Procedures to change after sirens were silent before tornado

Emergency officials near Georgia's coast are investigating how to prevent future failures of an outdoor tornado siren system.

The sirens were silent before a tornado passed through the Wilmington Island area east of Savannah on May 4, The Savannah Morning News reported.

A computer system used by emergency managers was undergoing scheduled maintenance that day, National Weather Service spokeswoman Maureen O'Leary said.

Ron Morales of the weather service's Charleston, South Carolina, office says the weather service typically emails customers when the system is offline for maintenance, but that didn't happen before the Saturday outage.

Chatham Emergency Management Agency Director Dennis Jones said his agency is changing its procedures in order to avoid a repeat of Saturday's situation.

The automated siren system is designed to activate each of the county's 62 outdoor sirens only when live radar data or a human spotter indicates the threat near it is imminent.

It relies on a signal from the NWS's Emergency Managers Weather Information Network - EMWIN - indicating a tornado warning has been issued.

"That feed comes into our siren controller downstairs," Jones said. "It says, 'Hey, there's a tornado warning in this polygon area, all of the sirens need to turn themselves on. So when that happens, the sirens auto-activate based on that polygon. And they keep activating until that polygon is gone. They activate for three minutes and then they're off for three minutes."

It was the EMWIN that was undergoing scheduled maintenance the day the tornado struck, officials said. EMWIN is designed to allow users to obtain weather forecasts, warnings and other information directly from the NWS in almost real time. It's intended to be used primarily by emergency managers and public safety officials who need timely weather information to make critical decisions.

"Maintenance was scheduled to replace the power supply in the NWS data center in Silver Spring, Maryland," O'Leary wrote in an email.

After reviewing Saturday's events, the Chatham Emergency Management Agency has changed this protocol, Jones said.

"What we've done is if a tornado warning is issued, first and foremost the duty officer is going to verify the sirens are activating before he calls Charleston Weather," he said. "Before, it was call Charleston Weather to get real time information. Now we're going to go through that verification process, make sure the sirens were activated. That way it helps us get the information out quicker. It helps us confirm the emergency warning system is operating the way it's supposed to operate. Then we'll get situational awareness after that. So we basically reversed the procedure."