A squall is a sudden, sharp increase in wind speed that is usually associated with active weather, such as rain showers, thunderstorms, or heavy snow. Squalls refer to an increase in the sustained winds over a short time interval, as there may be higher gusts during a squall event. They usually occur in a region of strong mid-level height falls, or mid-level tropospheric cooling, which force strong localized upward motions at the leading edge of the region of cooling, which then enhances local downward motions just in its wake.
There are different versions of the word's origins:
The term "squall" is used to refer to a sudden wind-speed increase, both historically and in the present day. In 1962 the World Meteorological Organization (WMO) defined that to be classified as a squall, the wind must increase at least 8 m/s and must attain a top speed of at least 11 m/s, lasting at least one minute in duration. In Australia, a squall is defined to last for several minutes before the wind returns to the long term mean value. In either case, a squall is defined to last about half as long as the definition of sustained wind in its respective country. Usually, this sudden violent wind is associated with briefly heavy precipitation.
Known locally as pamperos, these are characterized as strong downsloped winds that move across the pampas, eventually making it to the Atlantic Ocean.
Offshore Central America, a gully squall is characterized by strong increases of the wind forced through sharp mountain valleys on the Pacific Ocean side of the isthmus.
A bayamo is a squall emanating from tropical thunderstorms near the Bight of Bayamo.
In the East Indies, brubu is a name for a squall
In the Pacific Northwest, a squall is a short but furious rainstorm with strong winds, often small in area and moving at high speed, especially as a maritime term. Such a strong outflow occurring in fjords and inlets is referred to by mariners as a squamish.
Bull's Eye Squall is a term used offshore South Africa for a squall forming in fair weather. It is named for the appearance of the small isolated cloud marking the top of the squall.