Wind shear refers to the rate of wind speed or direction change with distance.Wind shear may be horizontal or vertical. Vertical wind shear is the rate of change of the wind with respect to altitude. Horizontal wind shear is the rate of change on a horizontal plane.
Thunderstorms often form 10 miles north of Sherman field. ASOS data can show winds that are coming from 30 to 40 degrees difference in direction at diffeent altitudes. This horizontal wind shear is often seen in thunderstorms.