South-West Indian Ocean tropical cyclone explained

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]

The Joint Typhoon Warning Center  - a joint United States Navy – United States Air Force task force  - also issues tropical cyclone warnings for the region.[4] 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.[5]

If a tropical storm in the basin strengthens to attain 10 minute sustained winds of at least 118km/h, 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).[6]

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.[1] 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.[7] Preliminary results from this reanalysis project include correcting an increasing trend in the number of very intense tropical cyclones in the basin since 1978.[7] This also revealed a seemingly systematic underestimation of tropical cyclone intensities in the past.[7]

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 65km/h. There are an average of five storms that become tropical cyclones, which have 10-minute winds of at least 120km/h.[8] 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 120km/h. The median start date for the season was November 17, and the median end date was April 20.[9]

Climatology

Generally, the monsoon does not cross into the Mozambique Channel until December; as a result, storms rarely form there before that time.[9] 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 26C. 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

Before 1900

See main article: List of South-West Indian Ocean cyclones before 1900.

1900–1950

See main article: 1900–1950 South-West Indian Ocean cyclone seasons.

1950–1959

See main article: 1950s South-West Indian Ocean cyclone seasons.

1960s

Season Strongest
storm
Deaths Notes and
References
6 1 Doris
14 5 Daisy
Maud
10 4 Delia
12 4 Giselle
14 1 Freda
17 5 Ivy 3
13 2 Gilberte
8 4 Georgette
Janine
38
8 4 Dany
Helene
82
13 8 Jane 30

1970s

Season Strongest
storm
Deaths Notes and
References
16 11 8 4 0 Maggie-Muriel 32
9 7 2 1 0 Fabienne 7
13 11 4 2 1 Lydie 11
8 7 1 0 0 Deidre-Delinda
10 6 2 0 0 Gervaise 9
8 6 1 1 0 Terry-Danae
9 8 3 1 0 Jack-Io 301
14 12 2 1 0 Aurore 2
10 6 4 2 0 Celine 74
11 11 4 2 0 Viola-Claudette 30

1980s

Season Strongest
storm
Deaths Notes and
References
12 10 3 2 Florine
14 10 5 2 Chris-Damia 100 $250 million
6 3 0 0 Bemany and Elinah 33 $23 million
14 11 4 4 356 $496 million
9 9 1 0 Helisaonina 0 Unknown
13 13 5 1 Erinesta 99 $150 million
10 8 1 0 Daodo 10 $2 million
11 11 4 1 Gasitao 100 $10 million
12 11 6 0 Leon-Hanitra and Krissy 11 $217 million
9 9 5 1 Walter-Gregoara 46 $1.5 million

1990s

Season Strongest
storm
Deaths Notes and
References
11 7 3 0 0 88
14 11 3 1 0 Harriet-Heather 2
18 11 4 2 0 Edwina 20 [14] [15]
18 14 8 4 0 558
20 11 5 3 0 Marlene [16]
21 11 6 3 0 11 [17]
21 12 5 3 0 Daniella 311
16 5 1 0 0 Anacelle 88
14 6 2 2 0 Evrina 2
14 9 4 3 1 1,073 The second deadliest season on record.[18]
167 97 41 21 1 Hudah 2,153

2000s

Season Strongest
storm
Deaths Notes and
References
11 6 4 2 0 Ando 4 [19]
15 11 9 5 1 52 [20]
14 12 7 3 0 169
15 10 5 3 1 396 Fourth deadliest season on record, also features the most intense storm in the basin, Gafilo.[21] [22]
18 10 4 3 1 Juliet 253
13 6 3 2 0 Carina 75 [23] [24]
15 10 7 6 0 188
15 13 6 4 0 123
12 10 2 2 0 Fanele and Gael 30 [25]
16 9 5 4 1 Edzani 40 [26]
144 97 52 34 4 Gafilo 1,339

2010s

Season Strongest
storm
Deaths Notes and
References
9 3 2 0 0 34 [27]
14 10 3 2 0 164
11 10 7 3 0 Felleng 35
15 11 5 5 2 11
14 11 4 3 2 Bansi 111
8 8 3 3 1 13 Features the strongest storm by windspeed recorded in the basin, Fantala.[28]
7 5 3 1 0 341
9 8 6 3 0 Cebile 108
15 15 11 10 0 1,672 Most active, costliest, and deadliest season on record
12 10 6 3 1 Ambali 45
112 89 49 32 6 Fantala 2,244

2020s

Season Strongest
storm
Deaths Notes and
References
16 12 7 2 2 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).
13 12 5 5 0 812 >$1.88 billion Latest start to an SWIO season, fifth deadliest season, and second costliest season
10 9 5 3 2 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.
9 8 4 2 0 25
4841 21 12 4 Darian 2,351>$2.566 billion

