jetsstreams

Jet streams are narrow bands of very strong winds that blow in the upper levels of the atmosphere, typically near the tropopause. They form where there is a pronounced horizontal temperature gradient between adjacent air masses, most notably between polar and mid-latitude air. The best-known jet streams occur in each hemisphere as a polar jet and a subtropical jet. They are predominantly westerly, meaning they move from west to east, and can reach speeds of roughly 80 to 200 mph (130 to 320 km/h), with stronger gusts in winter. Their cores are usually found at altitudes of about 9 to 12 kilometers (30,000 to 40,000 feet), though the exact height and position shift with season and latitude. The winds arise from the combination of the pressure gradient, the Coriolis force, and the need to balance forces in a rotating atmosphere, leading to a meandering flow shaped by Rossby waves.

Jet streams influence weather and climate by steering mid-latitude storms and affecting precipitation patterns and temperature distributions. They also have a major impact on aviation, offering advantageous tailwinds for eastbound flights and headwinds for westbound ones, while causing turbulence and routing considerations when jet cores are active. Seasonal shifts cause the jets to move north or south, and climatic patterns such as El Niño or La Niña can modify their strength and position. Ongoing research continues to examine how jet streams may respond to long-term climate change and what that means for regional weather extremes and aviation planning.