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County emergency official explains weekly siren tests and polygon-based tornado warnings
Summary
A county staff member explained why sirens are tested weekly, why warnings use a polygon system and noted a single siren in need of repair; residents were asked to report local issues to dispatch.
Nick, a county staff member who presented the update, said the county sounds sirens at noon every Monday to confirm they are working and urged residents to report any siren they do not hear to dispatch at 431-3131.
"The reason we set them off every Monday at noon is to make sure that they work," Nick said. He explained the county uses an automated polygon system tied to National Weather Service warnings; when the NWS issues a tornado warning it draws a polygon for the threatened area and the dispatch system automatically activates sirens inside that polygon.
Why it matters: the polygon system reduces false alarms in parts of the county not under immediate threat. Nick said that when the county previously sounded all sirens for warnings, some areas inside the polygon were sunny while other distant areas were in danger, creating public confusion. He said most sirens are on the automated system, but a few — including one near Donner (referred to in the transcript as "Double 0") and some city- or volunteer-run sirens — are manually activated or not on the polygon network.
Nick told commissioners the county is aware of at least one siren not sounding properly; the vendor working on the system planned to visit that site. He advised residents who notice reduced loudness at Monday tests to call dispatch and report their location so the county can respond.
What was not decided: no procurement or funding decision was recorded during the update; commissioners asked questions and staff described planned vendor troubleshooting and monitoring.
