Flammagenitus (cloud) This is a process not yet fully understood, but is probably in some way associated with charge separation induced by severe turbulence, and, perhaps, by the nature of the particles of ash in the cloud. Large flammagenitus can contain temperatures well below freezing, and the electrostatic properties of any ice that forms may also play a role. A flammagenitus that produces lightning is actually a type of cumulonimbus, a thundercloud, and is called cumulonimbus flammagenitus. The World Meteorological Organization formerly classified flammagenitus and cumulonimbus flammagenitus respectively as cumulus (mediocris or congestus) and cumulonimbus. In 2017, the WMO International Cloud Atlas
Wall cloud warm, moist air rises and converges, overpowering wet, rain-cooled air from the normally downwind downdraft. As the warm air continues to entrain the cooler air, the air temperature drops and the dew point increases (thus the dew point depression decreases). As this air continues to rise, it becomes more saturated with moisture, which results in additional cloud condensation, sometimes in the form of a wall cloud. Wall clouds may form as a descending of the cloud base or may form as rising scud comes together and connects to the storm's cloud base. Wall clouds can be anywhere from a fraction