@RobertClarkphoto While on an assignment for @nature_Org I photographed clouds before a rain storm in Ogallala Nebraska. The unquie #cloud formation is called, #Mammatus meaning "mammary cloud". They are a cellular pattern of pouches hanging underneath the base of a cloud, typically #cumulonimbus rain clouds. The name mammatus is derived from the Latin mamma breast.
According to the WMO International Cloud Atlas, mamma is a cloud supplementary feature rather than a genus, species or variety of cloud. They are formed by cold air sinking down to form the pockets contrary to the puffs of clouds rising through the convection of warm air.