Jet Stream Formation
Name: Kevin H.
Date: Wednesday, June 26, 2002
I have read the responses to other questions regarding
jet streams, but I still do not know why they form and how they do
so. Could you please explain this? Also, why are they so narrow
vertically and horizontally? Thank you.
The jet is normally narrow vertically because of being at the tropopause
transition zone; vertical gradients of temperature and pressure are usually
considerably greater than horizontal gradients. The jet can be much wider
horizontally, especially if there is a large horizontal extent of consistently
large gradients of pressure and temperature. I have seen the jet become up to
500 miles wide, although that is unusual. The strength of the pressure and
temperature differences and the distance over which those conditions exist
determine the width of the jet vertically and horizontally.
The jet stream results from latitudinally and vertically large gradients of
temperature and pressure at the intersection of a colder air mass from the
with a warmer air mass from the south. Just as high winds are seen behind a
strong cold front (because of large gradients of temperature and pressure near
the surface), the same happens in the middle atmosphere at the jet. The jet
tends to occur at about the height of the tropopause, the transition from the
troposphere (where temperature decreases with height) to the stratosphere
temperature increases with height). The combination of these differences in
mass, plus some help from the coriolis force (coriolis acceleration to use
precise terminology) creates the acceleration of winds into the jet stream.
David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory
Here are some links that discuss jet streams...
Jet Stream description - basic...
Jet Stream description - more detailed
Jet Stream description - more technical
(also nice graphic depicting location of jet streams relative to weather
If you do a search in one of the popular search engines, such as Google,
you will find LOTS of information on this subject. Some of it will be very
basic, and some very technical. Good Luck..!
Wendell Bechtold, meteorologist
Forecaster, National Weather Service
Weather Forecast Office, St. Louis, MO
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Update: June 2012