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Highveld storm season looms — be vigilant, SA Weather Service urges

Highveld storm season looms — be vigilant, SA Weather Service urges
SA Weather Service lead scientist in long-range prediction, Dr Christien Engelbrecht, speaking at a SAWS media briefing in Pretoria, 1 October 2024. At the rear are SAWS senior forecaster Puseletso Mofokeng (right) and senior manager for disaster Risk management Rudzani Malala. (Photo: Julia Evans)
Julia Evans
By Julia Evans
1 Oct 2024
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Following snowfall that, despite forewarning, left hundreds stranded on national highways and caused at least one fatality, the SA Weather Service has urged people to be weather-smart in possible severe spring weather.

‘Given South Africa’s vulnerability to hazardous weather events, such as severe thunderstorms, floods, droughts, heatwaves and wildfires, there is an urgent need for the public to be weather smart,” said Rudzani Malala, senior South African Weather Service (SAWS) manager for disaster risk management.

Halala was speaking at a media briefing in Tshwane on Tuesday, 1 October 2024, following the snowstorm over the heritage weekend (19-22 September), that caught out many South Africans – leaving 1,700 to 1,800 vehicles stranded on roads between the Free State, KwaZulu-Natal and the Eastern Cape, and at least one fatality due to hypothermia.

snowfall Snow strands KZN motorists in the snowstorm over the heritage weekend of 19-22 September. (Photo: Zola Hashatsi ka Motsiri / Facebook)



highveld storms season snowfall A vehicle trapped by the recent snowstorm over the heritage weekend of 19-22 September, on its way to Witsieshoek Mountain Lodge in the Drakensberg, about 3km from the lodge. Snow was about 2m deep in some places. (Photo: Groenewald Basson / Severe Weather and Information Centre SA)




 

As October and November in the Highveld region are known to be associated with severe storms, Malala urged people to remain vigilant.

An event forewarned


SAWS, the only mandated regulatory body in the country that can issue weather warnings, is responsible for providing weather and climate warning services.

But Malala emphasised on Tuesday that SAWS accurately predicted the system that caused the snow event and warned of its anticipated impact in advance.

As Daily Maverick reported after the event, SAWS issued warnings as early as Wednesday, 18 September for disruptive snow and indicated that heavy snow could lead to icy roads and major traffic disruptions. It instructed people to avoid travelling on affected roads.

As predicted, a well-developed upper air cut-off low system produced widespread, deep snow (as much as 30-40cm, or more) of accumulated snow depth over the heritage weekend.

Malala also emphasised that snow in late winter and early spring was not unusual or rare. 

highveld storm season engelbrecht SA Weather Service lead scientist in long-range prediction, Dr Christien Engelbrecht, speaking at a SAWS media briefing in Pretoria, 1 October 2024. At the rear are SAWS senior forecaster Puseletso Mofokeng (right) and senior manager for disaster risk management Rudzani Malala. (Photo: Julia Evans)



As Dr Christien Engelbrecht, lead scientist for long-range prediction at SAWS, noted, heavy snow in September 2008 necessitated roads to be closed in KwaZulu-Natal and Eastern Cape, and while infrequent, snow can even occur as late as October. There was snow in Johannesburg in October 2011.

What to expect: short-term


Malala explained that South Africa was subject to varying weather conditions in different seasons due to its unique geographical location.

This is why when spring arrived this year, many South Africans experienced very hot conditions, with some parts undergoing heatwave conditions, and then later the opposite – snow – brought by the onset of a cold frontal system and a cut-off low system.

Malala explained that cut-off lows were intense low-pressure systems that were notorious for causing widespread flooding – evidenced by the devastating KZN flooding in April 2022. 

“These weather systems can also bring damaging winds, severe thunderstorms and even snow, depending on the season in which they develop,” he said, adding that they were most frequent during autumn and spring, with the highest frequency in April.

Despite some light showers or rain expected over KZN and eastern Mpumalanga, and some thundershowers over Northern Cape in the week ahead, Malala said the weather was expected to be fairly benign with nothing particularly severe or extreme anticipated.

But he emphasised that people should remain vigilant as October and November were well known for severe storms, particularly in the Highveld region, which encompassed the northern Free State, Gauteng and eastern Mpumalanga. These areas were at risk of large, damaging hail and strong winds.

Medium-term: La Niña summer


Looking towards summer, Engelbrecht noted that the El Niño Southern Oscillation was in a neutral phase, with predictions leaning towards a weak La Niña event developing during spring (September to November) persisting through the 2024-25 summer season. 

 

Many seasonal prediction models have indicated that this will cause above-normal rainfall for spring and midsummer for the southeastern parts of the country. In terms of temperatures, maximum and minimum temperatures are predicted to be above normal over most of South Africa, in particular over the western interior on maximum temperature predictions.

“Given the expectation of a relatively hot summer over much of the country, communities should also be mindful of the likelihood of sustained spells of hot, dry weather as well as the possibility of heat waves,” said Malala.

“During such events, the aged, infirm as well as infants and toddlers are particularly susceptible to dehydration.”

Read more: How infants, children and the elderly are vulnerable to the impacts of climate change

As a result, SAWS strongly recommends that everyone take care to stay hydrated and to support and assist the elderly and small children at such times. It is an unfortunate but well-documented reality that heat waves often lead to numerous fatalities if no mitigating steps are taken.

Long-term: More intense weather under climate change


“We are living it, we can see it,” said Malala, reflecting on how climate change is manifesting through increasingly extreme weather events.

Dr Christopher Trisos, a senior researcher of the African Climate and Development Initiative at the University of Cape Town (UCT), explained to Daily Maverick that some weather events (such as heat waves, floods and droughts) are becoming more frequent, and some are becoming more intense, some are seeing both trends, and that since 2021, the evidence and confidence have continued to increase, thanks to attribution studies.

While the Intergovernmental Panel on Climate Change has high confidence in human contribution to observed changes in hot extremes for eastern southern Africa – for example – whether this recent snow event is linked to climate change is less clear.

Engelbrecht noted that while snow events in the South African region hadn’t been investigated, there had been research on frost days. SAWS looked at historical observational station data and found that frost-day events were not occurring as frequently as they once did here.

“From that, we can deduce that the same is possible when it comes to snow events,” said Engelbrecht. 

Engelbrecht also explained that while fewer frontal systems were reaching South Africa due to climate shifts, making snow less frequent, when they did, they might be more intense. 

“The weather is always striving toward balance,” explained Engelbrecht.

“If we think about how global warming [is causing] the mid-latitude regions to warm up, then one can also think that when a system does reach us within a warmer climate, the impacts associated with it will be quite intense, because of the energy that it has.”

Dr Peter Johnston, a climate scientist at UCT, agreed that the recent snow event was “not impossible, not very unusual, and probably not directly linked to climate change”.

He emphasised that while we could not say one specific event was more likely to occur because of climate change, climate change was making extreme weather more likely, including hot and cold spells. DM

https://www.youtube.com/watch?v=REeWvTRUpMk

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