The Jet Stream

Giving Rise to the Jet Stream: Online Animation of the Jet Stream

Jet Stream FAQ

How would you define a jet stream?

The jet stream, one of the most dramatic forces of nature, was discovered during World War II when aviators first tried to cross the Pacific. This strong westerly (west to east) wind current is often defined as a relatively narrow band of upper atmosphere winds that blow faster than 57 miles per hour.

The Jet Stream is located at 60 degrees N and S latitude, however a subtropical Jet also exists at 30 degrees N/S.

Jet streams form as a result of the earth's rotation and the differences in temperature between two large air masses.

How high?

At an altitude above 20,000 feet, or between six and nine miles above the Earth's surface, the jet stream winds make their presence known. This puts the jet stream near the top of the Earth's troposphere, where most of the Earth's weather occurs.

How fast?

The core of the jet, a fast-moving wind current that blows west to east around the Earth, can reach speeds upwards of 275 miles per hour in the winter. These winds are stronger during the winter months because at this time of year the surface temperature contrasts are greater. The greater the contrasts in surface temperature, the stronger the jet stream winds blow.

Length, width, and thickness?

Although the jet stream may stretch for thousands of miles around the world, it is only a few hundred miles wide and often less than three miles thick.

Does it affect weather?

This strong current of air pushes weather systems around the world, and greatly affects local weather patterns by propelling them forward.  In the winter the Jet Stream is the boundary between a cold air mass to the north and a warm air mass to the south.  If the Jet Stream dips below our latitude it brings COLD air.  If the Jet Stream rises above us the air temperature is temporarily WARM.

Does it ever blow north or south?

Because the jet stream winds are greatly affected by changes in temperature, their trajectory does not always flow in a uniform west to east direction. Often they might head due north and then arc down in a southerly direction, creating a wavy pattern or what meteorologists call troughs and ridges.

They meander (move up and down) around the globe, dipping and rising in altitude/latitude, splitting at times and forming eddies, and even disappearing altogether to appear somewhere else, much like a river where the current is strongest in the center with decreasing strength as one approaches the river's bank.  It can be said that the jetstreams are "rivers of air."

Jet streams also "follow the sun" in that as the sun's elevation increases each day in the spring, the jet streams shifts north moving into Canada by Summer. As Autumn approaches and the sun's elevation decreases, the jet stream moves south into the United States helping to bring cooler air to the country.

CHECK OUT TODAY'S JETSTREAM MAP AT INTELLICAST