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Convective weather events in Ireland/UK come in two different types which are dependent on the time of year. These types are, Atlantic driven convection during the Winter, followed by the eagerly awaited land-based convection. The former kind is produced when showers are blown inland by low pressure systems, usually at the rear of a cold front. The showers feed on the moisture and warm temps of the Ocean and can often form into thunderstorms and are big producers of Wintry precipitation. The problem for people like me who want to see storms during the Winter season is that these showers/storms often loose their supply of warm moist air when they move far inland. Western coastal areas will get the best storms but where I live in central N. Ireland it's a different story. By the time these cumulonimbus (cb) cells arrive from the W, or NW, they are most often at the decaying stage. The chances of lightning and strong convection are low with the anvil often taking on a weak fuzzy profile, or even becoming an orphan anvil which is quite common. These are often great producers of mammatus displays but seldom deliver much else, with the exception that is, of an intense cold front, which is an entirely different beast altogether.
Land based or 'home grown' convection is the very thing all storm photographers want to see. As Winter moves into Spring the Sea temps change and the Sun gets much higher in the sky which can heat the ground up in a more serious manner. This 'solar heating' is one form of lifting mechanism which can fuel storms inland. This transition period during March can be a hit and miss affair because cooler Sea temps tend to kill off any big convective events. However, with intense ground heating and enough atmospheric instability, big showers and decent pulse storms can grow without the influence of the Atlantic Ocean. The big advantage of land based convection is that you don't need to wait for showers/cbs to move from the coast to inland areas because the conditions are just rite for convective clouds to literally 'bubble up' out of nowhere by thermals/updraughts at any time provided several other conditions are met. Wednesday March 4th 2009 was expected to be the first day of serious home grown convection across the country and the many people I know who were interested in this sort of thing were waiting with anticipation of seeing something nice. Over the entire UK, CAPE (Convective Available Potential Energy) values between 200 and 400 were expected along with an LI (Lifted Index) of 1 to -0 due to an unstable polar maritime airmass descending over the country at the rear of a cold front which passed through from the W the previous day. Strong solar heating combined with other natural lifting mechanisms like mountains and convergence zones would invigorate any convection present, so large cbs, showers of hail, and pulse thunderstorms were expected to break out somewhere. The convective cloud tops in this environment where expected to reach up to 25,000ft high which is really good for early Spring. The frigid airmass would also mean there would be excellent visibility increasing the photogenic potential of 'shooting' convection against a crisp blue sky background. So in a nut shell, this was the start of the 2009 UK thunderstorm season!
I had my eye on this day for over a week in advance so I was naturally excited about seeing something cool. I began to get concerned however when I watched several different television forecasts the night before because they greatly contradicted one another. One showed wide spread convective showers across the entire country with a risk of hail and thunder while another showed no showers developing inland during the day at all. How could they be so different?. I checked the online RTE forecast and felt a little better when they stuck to their hail and thunder forecast for the Ulster region. The most intense showers were expected during the afternoon, which naturally coincided with the higher CAPE values, and they even mentioned the chance of snow showers over the Sperrin Mountains which where located to my W and within visual range so things were looking up. The next day I was disheartened by the whole thing. I checked the Met Office radar and noted with great frustration that the big convective showers where far to my W near coastal areas and by clicking between the recent half hour updates it was obvious that these clusters where not moving inland at all. It was a bust forecast. I looked out at the sky to my E, it was clear with some horrible patches of soft looking cumulus (Cu), I thought that was the end of that. I happened to glance out my window to the opposite side of the sky and immediately stopped in my stride and felt a good feeling growing very quickly. To my N where a number of towering cumulus clouds and I was instantly struck by their huge size and visual profile. I had been that used to the Atlantic driven convection over the Winter that it took my mind a few min's to work out what was happening. This convection was literally initiating from the ground-up due to solar heating. These where literally growing out of the lower atmosphere at my door step and because they were updraughts of air, and not producing any precipitation, that was why they didn't show on radar. Had I checked the visual sat images then I might have caught on to this fact sooner.
I kept watch on these towering cu and thought to myself that they wouldn't have looked out of place in Summer. These where very tall and solid with obvious vigorous 'boiling' motions evident on their tops which really caught my attention. As I watched, one updraught blew itself apart and detached itself into the blue sky then was immediately followed by a fresh new tower which seemed to shoot up into the sky from nowhere. This was happening constantly so I knew something interesting was taking place. I decided to make a mug of tea then check back again in short while to see what they were doing. When I did, I could see that they looked even better than before.
