Cumulonimbus Cloud - Effects

Effects

Cumulonimbus storm cells can produce heavy rain of a convective nature and flash flooding, as well as straight-line winds. Most storm cells die after about 20 minutes, when the precipitation causes more downdraft than updraft, causing the energy to dissipate. If there is enough solar energy in the atmosphere, however (on a hot summer's day, for example), the moisture from one storm cell can evaporate rapidly—resulting in a new cell forming just a few miles from the former one. This can cause thunderstorms to last for several hours. This multicell cloud structure exists until a cold downdraft preceding the cumulonimbus at ground level flows before the cloud at a distance sufficient to disrupt updraft (5–10 km). From this moment on the cumulonimbus cloud quickly degrades and dissipates, breaking into cumulus congestus, meaning a little rain may still fall and the cirrus spissatus anvil cloud. Eventually all that remains is some broken stratocumulus and altostratus and some strands of cirrus.

Mammatus clouds sometimes form on the underside of the cumulonimbus anvil.

Cumulonimbus clouds contain severe convection currents, with very high, unpredictable winds, particularly in the vertical plane (updrafts and downdrafts). They are therefore extremely dangerous to aircraft. Smaller, propeller-driven planes cannot cope with the conditions and must fly around them; larger jet aircraft fly over the smaller ones and around larger examples. Larger planes are also equipped with weather radar and wind shear detectors to help guide them through, in the event that they need to pass through such clouds to land. Snow and ice conditions can develop in the colder upper portions of the clouds, even when the air temperatures at ground level are moderate.

The air convection can also form mesocyclones, which can cause hail and tornadoes.