Wind Hazards

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).  

The National Centers for Environmental Information (NCEI) was formed in 2015 as a merger of NOAA’s three existing National Data Centers. This site is a rich data source for climate and historical weather information and contains historical event data on a host of natural hazards.

Developed by the Hazards & Vulnerability and Research Institute at the University of South Carolina, SHELDUS™ provides a county-level hazard loss data and map set for 18 different natural hazard events types, including wind hazards, and has been used by some Colorado communities in completing the risk assessments for their local or regional hazard mitigation plans.

A widely-recognized resource worth consulting for wind hazards is the American Society of Civil Engineers (ASCE), and particularly the data and information made available through Minimum Design Loads for Buildings and Other Structures (ASCE/SEI 7-10). This technical publication represents a national standard for requirements on general structural design and it contains ultimate event wind maps for determining wind loads which are suitable for inclusion in building codes and other documents. In addition, this publication includes a detailed commentary with explanatory and supplementary information designed to assist building code staff and regulatory authorities.

RMIIA is a non-profit insurance communications organization representing property and casualty insurers in Colorado, New Mexico, Utah, and Wyoming. RMIIA compiles overall estimates of insured losses and number of claims filed for catastrophes (insured natural disasters that cause more than $25 million in damages).

• Hail
• Tornadoes

The NWS is the official provider of U.S. weather, marine, fire, and aviation forecasts. The NWS issues warnings and provides data, products, forecasts, and information related to meteorology. The NWS is a component of the National Oceanic and Atmospheric Administration (NOAA). The NWS maintains a glossary of information on more than 2,000 terms, phrases, and abbreviations used by the NWS.