2024–25 South-West Indian Ocean cyclone season explained

Basin:SWI
Year:2025
Track:2024-2025 South-West Indian Ocean cyclone season summary.png
First Storm Formed:15 August 2024
Last Storm Dissipated:Season ongoing
Strongest Storm Name:Bheki
Strongest Storm Pressure:943
Strongest Storm Winds:105
Average Wind Speed:10
Total Disturbances:3
Total Depressions:3
Total Storms:2
Total Hurricanes:1
Total Intense:1
Total Super:0
Fatalities:None
Damages:None
Five Seasons:2022–23, 2023–24, 2024–25, 2025–26, 2026–27
Australian Season:2024–25 Australian region cyclone season
South Indian Season:2024–25 South Pacific cyclone season

The 2024–25 South-West Indian Ocean cyclone season is the current annual cycle of tropical cyclone and subtropical cyclone formation. It began on 15 November 2024, and will end on 30 April 2025, with the exception for Mauritius and the Seychelles, for which it will end on 15 May 2025. These dates conventionally delimit the period of each year when most tropical and subtropical cyclones form in the basin, which is west of 90°E and south of the Equator. However, tropical cyclones can form year-round with any cyclone forming between 1 July 2024 and 30 June 2025, such as 01 and Ancha, will be part of the season. Tropical and subtropical cyclones in this basin are monitored by the Regional Specialised Meteorological Centre in Réunion and unofficially by the Joint Typhoon Warning Center.

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Seasonal summary

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BarData = barset:Hurricane bar:Month

PlotData= barset:Hurricane width:11 align:left fontsize:S shift:(4,-4) anchor:till from:15/08/2024 till:17/08/2024 color:TD text:"01 (TD)" from:30/09/2024 till:05/10/2024 color:TS text:"Ancha (MTS)" from:12/11/2024 till:23/11/2024 color:IT text:"Bheki (ITC)"

bar:Month width:5 align:center fontsize:S shift:(0,-20) anchor:middle color:canvas from:01/08/2024 till:31/08/2024 text:August from:01/09/2024 till:30/09/2024 text:September from:01/10/2024 till:31/10/2024 text:October from:01/11/2024 till:30/11/2024 text:November from:01/12/2024 till:31/12/2024 text:December from:01/01/2025 till:31/01/2025 text:January from:01/02/2025 till:28/02/2025 text:February from:01/03/2025 till:31/03/2025 text:March from:01/04/2025 till:30/04/2025 text:April from:01/05/2025 till:31/05/2025 text:May

TextData = pos:(620,23) text:"(For further details, please see" pos:(764,23) text:"scales)"

This season's ACE index, as of November 21, is approximately 18.2 units.[1] This number represents sum of the squares of the maximum sustained wind speed (knots) for all named storms while they are at least tropical storm intensity, divided by 10,000. Therefore, tropical depressions are not included.

Systems

Tropical Depression 01

Basin:SWI
Track:01R 2024 path.png
Warningcenter:MFR
Formed:15 August
Dissipated:17 August
10-Min Winds:30
Pressure:1000

See also: List of off-season South-West Indian Ocean tropical cyclones. On 8 August, the MFR noted that in mid-August, tropical cyclogenesis was possible near the equator due to a westerly wind burst expected to form during the active phase of the Madden–Julian oscillation (MJO).[2] Three days later, a near-equatorial trough formed, with convective activity developing near the trough's axis.[3] Slowly developing, on August 13, a low-level circulation was seen, with convective bands wrapping around its circulation.[4] Two days later, the Joint Typhoon Warning Center (JTWC) began tracking the disturbance, noting that it was in a marginal environment for development.[5] Just a few hours later, the MFR designated the disturbance as Zone of Disturbed Weather 01.[6] Soon after, the JTWC issued a Tropical Cyclone Formation Alert (TCFA) on the disturbance, noting that despite being in an environment with high wind shear, it was intensifying.[7] Later that day, the disturbance had intensified into a tropical depression.[8] However, it weakened into a zone of disturbed weather, and after its window of development ended on August 17, the MFR issued their last warning on the system.[9] The JTWC soon cancelled their TCFA on the disturbance, noting that it could still develop.[10] As a result, early the next day, the MFR began re-monitoring the disturbance as it was developing despite being in an unfavorable environment.[11] However, as it entered an increasingly dry and sheared environment on 20 August, it degenerated into a remnant low.[12] The JTWC stopped tracking it later that day, as it had dissipated,[13] with the MFR following suit as well.[14]

