How Do Jet Streams Form?
Warm air masses in the south meet cool air masses from the north and create temperature and air pressure gradients. Essentially, you can compare a "gradient" to a hill on a ski trip. The steeper the hill, the faster you will reach the bottom due to a large difference in the grade of that hill. In wind speed, the pressure difference between a high and low pressure zone can be very large, thereby creating high winds. Pressure and temperature differences in the jet stream can be large as a global warm front from the south and a cold front from the north meet.
What Does the Jet Stream Do?
In the winter, areas in the Northern Hemisphere may get colder than normal periods as the jet stream dips "lower" bringing cold air in from the polar regions. Although the height of the jet stream is typically 20,000 feet or more, the influences on weather patterns can be substantial as well. High wind speeds can drive and direct storms creating devastating droughts and floods. A shift in the jet stream is a suspect in the causes of the Dust Bowl.