Multidisciplinary Analysis of an Unusual Tornado: Meteorology, Climatology, and the Communication and Interpretation of Warnings

On 22 May 2008, a strong tornado---rated EF3 on the Enhanced Fujita scale, with winds estimated between 136 and 165 mph (61 and 74 m/s)---caused extensive damage along a 55-km track through northern Colorado. The worst devastation occurred in and around the town of Windsor, and in total 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, including its intensity, its long track, its direction of motion, and the time of day when it formed. These unusual aspects and the high impact of this tornado also raised a number of questions about the communication and interpretation of information from National Weather Service watches and warnings by decision makers and the public.

The first focus of this study is the meteorological circumstances responsible for producing such an outlier to the regional severe weather climatology. Then, a climatology of significant tornadoes (defined as those rated F2 or higher on the Fujita scale, or EF2 or higher on the Enhanced Fujita scale) near the Front Range is shown to put the 22 May 2008 event into climatological context. This study then examines the communication and interpretation of severe weather information in an area that experiences tornadoes regularly but is relatively unaccustomed to significant tornadoes. By conducting interviews with local decision makers, the authors have compiled and chronicled the flow of information as the event unfolded. The results of these interviews demonstrate that the initial sources of warning information varied widely. Decision makers' interpretations of the warnings also varied, which led to different perceptions on the timeliness and clarity of the warning information. The decision makers' previous knowledge of the typical local characteristics of tornadoes also affected their interpretation of the tornado threat. The interview results also highlight the complex series of processes by which severe weather information is communicated after a warning is issued by the National Weather Service. mation is communicated after a warning is issued by the National Weather Service.