Mammatus (also known as mamma or mammatocumulus, meaning "breast-cloud") were clearly visable above Santa Monica Beach on Saterday just south of the Pier. Mammatus is a meteorological term applied to a cellular pattern of pouches hanging underneath the base of a cloud, often a cumulus or cumulonimbus. Their color is normally a bluish gray, the same as that of the host cloud, but direct illumination from the setting sun and other clouds may cause a gold or reddish cast. Mammatus can persist anywhere from minutes to hours, diffusing and disappearing over time. The atmosphere must also meet certain conditions, which include a moist and unstable middle to upper atmosphere over a very dry, lower layer of the atmosphere. An updraft then must occur, which shapes the mammatus into the pouch-like shape. Info on Mammatus cloud formation was courtesy of Wikipedia.org