Cloud Streets

Cloud streets are cumulus clouds that form in long bands along cylinders of rotating air and are roughly parallel to the ground.  Known also as  horizontal convective rolls or horizontal roll vortices, these clouds occur when when cold air blows over warmer waters with an overlying blanket of warm air.  Rising heat and evaporated water from the body of water hits the colder air, forming columns of heated air called thermals.  As this air rising into the atmosphere, it hits the blanket of warmer air which functions as a barrier and the air loops back over itself creating parallel cylinders of rotating air.  The cloud streets form when the moisture laden air cools and creates condensation in the form of these cumulous clouds.

Cloud streets can cover hundreds of kilometers, depending on the uniformity of the surface below.  The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured cloud streets over the Great Lakes on February 11, 2016.

Cloud streets over the Great Lakes, February 110, 2016. NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response.

Cloud streets over the Great Lakes, February 110, 2016. NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response.

What are Cloud Streets?

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