Cirrostratus (Cs)

A cloud genus belonging to the high-cloud family, taking the form of a whitish, milky-looking veil, sometimes so thin as to be nearly transparent. This cloud's appearance can be smooth and fairly uniform, or fibrous, with irregularly arranged streaks, similar to delicate brushstrokes of white paint. The Atlas Internacional de Nubes of the WMO establishes two different species for this cloud genus (fibratus and nebulosus) and as many varieties (duplicatus and undulatus). Cirrostratus can partially or fully cover the sky and is located between 6 and 12 kilometers of altitude, in the upper stretch of the troposphere. The ice crystals forming it frequently give rise to the optical phenomenon of the halo, whose appearance often anticipates the arrival of rain in the short term, as it is one of the clouds preceding a warm front.