What Is the Jet Stream?
The jet stream is a narrow band of strong wind in the upper atmosphere (around 9-12 km altitude), flowing from west to east. Wind speeds typically range from 150-300 km/h, sometimes exceeding 400 km/h.
Why It Exists
The jet stream forms at the boundary between cold polar air and warm tropical air. The temperature contrast drives the wind. The Earth's rotation bends the flow eastward.
How It Affects Weather
The jet stream acts as a boundary — warm air sits to its south, cold air to its north (in the Northern Hemisphere).
- When the jet stream dips south (trough), it pulls cold air with it → your region gets colder, stormier
- When the jet stream bulges north (ridge), warm air pushes in → your region gets warmer, drier
- Storms travel along the jet stream like boats on a river
Jet Stream and Flights
- Flying eastbound with the jet stream can cut an hour or more off transatlantic flights
- Flying westbound against it adds time and fuel
- Turbulence is common near the edges of the jet stream
Seasonal Changes
| Season | Jet Stream Position |
|---|---|
| Winter | Shifts south, becomes stronger (bigger temperature contrast) |
| Summer | Shifts north, becomes weaker |
Climate Change Impact
Research suggests that warming Arctic temperatures are weakening the jet stream, causing it to become wavier. These larger waves can lock weather patterns in place — leading to prolonged heat waves, cold spells, and droughts.
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