Probing Question: What is the jet stream?

If you've seen the movie Finding Nemo, you probably recall the depiction of the "EAC," a fast-moving ocean current that the film's surfer-dude sea turtles ride with flair. The jet stream could be viewed as something like that, except in the upper atmosphere instead of the ocean, allows climatologist Paul Knight , senior lecturer in meteorology at Penn State. "The jet stream is a current or river of wind, usually about 200 miles wide and about two miles deep, that flows about five to seven miles above the earth's surface," says Knight, Pennsylvania's state climatologist and longtime host, writer, and producer of the University's television show Weather World . "Like a river, it meanders with bends and curves and sometimes even odd-shaped wiggles. This air current directs the movement of high and low pressure at the surface." - What most people don't realize, says Knight, is that the jet stream "is the major player in how our weather changes." We know the most about two main currents of jet stream winds, he notes: the polar front jet and the subtropical jet, both of which travel around the earth from west to east. Jet streams form where air masses of different temperatures meet in the upper atmosphere, Knight says. The greater the difference in temperature, the faster the jet stream moves - up to 200 miles per hour, with 110 mph as the average.