Spring and Summer storm clouds

Let me stress first that everything on this blog is based on general knowledge as I am not a meteorologist. I do however make every effort ensure that the information I provide comes from credible sources. If any part of the information I provide is incorrect or inaccurate in any way, I will most certainly appreciate the correct information being provided by those with expert knowledge.

Cumulus Congestus. Largest of the cumulus family of clouds and the final cumulus stage before transition to cumulonimbus

Thunderstorms are in my book the most spectacular weather events on the planet. What other weather system on earth produces such a mix of awesome and sometimes violent weather that thunderstorms produce? In addition to the weather they produce, the clouds that produce them can be just as spectacular.

Near perfect classic cumulonimbus cloud that formed to the far east of Pretoria somewhere over Mpumalanga on 27 October 2013. Although it was never confirmed, it is possible that this storm may have been a supercell

A spectacular cumulonimbus cloud that developed explosively over the east of Johannesburg on 15 December 2013. You can get an idea of how explosive it was in the second of the three time lapse videos below 

From broad cauliflower like cumulus congestus to the massive, towering cumulonimbus clouds that reach high into the stratosphere, nothing beats summer storm clouds when it comes to their ability to inspire awe in those who witness them. In the spring and summer, warm moist air from tropical Africa moves down towards the northern and central parts of South Africa, producing the often spectacular thunderstorms that are a common feature here during that time of the year. That, coupled with the ground heating from the summer sun, creates the convection that's needed for the clouds to develop and eventually grow into the cumulus and cumulonimbus clouds that bring our thunderstorms.

A roll cloud that formed ahead of an approaching storm in Pretoria on the 20 October 2013

One of the things I really love about the clouds that create thunderstorms is the way they develop. From inception to dissipation, there is almost a magical surrealness in the way the thunderheads shoot vertically into the upper atmosphere and the top spreads out to form the characteristic anvil that is the very epitome of the cumulonimbus cloud. One of my favourite ways of capturing a thunderstorm as it develops is through time lapse photography. There's just something about watching the way a cumulus or cumulonimbus cloud just explosively shoot up into the sky and evolve and change shape as it reacts to the environment around it.

 

The time lapse videos above are three of my favourite because they really capture thunderstorms at their best. I love the third one just for its eerie beauty and the way the clouds at the base of the thunderstorm almost seem to swirl around each other. This storm later produced heavy torrential rain that led to some minor flash flooding in parts of Pretoria.

Shelf cloud approaching Moreleta Park in Pretoria on 8 October 2013

Shelf clouds are among the most spectacular features of spring and summer storms. Their ominous and menacing appearance strike fear into the hearts and minds of those who see them. They are often mistaken for wall clouds and people often fear a tornado might hit when they see them approaching. But fear not. Shelf clouds do not produce tornadoes as they are an indication of an outflow dominant storm, that is a storm that is dominated by downdrafts. Tornadoes and wall clouds mostly form in storms that are inflow dominant, that is where warm air is being sucked up into the usually rain free part of a storm. It is still wise though to take shelter if you see a shelf cloud approaching as it may indicate the presence of very strong winds, heavy rain and often large hail.  

Lightning in Pretoria on the 28 November 2013

 

And last but not least is of course lightning. For me personally this is the most spectacular of all thunderstorm features. Yes, even more than tornadoes. Powerful electrical discharges that light up the evening sky and are so hot (up to 30,000 degrees Celsius, five times hotter than the surface of the sun) that they cause the air to expand rapidly in the form of explosive shock waves we hear as thunder.