"Firenados" are more correctly called fire whirls, explained South African Weather Service chief forecaster Kevin Rae after a video capturing the phenomena made the rounds over the weekend.
"Recently, however, a popular concatenation of 'fire' and 'tornado' has resulted in colloquial use of the word 'firenado'," he said.
Firefighters have been braving near apocalyptic conditions along the Southern Cape's Garden Route.
A video by Working on Fire shows a "firenado" whipping through the vegetation in the De Vlugt area.
Rae said the phenomenon arose when one was dealing with a very hot, intense wildfire.
"Surface air rushes in, to replace air which is ascending very rapidly at the site of the fire. This sudden accumulation of air at the base of the fire tends to feed it further, increasing the intensity of the fire. One typically ends up with a very dramatic-looking column of rising air and flames, twisted into a helical (helix-shaped) column."
According to Wikipedia, a fire whirl can reach temperatures of up to roughly 1 090°C.
Rae said fire whirls were seldom associated with thunderstorms.
"Sometimes a thunderstorm is produced or initiated much later on, due to columns of rising hot air."
He emphasised the fact the firenados were, in actual fact, not tornados.
"Although a fire whirl looks superficially much like a tornado, it is not a tornado."
"Tornadoes are produced by severe thunderstorms. In a fire whirl, the twisting action arises at the surface, whilst in a tornado, the origin of the twisting force is within the rotating 'heart' (mesocyclone) of a supercell thunderstorm," he explained.
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