21 June 2023
WICHITA, Kan. (KSNW) – Julie Stimson, Sedgwick County Emergency Management director, explained why tornado sirens failed to sound in Derby on Saturday night during a tornado warning. She made a presentation to Sedgwick County Commissioners during their staff meeting on Tuesday.
Stimson said that three tornado warnings were issued for Sedgwick County that night by the National Weather Service. Luckily, the storms did not produce a tornado. However, high winds damaged power lines and trees.
Stimson said sirens worked in two areas of the county. However, the tornado sirens failed to sound in Derby during the tornado warning.
“The system got overloaded because we had three polygons very close together. So as the system was analyzing this data and sending information out, we did have a problem in the Derby area that they are working on right now,” Stimson told commissioners. “We tried twice through automation, and we also tried to manually activate it with our manual backup system. The signal went. It just wasn’t received because of all the other traffic going on in the software system.”
In 2007, the National Weather Service introduced Storm Based Warnings or polygons for tornadoes, severe thunderstorms, and flash floods that are more geographically specific and not restricted to geopolitical boundaries. Polygons focus on the true threat area. In those areas, the sirens will sound.
“It is now automatic. That is part of the upgrade we have now. As soon as that polygon drops, the sirens in that polygon are going to sound,” Stimson said.
The county is in a five-year capital improvement program to upgrade the tornado system to work with new technology. It can be hard to test the system because the National Weather Service doesn’t provide test polygons.
“It is a conversation that is happening across the country. We really wish we had the capability because we don’t know how the software will handle a lot of data coming in at one time,” Stimson said. “If we could test the polygon piece to this, we would be able to identify issues ahead of time.”
Sedgwick County tests tornado sirens to make sure they are working at noon on Mondays.
“That is a maintenance check. It is a different type of test, just to clarify. It is to make sure our sirens are physically activating and making the noises that we want them to make. It does not test that polygon piece,” Stimson said.
The test is not performed on holidays or in stormy weather.
Stimson adds that outdoor sirens go off to alert people outside and that they are not meant or designed to be heard indoors. She said people should have multiple ways to receive weather alerts, including signing up for civic alerts, tuning into local media such as KSN’s Storm Track 3 Weather, or getting a NOAA weather radio.
Stimson added that Sedgwick County 911 was overloaded with calls asking about the tornado warning. She said do not call 911 to ask about a warning as it is for immediate emergencies.