jetstreams

Jetstreams are narrow bands of strong, fast-moving winds in the upper troposphere, with some extension into the lower stratosphere. They transport air from west to east at high altitude, typically 9–12 km (30,000–39,000 ft) above Earth's surface. Their formation is linked to large horizontal temperature contrasts, especially at the boundary between polar and mid-latitude air, and to the planet’s rotation (Coriolis effect), which deflects winds and strengthens them into a westerly jet with fast-moving cores.

The main global jet streams are the polar jets, located roughly at 50–60° latitude in both hemispheres, and the subtropical jets around 30° latitude. Core winds usually range from about 80–140 knots (150–260 km/h), though brief gusts can exceed 200 mph in strong events. Jets meander in wave-like patterns caused by Rossby waves and may split or shift seasonally; winter tends to produce stronger, more persistent jets. The position and strength of jets are influenced by climate patterns such as El Niño–Southern Oscillation and Arctic warming.

Jet streams influence weather by steering mid-latitude storms and shaping precipitation patterns. For aviation, they can shorten west-to-east flights when a favorable tailwind is present and lengthen trips with adverse headwinds or turbulence along jet streaks. Accurate jet-stream forecasts are integral to weather prediction and flight planning.