The 2010–11 South-West Indian Ocean cyclone season was the least active cyclone season on record in the basin, tied with 1982–83, producing only three systems of gale intensity. This was due to cooler than normal water temperatures and the Walker circulation – a broad atmospheric circulation – causing unusually moist conditions in the eastern Indian Ocean and unusually dry conditions in the western Indian Ocean. The basin includes the waters of the ocean south of the equator and west of 90º E to the eastern coast of Africa.
There were nine tropical or subtropical cyclones during the season, including five weak tropical disturbances or depressions, mostly in the northeastern portion of the basin or to the east of Madagascar. The first of these systems developed on 25 October 2010, which had its origins in the northeastern portion of the basin. On 29 November, the first named storm – Abele – also formed in the same area, strengthening to become one of the season's two tropical cyclones – storms with maximum sustained winds of at least . The strongest system of the season was Cyclone Bingiza, which attained peak winds of off the northeastern coast of Madagascar in February. Bingiza was also the only storm to cause severe effects on land, causing heavy damage and 34 fatalities across Madagascar. Moderate Tropical Storm Cherono developed in March and traversed much of the ocean, only brushing by the island of Rodrigues. The final system was a subtropical depression that intensified south of Madagascar, becoming extratropical on 16 April to end the season.
Season forecast and summary
On 22 October 2010, the MMS released their seasonal outlook and predicted that there would be 8–10 named storms within the basin during the season. At the end of December, the MMS issued an updated seasonal outlook, predicting that only 6–8 named storms would develop.
As the season began, strong La Niña conditions persisted across the Pacific and Indian oceans, causing an increase in cyclonic flow near the equator over the Indian Ocean. However, atmospheric conditions over the basin significantly decreased tropical cyclogenesis. The Walker circulation – a broad atmospheric circulation – caused unusually moist conditions in the eastern Indian Ocean while producing an increase in subsidence and unusually dry conditions in the western Indian Ocean. In addition, sea surface temperatures were below normal from 5°–15° S and west of 90° E, which limited storm formation near the Chagos Archipelago, typically a common area of formation. By the end of the season, there were only three named storms, the fewest in 50 years, although there was also a subtropical cyclone with gale-force winds that could have been named. In terms of total days in which cyclones were active, the season was slightly behind the 1982–83 season, thus making the 2010–11 season the second-quietest on record. The season also marked a global trend of decreasing tropical cyclone activity over the preceding five years, although the basin experienced a sudden shift toward increased activity in the subsequent season.
Météo-France's meteorological office in Réunion (MFR) – the official Regional Specialized Meteorological Center for the South-West Indian Ocean – tracked and named all tropical cyclones from the east coast of Africa to 90° E. The Joint Typhoon Warning Center (JTWC), which is a joint United States Navy – United States Air Force task force that issues tropical cyclone warnings for the region, also issued advisories for storms during the season.