Wind gust 10 to 15 knots, the term "gusts" is used while "strong gusts" is used for departure of 15 to 25 knots, and "violent gusts" when it exceeds 25 knots. Wind gust A gust or wind gust is a brief increase in the speed of the wind, usually less than 20 seconds. It is of a more transient character than a squall, which last minutes, and is followed by a lull or slackening in the wind speed. Generally, winds are least gusty over large water surfaces and most gusty over rough land and near high buildings. The wind is measured using
Wind-powered vehicle sail. Both land yachts and ice boats have low forward resistance to speed and high lateral resistance to sideways motion. Aerodynamic forces on sails depend on wind speed and direction and the speed and direction of the craft ( "V" ). The direction that the craft is traveling with respect to the "true wind" (the wind direction and speed over the surface – "V" ) is called the "point of sail". The speed of the craft at a given point of sail contributes to the "apparent wind" ( "V" )—the wind speed and direction as measured on the moving craft.