Above: Altostratus
Below: Altostratus with a hint of the cumulus cloud type.


Look closely and notice the slight hint of cumulus in the cloud photo above. The lighting reveals little lumps scattered through the cloud. Cloud names are based on a cloud shape, size, and texture. Some clouds may have several structures embedded in the main cloud type. The cloud above would likely be categorized as altostratus even though there are very small cumulus textures. The texture is easier to see in this photo than with the naked eye. Overall, it is part of a broad sheet of altostratus covering the sky. The cloud has formed in an area of cold advection (cold air replacing warmer air) over the Midwest.