JACKSON HOLE, WYO – If you spend any amount of time outdoors—whether its weekend outings on the lake or long backpacking trips into the backcountry—knowing what to do in the event of a thunderstorm can be life-saving stuff.
“During the summer months in the mountains, lightning is probably the greatest weather hazard we face when recreating,” local meteorologist Jim Woodmencey says on his weather blog. “You don’t have to be climbing the Grand Teton (with a backpack full of metal objects, no less) to be struck. Even though the Grand is the absolute highest point around and your odds are considerably increased, it is also possible to be struck by lightning in the valley, on the baseball or soccer field, out on the lake or the golf course, as well.”
Lightning safety has always been a major concern of Woodmencey’s, even before the deadly thunderstorm that pounded the Grand Teton on July 21, 2010. It was so powerful and relentless it injured 16 people and killed one climber when he was knocked off the mountain.
Backcountry Zero will be offering a lightning safety course led by Woodmencey this Wednesday. The program will cover a variety of useful information about storms and lightning safety in particular. What are the early warning signs of an approaching t-storm? How can you lessen your chance of being struck by lightning? What are some of the do’s and don’ts—including popular myths about lightning?
Here are a few tips from Woodmencey to get you started. He’ll cover much more this Wednesday, May 31, from 6-7:30 pm at the TCSAR hangar.
When is it coming?
- The earlier in the day clouds start building; the earlier in the day thunderstorms can occur.
- The more cumulus cloud there are covering the sky, the better the chances of developing larger and more dangerous thunderstorms.
- The taller the cumulus clouds are, the more likely they will produce a thunderstorm.
- The darker the base of the thunderstorm, the taller the thunderstorm is, and the more likely it is to produce a heavy downpour of rain and/or hail. Very dark bases over a very broad area indicate potentially more violent thunderstorms, with strong wind gusts or even tornadoes.
- The “scattered sheep” or “fair weather” cumulus type clouds never develop vertically very much.
Their bases stay white all day, rather than turning gray, and they do not pose a threat. - Prime time for thunderstorm development is mid-afternoon to early evening (2 p.m. to 7 p.m.). Nocturnal (nighttime) thunderstorms are usually the result of a storm system or a cold front passing. Or, they may be related to “monsoon” moisture coming up from the south, usually in July and August.
When to take cover
- Timing Lightning to Thunder: Lightning travels at the speed of light. Thunder travels at the speed of sound. Therefore, lightning is seen before the thunder is heard.
You can time how far away the lightning is by counting, in seconds (one-thousand-one, one-thousand-two, etc.), from the time you see the flash, until the time you hear the thunder. - Take the number of seconds and divide by 5 to calculate the distance the lightning is from you in miles. (Seconds Counted / 5 Seconds per mile = Number of Miles Away.)
- 25 seconds = 5 miles away. 5 seconds = one mile away. 1 second = less than a quarter mile away.
(Note: Thunder can only be heard up to about 10 miles away, maybe 15 miles away on a good day!)
Where to take cover
- Get away from metal objects, including fences, hardware or machinery, chairlifts, golf clubs, etc.
- Never stand under a lone tree. Being in a grove of trees of similar height is a better option.
- Get off the ridgetops, get out of open fields, get out of the water!
Swimming or boating is also very dangerous during thunderstorms. - If you are on an exposed ridge: sit on an insulated pad or backpack. Be sure you are not in a natural water course, like a gully, these will conduct ground currents when bolts hit nearby.
- Retreat to a building or car, lie down in a dry ditch, or try to lie as low as possible.
- The most dangerous time for a fatal strike is beforethe thunderstorm is right over you. Lightning usually precedes heavy rainfall. It does not have to be raining to be struck by lightning
Lightning has been known to strike the ground from over 5 miles away!
20/20 Rule: If the time between the lightning flash and the thunder is 20 seconds or less, then the lightning bolt was less than 5 miles from your location. It is time to seek shelter IMMEDIATELY! After the last lightning bolt is seen, give it about 20 minutes until you return to any exposed area.
