A bizarre meteorological event hit the coast of New South Wales, Australia over the weekend. Dubbed a “cloud tsunami” on Twitter, this massive wave in the sky measured several kilometers long and swept over the city of Sydney, bringing with it powerful thunderstorms, heavy rains, and forceful winds that required the Australian Bureau of Meteorology to issue a warning for the surrounding area.
The massive formation is actually called a shelf cloud, composed of arcus clouds. The shelf cloud is typically the leading edge of a thunderstorm, attached to the base of the parent cloud that contains the storm. The strange wave-like appearance is caused by the cool sinking air from the storm’s downdraft spreading out over the land, meeting the warm air being drawn into the storm’s updraft.
The apocalyptic impression of this “cloud tsunami” caused quite a flurry on social media, along with the weather upset that it brought to Sydney. Check out some of the shots snapped of the extraordinary incoming storm, below.