Parts of southern Africa are experiencing torrential rain which is causing serious flooding.
Zimbabwe has been badly affected in recent days. At least a dozen people have been killed and the country’s lack of disaster management infrastructure has been blamed for some of the disruption that has followed.
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The country also experienced severe flooding in April 2014, when more than 20,000 people were displaced by what was reportedly the heaviest rainfall in 40 years.
That was very much a freak event, at the end of the rainy season. The current rain is to be expected, as it is falling at the peak of the seasonal rains.
At this time of year, the northeasterly monsoon of East Africa moves into the region forming a boundary with the easterly winds moving in from the Indian Ocean along the Intertropical Convergence Zone (ITCZ). Zimbabwe, Mozambique and Madagascar experience most of their seasonal rain from this system.
Another line of significant weather is produced by the interaction of those same easterly winds, and westerly winds which move in across Angola and the Democratic Republic of the Congo. This is known as the Zaire Air Boundary (ZAB). The ZAB fluctuates on a daily basis with areas of low pressure forming along it, bringing wet weather to Zambia and Angola.
Rainfall may turn even more extreme because of the formation of tropical cyclones in the southern Indian Ocean, from mid-January through February. These storm systems impact the east coast of Tanzania and Mozambique, although they rarely make much inland penetration.
The heaviest rain is currently in central Mozambique, and across the Mozambique Channel into Madagascar. Flooding is likely in the coming days.
A tropical cyclone, Bansi, has also formed to the east of Madagascar and this is bringing wet and windy weather to both Mauritius and Reunion. It is expected that Bansi will move away towards the southeast in the coming days.