The westerlies are prevailing winds found in the middle latitudes between 30 and 60 degrees latitude. They blow from the west to the east, and are part of the prevailing wind belt known as the mid-latitude cyclone. The westerlies are caused by the differences in air pressure between the poles and the equator. As air rises and cools near the equator it creates an area of low pressure, while air sinks and warms near the poles, creating an area of high pressure. This difference in pressure causes the air to flow from the area of high pressure to the area of low pressure, creating the westerlies.