|Pileus (Cap Cloud)
Tim Anderson imaged this cap cloud formed over a towering cumulus mass. The clouds are backlit and the cap cloud is seen dark in silhouette. It appears to be surrounded by iridescent clouds, these are actually slightly lower and the cap cloud is seen through them.
Cap clouds are themselves often strongly iridescent.
Images ©Tim Anderson, shown with permission
The story of thin and translucent pileus (cap cloud) starts with the development of lower and much thicker cumulus on a hot and humid day.