South Moravia Thunderstorms Yield Rare Roll Cloud

A second round of thunderstorms moved into South Moravia, reaching the town of Blansko on Friday evening. The storms produced heavy rain—exceeding 20 mm in places—strong winds, and downed trees, prompting fire crews to respond to 26 incidents across the region.

During the event a distinctive cylindrical cloud formation appeared at the leading edge of the storm. Meteorologists identified it as a roll cloud, a rare type of arcus cloud that separates from the main storm and can travel tens of kilometres independently. The Czech Hydrometeorological Institute noted that roll clouds form at the interface of cold outflows from thunderstorms and are far less common in Central Europe than the related shelf cloud.

Video footage captured between 21:30 and 21:42 showed the roll cloud moving above the storm front, providing a striking visual of the unusual phenomenon.