The prevailing westerlies are the dominant wind patterns that occur in the middle latitudes, generally between 30 and 60 degrees latitude, in both the Northern Hemisphere and the Southern Hemisphere. These winds are called “westerlies” because they blow from the west to the east, meaning their general direction is from west to east.
Here are some key characteristics of the prevailing westerlies:
- Direction: In the Northern Hemisphere, the prevailing westerlies blow from the southwest to the northeast, while in the Southern Hemisphere, they blow from the northwest to the southeast. The westerlies are located between the subtropical high-pressure zones and the subpolar low-pressure zones.
- Strength and Variability: The strength of the prevailing westerlies can vary depending on the season, latitude, and atmospheric conditions. They are generally stronger and more consistent in the southern parts of the middle latitudes, such as the Southern Ocean, due to the lack of significant landmasses that can disrupt their flow.
- Influence on Weather: The prevailing westerlies play a crucial role in shaping weather patterns in the middle latitudes. They contribute to the movement of weather systems, such as low-pressure systems and associated frontal boundaries. These winds help transport moisture and air masses across regions, influencing temperature, humidity, and precipitation patterns.
- Storm Tracks: The prevailing westerlies are closely associated with the tracks of extratropical cyclones (low-pressure systems) and the development of storms. The collision of warm and cold air masses within the westerly flow often leads to the formation of storms and the associated frontal systems.
- Impact on Travel and Trade: Historically, the prevailing westerlies were important for maritime trade routes and exploration. Sailing ships used these winds to navigate from Europe to the Americas and vice versa. In modern times, the prevailing westerlies still have implications for aviation routes and transoceanic travel.
- Influence on Climate: The prevailing westerlies have a significant impact on the climate of regions within the middle latitudes. They influence temperature moderation, moisture transport, and the distribution of precipitation. They also interact with other atmospheric circulation patterns, such as the polar jet stream, which can affect weather systems and climate variations.
It’s important to note that the strength and behavior of the prevailing westerlies can be influenced by other atmospheric phenomena, such as El Niño/La Niña events, oscillations in the North Atlantic Oscillation (NAO) or Southern Oscillation (SO), and other regional and global factors.