PORTLAND, Ore. (KOIN) – If there is one thing that you’ve definitely heard a meteorologist talk about in a forecast, it’s the jet stream.

Not only does the jet stream impact our weather locally, it is also a global influence. Isn’t that exciting!

Outside of the sun and ocean, the jet stream is one of the most governing elements that dictates our weather. Being situated in the mid-latitude region (region on Earth located from about 30 to 60 degrees north or south).

What exactly is a jet stream?

It’s essentially a stream of wind in the atmosphere. Compared to the surface, this is going to be relatively strong wind. Additionally, it’s almost a funnel or narrow path, just like a stream.

The major jet stream that dictates our weather is the polar jet. This is what we are typically tapped into during the fall, winter and spring months. This is going to determine our weather patterns. The polar jet generally separates the polar air from the mid-latitude air masses. Where as the subtropical jet will generally separate the tropical air and mid-latitude air masses.
The air within a jet stream mostly moves from west to east.

As we discuss above, the jet stream is what you can think of as a stream of wind that sets the line between air masses. Now the jet stream isn’t just one clear cut line across the earth. It will meander and bend just like any other stream. It is that dancing stream of air that troughs and ridges form.

Where the jet stream is dipping, that is what we call a trough. A trough will bring cold air further south from the polar and northern regions. Where as a ridge, or jet stream creating a mound or bending north will bring warm air from a southerly region. This is an ongoing process and it is constantly changing. That means, a forecaster will have an idea of where the cold and warm air is moving and generally where low pressure and high pressure systems are moving.


Below are two examples of weather models that are showing the organization of the jet stream. Notice how everything is twisting and meandering in different motions. Generally, the stream is moving from west to east with southerly and northerly hiccups. The photo on the left is at 250mb which is around 30,000’+ and the 500mb on the right which is around 18,000’+.