If you have ever seen the 1996 movie White Squall starring Jeff Bridges, you will have some idea of what a white squall looks like at sea. According to Wikipedia, “A white squall is a sudden and violent windstorm at sea which is not accompanied by the black clouds generally characteristic of a squall. It manifests as a sudden increase in wind velocity in tropical and sub-tropical waters, and may be a microburst.”
Microbursts also occur over land and have been identified as the main cause of some devastating aircraft landing accidents. Unsurprisingly, given the violent summer storms in the Natal Drakensberg, they happen there too.
My first experience of one happened many years ago when I was leading a group down from The Hub to Gxalingenwa Cave. It had been an oppressively hot afternoon, and at a narrow section of the Gxalingenwa Valley just above the cave, we stopped for a swim. With additional heat radiating off the rock faces there, it must have been close on 40 °C. A major storm had been building over the Giant’s Cup, and the first indication that something was about to happen was when a few large hailstones starting falling amongst us.
We made a beeline for the cave, entering it via the top approach and the waterfall to save time. We had no sooner arrived than a white wall passed down the valley in front of us. It was not mist – it was a vertical wall of white, marking a sharp boundary between the clear air in front of it and the hail and very heavy rain behind it. The precipitation was so intense that it did look a little like mist while it was over us. The worst was over in less than 5 minutes, but the storm continued unabated overhead for another hour.
One day, returning home after a hike, we ran into a microburst on the road just outside Bulwer, on the way down the Umzimkhulu Valley. I had the headlights on, and the wipers were making little difference to visibility even though they were on maximum speed. There was some hail too. The next moment we popped out of the wall of the microburst with the wipers flailing wildly, and us squinting in the sudden brightness. The road was bone dry. We passed a lady walking in the opposite direction. She could not have had any idea of what was coming her way.
On another hot afternoon, we were busy settling into Vaalribbokkop Cave in the Monk’s Cowl area, fetching water and washing off the sweat at the junction of the streams below the cave. I had just returned and was hanging stuff out to dry when I noticed a wall cloud coming up the valley. Some of the others were still making their way back and were about halfway to the cave. There is a big, smooth rock at the front of the cave which makes an excellent stage, so I jumped onto it, yelled at the stragglers, pointing to the wall cloud and miming for them to run!
They got the message and ran, making it into the cave as the wall cloud reached us. It had been approaching at probably around 20 km/h. Again, as it passed over the cave, it contained torrential rain and a lot of hail. Some of the hailstones were ricocheting off the rocks into the cave. And then it was gone!
Being by now fairly familiar with these wall clouds, or “white squalls” as I like to call them, put me at an advantage on the next occasion that I encountered one. We had stopped at Lakes Cave in the Cobham area for lunch, and a major storm was once again developing over Hodgson’s Peaks. We were headed for Glade Cave, so as soon as lunch was over, we left Lakes Cave and started making our way up to the tarns on the ridge above it. I was in the lead, and as I approached the summit of the ridge and could see over it, I looked straight into a wall cloud.
I yelled to everyone to get back to Lakes Cave as fast as they could, no explanation given other than that “all hell is about to break loose!”. I was even encouraging them to run if they could, but to be careful not to twist an ankle. We arrived back under the shelter of the cave only a few seconds apart, everyone looking at me in expectation of an explanation. All I said was “Watch!”. On cue, the wall cloud reached us and there was torrential rain and lots of large hailstones. This time, the wind was gusting so hard I thought we might even have a tornado on our hands, so we got the smallest kids to climb up onto the ledge at the back of the cave and wedge themselves in there. Again, it was all over is less than 5 minutes and we continued on our way.
I have never seen a fully developed tornado in the Natal Drakensberg, but I have little doubt that they do occur. The rural village of Impendle, which is not far from Underberg, has had two devastating tornadoes. I was on the plateau below Lammergeier Cave once, heading down to Surprise Cave, when we saw a funnel cloud drop out of a storm cloud over the Bushman’s Nek Valley. We watched fascinated, then with growing alarm, as the funnel slowly stretched downwards towards the valley floor. My mind was racing about what to do if it came our way. There was a long rock band just behind us with a low, shallow overhang, so I decided we would have to lie down on our sides using our shoulders to wedge ourselves under it and our backpacks for protection. When I looked back at the funnel though, it had slewed horizontally and then it disappeared.