Why jet streams form

The wind speeds within the jet core are relatively uniform. Since there is not much difference in speed, there is normally very little wind shear. If there had been a great amount of wind shear within the jet core, the aircraft during WWII may have been torn apart.

The jet axis is the axis of maximum wind speeds through the center of the jet core. Intermittent regions of the strongest wind speeds within the jet are called jet maxima or jet maxes.

The isotachs lines of equal wind speed which define the jet maximum are elliptically shaped both horizontally and vertically. The isotach gradient relationship described applies directly to the Polar Front Jet and to a lesser degree to the Sub Tropical Jet.

Shear and turbulence associated with the jet stream are directly related to the strength of the isotach gradient and stability. Shear is the difference between the wind speed or direction per unit distance. With the jet stream shear is due mainly to the change in wind speed. Because of this, the greatest shear will be found where the isotach gradient is the strongest. I think of wind shear as a busy highway moving at full speed and each car represents its own element of wind speed.

As the cars pass each other at different speeds, the shear is the difference in speed between two cars. The greater the speed one car passes another, the greater the wind shear. Jet stream turbulence is the shear produced by irregular motions within unstable air.

Very strong shear is not sufficient by itself to produce severe turbulence, unstable air thermal advection is also required. Areas of strong temperature advection baroclinicity are high threat areas for turbulence. This turbulence at times is strong enough to cause structural damage to aircraft. The polar front jet is located above and on the warm side of the polar leaf and below and on the cold air side of the mid-latitude leaf recall the 3 leaf concept.

This places the stratospheric air on the cold air side and above the jet, and tropospheric air on the warm side and below the jet. The polar front jet migrates with the season and moves toward the equator in the winter and toward the poles in the summer.

The continental polar air mass begins to move south out of its source region causing the temperature contrast between air masses to move with it. The height varies with the tropopause leaves and its relationship to a given constant pressure surface, mb and mb, will vary with the situation. The jet maximum speeds also vary with seasons.

Great Plains Satellite - C. Great Plains Satellite - S. A jet stream forms high in the upper troposphere between two air masses of very different temperature. The greater the temperature difference between the air masses, the faster the wind blows in the jet stream.

This river of air has wind speeds which often exceed mph, and sometimes peak over mph. Jet streams usually form in the winter, when there is a greater contrast in temperature between cold continental air masses and warm oceanic air masses. The following image shows an example of this from the National Weather Service's Aviation computer forecast model:.

Airplanes also fly in the mid to upper troposphere. So, if an airplane flies in a powerful jet stream and they are traveling in the same direction, the airplane can get a boost. A visualization of the Northern Hemisphere's polar jet stream swirling weather patterns from west to east across North America. The fast-moving air currents in a jet stream can transport weather systems across the United States, affecting temperature and precipitation.

However, if a weather system is far away from a jet stream, it might stay in one place, causing heat waves or floods. Jet streams typically move storms and other weather systems from west to east.

Everest, the world's tallest mountain, are actually jet streams. Jet streams can be so cold, and so strong, that climbers cannot leave the shelter of their tents.

Pilots Go With the Flow Jet streams are so fast and powerful that airplanes have difficulty flying against them. Pilots either fly with the jet stream or above it; they do not attempt to fly against it. Carbon dioxide is also the byproduct of burning fossil fuels. Monsoon usually refers to the winds of the Indian Ocean and South Asia, which often bring heavy rains. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.

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Weather is the state of the atmosphere, including temperature, atmospheric pressure, wind, humidity, precipitation, and cloud cover. It differs from climate, which is all weather conditions for a particular location averaged over about 30 years. Weather is influenced by latitude, altitude, and local and regional geography.