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Cape Town Lightning
Featured Image: Brendon Wainwright (via Instagram)

Lightning over Cape Town (and much of the the SW’ern Cape) is not frequent, by any stretch of the imagination. If my memory serves me correctly, I believe the average number of thunder days for Cape Town is in the order of 3-6/yr. By now I’m sure many of you have have seen (or at least heard of) the thunderstorms that rolled through Cape Town/SW’ern Cape on Sun night (23/08). If you haven’t, below are some of my favourite images, some of which featured on Cape{town}etc, KFM and traveller24.

Difference between CT and Highveld Lightning

While some of the photos are really amazing, what really intrigued me was that someone mentioned that the storms in Cape Town are louder than those in (I’m assuming) Gauteng (see below). Initially I didn’t think much of it until I did a little bit of research and speaking to a friend/colleague.

Lightning may look the same, but it can be either negatively- or positively charged. Positive lightning is far more powerful and much hotter; and thunder is the audible sound resulting from the sudden and rapid expansion of the air around a lightning bolt due to heating resulting in a sonic shock wave.

So, theoretically, positive lightning → hotter → more rapid expansion of air → louder thunder.

According to a journal article written by Morné Gijben and published in the South African Journal of Science the SW’ern Cape experiences a higher percentage (>20%) of total lightning flashes which are positively charged compared to Gauteng (4-8%).

So, when a storm does move over the SW’ern Cape, thunder/lightning might not be as frequent as with Highveld storms, the storms themselves might not even last as long, but it is plausible that they could, on average, be louder than Highveld storms.

This Post Has One Comment
  1. Thanks for sharing the photos Craig!

    Yes, positive cloud-to-ground flashes are much more powerful than the negative ones, and less frequent. They also usually originate from higher levels of the cloud (eg. the anvil) and sometimes come “out-of-the-blue” once a storm has moved through and clearance is taking place. So, very dangerous!

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