Moderate Tropical Storm Ancha

Basin:SWI
Track:Ancha 2024 path.png
Warningcenter:MFR
Formed:30 September
Dissipated:5 October
10-Min Winds:45
1-Min Winds:55
Pressure:992

See also: List of off-season South-West Indian Ocean tropical cyclones. On 24 September, the MFR noted that tropical cyclogenesis would be possible in late September due to the passage of an equatorial Rossby wave and an Kelvin wave, which would help cause the formation of a temporary near-equatorial trough.[15] The next day, a near-equatorial trough would begin forming, featuring moderate convective activity on its polar side.[16] The JTWC would begin tracking the disturbance late on 30 September, noting that it was in an environment marginally favorable for development east-southeast off Diego Garcia.[17] The next day, the MFR upgraded this system into a tropical depression.[18] The JTWC would upgrade it into Tropical Cyclone 01S later that day,[19] with the MFR following suit the next day, upgrading the depression into Moderate Tropical Storm Ancha.[20] A few hours later, it peaked with 1-minute sustained winds of .[21] Ancha's cloud pattern would improve on 2 October, causing it to peak as a high-end moderate tropical storm with 10-minute sustained winds of .[22] However, the next day, Ancha's low-level circulation began being exposed due to moderate wind shear, extensive dry air, and steadily cooling sea surface temperatures, prompting the JTWC to issue their last warning on it.[23] This caused Ancha to recurve westward due to the subtropical ridge[24] prior to degenerating into a remnant low a few hours later.[25] However, for a short time it regenerated into a moderate tropical storm.[26] However, increasing tropospheric shear caused this temporary regeneration to end, and the MFR would stop monitoring it on 4 October.[27]

Intense Tropical Cyclone Bheki

Basin:SWI
Track:Bheki 2024 path.png
Warningcenter:MFR
Formed:12 November
Dissipated:23 November
10-Min Winds:105
1-Min Winds:115
Pressure:943

See also: List of off-season South-West Indian Ocean tropical cyclones. On 11 November, the MFR noted that an elongated low-level circulation was developing despite being inside an environment with dry air and easterly shear, due to good divergence on the western side, steadily developing convection, and monsoonal flow.[28] Later that day, the JTWC began tracking the disturbance, noting that it was in an environment favorable for development southeast off Diego Garcia.[29] Further organization occurred, and early on 12 November, the MFR designated the system as Zone of Disturbed Weather 03.[30] Following convection beginning to surround the system's circulation, the MFR upgraded it to Moderate Tropical Storm Bheki on 14 November,[31] with the JTWC designating it Tropical Cyclone 02S a few hours later.[32] A developing central dense overcast and improving cloud pattern prompted the MFR to upgrade Bheki into a severe tropical storm early the next day.[33] Bheki strengthened rapidly and peaked as an Intense Tropical Cyclone on November 18, becoming the strongest November tropical cyclone on record in the basin based on sustained wind speeds. It was also the third-strongest November tropical cyclone in the basin based on minimum central pressure.

In Rodrigues, Mauritius, wind gusts of NaNkm/h were reported.[34] [35] The Rodrigues Emergency Operations Command reported that 64 % of the population had been left without electricity due to power outages caused by strong winds. Some 50 people had to seek shelter in centres across the island, some rescued by emergency services. Electricity company teams, military personnel and firefighters were dispersed across the territory to carry out necessary work, as well as clearing roads of fallen trees and branches, in order to return the situation to normal.[36] The strong NaNm (-2,147,483,648feet) swell caused coastal flooding and in Montagne-Goyave, the community school suffered heavy damage.[37]

Storm names

See main article: Tropical cyclone naming. Within the South-West Indian Ocean, tropical depressions and subtropical depressions that are judged to have 10-minute sustained windspeeds of 65 km/h (40 mph) by the Regional Specialized Meteorological Center on Réunion island, France (RSMC La Réunion) are usually assigned a name. However, it is the Sub-Regional Tropical Cyclone Advisory Centers in Mauritius and Madagascar who name the systems. The Sub-Regional Tropical Cyclone Advisory Center (Mauritius Meteorological Services) in Mauritius names a storm if it intensifies into a moderate tropical storm between 55°E and 90°E. If instead a cyclone intensifies into a moderate tropical storm between 30°E and 55°E then the Sub-Regional Tropical Cyclone Advisory Center (Meteo Madagascar) in Madagascar assigns the appropriate name to the storm. Storm names are taken from three pre-determined lists of names, which rotate on a triennial basis, with any names that have been used automatically removed. New names this season are: Ancha, Bheki, Chido, Dikeledi, Elvis, Faida, Garance, Honde, Ivone, Jude, Kanto and Lira. They replaced Ana, Batsirai, Cliff, Dumako, Emnati, Fezile, Gombe, Halima, Issa, Jasmine and Karim during the 2021–22 season, and also Letlama, which was not used, but the reason for its removal is unknown.[38]

