What Are Jet Streams?
By Joan Whetzel
Jet streams are high speed winds traveling at higher altitudes, stirring up weather patterns along the earth's surface as they go. They are sort of like air rivers that move with a current, much like a river of water, with the strongest current generated in the center of the "river flow" and weaker currents on the "outer banks" of the jet stream.
What Are Jet Streams?
Jet streams are defined as upper level air currents (at altitudes greater than 20,000 feet or 6,096 kilometers) having wind speeds of 57 to 300 miles per hour (91 to 483 kilometers per hour). Jet streams travel from west to east along a channel (narrow band) that separate arctic and tropical air masses with opposing temperatures, creating a boundary between the two opposing air masses. The greater the difference in temperatures between the two air masses, the faster the jet stream blows. Jet streams are associated with winter storm formation
What Do Jet Streams Do?
Jet Streams travel through tropospheric weather centers. They stir up winds (which removes what's left of the fall leaves and pushes aside warmer temperatures), precipitation (in the form of rain or snow that provides needed moisture for springtime planting), and lighting (which replenishes the soil's nitrogen) along their path.
How and Where Jet Streams Travel
- · Jet streams move in a generally west to east flow due to the spinning motion around the Earth's axis. Without the Earth's spinning motion, the equator's warm air masses would move outward toward the poles, resulting in a warmer environment for the entire planet.
- · The distance of any location away from the equator determines how fast the jet stream moves. The farther a place is from the equator, the faster the air flows. So the winds blow slower over the equator and faster the closer they get to the north and south poles
- · Jet streams don't always move exactly in west to east direction. Sometimes temperature differences in adjacent air masses cause them to shift to a more southward or northward flow.
- · Polar jet streams generally travel in the region between 500 and 600 North or South. The subtropical jet stream travels around the 300 north parallel.
Jet Streams Behavior
Jet streams are only able occur due to a intricate interaction between:
- · the location of high and low pressure systems,
- · regions of warm and cold air,
- · and changing seasons.
Jet streams flow in a meandering pattern, plummeting and rising in altitude and latitude. On occasion, a jet stream may split and form eddies or even disappear completely, only to reappear somewhere else. During the spring and fall months, jet streams appear to "follow the sun" - meaning they follow the seasons. During the fall months, North American jet streams drop down from Canada into the United States, bringing colder weather southward. During the spring months they recede back into northern Canada, bringing warmer temperatures back northward.
Nova Online: Frequently Asked Questions About the Jet Stream. http://www.pbs.org/wgbh/nova/balloon/science/jetstream.html
National Weather Service: The Jet Stream.
Jet Stream Analyses at 300Mb.
Jet Stream: Current of Rapidly Moving Air.
USA Today: Answers Archive, Jet Streams. http://www.usatoday.com/weather/resources/askjack/waskjet.htm
NWS. The Jet Stream
The Weather Channel. Winter Storms and Jet Streams.