Arcus cloud is attached to the base of the parent cloud, which is usually a thunderstorm cumulonimbus, but could form on any type of convective clouds. Rising cloud motion often can be seen in the leading (outer) part of the shelf cloud, while the underside often appears turbulent and wind-torn. Cool, sinking air from a storm cloud's downdraft spreads out across the land surface, with the leading edge called a gust front. This outflow cuts under warm air being drawn into the storm's updraft. As the lower cooler air lifts the warm moist air, its water condenses, creating a cloud which often
Mushroom cloud stabilization altitude. Significantly smaller fireballs produce clouds with buoyancy-governed ascent. After reaching the tropopause, the bottom of the region of strong static stability, the cloud tends to slow its ascent and spread out. If it contains sufficient energy, the central part of it may continue rising up into the stratosphere as an analog of a standard thunderstorm. A mass of air ascending from the troposphere to the stratosphere leads to the formation of acoustic gravity waves, virtually identical to those created by intense stratosphere-penetrating thunderstorms. Smaller-scale explosions penetrating the tropopause generate waves of higher frequency, classified as infrasound. The explosion