Wind shear

The variation experienced at a given moment by the wind vector or one of its components, either in direction or in magnitude (intensity), on a given plane. It is common for the term shear to implicitly refer to vertical shear, as this is the one of greatest aeronautical interest, sometimes becoming a hazardous factor for flight. In the atmosphere there is usually always shear present, since wind intensity normally increases with altitude, besides changing direction, but the shear that can affect an aircraft is only that occurring over short distances.