Lightening in Scotland; making good decisions in the mountains

Cover Photo: by Michał Mancewicz on Unsplash

Lightening in Scotland; a summer of experience

Its late afternoon and our legs are growing weary from a long and wonderful day of journeying through the Cairngorms National Park. An impromptu dip in a swirling waterfall pool brought joy and reinvigorated our footsteps for the final climb of the day. 

As we near the summit, beyond which lies a perfect high camp spot and our destination for the day, an increasing sense of unease rises in me. The forecasted overnight thunderstorms never materialised, and the day has been largely dry and bright but, as we climb, I am aware of a rapidly darkening sky to the West. We are heading for a high point and a broad open shoulder beyond, not good places to be should a storm arrive. 

We keep moving for another few minutes, but I can no longer ignore the voice in my head saying this is not the right time to be here, go down. I am always telling people to listen to their instinct. To allow it to shape good decision making in the mountains, to keep you safe. So, I take a deep breath and listen to mine. 

Trust your instinct

It isn’t easy to tell a group of tired people that have worked hard to climb a mountain carrying heavy camp packs and excited for the reward of the summit that the plan has changed. That we are turning round and making a hasty retreat to the relative shelter of the glen below but, in that moment, I had no choice. I gather the group together explain my decision which they take in great spirits, and we point our feet downhill. The moment we turn I feel instantly relieved. Fleeting phone signal allows Shona to check a lightning tracker on her phone, a red dot confirms a recent strike on the hills to the west of us. I didn’t need confirmation that I made the right decision, but it serves as a healthy reminder to trust your instincts. 

An hour or so later we are making camp in shelter of the glen. A dark sky encircles us, but the storm never comes. Cracks of sunset glow break through the moody sky and the heather in full bloom reflects the last of the days light. I look up at the surrounding hills in their cloak of cloud and I am very glad to be here, the right place for this night. 

Will it or won’t it?

This was the second time of the summer I had found myself making dynamic decisions on the hill due to lightning risk. The previous occasion was in a very similar scenario in the West Highlands.

Thunderstorms were again forecast but that time the persistently blue sky said otherwise. I discussed the weather and potential risks with my group, and we decided to stick with plan A and camp high. We were not on a summit, but it was still an exposed spot. We tucked in for the night with a plan for what to do if the weather suddenly changed. 

I spent the whole of the evening at unease, questioning my decision, checking the rain radar again and again. I watched the sky late into the night as the clouds rolled in and in the early hours of the morning I saw far away flashes of lightning across the black sky. So far away that I didn’t hear the accompanying thunder. The risk wasn’t such to move the group, but I did wish I had made a different decision the evening before. I was not having a good time, I hadn’t felt able to be present as a leader for the evening at camp and I promised myself that – next time we were going down. 

Lightening arrives

The day after I returned from this trip the storm arrived in earnest, three days after it first appeared in the weather forecasts. The epicentre landed somewhere directly above my house. For over 5 hours lightning cracked, thunder rumbled, and the rain lashed down. The whole house shook, the road turned in to a river, landslides cut off our only access and we were without power for 24 hours. I have never experienced a storm with such force over so many hours and I was very glad to be safe inside 4 walls. 

How to make good decisions

The uncertainty around lightning and the chance of strikes happening is one of the things I find the most difficult to reason with when guiding in the mountains. There is a large margin of error associated with when and where lightning storms will hit, often they don’t materialise at all. Throughout this summer they have been a frequent feature in the weather forecasts and as our climate changes are likely to be increasingly common. It would be quite difficult to spend time in the mountains if you didn’t go near them whenever a risk of lightning is forecast. So how can you keep enjoying the hills without taking unnecessary risks? 

Here are some of the things I’ve found useful in my decision making around recent experiences and some things I’ve learnt from a summer of watching the sky. Adding these into your approach will leave you well equipped to make good decisions in relation to lightening in Scotland: 

Determine the level of risk

• How the lightning appears in the forecast gives you a good idea of the associated degree of risk
• The Met Office forecasts have a % chance of lightning happening on their hourly forecasts. Also look out for whether there is an associated weather warning or not – if there is then the forecasted storms are much more likely to have an effect. Looking at the rain radar within the Met Office forecasts can give you more information about the pattern of movement and where the most likely risk areas are.
• Mountain Weather Information Service (MWIS) use different language to describe lightning in the forecast depending on its likelihood; ‘isolated chance’, ‘localised’, ‘chance of’, ‘likely’, ‘clustering’.
• Use a lightning tracker app to monitor where and when strikes do happen and compare these to forecasts.

Tune into the bigger picture

• Don’t just look at the weather for the specific day and location that you are planning for. Pay attention to what is happening in the days beforehand and the UK wide weather picture. This will give you extra information about how the storms are building and where and when they might play out. 
• The weather in days beforehand can give you clues about accuracy, is the weather matching the forecast? Has the forecast been consistent or is it changing hour to hour? The more consistent it is the higher the degree of certainty in the predictions and the more likely it is to match what actually happens. 
• Both the Met Office and MWIS have long range forecasts that help you better understand the influences behind the weather and how it is likely to unfold. I find the Met Office Deep Dive especially useful.
• If you live in the area that storms are forecast for compare the forecast to the sky. Notice if and when forecasted storms do materialise and what this looks like as it unfolds in skies around you. 

Understand the signs in the sky

• Be familiar with cloud shapes and patterns so that you can spot a storm building before it hits.
• Know that it’s not just about the clouds. High humidity, warm temperatures and gusty winds can also be indicators of a storm building. 

Be Adventure Aware

• If you do decide to go out when lightning is forecast in Scotland, then make a plan that takes this into account. 
• Setting out early is often a good idea as risk usually builds through the day 
• A flexible plan taking into account all variables is essential. What are the capabilities of your group? Can they move fast if needs be? What are the danger points? Where can you escape? Are there key places where a decision will need to be made as to whether to go on or not?
• In winter the Be Avalanche Aware process is used for decision making around avalanche risk and a recent MWIS article suggests using the same framework for decision making around lightning. I think this is a very useful tool and as per a suggestion from a fellow guide the ‘Avalanche’ can simply be replaced for ‘Adventure’.

Know what to do if you get caught out

• If the worst case happens and you do find yourself in the direct line of lightening in Scotland then make sure you know what the best course of action is. 
• There are loads of great resources out there to inform you on this so take the time to do the research.

Does it have to be today?

Once you have taken all of the above into account then ask yourself ‘What kind of a day do I want to have?’ If you are going to spend the whole time worrying about the risk and anxiously watching the skies, then is it really worth it? The mountains will always be there so perhaps it’s a day to enjoy a different kind of adventure. 

Useful Resources for understanding lightening in Scotland

• Met Office: Staying safe in thunder and lightening
• Mountaineering Scotland: Knowing the risks: lightening
• MWIS: Managing thunder storm risk in the mountains
• Mountaineering Scotland: lessons learnt in lightening
• Be [Adventure] Aware: decision making tool
• My Lightening Tracker app
• National Centre for Science Education: Understanding Thunderstorms