Durban — Shortly after 1pm on Monday, a tornado cut a path from Newcastle, KwaZulu-Natal, to Utrecht, about 45km away with minimal damage done.
However, the “wedge” type tornado that huffed and puffed in and around oThongathi later that afternoon blew many houses down, damaged schools and infrastructure, disrupted the lives of 7 000 households and killed 12 people, according to the Office of the Premier. A year ago, a tornado ravaged about 50 houses in Inanda, with no loss of lives recorded.
Kevin Rae, chief forecaster, Disaster Risk Reduction (DRR) at the South African Weather Service, said historically, many South Africans had the opinion that tornadoes are fairly rare, or at best, uncommon phenomena.
“Historic records dating back to the 1800’s indicate that tornadoes occurred from time to time, especially over the easternmost provinces of the country, in the summer months.
“That’s when thunderstorms are more prevalent. Naturally, a thunderstorm is a prerequisite, because tornadoes are spawned by thunderstorms.”
Rae indicated that about 12 to 18 tornadoes of varying intensity were reported annually. He said that the local tornado tendencies paled into insignificance when compared to parts of the US that get hit by a thousand or more tornadoes annually.
“One could be tempted to think that, in SA, tornadoes are on the increase, given that such phenomena were hardly talked about in earlier decades. With the advent of the internet, mobile phones and a plethora of social media platforms, almost everyone has the capacity to be a ‘citizen reporter’. Consequently, many tornadic events, even the more benign ones, are reported on, often in near real-time.”
He said the base of the parent thunderstorm cloud in oThongathi was very close to the ground, resulting in a very wide tornado tube, with very limited vertical height, between the ground and the cloud base.
“A tornado manifesting this type of visual impression is referred to as a ‘wedge’ tornado. While the more violent or intense tornadoes are often of the ‘wedge’ type, there is a lot of variation in terms of tornado intensity.”
Rae said generally the surface movement of tornadoes was strongly controlled or influenced by the relative speed of movement of the parent thunderstorm, which typically move at speeds between 20 to 60km/h.
Usually when the parent storm collapses, it “kills off” the tornado and longer-lived tornadoes are often observed over flat, uniform terrain, like the one that occurred in northern KZN.
“We have received no further information regarding any loss or damage. It is possible that the tornado occurred over an unpopulated, mostly rural area and may not necessarily have caused any damage.”
Professor Francois Engelbrecht, Director and Professor of Climatology, Wits Global Change Institute, agreed that the wide availability of mobile phones has led to many more tornadoes being recorded and documented in South Africa.
“I do not think there is any statistical proof though, that tornadoes are occurring more frequently, with greater intensity.”
He confirmed that KZN was a “tornado-prone province” because of its climatic conditions and proximity to the Indian Ocean and the Drakensberg Mountains.
“There is strong evidence that climate change has already resulted in an increase in the number of intense thunderstorms occurring every year in KZN, and also further westwards, over the Mpumalanga and Gauteng Highveld regions. However, no clear evidence exists that tornadoes are increasing in frequency or intensity in South Africa, as a consequence of climate change.
UKZN Professor Tafadzwa Mabhaudhi, a specialist in climate change, food systems and health, said the debate in the scientific community of whether “tornadoes” and “twisters” were the same type of storm is as old as time.
“Some scholars argue that these are different names used interchangeably for the same meteorological phenomenon often associated with severe thunderstorms. On the other hand, some scholars have tried to distinguish between the two, claiming that twisters, unlike tornadoes, are often accompanied by hail.”
Professor Mabhaudhi said the dissipation of a tornado can be due to several factors, such as friction upon contact with the ground and lack of moist, warm air that feeds the storm and sustains the tornado. And there was no way to prevent them from happening.
“Tornadoes are natural phenomena arising from the presence of very specific atmospheric conditions. Because of this, their formation is beyond our control. What we can do is focus on ensuring that correct drills and measures, such as Early Warning Systems and other components of preparedness, exist to minimise their localised impact,” he said.
Dr Phindile Sabela-Rikhotso, a lecturer in the Department of Environmental amd Geographical Science at the University of Cape Town agreed that a way of mitigating the impacts of tornadoes were through better early warning systems and effective evacuation plans that will save lives and building resilient structures will be helpful.
Sabela-Rikhotso said "wedge" tornadoes were characterised by the shape of their condensation funnel, which are wide at the ground as it is tall.
“These are indeed very large tornadoes. It is worth noting, however, that not every large tornado is a ‘wedge’.”
Sunday Tribune