Catching Cloud Inversions

Useful Information

Believe it or not, under specific weather conditions you can actually walk above the clouds. This is known as a ‘cloud inversion’ and can mainly be spotted during Autumn and Winter. I saw my first ever cloud inversion from Helvellyn in the Lake District, and I felt on cloud nine – pardon the pun. It was truly phenomenal! From that day, I became hooked and began studying these as I was determined to spot more in the future.

So you may be wondering, how does a cloud inversion form? Well, these occur when colder air gets trapped below a shield of warmer air. This creates a magical effect of fog sweeping over the area. Under usual conditions, the general rule is that the temperature drops as you gain height. However, on occasions, this general rule is reversed and a cloud inversion is formed.

Mam Tor, Peak District.
Cloud inversion viewed from Mam Tor, Peak District.

In the UK, there are two main types of cloud inversions, the most common being nocturnal inversions. Nocturnal inversions occur mainly under high pressure and settled conditions, which usually go hand in hand. They mainly occur in the winter half of the year due to the long nights. The conditions to look out for are high pressure, little to no wind, clear skies over night and more likely to occur in hilly mountainous terrain. The cooler air from up on the hills sinks into the valleys due to its density which then allows the less dense warmer air to be on top of the cooler air, creating a cap. As the air temperature quickly drops due to the clear skies and then reaches its dew point, the cooler air then condenses and this fog/cloud is then trapped under the warmer air creating a flat top.

The other main type of cloud inversion is called a Subsidence Inversion. It is called a Subsidence Inversion due to high pressure system having descending air which warms as it does so. These inversions occur when high pressure moves across Britain mainly from West to East. When the high pressure centre is centred just to the West of Britain, cooler air is drawn from the polar region to Britain. Due to the nature of the settled conditions which accompany high pressure systems, the layers of air from the atmosphere are less likely to be mixed. As the high pressure centre slowly moves across Britain, the descending air is at its strongest. If the high pressure centre remains in place for a few days or more, the layer of warmer air gets lower and lower, and sometimes descends to the height of the highest mountains in Britain. This means when climbing your favourite peak, you are likely to ascend into warmer air and if enough moisture is present in the lower cooler layer, cloud may be present. The moisture mainly occurs and gets added to the mix as the high pressure moves East across Britain which creates a change in wind direction, bringing more humid air from mainland Europe. Similar to the first type, the warmer air creates a capping layer which limits the height of the cloud top enabling you to be above the cloud. There are other types of cloud inversions but these are the main two.

Peel Tower cloud inversion

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When Patience Pays Off

Hiking Experiences

During the summer months, I was eager to get out in the mountains between lockdown restrictions and poor weather. After reading between the lines with the mountain weather forecast, it looked like there would be a small window of opportunity in the early hours of this particular morning which offered clear skies.

Starting out at Beddgelert and ascending the Watkin path, my destination was the amazing viewpoint between Snowdon and Y Lliwedd, which offers perhaps the best view in Wales, which looks out across the beautiful Llyn Llydaw. During the ascent I was greeted by numerous shooting stars that ripped through the dark skies of Snowdonia putting on such a spectacular show in the clear skies that were indeed forecast.

Halfway up the Watkin path and the intended ridge I was aiming for in sight, I caught a glimpse of 4 headtorches making their way across the ridge towards Snowdon summit. Despite being in the middle of nowhere and halfway up a mountain, I found it highly amusing that all I could hear was “watermelon sugar” being played loudly from a portable stereo. As I made my final push for the ridgeline, I was swamped by a bank of low cloud and the landscape quickly disappeared before me.

Watkin Path Route
Sun rising above Llyn Llydaw

After reaching my destination I sat for nearly an hour in low cloud with no view and contemplating calling it a day. There were signs the cloud was trying to break, teasing as I got glimpses of what I had come to see. I had been in this situation many times before and still never got the view, but for some reason on this morning I was convinced I would. At this point sunrise had passed and still nothing.

Just as I was starting to get my stuff together and packing my bag, the ground right before me lit up in a soft golden glow. As I stood there, the clouds began to part and I was eventually greeted with the view that can be seen in the image. When you have made the midnight drive and the climb by headtorch, it really is worth sticking it out because you just never know what might happen. One thing was for certain, nothing was wiping the smile off my face on the drive back home.

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