Solar Heating and Coriolis Forces

Since winds are just molecules of air, they are also subject to Coriolis forces. Winds are basically driven by Solar heating. As the adjacent (highly idealized) image indicates, Solar heating on the Earth has the effect of producing three major convection zones in each hemisphere.

If solar heating were the only thing influencing the weather, we would then expect the prevailing winds along the Earth's surface to either be from the North or the South, depending on the latitude. However, the Coriolis force deflects these wind flows to the right in the Northern hemisphere and to the left in the Southern hemisphere. This produces the prevailing surface winds illustrated in the adjacent figure.

For example, between 30 degrees and 60 degrees North latitude the solar convection pattern would produce a prevailing surface wind from the South. However, the Coriolis force deflects this flow to the right and the prevailing winds at these latitudes are more from the West and Southwest. They are called the prevailing Westerlies.