Cb

When I was a kid (yes, it’s one of those posts – please don’t interrupt.)

When I was a kid, living on RAF bases, I used to listen to the British Forces Broadcasting Service, (BFBS) in the mornings. One thing I remember from those days was the daily early morning weather report. BFBS did the equivalent of the shipping forecast for airmen. There would be a detailed weather forecast along with cloud types and heights to give the flight crews an idea of what to expect that day. I remember the strange sounding names, Cumulus, Stratus and Cirrus and their variations, and the figures that gave cloud cover and cloud base height.

Just over two years ago, Rufus and I got caught in a thunder storm while I was training for a trek. Ever since, I’ve taken an interest in weather prediction and in particular the early warning signs of thunder storms. We had a heavy storm here yesterday, with a lot of lightning and very heavy rain preceded by hailstones. It was well predicted and before the weather changed, I decided to read up on the cloud types. I wanted to try to identify them as they built up and so see first hand the early stages of a thunder storm.

Classic thunder clouds are generally Cumulonimbus clouds, (abbreviated to Cb). They are instantly recognisable as massive and billowing. They can form quite quickly, within 20 minutes sometimes, by warm air rising within the cloud and drawing cooler air in from below. The billowing part is sharply defined while it is formed of water droplets, although this sharpness may fade as the water freezes at higher altitudes. There will almost certainly be rain beneath this cloud, and more often than not hailstones and lightning.

I watched these kinds of clouds forming to the north of the house yesterday. They were so massive and high that it was hard to judge how far away they were. A quick check on the weather radar ‘app’ I have showed they were about 10 miles north, and they were indeed producing lightning. Later that night, the clouds formed over the house and we had our own storm.

This morning was bright and clear of cloud and I decided an early start was in order. There was still some humidity in the air and although the forecast said no clouds or rain for us, there was a lot of lightning activity in Europe and we often get their weather. So I read a little more from the cloud book and found out that there are a couple of early warning cloud species to keep an eye out for.

Altocumulus Floccus (small tufts of clouds) indicate humidity and unstable conditions at high altitude. These conditions can feed and energise cumulonimbus clouds, an already energetic cloud system. They can indicate a coming storm. Altostratus Castellatus clouds also reveal instability at higher altitudes but the clouds are more dense and usually result from more energetic conditions. Again, these clouds herald a coming storm (or at least the conditions necessary for one to form).

Armed with that information, Rufus and I headed north to Mynydd y Gwair. Yesterday, this seemed to be lightning central according to the website I’d been watching, with several dozen strikes recording in the area. I almost expected to see smoking craters but there were none – I guess that only happens in movies. The sky was clear and the morning was warm as we set off over the moorland north of the Upper Lliw reservoir. Sheep parted before us as we squelched through the surface water. Here at least was evidence of last night’s storm.

At the little river that feeds the reservoir, Rufus jumped in and paddled upstream while I walked the bank looking for little waterfalls to photograph. I’d forgotten about checking the weather until I noticed the sun had disappeared. I looked up and saw a few puffy clouds dense enough to obscure the sun. Nothing to worry about according to my new found knowledge, so I went back to setting the tripod up. I was using a very dense filter so exposure times were in the order of a minute or so. The next time I looked up into the sky I saw some familiar clouds; Altocumula Floccus.

I decided to move out of the river valley as it was hiding the horizon and most of the sky. I wanted to see how widespread the clouds were and what was coming up. I moved downstream and saw that it was a very isolated patch of cloud which was clearing to the west. So I went back to photographing waterfalls again. Rufus, uncaring of the cloud types, splashed and paddled and bobbed his way downstream. We played in the water and I threw stones for him to catch and dredge. In a deep part of the river, I threw dead bracken stems for him to swim after.

I looked up again and saw more Floccus. But now, to the south, a larger bank of cloud was forming beyond the reservoir. It had the appearance of an early thunder cloud and I decided, given the conditions, that we start heading back to the car. Out of the valley, there was a breeze blowing towards the reservoir. One of the signs of Cumulonimbus is that as the warm air rises within it, it drags the surrounding air towards it, causing a breeze. It often leads to people thinking the cloud is moving against the prevailing wind. A wind in the direction of the cloud is a warning sign.

The breeze also made the walk back pleasant and Rufus ranged far and wide, unconcerned about any coming storm. And after a few minutes, although the cloud was growing, I wasn’t so concerned either. By the time we’d reached the car, the cloud had grown but hadn’t moved and rather than jumping in and driving off, I left most of the kit in the boot and we walked off onto a man made bank on the opposite side of the moor. We spent another 10 minutes or so exploring the surroundings before finally making our way home. Ahead, over Morriston, the clouds were thick and dark but as we neared home, they broke up and as I write this, the sky is full of larger Cumulus clouds (‘fair-weather clouds’), normal for the time of day and year.

