wind shear


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wind shear,

a sudden, drastic change in wind direction or speed over a comparatively short distance. Most winds travel horizontally, as does most wind shear, but under certain conditions, including thunderstorms and strong frontal systems, wind shear will travel in a vertical direction. Microburst wind shear is an extremely violent downward blast of air that hits the earth and radiates outward. With its sharp shifts in wind direction and relative wind speed, it can cause an aircraft to lose lift and crash, especially during takeoff or landing, when the slower speeds and closeness to the ground make altitude correction more difficult. Since 1996 all U.S. airliners have been required to be equipped with instruments that provide the pilot with advance warning of wind shear. See also weatherweather,
state of the atmosphere at a given time and place with regard to temperature, air pressure (see barometer), wind, humidity, cloudiness, and precipitation. The term weather
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 and windwind,
flow of air relative to the earth's surface. A wind is named according to the point of the compass from which it blows, e.g., a wind blowing from the north is a north wind.
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.

wind shear

[′win ‚shir]
(meteorology)
The local variation of the wind vector or any of its components in a given direction.

wind shear

wind shear
Vertical wind shear near the ground.
The rate of change in the wind velocity in space, considered as a vector. A vertical shear is a change in the wind velocity with height, whereas a horizontal shear is the change in the wind with the horizontal distance perpendicular to the flow.
References in periodicals archive ?
This is consistent with loss of control in wind shear or a microburst.
Hurricane development in the Atlantic Basin depends on the combination of sea-surface temperatures, instability, wind shear (influenced in part by ENSO), dust, dry air and even sunspot activity.
Two methods of wind speed prediction are used, both using the power law (PL) method for wind speed extrapolation, (1), to estimate the wind speed at 80 m, 100 m, and 120 m from a known reference height using a fixed wind shear coefficient (FWSC) and a variable wind shear coefficient (VWSC), where [V.
Through their analyses and comparisons, they concluded that, under a microburst wind shear, wind gradients have such a significant influence upon the aerodynamic moments that they cannot be negligible.
The percentage change in the COE estimation for the two wind shear factors and three sites under study show that, if 10 m wind data extrapolated with WSC 0.
Wind shear is a sudden change in wind speed or direction and can be dangerous, especially for planes near the ground.
The NTS8's probable cause determination included "the flightcrew's decision to initiate and continue the approach into a cumulonimbus cloud," which they observed to contain visible lightning, and "the lack of specific guidelines, procedures, and training for avoiding and escaping from low-altitude wind shear; and the lack of definitive, real-time wind shear hazard information.
Although Phanfone is moving into an area of increasing vertical wind shear (changes in wind speed and direction with height) as well as cooler ocean waters, the storm will be slow to weaken and will still be a very intense system as it approaches the larger islands of Japan.
DEVELOPMENT Working to derive algorithms that allow aerial gliders to ride without human help on vertical wind shear or on thermals.
Klotzbach said the wind shear in the tropical Atlantic is much stronger than normal this season.