Cumulus cloud

A cumulus cloud is a heaped convective cloud with a flat base and often a cauliflower shape. It forms in unstable air when rising warm air cools to its condensation level. Cumulus clouds often mark thermals, so light to moderate turbulence can be expected below and near them. Pilots use them to judge convection and cloud base, and should watch their vertical growth because stronger development can lead to showers or cumulonimbus.