By: Marlene Affeld
Chinook ~ A Warm Sweet Wind Is Blowing
People who have spent some time in Montana tell eerie tales of the warm winter winds. Have you ever experienced a chinook? If so, you surely remember the sudden change in the weather. A dismal, gray, snowy day and suddenly everything doesn’t look quite so bleak. A bit of sunshine breaks through the dark cloud cover and the day begins to brighten. A frigid cold day warms.
Chinook winds offer a welcomed respite from the long winter. In Montana, Chinook winds are a fairly common climatic phenomenon that delight and amaze both weather experts and residents alike. It begins with the smallest whisper and grows as it whistles and dances down the valley. A Chinook “wind is a blowing!”
At the turn of the century, the Calgary Herald wrote, “Those who have not the warm, invigorating Chinook winds of this country, cannot well comprehend what a blessing they are. The icy clutch of winter is lessened, the earth throws off its winding sheet of snow. Humanity ventures forth to inhale the balmy spring like air. Animated nature rejoices.” (1900–Calgary weekly Herald)
A chinook wind, often just called “Chinook”, derives its name from a word in the language of the Chehalis Indian Tribe. In their language chinook means “snow-eater”. Aptly named, a chinook wind can melt over a foot of snow in a single day and raise the temperature as much as 40 degrees in less than an hour. The snow melt is caused partly by warmer temps and partly by the evaporation caused by the dry wind. Scientist tell us that adiabatic warming of downward moving air produces the warm chinook winds. Chinook winds are most remarkable in winter when the warm winds contrast with the ambient cold air.
Moist weather patterns that originate off the Pacific coast cool as they climb the western slopes and rapidly warm as they drop down the eastern side of the mountain ranges. A chinook, or Fohn wind, begins with a sudden change in wind direction, usually towards the west and a rapid, dramatic increase in wind speed. I really don’t understand this weather phenomena, but it feels wonderful.
Loma, Montana holds the United States record for the greatest recorded temperature change in a 24 hour period. On January 15, 1972 the temperature went from a nippy -56F (-48C) to a balmy 49F (9C) in less than 24 hours. In a much smaller time frame, on January 11, 1980 the temperature at the Great Falls International Airport rose from -32F to 15F in seven minutes as warm, Chinook winds eroded an Arctic airmass. This 47 degree rise in seven minutes stands as the record for the most rapid temperature change registered in the United States.
Chinook winds often produce hazardous fire conditions. The warm wind sucks the moisture from the air and any fires that may breakout are vigorously fanned. The infamous Santa Ana winds are just another name for a Chinook. Chinook winds are also called Cierzo or Mistral Winds.
Repeated or prolonged chinooks can be quite damaging to the eco-system of the forest. The dehydration caused by the warmth of the Chinook wind can be dramatic and trees lose their winter preparedness. The trees lose moisture through their needles and as the ground remains frozen, there is no fresh water to replace that lost through dehydration. Often the needles will then turn brown and die. This condition is referred to as Red Belt. It is not a disease but a reflection of a severe lack of moisture within the needles. White Birch, like many other trees, cannot survive rapid temperature changes and often die after a winter chinook. Often fruit trees and other vegetation will “awaken” and start to spout tender buds that will be destroyed by the next frost. An early spring chinook may destroy a season's crop.
Most Chinook winds are accompanied by a wide band of flat clouds that hover at high altitudes. Native Americans call this the Chinook Arch. Although these high clouds seem to hold the promise of rain, they rarely bring a drop. Chinook winds actually deplete the forest and fields of needed moisture. Viewing the Chinook Arch is often a breathtaking experience for photographers and all those that appreciate the artistic displays provided by Mother Nature. During a Chinook, sunrise and sunset are profoundly beautiful as the sky is painted vivid shades of fuschia, orange and red.
Soil not covered by snow is lost to wind erosion; flooding conditions often occur due to rapid snow melt in the high country and avalanche warnings abound.
The early settlers called these deep winter warm spells “false springs” as the wild chinook wind will sometimes linger for several days and it is easy to deceive one's self that Spring is on its way. However, when the chinook wind recedes, winter is back with all its fury.
Chinook winds have profound psychological effects on many people. Historical accounts tell of many people going “mad” when the Chinook winds blow.Many are joyful for the relief from sub-temperatures, they are energized and in general just feel better. Others will suffer headaches, depression and nervous disorders. They are restless, anxious and agitated. How do you feel when the warm wind blows?