Helping Business Weather the Storm

Chinook- a Fun Word to Say, but Do You Know What It Is?

by David Moran, on Dec 20, 2018 2:00:00 PM

Terrain can play an essential role in various weather conditions. Winds that blow down the leeward side of a mountain can affect temperature and snow cover, as well as health in some people. 

Chinook winds occur on the leeward side of a mountain when the prevailing winds are oriented west to east. As these winds descend, the air warms due to increasing pressure (called compressional warming) and also dries out. 

Schematic of a Chinook
Schematic of a Chinook

Chinooks can cause rapid warm-ups on the leeward side of a mountain, allowing snow and ice to melt quickly leading them to be called "snow eaters"; in fact, snow can melt at rates on the order of one inch per hour! The most significant temperature change due to a chinook occurred in January 1972 in Loma, Montana when the temperature went from -54°F to 49°F in 24 hours (that's a 103°F temperature change!). The fastest temperature change also occurred in January 1943 in the Black Hills of South Dakota; temperatures rose from -4°F to 45°F in two minutes. Once the wind dissipated, the temperature fell back to -4°F within half an hour.

As a chinook approaches, a stratus cloud formation known as a chinook arch is sometimes produced. However, these clouds do not usually produce precipitation.

Chinooks are known by different names in various regions. For example, in the Alps of Europe, they're called a foehn. In Argentina, it's known as a zonda. Whatever the name, they can have a wide range of effects from weather, affecting anything from aviation to agriculture.