Wind gust World Meteorological Organization. Any significant variation at this mean wind during the ten minutes preceding the observation are noted as gusts in messages such as METAR. It is generally reported in METAR when the peak wind speed reaches at least 16 knots and the variation in wind speed between the peaks and average wind is at least 9 to 10 knots. In marine meteorology, the top speed of a burst is expressed in meters per second (m/s) or in knots, while the Beaufort scale is used for reporting the mean speed. When the maximum speed exceeds the average speed by
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,