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I've heard reports of a massive storm that started at Giant's Castle on Tuesday, 16th of Feb, which then spread out towards Durban and caused a lot of havoc. Anyone have any more info or pics related to this storm, particularly at Giants Castle?

Can't comment on specifics of GC, but on 16 Feb a major system covering about 50 deg of latitude was directly over eastern southern Africa. These systems, known as tropical temperate troughs or tropical-temperate cloud bands, connect convection over central Africa with passing midlatitude storms. In this case, the band extended to 60 deg south. The bands perform a vital role in transferring heat poleward. Most of the work of the whole southern hemisphere climate system would have been done in this single band of longitude on 16th. Sat pic from that day:
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The storm at Giants would have been developing in perfect conditions for deep, sustained convection.

here is some pretty opaque stuff on the cloud bands....
http://www.geog.ox.ac.uk/~rwashing/research/publications/ttts_daily_rainfall.pdf

Interesting, thanks. Also interesting to see your field of study.

I experienced this storm first hand, but 2 hours drive from GC (In Hillcrest). It was intense. The plans for my scout meeting for the evening were boycotted by the boys in favor of duck-diving newly developed 15cm deep bodies of water.

A little bit more on the summer storms. Essentially the storms are a cooling mechanism for the atmosphere. They transport hot air which is full of water vapour to the top of the atmosphere. From here, the heat can be efficiently radiated to space - much more efficiently than it can from the surface. Also the tunderstorm clouds reflect sunshine and so put an end to some of the heating. At the back of ththe storms, cold air outflow from mid-levels (5 km up) moves down to the surface - this is the part of the storm that brings the rain.

In El Nino years (like this summer) there is a) unusual amounts of sinking air over southern Africa - the sinking air stops storms from forming easily b) unusually high amounts of water vapour (humidity) in the lowest layers because the SW Indian Ocean temperatures tend to be unusually high c) hotter than usual surface temperatures

(a) + (b) + (c) is a lethal mix. There is high energy available at the surface but a mechanism in the form of the sinking air to keep the high energy confined near the surface. When the storms do manage to form in these conditions, they release all the energy that has assumulated near the surface and are pretty wild as a result. For example, in El Nino years the occurrence of hail in the midlands of KZN is much higher than in non-El Nino years, pointing to more vicious storms.