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This image was captured from home looking N at several of these towers. I think 'still' images never truly convey a sense of scale and size in the way the human eye can, so it may be difficult for you the reader to appreciate just how big these were. Even though this is a wide angle image I was actually craning my neck to look up at these tops. From the repeating pattern of updraught growth, and with the increasing speed in which this was happening I felt certain this was organizing into something big. I felt an overwhelming urge to get a proper look at what was going on from an unobstructive viewpoint and study what was going on below those rooftops.
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I had no intention of going out anywhere far today so I just grabbed the camera and tripod and walked out the road to a country location to evaluate the sky and I'm glad I did. This is what I seen shortly after the first image was taken. Those towers over the rooftops I had seen where the canopy of this much larger and lively structure. This is looking N, the cell is moving from L to R (SW to NE) and away from me, however the airmass was moving so incredibly slow that I was able to watch this thing for a very long time. Again, I have to underscore the issue of size here. This is a wide angle 28mm capture, the convection was far away yet it looked HUGE with the naked eye, both in length and in vertical extent. I was highly impressed with it and now, with hindsight, it was my favourite sight of the day. Also, note how low it hugs the ground. I was really amazed to see such a solid structure, I mean this cell was rock solid like a crispy mountain for the majority of the time I observed it indicating serious air currents inside. This side-on view provides a good profile of this fascinating organized system. To the R is the solid primary Cb updraught region, to the L is another towering cu which was changing shape and height by the sec, and extending from this to the L (SW) for an extremely long distance was a solid flanking line of new cu updraughts which stretched far over the Sperrin mountains. Intense sunshine cast the cell in the most glorious bright white colour which contrasted beautifully with the green fields and clear blue sky above. These tops must have been close to the predicted 25,000ft mark.
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This is the same image which I have annotated to help those who are not well read on convective structures to understand the main features and what's going on. I was blown away by how fast this was growing and felt my heart beat quicken when I considered that this might actually be evolving into a full blown pulse storm. The cell was a living breathing entity due to the motions which I could see. To me it was no longer a cloud but a living thing. This is what happened, the Cb updraught would become rock solid to the point that the entire cell looked like a huge rectangular block which appeared so strong that I felt I could have thrown a stone at the cb walls and it would have bounced back. After some time the main updraught would weaken and fray at the periphery then get blown away from the cell with scudding attachments trailing in the wake of the 'head'. After this happened, in what seemed like sec's, a huge new towering updraught would erupt into the sky at incredible height then move into replace the old updraught becoming the new primary breathing mechanism of the cell. The flanking line produced a rich supply of new towers which fed into the main cb, so I watched in amazement as this process unfolded rapidly in front of me for a long time, much like a multicell would do. This was rapid fire 'pop corn' convection, a tower erupts, moves in, blows it's top, then another moves in to do the same. What an incredible sight it was. I have only been interested in this subject now for about five years or so, however NEVER in that time have I seen such impressive solid and active convection like this during the month of March before from N. Ireland!
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There was alot going on with this cell which is difficult for me to describe. I took many images and every one of them looked different due to the turbulent motions within the cell. This image is closer in and shows the size a little better. The shadow on the field in the above two images are those of a telegraph pole behind me. These were opportunity shots which I took from the road side. There was a house to my R with some activity in the yard. I could sense the owner watching me set up the camera and I don't think he liked my presence near his home. He was loading something into the back of his pick-up and made some very loud bangs which to me sounded like ''leave my property'' so I did just that. No point falling out with the guy over nothing, I would probably feel the same way in his position. So I went further out to the country and took countless images of this cell until those patches of mid level cloud obscured the best of it. It was difficult trying to choose an image to put up but I settled for these wide shots which are the most attractive. The cell began to produce hail from it's outflow region then more began to drip from the mid section walls as virga and eventually made it to the ground as great looking curves of white hail sweeping over the fields. After what seemed like a long time it eventually blew it's primary updraught and decayed (see video), and that was the end of it. Thank goodness I was out in time to see this at its best.
Here's a short video clip of the cell at it's mature then decaying stages.
