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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
NameChido
 • Maximum winds215 km/h (130 mph)
(10-minute sustained)
 • Lowest pressure935 hPa (mbar)
Seasonal statistics
Total disturbances4
Total depressions4
Total storms3
Tropical cyclones2
Intense tropical cyclones2
Very intense tropical cyclones0
Total fatalities80
Total damageUnknown
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 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, Ancha, and Bheki, 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.

The first system formed before the official start of the season, Tropical Depression 01, but the disturbance failed to organize into a tropical storm and dissipated on 17 August. In late September, Tropical Storm Ancha formed without making landfall, and a month later, three days before the official start of the season, Tropical Storm Bheki formed, which became the first intense tropical cyclone of the season a few days later, leaving heavy rains in the Mascarene Islands. In mid-December, Tropical Storm Chido formed and rapidly intensified into a Category 4-equivalent tropical cyclone two days later, then made landfall on Agaléga North Island. Chido then peaked as a high-end Category 4 equivalent cyclone before weakening down to a Category 3 then eventually to a Category 2 northeast of Madagascar. The cyclone then rapidly intensified back to a Category 4 equivalent cyclone and made landfall on Mayotte, becoming the strongest landfalling cyclone in the island on record.

Seasonal summary

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Cyclone ChidoTropical cyclone scales#Comparisons across basins

Background

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This season's ACE index, as of December 14, is approximately 40.3 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. Through 2024, five tropical cyclones, four of which became tropical storms, formed outside the cyclone season in the southwest Indian Ocean, becoming the highest off-season tropical storms in the year, surpassing 2002 and 2003 with three named storms. Overall, a total of four tropical cyclones formed, three of which intensified into nameable storms. Of those, two strengthened into tropical cyclones, with all of them reaching intense tropical cyclones.

Pre/early season activity

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The season officially started on 15 November 2024; however, the first system, Tropical Depression 01, formed on August 15, just three months before the official start. In late–September, Moderate Tropical Storm Ancha formed on September 30 and dissipated five days later without making landfall. Three days before the official start of the season, Tropical Storm Bheki formed, which days later became the first intense tropical cyclone in the basin. Bheki caused heavy rainfall in parts of the Mascarene Islands such as Réunion and Rodrigues. After the dissipation of Bheki, Tropical Storm Chido formed on December 9, and two days later became the second intense tropical cyclone of the season.

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] Later, increasing tropospheric shear caused this temporary regeneration to end, and the MFR would stop monitoring it on 4 October.[27]

Intense Tropical Cyclone Bheki

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Intense tropical cyclone (MFR)
Category 4 tropical cyclone (SSHWS)
 
Duration12 November – 23 November
Peak intensity195 km/h (120 mph) (10-min);
943 hPa (mbar)
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 100 to 122 km/h (62 to 76 mph) 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 5 to 7 m (16 to 23 ft) swell caused coastal flooding and in Montagne-Goyave, the community school suffered heavy damage.[37]

Intense Tropical Cyclone Chido

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Intense tropical cyclone (MFR)
Category 4 tropical cyclone (SSHWS)
 
Duration7 December – 16 December
Peak intensity215 km/h (130 mph) (10-min);
935 hPa (mbar)
Main article: Cyclone Chido

On 9 December, MFR noted that a tropical disturbance formed southeast of Diego Garcia. The JTWC began tracking the system later that day, noting that it was in an environment favorable for development. Late on 9 December, the MFR designated the system as Tropical Depression 04. At 00.00 UTC, the system intensified into Moderate Tropical Storm Chido. Chido continued to strengthen, eventually becoming a Severe Tropical Storm later on 10 December. On 11 December, Chido developed an eye, and rapidly strengthened into a mid-range Category 4-equivalent intense tropical cyclone, as it made landfall on Agaléga North Island with 1-minute sustained winds of 140 mph (230 km/h).[38] The next day, Chido intensified further, peaking as an intense tropical cyclone, with 1-minute sustained winds exceeding 155 mph (249 km/h). Shortly before traversing past the northern tip of Madagascar, Chido weakened on 13 December, but as it neared Mayotte, it quickly re-intensified, making its second landfall near Bandraboua at a low-end Category 4-equivalent cyclone by 12:00 UTC on 14 December. Chido briefly continued to intensify before weakening again, while heading towards mainland Africa in a west-southwestward direction. Chido maintained category 4 intensity as it moved towards Africa, making landfall south of the city of Pemba in Mozambique in the morning on 15 December as a strong Category 4-equivalent intense tropical cyclone, became the strongest cyclone to made landfall in Mozambique since Cyclone Kenneth in 2019.

