How a punch cloud formed over St. Louis

ST. LOUIS, Mo. — These images show a hole punch cloud, or officially a fallstreak hole. It is a large gap that appears in cirrocumulus or altocumulus clouds.

Several viewers sent images of the unique cloud formation to FOX 2 Monday. They say it was spotted over downtown St. Louis.

These mid and high-level clouds are made up of “supercooled” water droplets, or tiny droplets that are colder than freezing but not actually frozen. When these come into contact with ice crystals, maybe brought in by a passing airplane, the water droplets freeze and start to fall. A hole is left behind, and that hole expands as bordering droplets also start to freeze.