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Emergency management: Storm sirens not the best way to get tornado warnings


While outdoor storm warning sirens have been in use for decades, an analysis by the National Weather Service of weather warnings and the community’s response to those warnings related to the May 22 Joplin tornado says public complacency kept many people from responding to the sirens by seeking shelter.

That is why local emergency management officials recommend residents depend more on getting weather-related information from an all-hazard radio or the county’s IRIS alert system rather than from tornado sirens.

“In my opinion, sirens are the least effective way of warning the public,” said Kermit Hargis, emergency management director for the city of Bolivar. “It just tells you something is happening, and in the case of Joplin it doesn’t tell you the magnitude of what’s happening.”

Each municipality in Polk County with outdoor warning sirens establishes its own guidelines for when to activate the sirens, according to Rick Lewis, Polk County emergency management director, but he can activate the sirens through Central Dispatch if he sees the need.

The city of Bolivar will activate sirens anytime the city could be affected by a tornado or winds are expected to be 80 mph or greater, according to Hargis. The sirens will run for three minutes and stop. There may be a one- or two-minute lapse until a dispatcher at Central Dispatch re-activates the sirens. That pattern will continue until the tornado warning expires or the Weather Service issues an all-clear.

Lewis emphasizes that sirens are outdoor warning devices.

“They’re not designed to warn you inside your house,” he said. “We recommend everybody get an all-hazard radio and sign up for IRIS alerts.”

Authors of the NWS report said complacency toward outdoor warning sirens was apparent.

“There was a significant degree of ambiguity associated with the first alert regarding the magnitude of the risk, the seriousness of the warning and its potential impact,” the report states.

The “false alarm rate” — issuing a tornado warning but no tornado develops — shows that three out of four tornado warnings that are issued are false alarms. For all tornado warnings issued by the National Weather Service from Oct. 1, 2007, to April 1, 2011, the false alarm rate was 76 percent with an initial lead time of 12.5 minutes. For severe weather events, however, the warnings are more accurate, with a46-percent false alarm rate with an initial lead time of 18.6 minutes.

“Think how many times we’ve set them off and not had an actual tornado,” Hargis said. “People become complacent. But we in emergency management all have the responsibility to err on the side of safety. I’ve learned in this business, no matter what you do, you’re never going to please everybody.”

IRIS alerts

Polk County also has a vendor that provides emergency alerts delivered to e-mail nnboxes and/or cell phones via phone calls or text messages. The IRIS system costs $2 per year to join.

“We’ve had several people who have gotten the warning through IRIS while working outside in the field,” Lewis said.

IRIS alerts are sent out when there are weather warnings, and Lewis said it also is used for occasional public service messages that also allow them to test the system.

To sign up for the IRIS system, use the form below. The Polk County Emergency Management Office also will accept registrations at the Polk County Business Expo Saturday, Oct. 8, at Bolivar High School.

The system has about 400 participants now, a number that Lewis would like to be much higher to better be able to get severe weather information to people in a timely manner.


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