In April 2022, several days of unsettled weather brought copious amounts of rain to southern Africa. In KwaZulu-Natal, a province on the eastern coast of South Africa, the deluge spurred deadly flooding and landslides.
The South African Weather Service emphasized that the storm was not a tropical cyclone—a type of storm that forms over warm tropical waters. Rather, the storm developed farther from the equator, when an area of low pressure detached from the prevailing westerly flow of cold air and drifted north toward South Africa. Once separated from the westerlies, “cut-off lows” like this often lose momentum and can get stuck in place for days. In South Africa, this occurs most often during the southern hemisphere’s autumn, especially in April. Cut-off lows often produce severe weather.
The storm began dropping rain over coastal South Africa on April 9, 2022. The rain continued for days, enhanced by moisture-laden air from the southern Indian ocean. Rainfall totals were especially substantial between April 11-12. In a news release issued on April 12, the South African Weather Service wrote: “It appears that the exceptionally heavy rainfall overnight and this morning exceeded even the expectations of the southern African meteorological community at large.”
The map above depicts a satellite-based estimate of rainfall over a seven-day period ending on April 13, 2022. The darkest reds reflect the highest rainfall amounts, with some places in Botswana and South Africa receiving as much as 30 centimeters (12 inches) or more. The data are remotely sensed estimates that come from the Integrated Multi-Satellite Retrievals for GPM (IMERG), a product of the Global Precipitation Measurement (GPM) satellite mission. Local rainfall amounts can be significantly higher when measured from the ground.
In some parts of KwaZulu-Natal, ground-based measurements showed rainfall exceeding 30 centimeters (12 inches) during a 24-hour period spanning April 11-12. Preliminary data indicate that some of the province’s highest totals were observed in Margate (31.1 centimeters/12.2 inches), Mount Edgecombe (30.7 centimeters/12.1 inches), and Durban North (30.1 centimeters/11.9 inches). According to news reports, it was the province’s heaviest single-day deluge in 60 years.
Flooding and landslides across KwaZulu-Natal destroyed homes, bridges, and roads. At the Port of Durban, floodwaters swept away stacks of freight containers, and caused enough damage to temporarily suspended port operations. According to the KwaZulu-Natal Provincial Disaster Management, at least 300 people have died.
Forecasters are calling for a break in heavy rain from April 14-15. By the weekend, however, they expect thunderstorms to bring more rain and possibly additional flooding.
NASA Earth Observatory image by Joshua Stevens, using IMERG data from the Global Precipitation Mission (GPM) at NASA/GSFC. Story by Kathryn Hansen.