Prevailing westerlies are located in the area between 30 and 60 degrees in latitude. The winds play a major role in much of the weather movement in the United States and Canada.
These winds are referred to as westerlies because they originate in the west and blow toward the east. The winds are often stronger in the Southern Hemisphere because there is less land in the middle latitudes to slow them down. Land can cause wind to amplify, or become more oriented toward the north and south, and slow the westerlies. The area known as the Roaring Forties, or between 40 and 50 degrees in latitude, can often have the strongest westerly winds.