Britannica
Sources used in this answer
How do midlatitude westerlies contribute to changeable weather?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
Climate
Even in our warming world, there will be some chilly evenings.
The midlatitude westerlies are fundamental to the changeable weather experienced in middle latitudes because they facilitate the movement and interaction of contrasting air masses.1
This process occurs through the following mechanisms:
- Cyclonic Activity: The westerlies are associated with migrating extratropical cyclones and anticyclones. These systems develop along the polar front, a boundary where warm, moist air moving poleward from the tropics meets cold, dry air moving equatorward from polar regions.12
- Atmospheric Interaction: As these air masses collide, they create zones of strong temperature contrast. The resulting atmospheric disturbances lead to a variety of weather conditions, including rain, snow, thunderstorms, and sleet, which are often followed by periods of dry, sunny, or bitterly cold weather.1
- Upper-Level Steering: The westerly flow in the upper troposphere, often concentrated into jet streams, steers these surface-level waves and cyclones, dictating their path and intensity.34
These patterns are further complicated by seasonal changes, the presence of major landmasses, and mountain features, which can disrupt the flow and influence local weather outcomes.15