Cumulonimbus
What is cumulonimbus?
A cumulonimbus is a towering, vertically developed cloud packed with moisture and unstable air, capable of producing the most hazardous flying weather—lightning, hail, tornadoes, gusty winds, and wind shear. They require conditionally unstable air, a lifting action, and high moisture content to form, and when lined up in a row they create squall lines (nonfrontal bands of thunderstorms). Be aware they aren't always visible, as other clouds can obscure them. Think of it as the thunderstorm cloud—the one you always want to avoid.
Also known as: CB, thunderstorm cloud
Studying for an FAA written test?
Terms like cumulonimbus show up on the FAA knowledge test. Study them in context with ACS-aligned practice questions, AI explanations, and the cited FAA handbook reference behind every answer — free to start.
Learn more in the library
Related terms
- critical engine
- cross controlled
- crossfeed
- crosswind component
- current limiter
- cylinder head temperature
- datum
- datum (reference datum)