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 stress and sea states. The magnitude of this shear force per unit contact area ("τ", shear stress) is estimated through wind-shear or wind-drag formulas. These formulas parametrize the shear stress as a function of the wind speed at a certain height above the surface ("U") in the form where formula_2 is the density of the air; "C" is a dimensionless quantity wind-drag coefficient and is a repository function for all remaining dependencies. The height at which the wind speed is referred to in wind-drag formulas is usually 10 meters above the water surface. The expression of "C" contains, in first place,