Stratus (St)

A Latin word giving its name to one of the ten cloud genera established by the Atlas Internacional de Nubes of the WMO. It is the low cloud par excellence, sharing the low level of cloudiness with stratocumulus and nimbostratus (the latter clouds straddling both low and mid levels). A stratus is a gray-colored cloud layer, whose base is fairly uniform and can even coincide with the Earth's surface, in which case we refer to it as a fog. It can produce drizzle, small snowflakes, or cinarra, and present a fairly homogeneous, blurred appearance (species nebulosus), or a torn one, forming shreds (species fractus). Stratus clouds can be seen in three different varieties: opacus, translucidus, and undulatus.