Centurion shelf cloud: 22 November 2012

Today was unfortunately for me and I'm sure for countless other storm lovers across South Africa, another quiet sunny day. Don't get me wrong, I love sunshine, boring as it is. But there has been way too many sunny days in the past few weeks and I've quite frankly had enough of them. In the meantime, I'll post another storm from the past that blew me away. This is from the 22 November 2012.

And wow, what a day that was. It was a hot day on a Thursday and was the day of the Centurion Nikerun at Centurion mall. I saw this shelf cloud forming later that afternoon just after arriving in Centurion and decided to get snapping. The storm itself wasn't very severe in terms of it's overall intensity, but the shelf cloud was quite a beauty to watch. It was nowhere near as dramatic as Monday's shelf cloud, but still beautiful nevertheless.

Shelf cloud over Centurion in Pretoria, South Africa on 22 November 2012

 It took on many forms as it slowly over Centurion, crossing the N14 highway over the hill and the Gautrain viaduct, the long grey structure cutting across the landscape. The thing about it that really caught my attention though was the odd looking lowering to the left of the images. I didn't know what it was but it quite a spectacle to watch. It appeared to be rotating and kept lowering and rising back into the cloud almost like a tornado. It certainly wasn't a tornado though, since shelf clouds don't produce tornadoes. At one point it got down so low it seemed to almost touch the trees in the distance.

It was quite an experience indeed standing there watching this beauty make its way across the Centurion landscape. The lightning was also quite impressive, streaking and dancing across the sky and the several number of Gautrains moving back and forth on the viaduct didn't seem to be much affected by the storm. 

A wide view of the shelf cloud, also showing the size of the storm.

So what exactly is a shelf cloud and how does it form? According to general descriptions, a shelf cloud is a low, horizontal wedge-shaped cloud, usually attached to the base of a severe thunderstorm. To understand How a shelf cloud forms, think of a cold front and how it's formed. Now think of it on a smaller scale, but with the same properties. That's pretty much how shelf clouds form. http://weathersavvy.com/Q-Clouds_ShelfCloud.html. 

Shelf clouds are part of a family of clouds called arcus clouds, which also includes roll clouds. http://en.wikipedia.org/wiki/Arcus_cloud

Although they usually share the same general shape, as you can see from the three images below, shelf clouds still come in many different forms, sizes and intensity. 

Shelf cloud over the city of Enschede in The Netherlands (Courtesy of John Kerstholt)

Shelf cloud approaching Sydney, Australia (Courtesy of Nick Moir)

Very odd looking, but menacing shelf cloud in Crawfordsville, Iowa (Courtesy of Nick Nolte)

 Shelf clouds are very often mistaken for wall clouds and mesocyclones, and I know, I've made that mistake myself on numerous occasions. They may look similar in appearance by they couldn't be more different. Firstly, they form in different areas of thunderstorms. Shelf clouds form at the front, or leading edge of a thunderstorm and are associated with downdrafts and outflows. Wall clouds on the one hand form at the rear of severe thunderstorms, an area that is usually rain free and where the updrafts occur and are usually associated with inflow. http://vermilionweather.com/wallshelf.php

Finally, a big storm shows up: 07 October 2013

All I can say about today is just WOW!! After more that two weeks of quiet, sunny weather, Pretoria was finally treated to what I can only describe as a true Highveld thunderstorm. I must admit though, I didn't have much hope of anything happening today. We'd had other days in the past two weeks when thunderstorms were forecast but then nothing happened. I figured today would be another one of those days. Am I glad I was proven wrong.

Shelf cloud approaching

In many ways, it was the calm before the storm. And when the storm finally arrived, boy was it something. The shelf cloud was absolutely spectacular as it rolled over the horizon and approached. The lightning was also a hell of a sight to watch.  

At first I thought the storm was part of a squall tine. But I heard from one of my contacts on Facebook that it was part of something called a QLCS or quasi-linear convective system, http://www.meteor.iastate.edu/~ralliss/qlcsmesovorticies.pdf. Today's weather didn't disappoint. Some areas even got hail, although I wouldn't really look forward that. The satellite and radar images for this weather system were absolutely impressive, showing a line of storms stretching from south eastern Botswana all the way through Swaziland to the nothern KZN coast. This was a huge system indeed.

Satellite and radar map from 07 October 2013, showing the quasi-linear convective system over the north eastern part of South Africa. The capture on this map is 20:00. By now the system  had mostly moved on from Gauteng and was largely affecting Mpumalanga, parts of Limpopo and Swaziland. (Courtesy of Kobus Botha Weather, http://www.weatherphotos.co.za/photos/rain_severe_new.jpg)

It was quite amazing how quickly it moved once it had formed. The time that elapsed from the first photo to the last one was less that 10 minutes. During that time, the shelf cloud kept evolving and taking on different forms and the whole system itself looking really menacing as it inched ever closer. Eventually the lightning eventually begun striking a little too close for comfort and I had to pack up my equipment and head for shelter. Storms can very exciting to watch and document but they're also extremely dangerous and every precaution has to be taken to stay safe when outdoors during a storm. Safety always comes first. I shot these photos from the balcony of the first floor of the local shopping centre just outside the gym and as you can see, it left me dangerously exposed to the storm. Add to that the fact that I had a tripod with a remote trigger connected to the camera and the danger was upped tenfold. As soon as I realised that the lightning was dangerously close, I immediately went into action and took shelter. In fact I should have actually taken shelter the first moment I saw the storm on the horizon, but then that would have meant missing out on all the action, and I couldn't let that happen. However, it is still important to take shelter as soon as you see a storm approaching.   

