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Wind speed Wave height Sea conditions Land conditions Sea conditions (photo) Associated warning flag 0 Calm < 1 knot < 1 mph < 2 km/h 0–0.2 m/s: 0 ft 0 m Sea like a mirror Smoke rises vertically 1 Light air 1–3 knots 1–3 mph 2–5 km/h 0.3–1.5 m/s 0–1 ft 0–0.3 m Ripples with appearance of scales are formed, without foam crests
The fastest wind speed not related to tornadoes ever recorded was during the passage of Tropical Cyclone Olivia on 10 April 1996: an automatic weather station on Barrow Island, Australia, registered a maximum wind gust of 113.3 m/s (408 km/h; 253 mph; 220.2 kn; 372 ft/s) [6] [7] The wind gust was evaluated by the WMO Evaluation Panel, who found ...
A wind speed gradient of 4 (m/s)/km can produce refraction equal to a typical temperature lapse rate of 7.5 °C/km. [51] Higher values of wind gradient will refract sound downward toward the surface in the downwind direction, [52] eliminating the acoustic shadow on the downwind side. This will increase the audibility of sounds downwind.
The power law is often used in wind power assessments [4] [5] where wind speeds at the height of a turbine ( 50 metres) must be estimated from near surface wind observations (~10 metres), or where wind speed data at various heights must be adjusted to a standard height [6] prior to use.
ft/s 3.2808 The metre per second is the unit of both speed (a scalar quantity ) and velocity (a vector quantity , which has direction and magnitude) in the International System of Units (SI), equal to the speed of a body covering a distance of one metre in a time of one second .
The apparent wind is the wind experienced by an observer in motion and is the relative velocity of the wind in relation to the observer. [citation needed]The velocity of the apparent wind is the vector sum of the velocity of the headwind (which is the velocity a moving object would experience in still air) plus the velocity of the true wind.
Roughness length is a parameter of some vertical wind profile equations that model the horizontal mean wind speed near the ground. In the log wind profile, it is equivalent to the height at which the wind speed theoretically becomes zero in the absence of wind-slowing obstacles and under neutral conditions. In reality, the wind at this height ...
Lake Garda in Italy is a deep, elongated lake, measuring about 350 m in depth and spanning 45 km in length. With a wind speed of 25 m/s from the SSW, the Bretschneider and Wilson formulas suggest an H s of 3.5 m and a period of roughly 7 s (assuming the storm persists for at least 4 hours). The Young and Verhagen formula, however, predicts a ...