Jetstrømmenes

Jetstrømmenes are narrow bands of fast-moving air in the upper atmosphere, typically near the tropopause at altitudes of about 9 to 12 kilometers (30,000 to 40,000 feet). They form where large horizontal temperature contrasts between air masses are strongest and are shaped by the Coriolis effect from Earth's rotation. The most prominent are the polar jet streams and the subtropical jet streams. In the Northern Hemisphere they usually lie around 30 to 60 degrees latitude, though their exact position shifts with the seasons and weather patterns. Wind speeds in the jet streams commonly range from 80 to 250 kilometers per hour (50 to 155 mph) and can exceed 300 km/h (190 mph) in strong winter events. The jet streams are strongest where the jet core is located and exhibit meanders known as Rossby waves, which can split into multiple branches.

Their dynamics influence weather by steering mid-latitude cyclones and shaping storm tracks. They help advect heat and moisture and can intensify or weaken frontal systems. Seasonal variations are typical: winter jet streams tend to be stronger and positioned further toward the poles, while summer jets shift equatorward and weaken. Large-scale patterns such as El Niño–Southern Oscillation can shift average positions and strength.

For aviation, jet streams affect flight times and fuel efficiency. Aircraft often seek favorable tailwinds in the eastbound direction and avoid strong headwinds or turbulence in crossing jets. Meteorologists monitor jet streams to forecast weather and aviation routes.