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2024–25 South-West Indian Ocean cyclone season

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2024–25 South-West Indian Ocean cyclone season
Season summary map
Seasonal boundaries
First system formed15 August 2024
Last system dissipatedSeason ongoing
Strongest storm
NameAncha
 • Maximum winds85 km/h (50 mph)
(10-minute sustained)
 • Lowest pressure992 hPa (mbar)
Seasonal statistics
Total disturbances2
Total depressions2
Total storms1
Tropical cyclones0
Intense tropical cyclones0
Very intense tropical cyclones0
Total fatalities0
Total damage$0,000 (2025 USD)
Related articles
South-West Indian Ocean tropical cyclone seasons
2022–23, 2023–24, 2024–25, 2025–26, 2026–27

The 2024–25 South-West Indian Ocean cyclone season is the current annual cycle of tropical cyclone and subtropical cyclone formation. It begins 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, like 01 in August, 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.

Seasonal summary

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Tropical cyclone scales#Comparisons across basins

This season's ACE index, as of 09:00 UTC on October 2, is approximately 0.6 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

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Tropical Depression 01

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Tropical depression (MFR)
 
Duration15 August – 17 August
Peak intensity55 km/h (35 mph) (10-min);
1000 hPa (mbar)
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

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Moderate tropical storm (MFR)
Tropical storm (SSHWS)
 
Duration30 September – 5 October
Peak intensity85 km/h (50 mph) (10-min);
992 hPa (mbar)
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 60 mph (95 km/h).[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 50 mph (85 km/h).[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]

Storm names

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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.[28]

  • Ancha
  • Bheki (unused)
  • Chido (unused)
  • Dikeledi (unused)
  • Elvis (unused)
  • Faida (unused)
  • Garance (unused)
  • Honde (unused)
  • Ivone (unused)
  • Jude (unused)
  • Kanto (unused)
  • Lira (unused)
  • Maipelo (unused)
  • Njazi (unused)
  • Oscar (unused)
  • Pamela (unused)
  • Quentin (unused)
  • Rajab (unused)
  • Savana (unused)
  • Themba (unused)
  • Uyapo (unused)
  • Viviane (unused)
  • Walter (unused)
  • Xangy (unused)
  • Yemurai (unused)
  • Zanele (unused)

Season effects

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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.

Name Dates Peak intensity Areas affected Damage
(USD) 		Deaths Refs
Category Wind speed Pressure
01 15 – 17 August Tropical depression 55 km/h (35 mph) 1000 hPa (29.53 inHg) Chagos Archipelago None 0
Ancha 30 September – 5 October Moderate tropical storm 85 km/h (50 mph) 992 hPa (29.29 inHg) None None 0
Season aggregates
2 systems 15 August – Season ongoing 85 km/h (50 mph) 992 hPa (30 inHg) None None