See also

Notes and References

  1. Philippe Caroff. June 2011. Operational procedures of TC satellite analysis at RSMC La Reunion. World Meteorological Organization. 2014-01-11. https://web.archive.org/web/20141006123441/http://www.wmo.int/pages/prog/www/tcp/documents/RSMCLaReunionforIWSATC.pdf. 2014-10-06. etal.
  2. Web site: Aéroport de la Réunion Roland Garros.
  3. Lîle de La Réunion sous l'œil du cyclone au XXéme siécle. fr. Isabelle Mayer Jouanjean. Université de la Réunion. 2011. PDF.
  4. Joint Typhoon Warning Center. iii, 218, 240. Annual Tropical Cyclone Report. 2014-01-11.
  5. Web site: Subject: D4) What does "maximum sustained wind" mean? How does it relate to gusts in tropical cyclones?. Chris Landsea. 2006-04-21. Frequently Asked Questions. Hurricane Research Division. 2017-08-06.
  6. Web site: Chris Landsea. Hurricane Research Division. Frequently Asked Questions. Subject: A1) What is a hurricane, typhoon, or tropical cyclone?. 2015-02-20. 2001-07-15.
  7. Philippe Caroff. October 23, 2015. Review of recent (2012-2015) main activities and achievements at RSMC La Reunion. World Meteorological Organization. November 1, 2015. docx. Eighth tropical cyclone technical coordination meeting (TCM-8).
  8. Web site: Chris Landsea. Sandy Delgado. Subject: E10) What are the average, most, and least tropical cyclones occurring in each basin?. Frequently Asked Questions. 2014-05-01. Hurricane Research Division. 2014-10-13.
  9. Web site: Cyclone Season 2001–2002. RSMC La Reunion. Meteo-France. April 28, 2013.
  10. Corene J. Matyas. Tropical cyclone formation and motion in the Mozambique Channel. International Journal of Climatology. 35. 3. 375–390. 2014-04-07. 10.1002/joc.3985. 2015IJCli..35..375M . 130753010 .
  11. Web site: Gary Padgett. June 2004 Monthly Global Tropical Cyclone Summary. 2015-02-20.
  12. Cyclone Rehabilitation Project. 2015-02-20. World Bank. 1992-05-11.
  13. Preliminary Water Resources Assessment for the Limpopo River Basin. A. Mhizha. M. Musariri. E. Madamombe. Tererai. University of Zimbabwe. 2012-01-23. https://web.archive.org/web/20150402100828/http://www.waternetonline.ihe.nl/challengeprogram/IR29%20Mhizha%20prelim%20water%20res.pdf. dead. 2015-04-02. 2015-03-05.
  14. Number of tropical storms includes one subtropical depression that had winds above 40mph.
  15. Cyclone Season 1992–1993. RSMC La Reunion Tropical Cyclone Centre. Meteo-France. December 20, 2012.
  16. Cyclone Season 1994–1995. RSMC La Reunion Tropical Cyclone Centre. MeteoFrance. December 20, 2012.
  17. Cyclone Season 1995–1996. RSMC La Reunion Tropical Cyclone Centre. Meteo-France. December 20, 2012.
  18. Cyclone Season 1999–2000. RSMC La Reunion Tropical Cyclone Centre. Meteo-France. December 20, 2012.
  19. Cyclone Season 2000–2001. RSMC La Reunion Tropical Cyclone Centre. Meteo-France. November 26, 2012.
  20. Cyclone Season 2001–2002. RSMC La Reunion Tropical Cyclone Centre. Meteo-France. November 26, 2012.
  21. Cyclone Season 2003–2004. RSMC La Reunion Tropical Cyclone Centre. Meteo-France. December 20, 2012.
  22. 30–32. RA I Tropical Cyclone Committee for the South-West Indian Ocean Seventeenth Session. Final Report. RA I Tropical Cyclone Committee for the South-West Indian Ocean. World Meteorological Organisation. December 20, 2012. 2006-06-16.
  23. Cyclone Season 2005–2006. RSMC La Reunion Tropical Cyclone Centre. Meteo-France. December 20, 2012.
  24. 31. RA I Tropical Cyclone Committee for the South-West Indian Ocean Eighteenth Session. Final Report. RA I Tropical Cyclone Committee for the South-West Indian Ocean. World Meteorological Organisation. December 20, 2012. 2010-09-15.
  25. 5–8. RA I Tropical Cyclone Committee for the South-West Indian Ocean Nineteenth Session. Final Report. RA I Tropical Cyclone Committee for the South-West Indian Ocean. World Meteorological Organisation. December 20, 2012. August 3, 2011.
  26. Web site: July 25, 2012. 1997–2011. Monthly Global Tropical Cyclone Summaries. Padgett, Gary. February 18, 2020. live. https://web.archive.org/web/20200218084422/http://australiasevereweather.com/cyclones/tropical_cyclone_summaries_track_data.htm. Alt URL
  27. 2, 7, 8 . RA I Tropical Cyclone Committee for the South-West Indian Ocean Twentieth Session . Final Report . RA I Tropical Cyclone Committee for the South-West Indian Ocean . live . World Meteorological Organisation . February 22, 2014 . December 20, 2012 . December 3, 2012 . https://web.archive.org/web/20140222183933/http://www.wmo.int/pages/prog/www/tcp/documents/ra1_tcc-20_final_report_en.pdf .
  28. http://www.seychellesnewsagency.com/articles/5175/.+million+in+damages+from+cyclone+that+hit+remote+Seychellois+island,+World+Bank+says $4.5 million in damages from cyclone that hit remote Seychellois island, World Bank says (Seychelles News Agency, May 17, 2016)