If your sitting on a ridge with lightning cracking all around you and your fillings buzzing from the static in the air, you’ve probably made the wrong choices and missed something in your planning. I should know, in 2013 I got caught out during an incredibly violent thunderstorm. Since that day I’ve educated myself in how thunderstorms build and how I can reduce my risk in the mountains!
How do thunderstorms form?
Definition from the Met Office
Thunderstorms develop when the atmosphere is unstable – this is when warm air exists underneath much colder air. As the warm air rises it cools and condenses forming small droplets of water. If there is enough instability in the air, the updraft of warm air is rapid and the water vapour will quickly form a cumulonimbus cloud. Typically, these cumulonimbus clouds can form in under an hour.
As the warm air continues to rise, the water droplets combine to create larger droplets which freeze to form ice crystals. As result of circulating air in the clouds, water freezes on the surface of the droplet or crystal. Eventually the droplets become too heavy to be supported by the updraughts of air and they fall as hail.
As hail moves within the cloud it picks up a negative charge by rubbing against smaller positively charged ice crystals. A negative charge forms at the base of the cloud where the hail collects, while the lighter ice crystals remain near the top of the cloud and create a positive charge.
The negative charge is attracted to the Earth’s surface and other clouds and objects and when the attraction becomes too strong, the positive and negative charges come together, or discharge, to balance the difference in a flash of lightning (sometimes known as a lightning strike or lightning bolt). The rapid expansion and heating of air caused by lightning produces the accompanying loud clap of thunder.
How can we reduce our risk?
Planning – Checking the weather forecast is the easiest way to avoid danger spots (Ridges & Summits) . MWIS and the Met office offer some very accurate forecasts and you would be a fool not to check them out before starting your day. Route choice is also an area you must consider if the weather is forecast to turn. Being stuck on climb during a storm can be problematic ,however, it can become dangerous if you have no way of escaping to lower ground
Avoidance – Should a risk of lightning be likely, avoid the high risk places like ridges and summits, these features are prominent and a likely place for a lightning strike. Also avoid wooded areas like forests and coppices. While you may feel safer around trees, a lightning strike to a tree 10-20 meters away can still give you a lethal shock.
Action – Should you find a storm approaching, Descend, descend, descend. Being the most prominent point in the mountains is not a good idea. Getting to lower ground will reduce your risk dramatically. DO NOT abseil unless its un-avoidable, ropes are an excellent conductor especially when wet!
Sheltering under an overhang or a tree is a hazardous course of action because a lightning strike will bridge the gap taking the most economical route, in this case through the people and into the ground. It is much safer to sit out in the open wearing waterproofs.
Their is something of a myth that having metal objects on your person is going to increase your chance of a strike! Metal objects will cause burns but generally unless your holding a metal selfie stick high into the air your in no greater danger! Leaving your bags 30 meters away may help to reduce your chance of burns but is not essential. Descent is always your best option!
Its important to remember that deaths due to lightning strikes are rare. Planning is the key to reducing your risk and ensuring that you get the most out of the day. Wind and rain will increase during a storm and this must be taken into account when planning a day in the hills. I hope you found this article useful, I have listed some sources below that are certainly worth a read!
If you would like to know more about Mountain Matt simply click here. I offer Climbing courses in the Peak District and Wales. Click here to visit Mountain Matts Facebook Page
Met Office information about electrical storms- http://www.metoffice.gov.uk/learning/learn-about-the-weather/thunder-and-lightning
MCofS advice about the dangers of lightning http://www.mcofs.org.uk/lightning.asp
Guide Dolomiti- A pretty good guide on the avoidance of electrical storms! http://www.guidedolomiti.com/en/lightning-dangers/