Cities to trip sirens at 70 mph winds under new policy

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Perry is one of a dozen Dallas County cities that will start sounding its outdoor emergency sirens on the occasion winds exceeding 70 mph. One of Perry's six outdoor emergency sirens is located at the Perry Public Safety Building at 908 Willis Ave.

One of Perry’s six outdoor emergency sirens is located at Grove Street and Iowa Highway 141 near the Clearview Apartments.

Perry is one of a dozen Dallas County cities that will start sounding its outdoor emergency sirens on the occasion of winds exceeding 70 mph. The new policy will take effect Oct. 1.

Following the Aug. 10 derecho wind storm, many residents across northern Dallas County asked why the system of outdoor warning sirens was not activated prior to the destructive storm. The residents learned that the policy in 12 cities in Dallas County required sounding the sirens in the event of a tornado but not for winds exceeding a 70 mph threshold.

In response to the communities’ concerns, the Dallas County Emergency Management Commission (EMC) established a workgroup, including the National Weather Service, to evaluate and consider whether rural Dallas County should modify its existing outdoor warning siren activation criteria to include 70 mph wind.

The Dallas County EMC is made up of the mayors of the 18 cities in Dallas County, one member of the Dallas County Board of Supervisors and the Dallas County Sheriff. The EMC appoints an emergency management coordinator to manage the Dallas County Emergency Management Agency.

Dallas County Emergency Management Coordinator A. J. Seely issued a statement Monday on the results of the workgroup’s deliberation:

“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 mph winds during severe thunderstorm warnings.”

Seely said the revised siren policy will become effective Oct. 1 Adel, Bouton, Dallas Center, Dawson, De Soto, Dexter, Linden, Minburn, Perry, Redfield, Van Meter and Woodward. The six cities in Dallas County that already had a siren policy in place that included the 70 mph threshold are Clive, Granger, Grimes, Urbandale, Waukee and West Des Moines.

Seely said the 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 mph wind produces equally damaging effects as a weak tornado (EF-0),” Seely said in the statement. “As we have 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 mph 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 overdramatization of the threat, the potential for serious injury to unsheltered persons from 70mph winds are comparable to that of an EF-0 tornado.”

Historical weather records from the National Climatic Data Center show that over the last 15 years, on average, the sirens would have been activated one additional time each year for severe thunderstorms with winds at or exceeding 70 mph.

“The historical research alleviated the concern that we would be desensitizing the public by overuse of the sirens,” Seely said.

He said the policy change is intended to increase public awareness of the outdoor warning system by providing a consistent countywide approach. It is important to remember that outdoor warning sirens are only intended to alert people who are outdoors to take shelter and seek more information, he said. Outdoor warning sirens are not designed to be heard inside structures.

Once sheltered, individuals should monitor information on any source available, such as ThePerryNews.com, television, radio, internet, mobile device or National Oceanic and Atmospheric Agency weather alert radios.

The city of Perry has six emergency sirens strategically placed around the town. Sirens are located at:

  • Grove Street and Iowa Highway 141
  • Northgate Estates at 2801 First Ave.
  • Perry High School at 1200 18th St.
  • Perry Public Safety Building at 908 Willis Ave.
  • Violet Hill Cemetery at Eighth and Park streets
  • Willis Avenue and Diagonal Road

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