When a late-summer thunderstorm rumbled into Kansas City on Aug. 29, lots of people probably — and wisely — sought shelter. But one fearless photographer did pretty much the opposite: Perched on a downtown roof, he defied the danger of lightning to film a beautifully ominous time-lapse video.

This was no amateur with an iPhone, though. It was Stephen Locke, a renowned photographer and filmmaker who has shot more than a few epic storm portraits. Just three months ago, for example, he released a stunning time-lapse video of a supercell over southern Kansas that quickly went viral.

Not much can match the majesty of that supercell video, but Locke's latest effort at least gives it a run for its money. It follows the storm's "arcus cloud" — a low, lateral cloud associated with the front edge of a thunderstorm — as it undulates across the skyline, casting Kansas City in eerie darkness.

Arcus clouds fall into two basic categories: shelf clouds and roll clouds. This one is a shelf cloud, formed by cool, sinking air that spills from the top of a thunderstorm, slips below warmer updrafts and condenses into a horizontal, forward-facing "shelf." Roll clouds develop the same way, but they have become detached from their parent storms, letting them roll away like a loose axle.

Both are often mistaken for tornadoes, according to the National Weather Service, but there are key differences. Shelf clouds may resemble the "wall clouds" that spawn twisters, but they're usually at the front of a squall line and rotate horizontally. Wall clouds, on the other hand, are typically more compact, rotate vertically and form under a rain-free cloud base. Roll clouds can resemble tornadoes more directly, but their horizontal axis and separation from a storm betray their true identity.

Keep an eye out for more meteorological masterpieces from Locke, who isn't one to rest on his laurels. "I will be releasing many more of these over the coming months as I finish post production from the 2014 storm season," he writes on his website. He has already released some bonus imagery of the Kansas City storm, including a photo he describes on Facebook as his first "shelfie."

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Russell McLendon ( @russmclendon ) writes about humans and other wildlife.

Watch a monster arcus cloud sweep over Kansas City
An epic new time-lapse video follows the front edge of a thunderstorm as it darkens downtown K.C.