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Bubble-wrap sky: Storm chasers photograph mesmerizing mammatus clouds

The Sunday night sky in Oklahoma brought spectacular views of the pouch-shaped clouds

A display of mammatus clouds in eastern Oklahoma on Sunday. (Peter Forister)

Storm chasers are known for putting themselves in the path of some pretty gnarly storms in the hope of seeing something amazing. Once in a while, however, the best views don’t come from tornadoes or towering clouds. Instead, they appear after the storms have passed.

That’s what Peter Forister, a meteorologist and geographic information systems technician from Virginia, discovered Sunday night when he encountered a stunning display in Oklahoma of mammatus clouds — pouch-like appendages that hang beneath the anvil of a severe thunderstorm.

He had been crisscrossing the southern Plains and Ozarks all day, beginning with an early-morning trip to Joplin, Mo., from his temporary home in Arkansas. He intercepted a morning storm before blasting west and ending up south of Tulsa. From there, he chased storms near the border with Arkansas before returning to Missouri for Sunday night’s lunar eclipse.

Photos: A blood moon lunar eclipse lights up the night sky

“It was over 800 miles,” he said in a phone interview Tuesday morning, laughing at how crazy his day had been. “The kicker was, it was 20 hours of driving. I probably paid about $120 or $130 in gas.”

The photos Forister captured, however, are mesmerizing — including that of a sky that looks as though it’s covered in bubble wrap.

Forister was among many storm chasers who photographed the otherworldly display.

“Mammatus” originates from the Latin word “mamma,” meaning “udder” or “breast.” Each lobe in a mammatus cloud is usually a few hundred yards across. The lobes organize in disjointed fields that can stretch for miles. Although the clouds in and of themselves are harmless, they often portend severe weather nearby.

Atmospheric scientists still don’t fully understand what makes the clouds. Some hypothesize that pockets of dry and saturated air subsiding from beneath a thunderstorm anvil warm at different rates in their descents, causing turbulent overturning that makes for a lumpy cloud base.

Another possibility is that evaporative cooling occurs as parcels of air containing precipitation sink beneath an anvil cloud. That cooling causes sinking until the air pocket reaches “equilibrium.” A “restoring force” of rising air curls the edges of that air pocket upward, shaping the base of the clouds into lobes.

Whatever the case, mammatus clouds are a staple of storm chases, especially during sunset, when underside lighting can bathe the protuberances in amber and red hues.

The storm Forister chased began in eastern Oklahoma and was one of several that formed along an “outflow boundary,” or the leading edge of cool-air exhaust left behind by the previous day’s storms.

“There was a very obvious outflow boundary lined up just north of Interstate 40, and it was intersecting all little outflow boundaries,” he said. “I just sat there and, eventually, storms fired up.”

Since the storms formed in an environment characterized by high cloud bases and northwest flow, the tornado risk was minimal. Instead, large destructive hail proved the primary hazard. Softball-size stones fell in Okemah in eastern Oklahoma, with reports of baseball-size hail in Wetumka.

“Basically, I didn’t want to [core] punch the supercell because I didn’t want to total my car,” Forister said. Instead, he bailed off the storm, encountering a brief burst of 70 mph winds wrapping around the back side of its circulation.

“Then I sat there and enjoyed the view, and the mammatus display started,” he said. “It ended up being the entire sky being filled with them. They were the perfect shape, size, golden-hour lighting ... the contrast, too.”

Mammatus clouds aren’t rare, and even garden-variety thundershowers in the Mid-Atlantic and Northeast frequently have a few bumps in them. But next-level displays like what Forester encountered are special.

“I stopped at a gas station, and we met up with a whole bunch of friends who had been on the storm, as well,” he said. Among them were Virginia Tech colleagues and University of Oklahoma friends like Andrew Shearer and Elizabeth Spicer, who also had been chasing the storm.

Spicer called the display “truly spectacular.”

“They seemed to grow across the sky, leaving us with an almost 360 degree view,” she wrote. “I had seen these clouds before but never like this. I couldn’t decide where the best view was since we were literally surrounded by these beautiful bulbous clouds.”

The mammatus clouds wound up being a blessing and a curse for Forister. While they were an ephemeral treat in the sky, the parent thunderstorm anvil grew so large that it threatened to blot out another celestial spectacle — the anticipated total lunar eclipse.

“I drove back to southern Missouri, since the anvil of the storms went all the way up to the Kansas line,” Forister said of his pursuit of clear skies.

In the end, he spent 20 hours driving and covered a distance equivalent to traveling from New Hampshire to Raleigh, N.C., but he says it was worth it. His photography site is replete with new adventures, but, more important, he has the memories from his experiences.

“My day yesterday. Witnessed some of the most remarkable views nature has to offer,” he tweeted.

More mammatus cloud stories

Stunning mammatus south of Washington, D.C., in 2013

Pic of the week: Incredible mammatus clouds make for a bumpy ride in 2016

Unbelievable mammatus display in Mid-Atlantic in 2017

This 2017 photo of post-storm mammatus clouds is absolutely stunning

An insanely structured thunderstorm created a scene that resembles a time warp in 2018