Lightning notes

2011-06-22 18:33:06.000 – Ryan Knapp,  Meteorological Observer

Lightning seen a few shifts ago.

As you may have read in yesterday’s comment, this week is the National Weather Services’ Lightning Safety Week (June 19-25). And while only this week is officially designated as lightning safety week, lightning safety should be on the mind of any hiker, especially during the summer season. I’m not saying we don’t get lightning in the winter, it’s just less common than the summer season. So, since it is summer, and I overhear a lot of hikers up here and down in the various stores and visitor centers around the valleys, I thought I would clear up at least three common misconceptions I hear people mention when thinking about hiking up/down on a day with thunderstorms predicted.

Number one: “…I can hike until I hear thunder then take shelter.” In ideal atmospheric conditions, thunder has been heard as far away as 20 miles, but ideal conditions are rare on the summit. Wind, haze, humidity, vegetation, etc can absorb those sound waves and shorten the distances they can be heard. So in general, thunder is seldom heard beyond 10 miles. And having worked 5 years in the White Mountains, I can confidently say that you usually won’t be able to hear it until even less than 10 miles.

Number two: “…well, if I can’t hear it, I will just look for lightning instead.” This is a slightly better method except for some limiting factors. Summit fog, haze, the direction your head up a mountain compared to the fronts direction, other mountain ridges or other clouds can limit your line of sight. While this method may work in the Midwest, most of the time you won’t see them coming until it’s too late. Even if we might be able to see them coming (ie, no fog), we usually have to rely on radar for enough warning even on the highest summit in New England.

Number three: “I’ll just use my cell phone.” While this can be true, service is very spotty on and around the summits so you may not have the 3G/4G you need. Keeping it on drains your battery as it searches for services. And most online services delay strike reports by 12-20 minutes. So, a cell phone should be used as a tool but not your only resource.

So what to do: Check the weather report by MWO, NWS, or any other provider you’re comfortable with. If thunderstorms are likely, hike another day. Understand weather patterns in the area you will be hiking. If the storm’s moving west to east and the front is over VT when you look, lightning is inevitable. Hike early since most thunderstorms (not all) form in the afternoon after daytime heating. Look at cloud formations. If they are building around you, that should be a warning. And if all else fails, start using the sight and sound methods. And remember, if thunder roars, head indoors. I could go on, but to learn more about lightning safety or risk reduction, you can check out the NWS lightning safety page, the outdoor risk reduction page, or if in North Conway, NH Thursday, June 23 at 7 pm, you can stop by the Weather Discovery Center for an informative and hands on understanding of lightning.

Ryan Knapp,  Meteorological Observer