See also

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References

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  1. ^ "Real-Time Tropical Cyclone South Indian Ocean Statistics". Fort Collins, Colorado: Colorado State University. Retrieved October 1, 2024.
  2. ^ Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean (PDF) (Report). Météo-France. 8 August 2024. Retrieved 8 August 2024.
  3. ^ Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean (PDF) (Report). Météo-France. 11 August 2024. Retrieved 11 August 2024.
  4. ^ Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean (PDF) (Report). Météo-France. 14 August 2024. Retrieved 14 August 2024.
  5. ^ Significant Tropical Weather Advisory for the Indian Ocean, 01Z 15 August 2024 Reissued (Report). United States Joint Typhoon Warning Center. 15 August 2024. Archived from the original on 2024-08-15. Retrieved 15 August 2024.
  6. ^ Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean (PDF) (Report). Météo-France. 15 August 2024. Retrieved 15 August 2024.
  7. ^ Tropical Cyclone Formation Alert (Invest 90S) (Report). United States Joint Typhoon Warning Center. 15 August 2024. Archived from the original on 2024-08-15. Retrieved 15 August 2024.
  8. ^ 01 - 14/08/2023 TO 17/08/2024 (Report). Météo-France. 2024. Retrieved 2024-08-22.
  9. ^ Zone of Disturbed Weather 01 Warning Number (6/1/20242025) (PDF) (Report). Météo-France. 17 August 2024. Retrieved 17 August 2024.{{cite report}}: CS1 maint: url-status (link)
  10. ^ Tropical Cyclone Formation Alert (Invest 90S) Cancellation (Report). United States Joint Typhoon Warning Center. 17 August 2024. Archived from the original on 2024-08-17. Retrieved 17 August 2024.
  11. ^ Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean (PDF) (Report). Météo-France. 18 August 2024. Retrieved 18 August 2024.
  12. ^ Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean (PDF) (Report). Météo-France. 20 August 2024. Retrieved 20 August 2024.
  13. ^ Significant Tropical Weather Advisory for the Indian Ocean, 1800Z 21 August 2024 (Report). United States Joint Typhoon Warning Center. 21 August 2024. Archived from the original on 2024-08-21. Retrieved 21 August 2024.
  14. ^ Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean (PDF) (Report). Météo-France. 22 August 2024. Retrieved 22 August 2024.
  15. ^ Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean (PDF) (Report). Météo-France. 24 September 2024. Retrieved 27 September 2024.
  16. ^ Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean (PDF) (Report). Météo-France. 25 September 2024. Retrieved 27 September 2024.
  17. ^ Significant Tropical Weather Advisory for the Indian Ocean, 2230Z 30 September 2024 Reissued (Report). United States Joint Typhoon Warning Center. 30 September 2024. Archived from the original on 2024-09-30. Retrieved 30 September 2024.
  18. ^ Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean (PDF) (Report). Météo-France. 1 October 2024. Retrieved 1 October 2024.
  19. ^ Tropical Cyclone 01S (One) Warning No. 1 (Report). United States Joint Typhoon Warning Center. 1 October 2024. Archived from the original on 1 October 2024. Retrieved 1 October 2024.
  20. ^ Moderate Tropical Storm 02 (Ancha) Warning Number (3/2/20242025) (PDF) (Report). Météo-France. 2 October 2024. Retrieved 2 October 2024.{{cite report}}: CS1 maint: url-status (link)
  21. ^ Tropical Cyclone 01S (Ancha) Warning No. 4 (Report). United States Joint Typhoon Warning Center. 2 October 2024. Archived from the original on 2 October 2024. Retrieved 2 October 2024.
  22. ^ Moderate Tropical Storm 02 (Ancha) Warning Number (4/2/20242025) (PDF) (Report). Météo-France. 2 October 2024. Retrieved 2 October 2024.{{cite report}}: CS1 maint: url-status (link)
  23. ^ Tropical Cyclone 01S (Ancha) Warning No. 6 (Report). United States Joint Typhoon Warning Center. 3 October 2024. Archived from the original on 3 October 2024. Retrieved 3 October 2024.
  24. ^ Moderate Tropical Storm 02 (Ancha) Warning Number (9/2/20242025) (PDF) (Report). Météo-France. 3 October 2024. Retrieved 3 October 2024.{{cite report}}: CS1 maint: url-status (link)
  25. ^ Filling Up 02 (Ancha) Warning Number (10/2/20242025) (PDF) (Report). Météo-France. 3 October 2024. Retrieved 3 October 2024.{{cite report}}: CS1 maint: url-status (link)
  26. ^ Moderate Tropical Storm 02 (Ancha) Warning Number (11/2/20242025) (PDF) (Report). Météo-France. 4 October 2024. Retrieved 4 October 2024.{{cite report}}: CS1 maint: url-status (link)
  27. ^ Filling Up 02 (Ancha) Warning Number (12/2/20242025) (PDF) (Report). Météo-France. 4 October 2024. Retrieved 4 October 2024.{{cite report}}: CS1 maint: url-status (link)
  28. ^ RA I Tropical Cyclone Committee (2023). Tropical Cyclone Operational Plan for the South-West Indian Ocean (PDF) (Report). World Meteorological Organization. Archived from the original (PDF) on 2024-07-02.
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