The jet stream
The fast river of wind high above us that steers storms and shapes weather patterns.
This explanation is written conservatively from textbook-level science and has not yet been reviewed by a meteorologist. Treat it as a draft.
The mechanism
Follow the chain: each step causes the next.
01
Temperature contrast
Air near the poles is much colder than air in the tropics.
02
Pressure gradient aloft
That contrast creates a strong difference in pressure at high altitude between warm and cold air masses.
03
Earth's rotation turns the flow
The Coriolis effect turns the resulting flow so that it blows mainly from west to east.
04
A meandering jet
The jet develops large waves (Rossby waves) that guide low- and high-pressure systems along its path.
Explore it
Step through the mechanism one stage at a time.
Step 1 of 4
Temperature contrast
Air near the poles is much colder than air in the tropics.
In short
Where it is
Jet streams are narrow bands of strong wind near the top of the troposphere, roughly 9 to 12 km above the surface in the mid-latitudes. The polar-front jet sits where cold polar air meets warmer mid-latitude air; a subtropical jet lies closer to the tropics.
Deeper science
Open a section for more detail.
How it shapes weather
Storms in the mid-latitudes tend to form and travel along the jet. When the jet's waves grow large and slow down, weather patterns can stall — a situation known as blocking, which is associated with prolonged heat, cold, drought or rain.
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