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Short answer

Jet streams are narrow bands of strong wind high in the atmosphere, usually around 30,000 feet. They blow from west to east but wander north and south because they follow the boundary between hot and cold air. [S1]

Why they exist

They are part of global atmospheric circulation, the movement of air that carries heat and storms around the planet. Each hemisphere has three circulation cells; the Hadley cell near the equator lifts heated air and sends it poleward aloft. [S2]

Claims

• id: C1 claim: Jet streams are narrow bands of strong upper-level wind. source: S1 evidence: "Jet streams are relatively narrow bands of strong wind in the upper levels"
• id: C2 claim: Jet stream winds blow from west to east. source: S1 evidence: "Within jet streams, the winds blow from west to east"
• id: C3 claim: Global circulation moves heat and storms around the Earth. source: S2 evidence: "It explains how thermal energy and storm systems move over the Earth's surface."
• id: C4 claim: There are three circulation cells in each hemisphere. source: S2 evidence: "there are three circulations in each"

Sources

• [S1] The Jet Stream. NOAA. https://www.noaa.gov/jetstream/global/jet-stream . License: US government work, public domain. Accessed 2026-11-04.
• [S2] Global Atmospheric Circulations. NOAA. https://www.noaa.gov/jetstream/global/global-atmospheric-circulations . License: US government work, public domain. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_4zntc1bf,
  author = {{iinventedlight}},
  title = {{What is the jet stream?}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/jet-stream/},
  note = {Permanent ID iil:note:4zntc1bf. License: CC-BY-4.0.},
}

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