# Wind speed

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Wind speed

Wind speed is the speed of wind, the movement of air or other gases in an atmosphere. It is a scalar quantity, the magnitude of the vector of motion.

Wind speed has always meant the movement of air in an outside environment, but the speed of air movement inside is important in many areas, including weather forecasting, aircraft and maritime operations, building and civil engineering. High wind speeds can cause unpleasant side effects, and strong winds often have special names, including gales, hurricanes, and typhoons. See the Beaufort scale.

peed and velocity

Technically, wind speed is given by

:$|mathbf\left\{v\right\}|=sqrt\left\{u^2+v^2+w^2\right\}$,

where "u", "v", and "w" are zonal, meridional, and vertical components of wind velocity. Except in unusual circumstances (e.g. in cumulus updrafts), the vertical component of the velocity is much smaller than the horizontal components.

Factors affecting wind speed

Wind speed is affected by a number of factors, situations, operating on varying scales (from micro to macro scales). These include the pressure gradient, Rossby waves and jet streams and local weather conditions. There are also links to be found between wind speed and wind direction, notably with the pressure gradient and surfaces that the air is to be found over.

Pressure gradient is a term to describe the difference in air pressure between two points in the atmosphere or on the surface of the Earth. It is vital to wind speed, because the greater the difference in pressure, the faster the wind flows (from the high to low pressure) to balance out the variation. The pressure gradient, when combined with the Coriolis Effect and friction, also influences wind direction

Rossby waves are strong winds in the upper troposphere. These operate on a global scale and move from West to East (hence being known as Westerlies). The Rossby waves are themselves a different wind speed to what we experience in the lower troposphere.

Local weather conditions play a key role in influencing wind speed, as the formation of hurricanes, monsoon or cyclones as freak weather conditions can drastically affect the velocity of the wind.

Highest speed

The highest surface wind speed ever officially recorded is 372 km/h (231 mph) at the Mount Washington (New Hampshire) Observatory in the US on 12th April 1934, using a heated wire anemometer. The anemometer was later tested by the US National Weather Bureau and confirmed to be accurate. The highest surface wind speed ever officially recorded in Asia was recorded in Afghanistan on 14 August, 2008: 328 km/h in Ab-Paran, Ghowr.

A higher windspeed recorded at 380 km/h (236 mph) during Typhoon Paka in 1997 in Guam was declared invalid because the instrument was damaged during the storm and could not later be checked for accuracy.

Windspeeds within certain atmospheric phenomena (such as tornadoes) may greatly exceed this value but have never been accurately measured. The figure of 509 km/h (316 mph) during the F5 tornado, Moore in Oklahoma, USA is often quoted as the highest surface wind speed but was measured 30 m (100 feet) above ground.

* Wind direction
* Beaufort scale
* Saffir-Simpson Hurricane Scale
* Fujita scale and Enhanced Fujita Scale
* TORRO scale

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### Look at other dictionaries:

• wind speed — vėjo greitis statusas T sritis ekologija ir aplinkotyra apibrėžtis Vėjo judėjimo nuotolis per tam tikrą laiką. Matuojamas metrais per sekundę, kilometrais per valandą, balais (pagal tarptautinę Beauforto (Boforto) skalę – nuo 0 iki 12 balų).… …   Ekologijos terminų aiškinamasis žodynas

• wind speed — noun The local speed of the wind …   Wiktionary

• Wind Speed —   The rate of flow of the wind undisturbed by obstacles …   Energy terms

• Wind Speed Duration Curve —   A graph that indicates the distribution of wind speeds as a function of the cumulative number of hours that the wind speed exceeds a given wind speed in a year …   Energy terms

• Wind Speed Profile —   A profile of how the wind speed changes with height above the surface of the ground or water …   Energy terms

• Wind Speed Frequency Curve —   A curve that indicates the number of hours per year that specific wind speeds occur …   Energy terms

• geostrophic wind speed — The speed of a geostrophic wind calculated from the pressure gradient, air density, rotational velocity of the earth, and latitude. The calculation ignores the curvature of the wind’s path. A geostrophic wind is proportional to the pressure… …   Aviation dictionary

• gradient wind speed — noun the speed of the wind calculated as for geostrophic wind speed, but taking into account the curvature of the path of the air …   Australian English dictionary

• Average Wind Speed — (or Velocity)   The mean wind speed over a specified period of time …   Energy terms

• Mean Wind Speed —   The arithmetic wind speed over a specified time period and height above the ground (the majority of U.S. National Weather Service anemometers are at 20 feet (6.1 meters) …   Energy terms