The Westerlies, anti-trades, or Prevailing Westerlies, are prevailing winds in the middle latitudes between 30 and 60 degrees latitude, blowing from the high pressure area in the horse latitudes towards the poles. These prevailing winds blow from the west to the east, and steer 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.
The Westerlies are strongest in the winter hemisphere and times when the pressure is lower over the poles, while they are weakest in the summer hemisphere and when pressures are higher over the poles. The 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, which slows the Westerlies down. The strongest westerly winds in the middle latitudes can come in the Roaring Forties, 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.
Read more about Westerlies: Behavior, Impact On Ocean Currents, Extratropical Cyclones, Interaction With Tropical Cyclones