often implicated in crashes because of their rapid onset and swift changes in wind and aerodynamic conditions over short distances. Most downbursts are associated with visible precipitation shafts, however, dry microbursts are generally invisible to the naked eye. At least one fatal commercial airline accident was associated with flying through a tornado. Life cycle or stages In general, cumulonimbus require moisture, an unstable air mass, and a lifting force in order to form. Cumulonimbus typically go through three stages: the developing stage, the mature stage (where the main cloud may reach supercell status in favorable conditions), and the dissipation stage. The average thunderstorm has a diameter and a height of approximately . Depending on the conditions present in the atmosphere, these three stages take an average of 30 minutes to go through. Cloud types Clouds form when the dew point temperature of water is reached in the presence of condensation nuclei in the troposphere. The atmosphere is a dynamic system, and the local conditions of turbulence, uplift, and other parameters give rise to many types of clouds. Various types of cloud occur frequently enough to have been categorized. Furthermore, some atmospheric processes can make the clouds organize in distinct patterns such as wave clouds or actinoform clouds. These are large-scale structures and are not always readily identifiable from a single point of view. See also Atmospheric convection Atmospheric thermodynamics Convective instability Hot tower Lifted condensation level (LCL), convective condensation level (CCL), level of free convection (LFC), and free convective layer (FCL) William Rankin Ewa Wiśnierska References External links Clouds-Online.com Cloud Atlas with many photos and description of the different cloud genera MetOffice.gov.uk Learn about thunderstorms and how cumulonimbus clouds form Cirrus Cumulus Severe weather and convection