Weather models suggest that La Niña conditions and a favourable Indian Ocean Dipole (IOD) could bring average to above-average rainfall to much of South Africa over the next three months.

By Alani Janeke, Senior Journalist at African Farming and Landbouweekblad

Two of the four main Niño regions are now La Niña-leaning, meaning the sea surface temperature deviation is 0,5°C cooler or more than normal, according to independent agricultural meteorologist Johan van den Berg.

Forecasts show that a rapid cooling of sea surface temperatures is expected in November, before warming again in December to reach neutral levels by that month or in January. After that, sea surface temperatures could become El Niño-leaning, he says.

The IOD is also in a very favourable phase for rainfall in South Africa’s summer rainfall regions over the next month or two.

The combined effect of the La Niña trend and a favourable IOD could result in average to above-average rainfall from November to January, Van den Berg says.

Also read: Hail, storms and fluctuating temperatures expected until mid-November

Cyclones in the Indian Ocean

A tropical storm formed north of Madagascar in the third week of October but quickly dissipated. Currently, a thin band of slightly warmer-than-normal sea surface temperatures extends east-west north of the island.

Overall, however, the north-western Indian Ocean closer to Africa’s coastline is fairly normal, or even a little cooler than normal. This pattern supports the negative phase of the IOD, which benefits Southern Africa’s rainfall prospects.

Warmer water is more concentrated in the north-eastern Indian Ocean.

This set-up reduces the risk of very strong cyclones in the western Indian Ocean but increases the risk for the region between India and Australia and further east, Van den Berg says.