How tornado warning systems work

Dana Ulepich searches inside a room left standing at the back of her house destroyed after a powerful tornado ripped through Moore, Okla., May 20, 2013.
Brett Deering/Getty Images

Tuesday's tornado warning systems like the ones in Moore, Oklahoma are highly sophisticated often operating in conjunction with targeted text messages and announcements. For example, the system in Oklahoma City has 181 sirens and costs millions of dollars.

The city of Moore's sirens are made by the Illinois-based company Federal Signal. The city upgraded to 36 sirens in 2011 from 33. While some cities have switched to sirens that turn on automatically when a tornado warning is issued, Moore's system still relies on someone pulling a lever to activate the alarm according to Federal Signal.

"Most people want validation before taking action," says John Von Thaden with Federal Signal. He says people might hear a warning but still want to hear from another source like a text message or radio announcement that they should take shelter. His company has surveyed the public on their reaction to emergency warnings.

Von Thaden says as the number of ways to communicate with people has grown, it's become more complicated to reach out to them - older people count on TV, younger people on texting and some people won't take action at all, he says, until they see a reason to act.

Business for outdoor warning systems usually ticks up after disasters and the emergency notification systems companies CBS spoke to say business has been brisk the last few years.

2011 was one of the worst years on record for tornadoes with 553 deaths. That's compared to 35 deaths so far this year.

Dan Catan, CEO of McCord Communications that sells tornado sirens around the country, "I'm not a meteorologist but it seems like the weather is getting more dramatic in the last few years."

Catan says after a disaster strikes, it usually takes communities a year or two to apply for the money, obtain it and then install the new systems. As a result he says it's only now that communities in Alabama that were hardest hit by tornadoes two years ago are upgrading their systems.