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thunderstorm In general, a local storm invariably produced by a cumulonimbus cloud, and always accompanied by lightening and thunder, usually with strong gusts of wind, heavy rain, and sometimes with hail. It is usually of short duration, seldom over 2 hours for any one storm. A thunderstorm is a consequence of atmospheric instability and constitutes, loosely, an overturning of air layers in order to achieve a more stable density stratification. A strong convective updraft is a distinguishing feature of this storm in its early phases. A strong downdraft in a column of precipitation marks its dissipating stages. Thunderstorms often build to altitudes of 40,000 to 50,000 feet in middle latitudes and to even greater heights in the tropics; only the great stability of the lower stratosphere limit their upward growth. Sometimes called electrical storm. In NAVTEX broadcasts and other places thunderstorms is abbreviated TSTMS. Map symbols for thunderstorms are shown in G301. The density of thunderstorms is often described as scattered, moderate, or numerous. See numerous thunderstorms. See also convection. See also squall.

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