Topics Earth, weather and climate

What is the jet stream?

The jet stream is a narrow band of very fast wind high in the atmosphere, usually around six to nine miles up. Winds inside it can pass 100 miles per hour, and in the strongest stretches they go well beyond that. It is not a single stream but a few of them, the main ones circling the planet in the middle latitudes of each hemisphere, flowing mostly from west to east.

What makes it interesting is the cause. Air near the equator is warmer than air near the poles, and that temperature contrast, combined with the spin of the Earth, pulls the high-altitude winds into a fast, wavy ribbon. The wiggles matter: they help steer storms, pull cold air south or warm air north, and can leave weather stuck in one place for days. Pilots use it too, because a tailwind can shorten a flight across the Atlantic.

An episode would start with that picture of a river of air, then walk through why it forms, why it bends, and how forecasters use it. It would also say plainly where scientists still disagree, especially on how a warming climate might change it. bre's hosts are AI, so they can be wrong, and you can press Talk to ask a question mid-episode.

What a bre episode would cover

An outline of the episode bre would make for this question. Every episode is written fresh when you ask, so yours will differ.

  1. A river of air, six miles upWhat the jet stream is, how high it flows, and how fast. The picture to hold: a narrow ribbon of wind, not a layer that covers the sky.
  2. Why it exists at allWarm air at the equator and cold air at the poles create a temperature contrast. The spinning Earth turns that contrast into fast west-to-east winds.
  3. The wiggles called Rossby wavesWhy the jet bends into big loops, and how those loops carry cold air south and warm air north. Their shifting is a big part of daily weather.
  4. Steering storms and stalling weatherHow the jet guides storm tracks, and what happens when its pattern slows down and a heat wave or a rainy spell lingers.
  5. Flying with it and against itWhy eastbound flights across the Atlantic are often quicker than westbound ones, and how airlines plan routes around the jet.
  6. Is climate change shifting it?What researchers do and do not agree on. The link between a warming Arctic and a wavier jet is debated, and the answer is not settled.

How the episode might open

A sample exchange between two of bre’s AI hosts, bre and Arlo. Both are AI; this is written by AI, as every bre episode is.

  1. breAI host

    Picture a plane crossing the Atlantic. Some days it arrives early and nobody pushed it. Up around six to nine miles, there's a ribbon of wind that can top 100 miles an hour, and that's the jet stream.

  2. ArloAI host

    A ribbon. How big?

  3. breAI host

    Often a few hundred miles wide and only a few miles thick, give or take. On a planet roughly eight thousand miles across, that's thin.

  4. ArloAI host

    Who counted that? Few hundred, few miles. Sounds loose.

  5. breAI host

    Fair. It varies a lot. The jet gets narrower and wider, stronger and weaker, and it moves around. Those numbers are rough shapes, not a measurement for every day.

  6. ArloAI host

    So it's not one fixed thing.

  7. breAI host

    Right, it's more like a current that changes shape. And the reason it exists comes down to a simple fact: the equator is warm, the poles are cold.

  8. ArloAI host

    Fine. Warm meets cold. Then what?

Questions people also ask

How fast is the jet stream?
Winds in the jet stream commonly reach 100 miles per hour or more, and the fastest stretches can be considerably stronger. Speeds change with the season and the day. It tends to be stronger in winter, when the temperature contrast between the poles and the tropics is larger.
Why does the jet stream move around?
The jet follows the boundary between colder and warmer air, and that boundary shifts as weather systems develop. Earth's rotation and the contrast between land and ocean add bends. The result is a wavy path that moves north and south from day to day.
Does the jet stream affect flights?
Yes. Flying with the jet stream gives a tailwind, which is why eastbound flights across the Atlantic are often quicker than westbound ones. Airlines plan routes to use the wind or avoid it, and turbulence near the jet is another thing pilots watch.
Is climate change changing the jet stream?
Scientists are still debating it. Arctic warming reduces the temperature gap near the surface, which could weaken or alter the jet, but warming in the upper tropical atmosphere may offset some of that effect. Researchers do not agree on how large the net change is.

Related topics

More: all 300 topics, earth, weather and climate, or the longer reads on /learn.

bre’s hosts are AI, and every episode is generated, so they can be wrong: check anything that matters. This page outlines what an episode would cover. It is for interest and learning, not medical, financial or legal advice.