Marine Glossary

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squall

A wind of considerable intensity caused by atmospheric instability. It comes up and dies down quickly, and is often accompanied by thunder, lightening, and precipitation, when it may be called a thundersquall. An arched squall is one relatively high in the center, tapering off on both sides. A bull's eye squall is one formed in fair weather, characteristic of the ocean off the coast of South Africa.

See also gust, line squall, squall line, white squall. The term is also used to describe the local convective cell, its clouds, and neighboring winds, that give rise to squall winds. See examples in G445 and G437, from a different place at a difference time, but about the same weather.

See ART-23 on squalls. G130 gives a vertical profile of a squall. G131 and associated pictures how the development of local winds around a squall.

There is extended discussion of squalls in the Ask-me Book. See for example, AM-906 and other questions in the Squalls topic.

According to the NWS Observer's Handbook No. 1 (see Source Book), a "squall" is defined as a wind event, independent of cloud formations or lack of clouds. It is a sudden increase of the average wind speed to at least 16 knots or more which is sustained at 22 knots or more for at least 1 minute.