Which means I have no excuses for not finishing off the lawn, tidying up the boarders and cutting down a couple of dead bushes.

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Lightning

On Sunday, I wrote about a few minutes coming down off Fan Fawr when I thought there might be a thunder storm. I can think of nothing else that frightens me as much as being caught out on the hills in a thunder storm.

Fast forward to today. I finished work at 11, picked Rufus up shortly afterwards and at just after midday, we set off from the car to climb up to Llyn y Fan Fawr. The mountains looked lovely in the sun, with a sprinkling of snow on them. It was soggy underfoot but this route usually is, and my boots are waterproof.

Not long after we started, a light sleety snow started to fall, and it turned into hails stones. But it was a light shower. All morning I’d watched short, sharp showers pass over. Rarely did they last more than 10 minutes. The clouds ahead were nothing more than another shower. As we started to climb, the hail got heavier and the wind picked up. I knelt down and for a few minutes, sheltered Rufus from the worst of the hail. There was tail wagging and I got a lot of kisses – I think Rufus likes my beard, which I’ve left grow a bit recently.

The hail got a lot lighter and we set off again. A little way up the hill, the wind picked up and once again the hail started. And then there was an ominous rumbling. I knew straight away what it was, and I was frightened. Thunder coming from the clouds directly ahead.

I immediately turned around. There was no thought of sheltering. I made sure I could see Rufus and we started back down the path.  It had taken us about 30 minutes to get here. The thought of walking back with the risk of lightning for 30 minutes was rather unpleasant. So I began to jog. I was conscious of the risk to my knee but that was secondary. I kept talking to Rufus as he’s not happy with thunder and there were several claps going off. He seemed okay, treating the jogging as a game and criss-crossing in front of me. But he stayed close, which is not his preferred way when he’s out. It was clear he was aware something was up.

I took the direct route back towards the car. That meant missing out the detour to cross the river and I found myself on the wrong side of it. But the ground underfoot was a little flatter so we made good progress. And then I saw the first lightning bolt. It was over to the right, and I saw it out of the corner of my eye. Almost immediately there was a loud clap of thunder. I checked on Rufus, who was hesitating a bit, and I kept talking to him in what I felt was a normal tone of voice, although I was beginning to feel quite scared.

We got to the point where we had to cross the river. Without any hesitation, I waded through the shallows, the water slopping over my boots. Rufus was over quickly and we were about a minute from the car. Then I saw the second lightning bolt, directly overhead. Once again, fortunately, it didn’t touch the ground.The thunder broke at the same time as the lightning.  A little bit of my mind was wondering if a bolt struck the ground, how far away it would have to be so that we wouldn’t be affected. All around me was bog, waterlogged grass and river. I decided to concentrate on getting to the car.

The last few hundred metres was covered in a dash. Rufus was still by my side and he leapt into the car as I opened the door for him. I made sure he was in and shut the door, then climbed in to the passenger seat and closed that door.

Another flash and thunderclap happened at the same time, but I felt so much safer in the car. Rufus was standing, staring at me and I was trying to get my breath back. I gave him a lot of fussing but he was clearly wound up with the excitement of it all. A treat helped. The wind buffeted the car and blew snow up against the windows. In the time it had taken us to get back, I hadn’t noticed the hail turn to snow.

It took me five minutes to stop panting (I’m no runner) and by the time I’d calmed down, Rufus was lying on the back seat, watching me. Several more claps of thunder sounded while we were there but I saw no more lightning. Checking the GPS tracker, I saw that the 30 minute journey up had taken just over 16 minutes to cover on the way down.

The road was white with snow or hail, and I took it slowly at first as I drove down and away from the mountains,. The wind blew snow directly into the windscreen and the visibility wasn’t the best. After a few minutes of careful driving, we reached the main road. And a few minutes after that, the sun was shining and there was blue sky! As had recovered, and both of us had been robbed of a decent walk, I decided to stop on the way back so that we could walk a bit further. Careful to check the clouds,  we walked along side the River Tawe near Ystalafera. Compared to our ordeal, it was pleasant walking.

I’ve been in a white out on Ben Nevis, I’ve taken the wrong path on Blencathra and ended up clinging to the side of a vertical drop several hundred feet high, and I’ve walked along Crib Goch in a gusty breeze. But today was the most scared I’ve ever been on the hills.

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