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How does the National Weather Service issue warnings?

Keith Stellman, the Meteorologist in Charge at the National Weather Service in Peachtree City, takes us behind the scenes of the warning process.

PEACHTREE CITY, Ga. — At 13WMAZ, we track storms, show you potential dangers, tell you when you need to take cover, and let you know when you're in the clear. But, only the National Weather Service can issue a watch or warning.

"We've used our education, all the tools, and all the data, and we analyzed it and believe there is a threat," said Keith Stellman, Meteorologist in Charge at the National Weather Service office in Peachtree City, GA.

The office is responsible for forecasting each day and alerting the public of hazardous weather in 96 counties, including all of central Georgia. 

In the event of a severe weather outbreak, the office works as a team to not only get the word out, but also continue with their forecasting beyond the threat.

"As the event unfolds, we'll have multiple radar operators looking at the data as it's constantly spinning, making sure the equipment is in the right mode, making sure that things are still going," said Stellman. 

And once the criteria is met to issue something like a Severe Thunderstorm Warning or Tornado Warning, a meteorologist begins the process of issuing the product. 

"It gives me this dot which I can then move to the center of the storm. I'll drop it on the center of the storm, it immediately draws up this box," Stellman said. "I can then choose the warning, choose the type I want it to be."

Then, the meteorologist issuing the warning can adjust the box based on speed and direction of the storm. More often than not, the box becomes a polygon, highlighting only areas that have a threat from the storm. 

In the example Stellman showed us, the sample storm was located in Crawford County, moving north-northwest. The sample warning included Monroe County and part of northern Bibb County.

"It doesn't include the city of Macon," Stellman said. "So in this particular case, we chose not to warn the city of Macon because we believe based on our storm motion that the threat is confined to the north."

Meteorologists makes it a point to not over warn. They try to cut down on the area included in the warning while still allowing room for a right-turning storm.

From there, the meteorologist has a menu of potential threats and recommended actions. They can select all that apply to the storm. Things like hail size, threat confirmation, even the Tornado Emergency option are included here.

Then, the warning is sent. 

"It goes out through those channels to the broadcast media where it is displayed almost instantly," Stellman said.

See a sample severe warning be issued 

What does it mean to have a Severe Thunderstorm Warning with a "tornado possible" tag?

Whenever a Severe Thunderstorm Warning is issued with a "tornado possible" tag, it doesn't necessarily mean the storm is about to drop a tornado. Rather, it means that the storm is in an environment conducive for tornadoes. 

How are severe watches issued? 

The Storm Prediction Center in Norman, OK issues Severe Thunderstorm Watches and Tornado Watches. Watches for other weather hazards are issued from Peachtree City.

The SPC will contact the local weather service office with a preliminary list of counties to include in the watch. Then the local office will provide feedback based on timing and location. They try to avoid splitting major populated areas, putting everyone in the watch or leaving the area out. 

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