If you would like to know more about quasi-linear convective systems, you can look up Ron Przybylinski, an American meteorologist who is also a leading expert on QLCS and other associated weather phenomenon. You can find one of his many studies on these often mysterious weather systems at this link: http://www.crh.noaa.gov/lsx/?n=qlcslatest

First lightning shot: November 2006

My very first lightning shot. 

This here is my very first photograph of a lightning bolt. I shot it sometime in November 2006 in Elardus Park in Pretoria. I shot a number of other shots that came out terribly. It was very frustrating. At some point I wanted to give up but kept shooting. Eventually I managed to get this amazing shot and when I saw it on the screen of my camera, I couldn't contain my excitement. I didn't even bother waiting around for the rest of the storm. I just went straight to the computer and uploaded it. 

The first lightning shot, no matter how much better subsequent shots are, is always the most sentimental. I keep this one in my special archive where it will hopefully be forever a constant reminder of how far I've come.

When was your first lightning shot and how did it feel to capture this force of nature on camera for the first time?

Midnight storm 12 January 2012

This was one hell of a night I'll never forget. It was just under an hour after midnight and I had only just fallen asleep when I was woken up by a loud rumble of thunder. As I looked out the window I could already see the bolts of lightning streaking across the sky and even though it hadn't gotten that intense at the time, something in me just told me that this is a storm I do not want to miss. Well, boy am I glad I followed my instincts, cause within barely a few minutes of me grabbing my camera this thing just went ballistic. 

This was one of the closest strikes. The thunder clap from
this one was absolutely deafening.

 For the next half hour or so, I had the privilege of witnessing and photographing one of, if not the most intense and most breathtaking lightning storm I've ever experienced. The strikes were almost continuous for nearly the entire duration of the storm and as you can see in the photos, often a little too close for comfort. The thunder was spectacularly deafening, rattling the windows so hard it almost felt like an earth tremor. Fortunately I was indoors the entire time although I'm aware that's not always a guarantee of safety, especially if you're pressing the camera against the window and holding on to steel burglar proof bars. Interestingly, for a storm of this intensity, there was very little to no wind. I found that very strange indeed.    

A lone but very intense strike. 

Pretoria and Johannesburg are located in what's known as the Summer rainfall belt region, an area encompassing basically the entire eastern half of South Africa. One particular region though, in which Pretoria and Johannesburg are located, is especially legendary when it comes to thunderstorms. Known as the Highveld, it's a region located in the inland central region of South Africa and is basically a high altitude plateau encompassing parts of the Northern Cape, Northwest Province, Limpopo, Mpumalanga and pretty much all of Gauteng and the Free State: http://en.wikipedia.org/wiki/Highveld. Thunderstorms like the one covered in this and the previous post are a common feature of the highveld during the spring and summer months. But I must admit though that the one covered in this post was quite insane, even for a Highveld thunderstorm.

Lightning ground flash density map for South Africa (Courtesy of http://www.wattronics.co.za/wp/page/2/ and the CSIR ) 

As you can see in the lightning ground flash density map above, much of the lightning activity in South Africa, which in turn translates to thunderstorm activity is concentrated mostly in the eastern half of the country (the summer rainfall belt). As is evident in the map, the Highveld makes up a significant portion of this area with a high density of lightning ground flashes. Cooler colours indicate a higher density of lightning ground strikes while the warmer colours indicate a lower density of strikes. As you can see, Johannesburg and Pretoria both fall inside the blue area, cementing their reputation as high density lightning strike locations. The areas with the highest density of ground strikes, shaded in black, are in the central Drakensberg region of north eastern Lesotho and southern Kwazulu-Natal and northern Kwazulu-Natal, the south of Swaziland and south easten Mpumalanga. 

Massive double strike. This one just took my breath away. I
couldn't believe how beautiful it was.

I'm sure some or most of us have experienced a storm that was either the most exciting, intense or most terrifying. I would very like you to share your experience of a storm you consider to be any of, or a combination of those three things and tell me what is like for you to go such an event.  

New Year's Eve storm 2011

I've decided to start this blog about severe weather in South Africa as there aren't many of them around. Although this blog will cover severe weather in general, the main theme will be mostly lightning. Let me first start by clarifying that I am not a meteorologist nor am I an expert in severe weather, or any other kind of weather. I'm just a guy who's fascinated by severe weather and the power and beauty that it displays.

Bright lightning flashes over Moreleta Park in Pretoria on 31 December 2011

Anyway, as most of us know, lightning a one of the deadliest natural phenomenon in the world and kills a large number of people every year. South Africa is considered to be a lightning prone country, with a high number of lightning strikes recorded across the country every year. I'm fortunate to live in the part of the country that experiences one of the highest number of lightning strikes. Being located in the Highveld region of South Africa, Gauteng is struck by numberous thunderstorms during the spring and summer period from around October to March every year. Some of these thunderstorms can be very intense and often very severe, bringing heavy rain, lightning, strong winds, sometimes large hail and occasionally even tornadoes.

Lightning however, being the most common of the features of thunderstorms in South Africa is considered to be the big threat when summer storms approach. This article by Morne Gijben highlights just how important lightning research is in South Africa. http://www.sajs.co.za/sites/default/files/publications/pdf/740-8137-1-PB.pdf. 

Intra-cloud lightning from the  same New Years Eve storm in Pretoria.