	2	2	VITC  Faraji  VITC  Habana	56	$11 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	ITC  Batsirai	812	>$1.88 billion	Latest start to an SWIO season, fifth deadliest season, and second costliest season
2022–23	10	9	5	3	2	VITC  Darian	1,483	>$501 million	Features two very intense tropical cyclones named in the Australian Region. Features Freddy, the longest lasting tropical cyclone ever recorded. Third deadliest season.
2023–24	9	8	4	2	0	ITC  Djoungou	25
2024–25	4	3	2	2	0	ITC  Chido	119+	Unknown	Features Chido, the strongest system to ever make landfall on Mayotte since records began.
	52	44	23	14	4	Darian	2,365	>$2.566 billion

See also

• Tropical cyclone
• Atlantic hurricane season
• Pacific hurricane season
• Pacific typhoon season
• North Indian Ocean tropical cyclone
• Australian region tropical cyclone
• South Pacific tropical cyclone
• South Atlantic tropical cyclone
• Mediterranean tropical-like cyclone

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. "Aéroport de la Réunion 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. S2CID 130753010.
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 February 22, 2014. 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)