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.[39]

  • Ancha
  • Bheki
  • Chido
  • 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
Bheki 12–23 November Intense tropical cyclone 195 km/h (120 mph) 943 hPa (27.85 inHg) Mascarene Islands Unknown 0
Chido 7–16 December Intense tropical cyclone 215 km/h (130 mph) 935 hPa (27.61 inHg) Agaléga, Farquhar, Madagascar, Mayotte, Comoros, Mozambique, Malawi Unknown 63
Season aggregates
4 systems 15 August – Season ongoing 215 km/h (130 mph) 935 hPa (27.61 inHg) None 63

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 December 14, 2024.
  2. ^ Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean (PDF) (Report). Météo-France. 8 August 2024. Archived (PDF) from the original on 9 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. Archived (PDF) from the original on 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. Archived (PDF) from the original on 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. Archived (PDF) from the original on 17 August 2024. Retrieved 17 August 2024.
  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. Archived (PDF) from the original on 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. Archived (PDF) from the original on 3 October 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. Archived (PDF) from the original on 5 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. Archived (PDF) from the original on 3 October 2024. Retrieved 2 October 2024.
  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.
  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.
  25. ^ Filling Up 02 (Ancha) Warning Number (10/2/20242025) (PDF) (Report). Météo-France. 3 October 2024. Retrieved 3 October 2024.
  26. ^ Moderate Tropical Storm 02 (Ancha) Warning Number (11/2/20242025) (PDF) (Report). Météo-France. 4 October 2024. Archived (PDF) from the original on 8 October 2024. Retrieved 4 October 2024.
  27. ^ Filling Up 02 (Ancha) Warning Number (12/2/20242025) (PDF) (Report). Météo-France. 4 October 2024. Retrieved 4 October 2024.
  28. ^ Bulletin for Cyclonic Activity and Significant Tropical Weather in the Southwest Indian Ocean (PDF) (Report). Météo-France. 11 November 2024. Archived (PDF) from the original on 11 November 2024. Retrieved 11 November 2024.
  29. ^ Significant Tropical Weather Advisory for the Indian Ocean, 18Z 11 November 2024 Reissued (Report). United States Joint Typhoon Warning Center. 11 November 2024. Archived from the original on 2024-11-12. Retrieved 11 November 2024.
  30. ^ Zone of Disturbed Weather 03 Warning Number (1/3/20242025) (PDF) (Report). Météo-France. 12 November 2024. Archived (PDF) from the original on 27 November 2024. Retrieved 12 November 2024.
  31. ^ Moderate Tropical Storm 3 (Bheki) Warning Number (9/3/20242025) (PDF) (Report). Météo-France. 14 November 2024. Retrieved 15 November 2024.
  32. ^ Tropical Cyclone 02S (Bheki) Warning No. 1 (Report). United States Joint Typhoon Warning Center. 14 November 2024. Archived from the original on 14 November 2024. Retrieved 15 November 2024.
  33. ^ Severe Tropical Storm 3 (Bheki) Warning Number (11/3/20242025) (PDF) (Report). Météo-France. 15 November 2024. Retrieved 15 November 2024.
  34. ^ "Cyclone Warning Bulletin Rodrigues (French Version)" (in French). Mauritius Meteorological Services. 2024-11-20. Archived from the original on 2024-11-20. Retrieved 2024-11-20.
  35. ^ Mathieu Saintomer (2024-11-20). "Forte tempête tropicale Bheki : Rodrigues passe en alerte de classe 4". Linfo.re (in French). Retrieved November 20, 2024.
  36. ^ "Cyclone Bheki: 64% des Rodriguais ont été privés de courant". lexpress.mu (in French). 2024-11-21. Retrieved 2024-11-21.
  37. ^ "Cyclone Bheki: Rodrigues balayée par le choc de l'alerte IV". lexpress.mu (in French). 2024-11-21. Retrieved 2024-11-21.
  38. ^ "CYCLONE et ACTIVITE CYCLONIQUE par Météo-France La Réunion". meteofrance.re. Retrieved 2024-12-12.
  39. ^ 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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