January 22, 2024

One of the longest jet streams in memory

This week I gave a lecture to my junior weather analysis class on the jet stream, a current of strong winds in the upper troposphere (25,000 to 35,000 ft above sea level) in the midlatitudes.   So I have been musing about this topic a bit.

Yesterday I saw the current map of winds at 300 hPa (about 30,000 ft) for the entire Northern Hemisphere and was taken aback:  the longest continuous jet stream I can remember.

As shown by the map valid 1 PM Sunday, strong westerly winds exceeding 100 knots stretch from Iran to Baja, California.   Halfway around the entire Northern Hemisphere.  About 8000 miles.

Looking closer, the entrance to the jet stream is over Iran, passing over northern India and then China before heading out into the Pacific.

The jet stream crossed the Pacific and then plummeted southward over Baja (see below).

With such an extraordinary jet stream in existence, I wondered where the air that reached, say, San Diego was during the previous days.

To answer this question, I ran the NOAA Hysplit trajectory model, creating what is called "back trajectories" ending at various elevations above San Diego (see below). I traced the air back ten days.

Not unexpectedly, the air could be traced back over China and Iran over a week before!

Now considering the current world situation and past concerns about Chinese spy ballons, perhaps we should keep this as a little secret just between us.  😊


  1. While reading, I opened the Ventusky App to see how this jet looked on a different map projection. How accurate things are there I have no idea. Being animated helps. The two big loops, one over eastern Russia and another over the north Pacific show better, although they are in your first (top) image.
    Cool stuff -- Thanks!

  2. Thanks for this. I keep a good eye on the jets, and have been marveling at their length and strength. Last winter was impressive as well. It is interesting to compare the northern jets with the southern, even though I don't fully understand what I am looking at. It seems like the southern jet streams stay much stronger throughout their summer?

  3. I was immediately struck by the hexagonal shape, just like the jetstream on Saturn.

    1. Thanks for pointing that out. Very interesting!

  4. If only there had been an Iranian endurance balloonist with enough helium to leave and dreams of Mexican beaches.

  5. With XM displays now available in the cockpit, the source of the WX we are flying through is genuinely impressive, particularly that generated by the jetstreams. I've taken pictures of these WX system displays, and as of late, they are beautiful! Probably only a WX nerd would say that!


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