Definition

Wind shear is defined as a sudden change of wind velocity and/or direction.

Windshear may be vertical or horizontal, or a mixture of both types. ICAO defines the vertical and horizontal components of wind shear as follows:

• Vertical wind shear is defined as change of horizontal wind direction and/or speed with height, as would be determined by means of two or more anemometers mounted at different heights on a single mast.
• Horizontal wind shear is defined as change of horizontal wind direction and/or speed with horizontal distance, as would be determined by two or more anemometers mounted at the same height along a runway.

Description

Low Level Turbulence, which may be associated with a frontal surface, with thunderstorms or convective clouds, with microbursts, or with the surrounding terrain, is particularly hazardous to aircraft departing or arriving at an aerodrome. Wind shear is usually associated with one of the following weather phenomena: