Why didn't Sioux Falls' storm sirens go off during the derecho Thursday?

Sioux Falls city officials are on the defensive about why warning sirens didn't sound as a deadly storm producing tornado-like winds ripped through Sioux Falls on Thursday night.

For Mayor Paul TenHaken, it's a simple answer: There was no tornado in Sioux Falls.

"They are tornado sirens," TenHaken said at a Friday morning press conference after fielding questions about why the sirens weren't used. "We sound the sirens when there is a tornado, a confirmed tornado. There was not a confirmed tornado in Sioux Falls, or even in Minnehaha County, so our sirens do not sound."

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According to the National Weather Service, there was not a tornado in Sioux Falls Thursday, although the damage that occurred was a result of wind speeds "reminiscent of a high-end EF0 tornado or a low-end EF1 tornado," said Todd Heitkamp, meteorologist In charge at NWS in Sioux Falls.

It's not the first time TenHaken has had to address the city's siren policy following a weather disaster. A 2019 storm that produced a trio of tornadoes in Sioux Falls prompted the city to trigger the sirens. But the 77-horn siren system only sounded in the southeast quadrant of the city, due to what TenHaken described as "human error."

When asked Friday by reporters if the city should re-evaluate its policy, TenHaken, responded: "Will we look at the policy? Sure. But you can see where they start to lose their effectiveness when you cry wolf too often and use the sirens for multiple purposes," he said.

Sioux Falls Emergency Manager Regan Smith said activating the sirens too often could lead to complacency and confusion, adding that the policy not to sound them during non-tornado weather events is supported by commonly-supported best practices in the emergency management and meteorology industries.

"We have just come to the conclusion this is the easiest, most effective way to save lives," he said, adding that straight-line winds are significantly harder to predict compared to a tornado.

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TenHaken: Nobody should have been caught off-guard about storms

As was the case following the 2019 tornadoes, TenHaken and other officials who spoke Friday morning reminded the public that even in the event of an actual tornado, warning sirens are only part of infrastructure used to alert the public of pending weather danger.

There are "multiple ways to keep informed on the weather," TenHaken said, including weather radios, cell phones and "seeing the sky that looks like beef stew, that tells you you should not be out right now."

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"Yesterday it was pretty apparent something was going to happen," Smith said.

TenHaken agreed, stepping forward and saying "there's so many ways (to be alerted of pending weather) that the public has responsibility to stay informed of their surroundings."

Pointing to weather warnings and local media reports, TenHaken said no one was caught off guard by Thursday's storms.

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Heitkamp echoed the city officials, saying that people shouldn't rely on the sirens — intended to let people who are outside know there's a tornado — to let them know the weather is producing dangerous conditions.

"If you were standing outside when the storm hit, waiting for that siren to go off, you were doing something wrong at that time, folks," he said.

This article originally appeared on Sioux Falls Argus Leader: Here's why Sioux Falls' sirens didn't go off during Thursday's storm