Johannesburg - Tropical storms may start affecting South Africa more and more as they start originating further south and move towards our coastline.

This is according to new research carried out by Wits University scientists, who said that although the storms are not increasing in number, they appear to be moving further south.

The study, which was published in the International Journal of Climatology, predicts that South Africa could be at an increased risk of being directly affected by tropical cyclones in the next 40 years.

The study’s authors – Jennifer Fitchett and Professor Stefan Grab – from the Wits School of Geography, Archaeology and Environmental Studies, looked at where storms have been occurring in the south-west Indian Ocean over the past 161 years.

They found that the oceans have warmed and the minimum sea-surface temperature necessary for a cyclone to develop has moved further south, with the storms following suit.

Most cyclones hit Madagascar and do not continue to Mozambique. Those which hit Mozambique develop to the north of Madagascar. But in the past 20 years there have been four storms that originated south of Madagascar hitting Mozambique.

“This definitely looks like the start of a trend,” Fitchett said.

South Africa is already feeling the effects of this shift. The cyclones that hit southern Mozambique cause heavy rain and flooding in Limpopo. “At the current rates (of climate change), we could see frequent serious damage in South Africa by 2050,” she added.

“This is not what we expected from climate change. We thought tropical cyclones might increase in number, but we never expected them to move.”

Fitchett said there has been an assumption that increasing sea-surface temperatures caused by global warming was causing an increase in the number of tropical cyclones.

But the authors found that there has been no increase in the number of tropical cyclones, and that much of the perceived change in numbers is a result of improved storm-detection methods.


Willem Landman, chief researcher and meteorologist at the csir, said the results of the study were different from those predicted in the movement of tropical storms in the area.

This data could help inform better models used to predict the movement of the storms, as it was based on actual observations, he added. - The Star