Question submitted by Terry Bolton (Salt Spring Island)
Terry, you will notice that I do not use the jet stream very much on my weather presentations! I strongly believe that it is a term that is often over-used and also frequently used misleadingly. It is basically a 'ribbon' thin layer of very fast moving air aloft. However to refer to the jet stream singularly is incorrect. Basically there are many ribbons of fast moving air above the earth. Some of these ribbons become more pronounced and can force very large weather systems (that extend deep into the atmosphere) to move around.
The NOVA online web site has a great discussion on the existance of jet streams: