How To Survive A Thunderstorm: Prediction (Part 2 of 4)

One of the best ways to protect yourself from lightning strikes is to avoid being in a compromising position in the first place.

I know this doesn't help if you're in the backcountry when you're caught in a storm, but since there is no safe place outdoors during a thunderstorm (and since there's no such thing as a “surprise thunderstorm” – you'll see it coming), staying out of them in the first place is your best defense.

If you're not going to be able to get to shelter (inside a modern building or into a car), then it's best to be able to recognize the start of a storm and get to the least dangerous place possible before the real danger begins (note the intentional use of “least dangerous” since there is no safe place outdoors during a thunderstorm – remembering this yet?).

Thunderstorms are most common in the afternoon (think 15:00-17:00), and typically occur in the summer (in the US, July is lightning's deadliest month).

THUNDERSTORM PRECURSORS

The harbingers of thunderstorms are not difficult to recognize, and being able to do so can buy you some valuable time in preparing yourself for an approaching storm (and your impending doom).

Here are the things to look out for:

• CUMULUS CLOUDS | If you see huge cumulus clouds forming (those are the pretty, puffy, white ones), then you may be in conditions right for breeding a thunderstorm. What do you see in the clouds? Death? Get to safety.
   
• CUMULONIMBUS CLOUDS | These are the big brothers of cumulus clouds, and form when cumulus clouds grow vertically – if you see these monsters on the horizon, a thunderstorm may be imminent. Cumulonimbus clouds are also known as thunderheads, thunder cells, or “those anvil looking clouds”.
   
• VIRGA | The presence of virga (your word of the day) can indicate an oncoming storm. What's virga? It is visible shafts of precipitation that fall from clouds and evaporate or sublime before reaching the ground.
   
• RED MORNING SKY | A red sky in the morning, can indicate that a storm is on its way (conversely, a red sky at sunset can mean good weather). It means (though not always) that a high-pressure system has already passed and a low-pressure system (the ones that carry moisture) is on its way. Note: this only applies at mid-latitudes where winds generally travel west to east (sorry, Patagonia, Alaska, and Scandinavia).
   
• AIR PRESSURE | Not everyone carries around a barometer whilst in the backcountry (because not all of us are that cool), but if your internal barometer is finely tuned, then you should pay close attention to changes in air pressure – particularly large drops in air pressure, which can indicate an approaching storm.
   
• ANIMAL BEHAVIOR | Summon your inner Pocahontas and see what the animals are telling you about the weather. Have all the bees and butterflies suddenly disappeared? Are birds moving to lower elevations? Has a talking rabbit told you to get the hell off the mountain? All of these can be signs of an approaching storm.
   
• GAZE INTO THE FIRE | Ever wanted to be able to read the flames of your campfire like a crazy red priest? Well good news, now you can (kind of). If you're at a campfire (or just watching some trees burn), watch the smoke. If the smoke rises steadily, then it's a good indicator of fair weather, but if the smoke swirls and descends it may indicate an approaching low-pressure system (and adverse weather).
   
• A THUNDERSTORM | Just because you don't necessarily see any of these things, it doesn't mean that a storm isn't on its way. If you look out on the horizon and think to yourself, “hey that looks like a thunderstorm”, then it probably is. Get to safety.

So let's say you see one or all of these things and eventually you begin to hear thunder and see lightning. Lucky you!

There are several ways of determining how far away an approaching storm is, but unfortunately not all of them are accurate. For example, at one point I believed that the number of seconds between lightning and thunder was equal to the number of miles away the storm was (spoiler alert: this is very wrong).

Here are two rules you should know for calculating your risk:

• Lightning 30/30 Rule | If you hear thunder within 30 seconds of seeing lightning, then you're in the danger zone; after you hear the last clap of thunder, wait 30 minutes before resuming your death march through the wilderness.
   
• The Flash to Bang Method | To tell how far a storm is from you, first count the number of seconds between the lightning flash and the thunder. Then divide by 5 to get the storm's distance in miles (divide by 3 for kilometers) – 5 seconds = 1 mi / 3 km.

In the next installment we'll dispel some of the most common myths surrounding thunderstorms and lightning. If you're thinking to yourself, “I don't know any myths about lightning”, then it's probably because you have already accepted them as factual.

Prepare to have your mind blown.

How To Survive A Thunderstorm: The Myths (Part 3 of 4)