what is it?
A Jet stream
Jet stream
The strongest jet streams are the polar jets, at above sea level, and the higher altitude and somewhat weaker subtropical jets at 
where are the two main hemispheric jet streams located The polar jets, at above sea level, and the higher altitude
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Jet stream [SEP] Introduction
Jet streams are fast flowing, narrow, meandering air currents in the atmospheres of some planets, including Earth. On Earth, the main jet streams are located near the altitude of the tropopause and are westerly winds (flowing west to east). Their paths typically have a meandering shape. Jet streams may start, stop, split into two or more parts, combine into one stream, or flow in various directions including opposite to the direction of the remainder of the jet. The strongest jet streams are the polar jets, at above sea level, and the higher altitude and somewhat weaker subtropical jets at .