The Washington PostDemocracy Dies in Darkness

End of days? Nope. Here’s the real science behind the ‘mysterious’ Costa Rica cloud

Watch: Strange iridescent cloud forms over Costa Rica (Video: Youtube/Jessielou121)

When this eerie, iridescent cloud formed over Costa Rica on Tuesday, people were awe-struck.

“You guys, I have never seen anything like this,” said Jessie Montealegre as she recorded the colorful cloud over Escazu, Costa Rica. The skies “opened up as if it were the end of times,” she wrote on YouTube.

ABC News reports that the “mysterious” cloud was seen far and wide across Costa Rica, in San Jose, Parrita, Pavas, Escazu and Hatillo. Joey Petit told ABC he was at a playground when his son noticed the cloud. “He immediately grabbed the camera and started taking video and photos,” Petit said. “We were just so amazed. We had no idea what it was and we’d never seen anything like it.”

While these types of clouds are among the most beautiful that Mother Nature has to offer, they are not a sign of “the end of times.” They’re neither a mystery nor that rare — but don’t let that spoil the fun.

This is a pileus cloud, sometimes called a “cap” cloud because of the way it caps the top of the cumulus cloud. They typically form during the early stages of thunderstorm development, when a strong updraft of rising air is present in cumulus clouds. The upward motion of the building cumulus cloud causes the whole layer of air above the storm to rise. The moisture in this thin layer cools and condenses into cloud droplets, which forms the wispy, flat cloud that caps the storm.

The colorful iridescence doesn’t always accompany pileus clouds , but it’s caused by the same thing that causes rainbows, when sunlight passes through the small cloud droplets and is reflected and refracted into distinguishable colors.

The best way to spot these clouds are during the early stages of thunderstorm development, but you have to be vigilant since they don’t typically last very long. The iridescence can be seen when the sun is positioned behind the building storm clouds so that the refracted light can pass through the pileus and to your eyes.