WATCH: Mystery cloud vortex stumps Czech meteorologists

A strange cloud formation has stumped experts at the Czech Hydrometeorological Institute, and they are asking people who witnessed it to send them any photos or videos they have. An ominous whirling vortex reminiscent of something in an apocalyptic sci-fi film was seen over the Sázava river.

“In the morning of Sept. 21, 2021, some of you alerted us to an extraordinary meteorological phenomenon in the form of a pronounced cloud vortex. It probably originated in the early morning hours southeast of Prague and then proceeded approximately along the Sázava river, toward Zruč nad Sázavou to Ledeč nad Sázavou. According to satellite images, it disappeared there sometime after 2 pm,” the Czech Hydrometeorological Institute (ČHMÚ) said on Facebook.

They said that, despite appearances, the phenomenon was not a tornado or supercell, as it might have seemed at first glance from the earth. “It was limited to the lowest levels of the atmosphere, up to about 2.5 km above the earth's surface. It wasn’t detected on radar,” ČHMÚ added.

They now “welcome any other relevant observations of this phenomenon” such as photos or video, which can be sent to info@chmi.cz. When the additional data is analyzed, they promise to publish more detailed information.

A supercell, which has been ruled out, is a type of rotating thunderstorm with a large updraft. They are always accompanied by rain and are usually isolated from other storms. The phenomenon in question was not accompanied by rain, and the clouds had the wrong overall structure. While supercells do occur in Europe, they are much more common in the U.S., South America, India, and western Australia.

Tornados also are uncommon in Europe. There are several types but none exactly match what is seen in the video. While a vortex does descend from the cloud bank above, it doesn’t have the tight cone-shaped mass needed for a funnel cloud, the defining feature of a tornado.

Whatever the swirling cloud was, it did not touch the ground or cause any damage. After moving southeast for a few hours, it simply vanished.

There have been destructive storms in the Czech Republic. A tornado hit several villages in Moravia on June 24, 2021, resulting in six deaths and an estimated CZK 15 billion in damages. Around 1,200 houses were heavily damaged. Fields, farmland, and vineyards were also been affected.