Lyle Collie posted this photo of a so-called “fallstreak cloud” or “hole punch cloud,” formally known as a cavum, that appeared over Chilliwack on Dec. 9, 2019. (Facebook)

Bizarre ‘hole punch cloud’ forms over Chilliwack

Several people posted images of the odd formation, which is scientifically known as a cavum

No, it wasn’t aliens.

Several people posted photos of a bizarre cloud formation over Chilliwack on Monday. What appeared as a giant hole in a flat, thin cloud is what’s known as a “fallstreak cloud” or “hole punch cloud.”

(See below for more photos.)

But the formal name of the cloud formation, which was added to the 2017 version of the International Cloud Atlas is a “cavum,” according to an article on The Weather Network from that year.

“This supplemental feature is caused when ice crystals are introduced into a thin cloud comprised of super-cooled water droplets, usually due to an aircraft passing through the cloud on takeoff or landing,” according to meteorologist and science writer Scott Sutherland. “With the sudden appearance of the ice crystals, the water droplets in the vicinity all rush in – creating a clear spot in the cloud – where they freeze and grow the crystals into snowflakes, which then fall out of the sky.”

The cloud also included a wispy feature below it, almost appearing like a tornado, which is a shaft of precipitation produced by the falling snow.

A similar cavum was seen over Abbotsford earlier this year prompting social media posts.

• READ MORE: Strange cloud forms over B.C.’s South Coast

People posted images of the one on Dec. 9 over Chilliwack from as far east as Bridal Falls and as far west as Langley.


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