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Thermal wind is a meteorological term not referring to an actual wind, but a difference in the geostrophic wind between two pressure levels p 1 and p 0, with p 1 < p 0; in essence, wind shear. It is only present in an atmosphere with horizontal changes in temperature (or in an ocean with horizontal gradients of density ), i.e., baroclinicity .
Pilots may decide whether to land (or conduct a missed approach) after wind shear alerts are issued. LLWAS wind shear alerts are defined as wind speed gain or loss of between 20 and 30 knots aligned with the active runway direction. "Low level" refers to altitudes of 2,000 ft (610 m) or less above ground level (AGL).
The airborne wind shear detection and alert system, fitted in an aircraft, detects and alerts the pilot both visually and aurally of a wind shear condition. A reactive wind shear detection system is activated by the aircraft flying into an area with a wind shear condition of sufficient force to pose a hazard to the aircraft. A predictive wind ...
Understanding how wind shear influences weather patterns is somewhat complex as there are multiple types of wind shear and because it can be a factor Wind shear can be a storm's best friend or ...
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere.Wind shear can be broken down into vertical and horizontal components, with horizontal wind shear seen across weather fronts and near the coast, and vertical shear typically near the surface, though also at higher levels in the ...
Vertical wind shear above the jet stream (i.e., in the stratosphere) is sharper when it is moving upwards, because wind speed decreases with height in the stratosphere. This is the reason CAT can be generated above the tropopause, despite the stratosphere otherwise being a region which is vertically stable.
The second mechanism involves wind shear forces on the water surface. John W. Miles suggested a surface wave generation mechanism that is initiated by turbulent wind shear flows based on the inviscid Orr–Sommerfeld equation in 1957. He found the energy transfer from the wind to the water surface is proportional to the curvature of the ...
In meteorology the Ellrod index is a technique for forecasting clear-air turbulence (CAT). It is calculated based on the product of horizontal deformation and vertical wind shear derived from numerical model forecast winds aloft.