Fascinating Meteorology Terms: Chinook Wind

If you are living or spending some time east of the Rocky Mountains, you may experience a certain type of weather that may raise your eyebrows as much as it raises the temperatures. Occurring through the winter months, a warm, dry air mass may descend from the Rockies and blow through your area. Temperatures within this air mass are much warmer than the cold air they displace. Temperatures can rise by 50 degrees Fahrenheit or more from the previous air temperature. This could make the weather change quickly, turning the day from winter in the morning to spring in the afternoon. This type of weather phenomena is called Chinook wind.  

This wind originates from a moist, warm maritime air mass that moves inland from the Pacific Ocean and over the western windward side of the Rockies. The moist, warm air rises up over the mountains cooling as it ascends. As the air cools the moisture starts to condense into clouds and then rain droplets. By the time the air mass reaches the top, it is all rained out. This now dry air descends on the leeward side of the mountains; warming as it sinks. Once it hits the Plains it picks up speed. With little to no trees in the Great Plains, there is nothing to hold back the wind as it travels freely over the grasslands. Chinook wind can get up to 80 mph when it has the least bit of vegetation to navigate around.

The name “Chinook” comes from a Native American tribe that took territory over the western, northwestern and coastal areas of Washington and Oregon. Actually, this type of wind has many names, for it doesn’t only occur east of the Rocky Mountains, but east of many different mountain ranges all over the world. Chinook winds, also called Foehn winds, occur in Germany, east of the Swiss Alps. In central Asia, east of the Himalayas, they are called Afganet. East of the Andes in South America, they are called Puelche and in southern California, they are called Santa Ana winds.

Chinook winds can drastically change the temperature and climate in a certain area. When Chinook winds pass through, the air is so warm and dry, snow disappears in a matter of hours. The air mass can be so dry that the melting snow may even evaporate into water vapor just as rapidly as it melts. This is a process called sublimation where the frozen liquid can change directly to a gas. The dry Chinook wind may even evaporate moisture from soil, drying out the soil and starving vegetation of water. In most cases the warmth of the air awakens hibernating vegetation. When the vegetation wakes up and tries to gain water from the soil, it ends up empty handed. The vegetation then dries out as well and eventually dies.

Chinook winds can bring huge change to the climate of an area. It has a very interesting name too; one you won’t forget especially if you ever experience it. That is why it is on the list of Fascinating Meteorology terms! Up next, dive into some knowledgeable information about another interesting meteorology term for wind.

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© 2019 Meteorologist Alex Maynard

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