  • Ancha
  • Bheki

Season effects

This table lists all of the tropical cyclones and subtropical cyclones that were monitored during the 2024–2025 South-West Indian Ocean cyclone season. Information on their intensity, duration, name, areas affected, primarily comes from RSMC La Réunion. Death and damage reports come from either press reports or the relevant national disaster management agency while the damage totals are given in 2024 or 2025 USD.|-| || || bgcolor=#| || bgcolor=#|30kn || bgcolor=#|1000hPa || Chagos Archipelago || || |||-| || || bgcolor=#| || bgcolor=#|45kn || bgcolor=#|992hPa || None || || |||-| || || bgcolor=#| || bgcolor=#|105kn || bgcolor=#|943hPa || Mascarene Islands || || |||-

See also

External links

Notes and References

  1. Web site: Real-Time Tropical Cyclone South Indian Ocean Statistics. Colorado State University. Fort Collins, Colorado. October 1, 2024.
  2. Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean . 8 August 2024 . . 8 August 2024 . 9 August 2024 . https://web.archive.org/web/20240809150556/http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/activiteope/bulletins/zcit/ZCITA_202408081121.pdf . live .
  3. Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean . 11 August 2024 . . 11 August 2024 . 11 August 2024 . https://web.archive.org/web/20240811212351/http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/activiteope/bulletins/zcit/ZCITA_202408111119.pdf . live .
  4. Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean . 14 August 2024 . . 14 August 2024.
  5. abio. 90S. https://www.metoc.navy.mil/jtwc/products/abioweb.txt. 2024-08-15. https://archive.today/20240815084533/https://www.metoc.navy.mil/jtwc/products/abioweb.txt. 01Z. 2024-08-15. 1.
  6. Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean . 15 August 2024 . . 15 August 2024 . 15 August 2024 . https://web.archive.org/web/20240815113437/http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/activiteope/bulletins/zcit/ZCITA_202408151102.pdf . live .
  7. tcfa. 90S. https://www.metoc.navy.mil/jtwc/products/sh9025web.txt. 2024-08-15. https://archive.today/20240815184533/https://www.metoc.navy.mil/jtwc/products/sh9025web.txt. 18Z. 2024-08-15.
  8. 01 - 14/08/2023 TO 17/08/2024. 2024. 2024-08-22 . Météo-France.
  9. Zone of Disturbed Weather 01 Warning Number (6/1/20242025). Météo-France. 17 August 2024. 17 August 2024. live. 17 August 2024. https://web.archive.org/web/20240817130131/http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/activiteope/bulletins/cmrs/CMRSA_202408170630.pdf.
  10. tcfa. 90S. https://www.metoc.navy.mil/jtwc/products/sh9025web.txt. 2024-08-17. https://archive.today/20240817183007/https://www.metoc.navy.mil/jtwc/products/sh9025web.txt. 1751Z. 1. 2024-08-17.
  11. Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean . 18 August 2024 . . 18 August 2024 . 18 August 2024 . https://web.archive.org/web/20240818150447/http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/activiteope/bulletins/zcit/ZCITA_202408181217.pdf . live .
  12. Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean . 20 August 2024 . . 20 August 2024.
  13. abio. 90S. https://www.metoc.navy.mil/jtwc/products/sh9025web.txt. 2024-08-21. https://archive.today/20240821181647/https://www.metoc.navy.mil/jtwc/products/abioweb.txt. 1800Z. 2024-08-21.
  14. Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean . 22 August 2024 . . 22 August 2024.
  15. Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean . 24 September 2024 . . 27 September 2024.
  16. Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean . 25 September 2024 . . 27 September 2024 . 3 October 2024 . https://web.archive.org/web/20241003165158/http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/activiteope/bulletins/zcit/ZCITA_202409251135.pdf . live .
  17. abio. 90S. https://www.metoc.navy.mil/jtwc/products/abioweb.txt. 2024-09-30. https://archive.today/20240930235038/https://www.metoc.navy.mil/jtwc/products/abioweb.txt. 2230Z. 2024-09-30. 1.
