This article was compiled by Puseletso Mofokeng (Senior Forecaster), Luthando Masimini (Senior Forecaster), and Lehlohonolo Thobela (Forecaster). It was proof-read by: Tokelo Chiloane (forecaster) and approved by: Senior Manager: Disaster Risk Reduction.
The South African Weather Service (SAWS) can confirm, from evidence gathered from meteorological RADAR, that the storm damage and recorded circulating debris in the Randfontein area on Wednesday, 27 November 2024, was due to a tornado event.
The SAWS issued a Level 2 warning for severe thunderstorms with the possibility of heavy downpours, strong gusty winds, and large amounts of small hail, but with large hail in some areas across Gauteng.
The warning was issued at 08h30 on the morning of 27 November 2024. A thunderstorm marked X in Figure 1 below moved to the east across the Randfontein region between 12h30 and 12h45.
Another storm marked Y in Figure 1 above, blew its outflow (i.e. gust front) that was channelled by the V-shaped valley (in a green circle in Figure 3) to the north of Randfontein. The black arrow in Figure 3 shows the direction of the storm and its outflow. Due to the channelling by the valley, this outflow rapidly and significantly strengthened, connecting and intensifying the storm marked X. However, it was almost impossible to determine the magnitude of this outflow.
The interaction of this stronger gust front with the thunderstorm which moved across Randfontein triggered the ground-up rotation, which later supported the development of a tornado.
Based on the analysis, the storm can be rated as an EF2 on the enhanced Fujita scale.
The impacts of this storm resulted in the damage of a vehicle which seemed to have been hit by a solar panel from a roof (Figure 5); and roof sheets being torn off, peeling of roofs at the corners of the buildings (Figure 6) across a relatively large area.
Preliminary reports on Wednesday indicated that at least 21 injured persons were transported from Imphakasi Mall, and damage assessments were conducted in nearby areas.
In a SAWS study conducted from June 2016 to June 2021, it was found that 76% of tornadoes developed from the cross-interaction of the strong gust front of an upwind storm with a downwind thunderstorm.
Tornadic events are part of severe thunderstorms, but weather models have difficulty in predicting them due to their small size in comparison to that of the models. These events can picked up with RADAR technology, but at a very short lead-time. The SAWS is exploring incorporating emerging technologies such as Artificial Intelligence, Machine learning, and other technology to enhance its forecasting capabilities.
The following precautions can be taken in the event of seeing a tornado approaching:
• In the event of seeing a tornado, move to the pre-designated building or else move into the smallest room or get under a strong piece of furniture, such as a table.
• Get out of vehicles, caravans and mobile homes, as they can be moved, overturned and even destroyed by the strong winds and flying debris.
• Stay away from windows, as flying glass and debris cause the most deaths.
• Do not attempt to outrun a tornado in your vehicle. Leave it immediately and seek shelter.
• If caught outside in the open, lie flat in a ditch or depression but beware of flooding if there is heavy rain.
In respect of the short term forecast, the good news is that no further severe thunderstorms are expected across Gauteng from Thursday through the weekend.
For technical and weather enquiries:
National Forecasting Centre: Tel: 012 367 6041