Cirrus spissatus

Cirrus Spissatus are the highest of its kind, with altitudes of up to 20 km. They often originate from the top of a Cumulonimbus or may still be part of it; That's why Cirrus spissatus can be so tall. They indicate the approach of Cumulonimbus, precisely because they usually originate from them. Its thickness is sufficient to make them look gray when they are towards the sun. It is one of the only types of Cirrus that present optical phenomena (halos, parelios).