If nothing else had happened then I was more than happy just to have seen this. The Sun was extremely strong now and I actually felt my skin burning which was a shock. New updraughts where exploding up in the E and N so I just stood there for a while watching and trying to decide what to do next. A van suddenly appeared out of nowhere and pulled onto the grass verge near the field where I was standing. I thought to myself ''not again'', someone was going to give off to me and this time I was very tempted to tell them to get lost because I wasn't on anyone's property. The driver got out and walked towards me and then I realized that it was an old friend I hadn't been talking to in years. We must have stood there under the hot Sun for 2-3 hours chatting about everything and everyone which was great fun. He was wondering what I was doing and when he seen the camera, tripod-mounted, pointing in the direction of clouds I'm sure he thought I was a nutter. The subject got brought up and I got a chance to explain briefly about the towering cumulus and anvils visible, the speed of the air inside them and the thunderstorm potential. This led to a great chat about this subject and he did seem genuinely interested. I was delighted to hear that he had seen the night time thunderstorm which passed over here last May, everyone else I asked was asleep at the time and didn't even hear the thunder which amazed me but he did, and was actually out under it at it's worst in Coleraine. He also knows a guy to took images of a tornado in N. Ireland years ago and might be able to track them down for me which was great. Funny how everything comes together like that from a chance encounter.
Next thing I know the Sun is on its way down to the W so we part company and I headed home. Just before sunset I looked out the window to the E and saw a stunning cu tower which wasn't there before. I went back to doing other things then returned for another look. The tower had now changed into a giant line of cbs and updraughts, the whole thing just grew from nothing, it was awesome and extremely photogenic so I went back outside again and climbed a hill to give me a better view of the E.
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This is the view to the E. This line of convection was very long and stretched outside the frame for a substantial distance on each side. I had to use the zoom lens here and it was a nightmare to get a good focus. The Sun was turning the convection a nice pink colour but was setting fast so I needed to get these very quickly. This is the mid section of that huge line. Moving R to L. In the foreground are towering cumulus with explosive updraughts, behind these are large cbs with solid anvils. Again, more rock solid cells!.
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These where miles away and if my bearings are correct then possibly over the Antrim area near the Lough Neagh shore, or that general region. To see such big storm clouds at that distance is really something for March. The Sun was projecting the shadows of the cu onto the side of the cbs which looked great. At centre you can see several mammatus pouches under the anvil. The bumps to the upper L are an overshooting top (s) indicating severe updraughts. That black horizontal streak of cloud below is not part of the anvil, just mid level foreground cloud.
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I watched it for a period and was sure the overshooting top was serious. The anvil was solid and strong so those bumps were the real thing. I had these confirmed by John McConnell who lives further E in Maghaberry. From his position the cells looked darker because they where back-lit by the Sun, but even so, he was out driving and seen this line to his SW (the same one above) and noted the overshooter with ease. Unfortunately he didn't have his camera with him at the time but at least he seen it.
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Those cu were much more crisp in reality. Getting a sharp focus using the long end of a zoom lens with my camera was an extreme challenge.
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That tower was like watching a mushroom cloud expanding in real time. Bang!
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This is a 300mm capture showing the top of that cu tower with a portion of the anvil behind. The shutter speed was about 240/sec. I took a rapid fire sequence of images one after the other and when I previewed them on the LCD screen and flicked through them in correct order I was stunned to see this updraught exploding with energy, in fact, I found it difficult to believe we could get something like this in early Spring. Each frame showed a completely different view as those bubbling tops expanded, changing shape and size all at once. So this was actually happening in a notable fashion each sec!. When I did the same thing with the wider shots above it was the same result. Phenomenal!. I wish I knew how to make an animated gif to show this motion.
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Mammatus getting more wide-spread under that anvil.
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Anybody living further E must have had a terrific view of this line, it probably filled much of the sky up close. I'm sure there are other images somewhere. I would love to see them.
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Gorgeous!
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The last of the strong colours of the setting Sun does it's thing on the cells before it fades to twilight then dusk. What an interesting day it turned out to be. Even though I didn't get any lightning I was still extremely impressed by the quality of the convection. There where a few sferics around so it's possible that those sunset cbs might have been responsible for them. If there had been more wind shear and more moisture I'm certain there would have been some local storms on this day. In any case it was impressive and hopefully a good omen for more serious t-storms in the near future. After dark we had some snow showers which added to an already interesting day. Just when I thought the fun and games were over, the next morning we had some really intense hail showers as well as a few lightning strikes to the W over the Sperrins with a few others to the S of Lough Neagh, so I think it's safe to say that the storm season has well and truly begun. Thanks very much for reading.
Martin McKenna