and what does it consists of?
They consist of water vapor after they undergo deposition at altitudes above
Cirrus cloud
From the surface of Earth, cirrus clouds typically appear white, or a light grey, in color; they form when water vapor undergoes deposition at altitudes above , in temperate regions, and above in tropical ones. They also form from the outflow of tropical cyclones, and from the anvils of cumulonimbus clouds. They also arrive in advance of those storms' associated frontal systems, likely presaging a deterioration in weather conditions. Though indicating the arrival of precipitation, these clouds produce, themselves, at most fall streaks, whose ice crystals evaporate in warmer and drier air, without reaching ground level.

when do cirrus clouds usually appear in the sky They appear in advance of those storms' associated frontal systems, likely presaging a deterioration in weather conditions what is this cloud about? It is generally characterized by thin, wispy strands, giving the type its name from the Latin word "cirrus", meaning a ringlet or curling lock of hair is it the name of a storm or a cyclone? It is a atmospheric cloud
wiki:11608510
Cirrus cloud [SEP] Introduction
They also form from the outflow of tropical cyclones, and from the anvils of cumulonimbus clouds. They also arrive in advance of those storms' associated frontal systems, likely presaging a deterioration in weather conditions. Though indicating the arrival of precipitation, these clouds produce, themselves, at most fall streaks, whose ice crystals evaporate in warmer and drier air, without reaching ground level. Jet stream-powered cirrus can grow long enough to stretch across continents, while remaining only a few kilometers deep. Interaction of visible light with the ice crystals in them produces, below, optical phenomena such as sun dogs and halos. Cirrus is known to raise the temperature (due the heat released as water vapor freezes) of the air beneath the main cloud layer, by an average of 10 °C (18 °F), When the individual filaments become so extensive as to be virtually indistinguishable, one from another, they form a sheet of high cloud called cirrostratus.