Rural Dallas County to modify Outdoor Warning Siren Criteria to include 70MPH+ winds, effective October 1, 2020.
The Dallas County Emergency Management Commission recently established a workgroup involving the National Weather Service to evaluate and consider whether rural Dallas County should modify existing outdoor warning siren activation criteria to include 70 mile per hour wind. After careful consideration of neighboring county outdoor warning siren policies, case analysis and discussion on over-alerting, the workgroup instructed the Emergency Management Agency to make a recommendation for Dallas County communities that currently only include tornado warnings in their activation criteria to begin including 70 mile per hour winds during severe thunderstorm warnings. Following engagement from each jurisdiction, this change will become effective October 1, 2020.
The established workgroup considered several factors surrounding activation many of which centered on one common concern, public confusion hinders response. There is mounting evidence to support that 70 mile per hour wind produces equally damaging effects as a weak tornado (EF-0). As we seen recently, some storms create straight-line winds, which often have far wider geographic impact than tornadoes. These wind speeds have been known to be well in excess of 70 miles per hour and peel the surface off some roofs, break large branches from trees, damage gutters and siding, push over shallow-rooted trees and turn unsecured lawn furniture and other items into dangerous projectiles. Far from an over-dramatization of the threat, the potential for serious injury to unsheltered persons from 70mph winds are comparable to that of an EF-0 tornado.
Historical research of weather records from the National Climatic Data Center over the last 15 years indicate that on average, the sirens would be activated one additional time per year for severe thunderstorms with winds at or exceeding 70mph. This research alleviated the concern that we would be desensitizing the public by overuse of the sirens.
The intent of this change is to increase public perception of the outdoor warning system by providing a consistent and county-wide approach. It is important to remember that outdoor warning sirens are only intended to alert those outdoors to take shelter and seek more information. Outdoor warning sirens are not designed to be heard inside structures. Once in a place of shelter, individuals should monitor any source of information they have available, common methods include, television, radio, internet, mobile device and NOAA weather alert radios.
Please note that this change only affects the communities of Van Meter, Desoto, Dexter, Redfield, Adel, Dallas Center, Linden, Dawson, Perry, Minburn, Bouton and Woodward. The remainder of communities with jurisdiction within Dallas County have included the 70 mile per hour threshold for several years.