NaturalHazards.org

photograph of an anemometer

An anemometer measures wind speed and direction from the top of a weather station on the Colorado Front Range.

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WHAT is wind?

Wind is commonly associated with tornadoes, hurricanes, and other storms. However, damaging wind events can occur on beautiful sunny days. In fact, the greatest threat of damaging winds in mountainous areas occurs on cloudless nights. These winds, known as katabatic winds, can reach speeds of over 160 kph (100 mph) as a gust, with sustained speeds of over 80 kph (50 mph) as they descend downslope. Damage to buildings, damage to crops, power outages, personal injuries, and several fatalities have all been attributed to the force of katabatic winds. In addition to their high speeds, katabatic winds can bring a dramatic temperature increase, sometimes by as much as 80 degrees F in an hour or less. This unusually warm air also brings a substantial drop in humidity and therefore poses a signficant wildland fire risk. On the Colorado Front Range and in the mountains of southern California, katabatic winds have started and driven large wildland fires that burned for several weeks across thousands of acres.

Unless the wind is interacting with dust, snow, or other loose particles, it is invisible to our eyes and therefore difficult to predict without special instruments. When it does interact with dust or snow, a duststorm or blizzard can occur. These events can reduce visibility to a few feet and cause breathing difficulties in humans and other organisms. When high wind speeds mix with cold temperatures, a windchill effect is created, which can lower our body's temperature to dangerous levels and cause frostbite.


WHERE does wind occur?

Communities on the leeward side of mountain ranges have the greatest risk of high wind events. Although any strong downslope wind is referred to as a katabatic wind, they are given different names in different places. On the eastern slope of the Rocky Mountain Front Range in Colorado, katabatic winds are called Chinook winds. In southern California, they are referred to as Santa Ana winds. They are given the name Foehn Wind in the Alps of Europe. Katabatic Winds occur around every signficant mountain range in the world, from Antartica to Greenland.

Quick Fact:
Boulder, Colorado suffers an average of $1 million per year in property damage from katabatic winds, some of which have reached Category 3 Hurricane strength.


WHEN does wind occur?

In North America, late Fall and Winter bring the greatest threat of high wind events. During these seasons, strong westerly winds descend over the north-south trending mountain ranges and accelerate as they move downslope. This compresses the air and causes it to warm substantially. Around the world, the timing of katabatic wind events varies with the local climate and local landscape.


HOW do we cope with wind?

Forecasting can help prepare communities for wind events. In the United States, the National Weather Service issues wind advisories and warnings when conditions favor the development of strong wind. The Colorado Department of Transportation maintains a network of over 100 weather stations that include wind speed and wind direction measurements. Such stations help meteorologists issue advisories to the public, and close highways when wind speeds threaten high profile vehicles. Some cities, such as Boulder, Colorado, have adopted building codes similar to those used in hurricane prone areas to reduce damage to buildings. Trees and other structures are placed along highways on the eastern slope of the Rocky Mountains to reduce wind speeds. These barriers also act as snow fences, reducing drifting on highways.


WHO has more information on wind?