A fast band steering the weather
What Is the River of Wind Up High?
A jet stream is a narrow ribbon of very fast wind high up, driven by the clash of warm and cold air.
-
Step 1 of 5
The planet is heated very unevenly.
The tropics receive far more sunlight than the poles, which leaves a permanent and enormous temperature difference between them.
-
Step 2 of 5
Where warm and cold meet, air moves fast.
A sharp temperature difference creates a sharp pressure difference, and air responds by rushing along the boundary between them.
-
Step 3 of 5
Earth's spin bends the flow sideways.
Rather than flowing straight from warm to cold, the moving air is deflected by the planet's rotation into a band running west to east.
-
Step 4 of 5
The result is a narrow, very fast ribbon.
The jet is only a few hundred kilometres wide and a couple deep, yet winds inside it routinely exceed two hundred kilometres an hour.
-
Step 5 of 5
Storms ride along it, so it steers our weather.
Weather systems are carried by the jet, and when it buckles into big waves those systems get steered far north or south of normal.
Flights from New York to London ride the jet stream and arrive around an hour sooner than the return journey against it.
The short version
A jet stream is a narrow ribbon of very fast high wind formed where warm and cold air clash, and its shape steers storms across the map.
Try it yourself
Compare the scheduled flight times for an eastbound and westbound transatlantic flight. The difference is the jet stream.
Topics