photo #6508366

Smooth caps of cloud can form over mountains and hills. A cloudspotter might think there’s a mountain hidden from view beneath these ones, but caps of cloud can also form over the top of other clouds. And that’s what has happened behind these ones spotted by Sylvia Archer (Member 42,582) over Little Switzerland, North Carolina, US – far from the actual Swiss Alps. Known as pileus, these cloud caps have developed over huge, building Cumulus clouds, known as Cumulus congestus. Just like the cap clouds that form over mountains, pileus develop in airflows that are being lifted to pass over obstacles, but in their case, the obstacles are the powerful, ever-shifting updrafts of air within building convection clouds rather than fixed, solid terrain. As Sylvia’s Cumulus congestus cloud continues to grow, perhaps developing into a fully fledged Cumulonimbus storm cloud, its rough summit will eventually push through the smooth, delicate-looking pileus, revealing that it is not a mountain after all.