The 22 May 2008 Weld County, Colorado tornado: Analysis of meteorological conditions and the communication of weather information

On 22 May 2008, a strong tornado (rated 3 on the Enhanced Fujita scale, with winds estimated between 136 and 165 mph) caused extensive damage along a 34-mile track through northern Colorado. The worst devastation occurred in the town of Windsor, where there was one fatality, numerous injuries, and hundreds of homes significantly damaged or destroyed. Several characteristics of this tornado were unusual for the region from a climatological perspective: 1) the storm formed in the late morning hours, in contrast to the climatological late afternoon maximum; 2) the storm moved very quickly toward the northwest (taking it toward the densely populated urban corridor of the Front Range) as opposed to more common eastward-component storm tracks away from population centers; and 3) the intensity of the tornado in such close proximity to the Front Range where weaker tornadoes are more commonly observed. The unusual meteorological aspects of the event and the high impact of this tornado also raised a number of questions about the communication and use of information from National Weather Service watches and warnings by decision makers and the public.

The meteorological circumstances responsible for producing such an outlier to the regional severe weather climatology is one focus of this study. Here, we will present a climatology of significant tornadoes that have occurred near the Front Range and an analysis of the synoptic and mesoscale environmental conditions that were favorable for significant tornadoes on 22 May 2008. Another important aspect of this study involves an examination of the communication and use of severe weather information in an area that is relatively unaccustomed to the occurrence of significant tornadoes. By conducting interviews with local officials and decision makers, we have compiled and chronicled the flow of information communicated as events unfolded. Preliminary results from these interviews point to potential issues with some aspects of the communication of warning information and its interpretation by decision makers and the public on that day. These results support the growing realization that societal factors are often just as important to the effectiveness of weather warnings as the information provided in those warnings, and that these factors should be considered in future research in addition to the attention given to improving detection and warning capabilities.