The Story Behind The Flash Flood Alert/Tornado Siren Muddle In Kansas City | KCUR

The Story Behind The Flash Flood Alert/Tornado Siren Muddle In Kansas City

May 18, 2015

If you were awake in the Kansas City metro around 11:25 p.m. Saturday, you may have heard a tornado siren ... but you may have not.

Around the same time, the National Weather Service was sending emergency alerts warning about flash floods in the area, creating confusion for many Kansas Citians.

Check out what Kansas Citians were tweeting:

Steven Bean, who works for the city’s office of emergency management, oversees Kansas City’s 127 tornado sirens.

We met Bean last month when he was on KCUR's Central Standard talking about what it is like to make the call on sounding the sirens. On Monday, we invited him to be on Up To Date to talk about the confusion Saturday night. 

Here's three questions we asked Bean to get some clarification about what went down, and why.

Why did we hear sirens in some parts of the city, but not others?

Bean says that when the National Weather Service issues a weather warning, the fire departments in each city are primarily responsible for sounding the sirens.

“When we push the button for Jackson County, all of the sirens that are within the city limits — Kansas City, Missouri city limits — will go off,” Bean told host Steve Kraske.

Which is why you may have heard sirens in some parts of Kansas City, but not others.

“Normally, and as is the case on Saturday night, they sound them by county," he said. "We have a button that is marked Clay County. We’ll sound all the sirens within Clay County within Kansas City, Missouri. So that’s not going to sound Liberty, it’s not going to sound Claycomo or Excelsior Springs. People in Liberty and Claycomo may hear ours, but that’s not the intention.”

Why didn’t I get an emergency text about a tornado?

Emergency weather alerts are issued directly by the National Weather Service, using Wireless Emergency Alerts (WEA), which sends messages to cellphones that are checked into towers within the area of the warning. That allows it to be even more localized than county-wide sirens.

Ultimately, different entities are deciding who sends text message warnings and who pushes the button to sound the sirens.

According to a representative at the NWS in Pleasant Hill, Missouri, in the case of Saturday’s storms, the tornado threat wasn’t severe enough in the metro area to send emergency text alerts — though they did send out alerts for emergency flash flooding throughout the metro.

If the NWS didn't think there was a severe enough threat in the metro for text alerts, why did we hear sirens?

According to Bean, the system the National Weather Service uses to send out emergency alerts specifies an area of cellphone towers, or "polygons." They can send alerts to any number of polygons in a county — one polygon, or all the polygons, or some number in between. 

The city makes decisions based on what county polygons that are under threat fall in.

"When it comes to sirens, we have to make a quick decision," Bean says.

Which means that if one polygon in a county is in need of a tornado warning, the entire county will hear the sirens, but only people in that polygon will get a text alert.