Snow not unusual during spring in SA, say experts

The weather service predicts a La Nina event bringing hotter temperatures for the next few months but the rain outlook is unclear

People walk in the snow in Swinburne, between Harrismith and Van Reenen in KwaZulu-Natal in September 2024.
People walk in the snow in Swinburne, between Harrismith and Van Reenen in KwaZulu-Natal in September 2024.
Image: DARRYL HAMMOND

A historical overview of the frequency of snowfall shows snow in September is not unusual, the SA Weather Service says (Saws).

Before motorists were trapped overnight between Gauteng and KwaZulu-Natal a week ago, Saws lead scientist for long-range prediction Christien Engelbrecht said heavy snowfall caused roads to be closed in the KwaZulu-Natal Midlands and the Eastern Cape in September 2008.

Significant snow events have also occurred in October, though not frequently, she told the Pretoria press club on Tuesday.

Saws disaster risk senior manager Rudzani Malala said snow in late winter and early spring is not rare. 

“Snow is not restricted to winter only.”

The more intense, extreme snow systems tend to affect Southern Africa in late winter, especially over the eastern provinces, he said. However, “we have had snow in Johannesburg as late as October in 2011”.

“On rare occasions (three times in the past century) snow has occurred on New Year’s Day over the Drakensberg.”

Providing a forecast for the next few days, Malala said a surface high ridging south of the subcontinent will continue to see cool, moisture-laden air over the eastern provinces, resulting in a chance of light rain showers over KwaZulu-Natal and eastern Mpumalanga.

“A surface high ridge is a high-pressure system, the consequence of which is rain. Then, towards the end of the week, the eastern parts will dry out and warm up, with the emphasis shifting to the western extremities of the country, where an approaching upper air disturbance over the Atlantic Ocean is expected to promote the development of isolated showers and thundershowers over Namibia as well as the coast and adjacent interior of the Northern Cape. Consequently, in the week ahead, the weather is expected to be benign, with no severe or extreme weather expected,” he said.

He advised the public to remain vigilant as October and November in the highveld region — the northern Free State, Gauteng and the eastern highveld of Mpumalanga — are known to be associated with severe storms and the possibility of large, damaging hail and/or strong, damaging winds. The public must also be mindful of heatwaves.

Providing a seasonal outlook, Engelbrecht said the El Nino Southern Oscillation (Enso) is in a neutral phase with a high likelihood of a La Nina event developing during Spring (September to November).

A weak La Nina event is expected in the 2024-2025 summer season. 

“The seasonal prediction can be generated to midsummer (December-January-February). Without strong Enso forcing, rainfall predictions from different seasonal prediction models show variation or no clear signal whether above normal or below normal rainfall is favoured over a particular area.”

She said the exception is the southeastern parts of the country, where seasonal prediction models indicate above normal rainfall for spring and midsummer.

“Maximum and minimum temperatures are predicted to be above normal over most of South Africa, in particular over the western interior when it comes to the maximum temperature predictions.”

Engelbrecht said in terms of rainfall patterns for the remainder of spring and midsummer over Southern Africa, “we are not that certain — the probabilities for above normal rainfall which is usually expected during a La Nina event is low and a bit patchy”.

The only area where most seasonal models indicate a higher or most consistent sign of rainfall outcome is over the eastern part of the country.

“For the interior, the rainfall outlook is not that favourable and the signal is weak. We are not sure what is going to happen over the remainder of the country in terms of the rainfall prediction for the rest of the spring season and the midsummer period,” Engelbrecht said.

TimesLIVE


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