Wind Hazards

Wind hazards in Colorado take three forms:  high wind, tornadoes, and severe thunderstorms. It is not unusual to see tornadoes spin out of major thunderstorms or see severe wind accompany thunderstorms.  

High winds are wind events with sustained wind speeds of 40 mph or greater and lasting for one hour or longer, or winds of 58 mph or greater for any duration (National Weather Service, 2009). Common in Colorado, Chinook winds are warm dry winds that descend from the eastern slopes of the Rocky Mountains, causing a rapid rise in temperature. Sometimes these winds move with considerable force. Cold, dry Bora winds are also experienced in Colorado. These winds are experienced after cold fronts pass through the state from the northwest. Bora winds can reach speeds of over 100 mph (Colorado Natural Hazards Mitigation Plan, 2013, p. 3-88).        

A tornado is a localized, violently destructive windstorm occurring over land. Tornadoes are generated by severe thunderstorms. Tornadoes in Colorado are most frequent in the spring and early summer when warm, moist air from the Gulf of Mexico collides with cold air from the polar regions to generate severe thunderstorms. These thunderstorms often produce the violently rotating columns of wind know as funnel clouds (National Weather Service, 2009).  

A thunderstorm is characterized by the presence of lightning and its resulting thunder. Thunderstorms are usually accompanied by strong winds, heavy rain, and hail, or sometimes no precipitation at all. Thunderstorms may line up in a series of rain bands known as a squall line. A severe thunderstorm is a storm that produces a tornado, winds of at least 58 mph (50 knots), and/or hail at least one inch in diameter. Structural wind damage may imply the occurrence of a severe thunderstorm. Strong or severe thunderstorms that rotate are known as super cells (National Weather Service, 2009).