SIREN, Wis. -- The devastating tornado that swept through Siren points out the need not to depend on outdoor sirens for tornado warnings.

Fire chief Tom Howe of the village of Siren said that there wasn't much warning because the village alert siren wasn't working. It was struck by lightning several weeks ago and repairs had yet to be made.

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The National Weather Service had issued a tornado warning for Burnett County including the village of Siren at 7:31 PM, almost 50 minutes before the tornado struck the town.

The situation is very similar to the deadly Spencer, S.D., tornado of May 30, 1998. Six people were killed as a violent tornado swept through the town, even though a tornado warning had been issued several minutes in advance. The tornado cut power lines leading to the town, resulting in failure of outdoor warning sirens to sound.

Many people still depend on outdoor warning sirens as their warning of an impending tornado. Although many cities and counties have expanded their siren coverage and have installed emergency power back-up systems for them, there are reasons not to depend solely on them for warnings.

The warning sirens are primarily designed to alert people who are out-of-doors. People who are indoors may have trouble hearing the sirens because houses today are better sealed and insulated against the elements. This also cuts down on sound from outside the house being heard indoors.

Televisions, stereos, and air conditioners create their own sound that may further mask the sound of outdoor sirens from being heard indoors.

The National Weather Service has a network of NOAA Weather Radio stations which provide 24-hour a day weather broadcasts to much of the country. During times of severe weather, special alert tones are used to activate receivers that are in a muted mode to inform of the impending weather hazard. The village of Siren is outside of the normal range of the nearest weather radio station for most receivers, although use of an external antenna would have allowed the warning to get through.

Warning Coordination Meteorologist Rusty Kapela from the National Weather Service in Milwaukee has some good advice about the warning process, "Individuals should take it upon themselves to use multiple sources to receive warnings. Any one source is subject to failure."