  18. Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean . 1 October 2024 . . 1 October 2024 . 5 October 2024 . https://web.archive.org/web/20241005213902/http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/activiteope/bulletins/zcit/ZCITA_202410011311.pdf . live .
  19. warn. tc. 01S. One. 1. 1 October 2024. 1 October 2024. 1 October 2024. https://www.metoc.navy.mil/jtwc/products/sh0125prog.txt. https://archive.today/20241001214744/https://www.metoc.navy.mil/jtwc/products/sh0125prog.txt.
  20. Moderate Tropical Storm 02 (Ancha) Warning Number (3/2/20242025). Météo-France. 2 October 2024. 2 October 2024. live. 3 October 2024. https://web.archive.org/web/20241003094139/http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/activiteope/bulletins/cmrs/CMRSA_202410020101.pdf.
  21. warn. tc. 01S. Ancha. 4. 2 October 2024. 2 October 2024. 2 October 2024. https://www.metoc.navy.mil/jtwc/products/sh0125prog.txt. https://archive.today/20241002180134/https://www.metoc.navy.mil/jtwc/products/sh0125prog.txt.
  22. Moderate Tropical Storm 02 (Ancha) Warning Number (4/2/20242025). Météo-France. 2 October 2024. 2 October 2024.
  23. warn. tc. 01S. Ancha. 6. 3 October 2024. 3 October 2024. 3 October 2024. https://www.metoc.navy.mil/jtwc/products/sh0125prog.txt. https://archive.today/20241003225701/https://www.metoc.navy.mil/jtwc/products/sh0125prog.txt.
  24. Moderate Tropical Storm 02 (Ancha) Warning Number (9/2/20242025). Météo-France. 3 October 2024. 3 October 2024.
  25. Filling Up 02 (Ancha) Warning Number (10/2/20242025). Météo-France. 3 October 2024. 3 October 2024.
  26. Moderate Tropical Storm 02 (Ancha) Warning Number (11/2/20242025). Météo-France. 4 October 2024. 4 October 2024. live. 8 October 2024. https://web.archive.org/web/20241008125239/http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/activiteope/bulletins/cmrs/CMRSA_202410040658.pdf.
  27. Filling Up 02 (Ancha) Warning Number (12/2/20242025). Météo-France. 4 October 2024. 4 October 2024.
  28. Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean . 11 November 2024 . . 11 November 2024 . 11 November 2024 . https://web.archive.org/web/20241111153436/http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/activiteope/bulletins/zcit/ZCITA_202411111157.pdf . live .
  29. abio. 90S. https://www.metoc.navy.mil/jtwc/products/abioweb.txt. 2024-11-11. https://wiki.chlod.net/jtwc/text/2024-11-11-1830-abioweb.txt. 18Z. 2024-11-12. 1.
  30. Zone of Disturbed Weather 03 Warning Number (1/3/20242025). Météo-France. 12 November 2024. 12 November 2024. live. 27 November 2024. https://web.archive.org/web/20241127051328/http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/activiteope/bulletins/cmrs/CMRSA_202411121336.pdf.
  31. Moderate Tropical Storm 3 (Bheki) Warning Number (9/3/20242025). Météo-France. 14 November 2024. 15 November 2024.
  32. warn. tc. 02S. Bheki. 1. 14 November 2024. 15 November 2024. 14 November 2024. https://www.metoc.navy.mil/jtwc/products/sh0225prog.txt. https://wiki.chlod.net/jtwc/prog/2024-11-14-1410-sh0225prog.txt.
  33. Severe Tropical Storm 3 (Bheki) Warning Number (11/3/20242025). Météo-France. 15 November 2024. 15 November 2024.
  34. Web site: fr . Cyclone Warning Bulletin Rodrigues (French Version) . 2024-11-20 . Mauritius Meteorological Services . 2024-11-20 . 2024-11-20 . https://web.archive.org/web/20241120042422/http://metservice.intnet.mu/cyclone-bulletin-french-rodrigues.php . live.
  35. News: fr . Mathieu Saintomer . Forte tempête tropicale Bheki : Rodrigues passe en alerte de classe 4 . Linfo.re . 2024-11-20 . November 20, 2024.
  36. Web site: fr . Cyclone Bheki: 64% des Rodriguais ont été privés de courant . 2024-11-21 . lexpress.mu . 2024-11-21.
  37. Web site: fr . Cyclone Bheki: Rodrigues balayée par le choc de l'alerte IV . 2024-11-21 . lexpress.mu . 2024-11-21.
  38. RA I Tropical Cyclone Committee . World Meteorological Organization . Tropical Cyclone Operational Plan for the South-West Indian Ocean. 2023. PDF . https://web.archive.org/web/20240702081536/https://www.theedkins.co.uk/storms/RAI_TCC-25_OperationalPlan_WMO-Nr1178_EN.pdf. 2024-07-02.