Behind the scenes: The process of issuing tornado warnings

Storm Team 10's David Siple gives us a behind-the-scenes look at how the N.W.S. issues tornado warnings and then where exactly that warning gets sent to.

Posted: Mar 24, 2021 5:50 PM
Updated: Mar 24, 2021 7:25 PM

SULLIVAN COUNTY, Ind. (WTHI) - The National Weather Service is the first one to make the call when it comes to issuing tornado warnings. But the process begins there.

Sam Lashley, the Warning Coordination Meteorologist with the N.W.S. in Indianapolis, says it takes them very little time to be able to issue a warning.

“It takes anywhere from 30 seconds to one minute from the time we decide we are going to issue a tornado warning until that is going out the door and sounding the alarms and sirens and setting off the weather radios.”

Lashley says they base their warnings on three criteria.

  • Satellite and weather computer model data to analyze the atmospheric environment.
  • They will analyze and dissect storms that have formed to see if any are showing signs of rotation.
  • Trained storm spotter reports and amateur radio operators will send ground truth if a tornado has actually formed.

It will take 2 of the 3 criteria for the N.W.S. to issue a tornado warning.

To issue the actual tornado warning, Lashley says they have specific technology that allows them to draw the warning polygon.

“'WarnGen' which stands for Warning Generation. It pops up a default box and then we quickly adjust those points and then make a few selections on our control panel and out the door the warning goes. Once that button is pressed."

That warning gets automatically sent out to the impacted county. One of those locations is the Sullivan County Dispatch Center. Where it’s up to them to sound the sirens for their county.

We spoke with Eric Cox, who is the Communications Supervisor for Sullivan County Dispatch. He gives us a little insight into what happens when a warning gets issued.

“We receive that via computer from the National Weather Service that a warning’s been issued for Sullivan County and at that time once we receive that we’ll activate all the tornado sirens here in Sullivan County to alert all of the citizens across the county.”

It is up to each county, each city, and each locality to have their own guidelines for when and how they will sound their sirens. In the case of Sullivan County, they will manually press a button to sound the correct sirens for the areas. But they are in works for this system to be upgraded. 

But, those sirens are only meant for people outside. So you have to make sure you have multiple ways to get severe weather alerts.

Cox has important advice he wants to pass along to anyone.

“It’s important that they pay attention to their cell phones, and for the alerts to come across your cell phone and to the radio and television. And prepare for that incoming weather as you said in case you are not outside and don’t hear the sirens from inside your residence.”

It is always important to have an N.O.A.A. weather radio. As well as always keeping up to date with the Storm Team 10’s forecasts.

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