Wind shear is the variation in wind speed or direction between two nearby points in space. It can be vertical (change with altitude) or horizontal (change over lateral distance). It is one of the most important parameters for predicting severe storms and assessing aviation hazards.
Types and dangers
Vertical shear between low and mid-levels favours the rotation of supercells and tornado formation. In aviation, low-level shear during landing or take-off is extremely dangerous: a microburst can cause an aircraft to lose lift in seconds. Kelvin-Helmholtz clouds are a visual indicator of intense shear.