Contact Details Wind Wind is the horizontal velocity of air at a point. Winds are always known by the direction from which they come, thus a wind blowing from the west is a westerly.
Pressure Gradients arise from differences in temperature.
When a coloumn of air is heated it expands and becomes less dense than its surroundings. This sets up a slight pressure gradient and cooler, denser air moves in, lifting the warm air away from the surface. A convection circulation is then set up. Small pressure gradients at certain altitudes produce strong horizontal winds. Air cannot flow directly from high to low pressure areas due to the Earth's rotation which is faster at the equator than at the poles.