Cloud
High clouds form at altitudes of in the polar regions, in the temperate regions and in the tropics. All cirriform clouds are classified as high and thus constitute a single genus "cirrus" (Ci). Stratocumuliform and stratiform clouds in the high altitude range carry the prefix "cirro-", yielding the respective genus names "cirrocumulus" (Cc) and "cirrostratus" (Cs). When limited-resolution satellite images of high clouds are analysed without supporting data from direct human observations, it becomes impossible to distinguish between individual forms or genus types, which are then collectively identified as "high-type" (or informally as "cirrus-type" even though not all high clouds are of the cirrus form or genus).Non-vertical clouds in the middle level are prefixed by "alto-", yielding the genus names "altocumulus" (Ac) for stratocumuliform types and "altostratus" (As) for stratiform types. These clouds can form as low as above surface at any latitude, but may be based as high as near the poles, at mid latitudes, and in the tropics. As with high clouds, the main genus types are easily identified by the human eye, but it is not possible to distinguish between them using satellite photography. Without the support of human observations, these clouds are usually collectively identified as "middle-type" on satellite images.
Low clouds are found from near surface up to . Genus types in this level either have no prefix or carry one that refers to a characteristic other than altitude. Clouds that form in the low level of the troposphere are generally of larger structure than those that form in the middle and high levels, so they can usually be identified by their forms and genus types using satellite photography alone.
Atmospheric convection
There are four main types of thunderstorms: single-cell, multicell, squall line (also called multicell line) and supercell. Which type forms depends on the instability and relative wind conditions at different layers of the atmosphere ("wind shear"). Single-cell thunderstorms form in environments of low vertical wind shear and last only 20–30 minutes. Organized thunderstorms and thunderstorm clusters/lines can have longer life cycles as they form in environments of significant vertical wind shear, which aids the development of stronger updrafts as well as various forms of severe weather. The supercell is the strongest of the thunderstorms, most commonly associated with large hail, high winds, and tornado formation.