Cloud of the Day – Cumulus Flammagenitus
The International Cloud Atlas fifth edition, published in 2017, has included cloud types that were not recognized before, including types that are caused by humans and other unexpected sources. I’ve already posted on cirrus homogenitus, upper etage clouds forming from the condensation trails of aircraft. Today’s post is about cumulus flammagenitus, cumulus clouds formed by convection caused by a heat source. The heat source could be a wildfire or a volcano, for example, but the cloud can’t be just smoke or ash. It must include water droplets to qualify as a cloud. This type of cloud is also known by the name “pyrocumulus,” or “fire cloud,” which combines fire and the basic cloud type.
Wikipedia has a more in-depth article on flammagenitus than does the Cloud Atlas. As with other cumulus clouds, the convective clouds of the lower etage, flammagenitus can vary in vertical development, with bigger clouds being named accordingly. So we can have cumulus congestus flammagenitus, also known as towering cumulus flammagenitus, and cumulonimbus flammagenitus, complete with the lightning, wind and precipitation associated with thunder clouds.
I have seen flammagenitus rising above forest fires, and it is impressive. The heat is so intense that the smoke, combined with the water driven out of the burning trees, can be driven rapidly high into the atmosphere. These clouds easily rival regular towering cumulus and cumulonimbus in their size and appearance.