The strangeness of lightning

Lightning over Wickenburg as seen from the News Chopper (Source: 3TV/CBS 5)

Most of the lightning we see is rather fleeting. A single flash averages only 30 microseconds and travels about 6 miles. So it was surprising reading up on the longest ever lightning flash by distance and the longest ever flash by duration.

In a report published by the World Meteorological Organization, the longest distance flash occurred back in 2007 over the state of Oklahoma. A line of storms was crossing the state that night and the start of the bolt start in the clouds well east of Oklahoma City and traveled just under 200 miles to the west.

Imagine a lightning flash that starts in Flagstaff and ends in Tucson. That’s about the same distance.

The flash took 5.7 seconds to make the erratic path and was confirmed by high tech lightning detection systems. But that wasn’t the longest duration lightning flash. That occurred over southern France on Aug. 20 of 2012. It started in the mountains there.

The flash traveled about 100 miles but took 7.74 seconds to complete its path. And again, it was a flash that went from cloud to cloud to cloud to cloud, etc. It didn’t strike the ground.

The question is, does this change the safety guidelines associated with lightning. According to one of the authors of the article, Randy Cerveny from Arizona State University, the answer is “no” since the flash did not strike the ground. He says the 30-30 Rule is still a very good guideline.

If you see a lightning flash and are not able to count to 30 before you hear thunder, then you’re close enough to a storm to get hit. Every five seconds equates to about a mile’s distance for the bolt. Counting to 30 and more would mean you’re more than 6 miles away and relatively safe. Although some golf courses, resorts and outdoor sporting events are going to a margin of 10 miles away from lightning to be safe. Part of that may be, in part, due to the time it takes to clear a golf course or stadium.

Finally, you should wait 30 minutes after the storm to make sure it has cleared away from you. The 30-30 Rule.

There is also a more generic saying of late that says, “If thunder roars, get indoors.”


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