Cirrocumulus lacunosus in the early morning of 1 Aug 2014 (Jerry Tangren, East Wenatchee, WA)
Cirrocumulus clouds occur high in the sky, typically short-lived as the ice crystals that comprise them are carried away in the strong upper-level winds. Even more fleeting is the variety of these clouds referred to as lacunosus. This word is Latin for “full of holes” and is commonly referred to as appearing like a honeycomb.
The American Meteorology Society’s glossary defines this cloud variety as follows:
A cloud variety characterized more by the appearance of the spaces between the cloud elements than by the elements themselves. The gaps are generally rounded and often have fringed edges. The overall appearance is that of a honeycomb or net, the negative of that of clouds composed of separate rounded elements. This variety is a modification mainly of the genera cirrocumulus and altocumulus and may apply to the species stratiformis, castellanus, or floccus.
How do these form? The holes indicate areas of sinking air, while the fringed edges indicate localized areas of compensating rising motion. This can happen when a layer of colder air moves over warmer air. The cold air is more dense, creating those pockets of sinking motion. This process is relatively quick so it’s rare to see this pattern persist for very long.