The Vortex: Roll cloud over Lake Michigan

The Vortex, photo by Nick Nerbonne

My corner of Northern Michigan was all abuzz last weekend due to a relatively rare meteorological phenomenon known as a “roll cloud.” Wikipedia’s entry on Arcus clouds explains:

An arcus cloud is a low, horizontal cloud formation. Roll clouds and shelf clouds are the two types of arcus clouds. A shelf cloud is usually associated with the leading edge of thunderstorm outflow; roll clouds are usually formed by outflows of cold air from sea breezes or cold fronts in the absence of thunderstorms.

…A roll cloud is a low, horizontal, tube-shaped, and relatively rare type of arcus cloud. They differ from shelf clouds by being completely detached from other cloud features. Roll clouds usually appear to be “rolling” about a horizontal axis. They are a solitary wave called a soliton, which is a wave that has a single crest and moves without changing speed or shape.

View Nick’s photo background big, scroll through his pictures on Facebook, and watch this time-lapse of the cloud…