Prevailing Westerlies are the winds in the middle latitudes between 35 and 65 degrees latitude.
They tend to blow from the high pressure area in the horse latitudes towards the poles.
These prevailing winds blow from the west to the east steering extratropical cyclones in this general manner.
Tropical cyclones which cross the subtropical ridge axis into the Westerlies recurve due to the increased westerly flow.
The winds are predominantly from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere.
Westerlies are generally strongest in the winter hemisphere and at times when the pressure is lower over the poles.
Futhermore, they are weakest in the summer hemisphere and when pressures are higher over the poles.
Westerlies are particularly strong, especially in the southern hemisphere, where there is less land in the middle latitudes to cause the flow pattern to amplify or become more north-south oriented.
This creates frictional or drag in the motion which ultimately slows the Westerlies down.
The strongest westerly winds in the middle latitudes can come in the Roaring Forties which is between 40 and 50 degrees latitude.
The Westerlies play an important role in carrying the warm, equatorial waters and winds to the western coasts of continents, especially in the southern hemisphere because of its vast oceanic expanse.