Vicious-looking black and gray clouds boil in a cauldron that only moments ago was clear sky. Television networks suspend regular programming and weathercasters point at maps pulsating with color.

Reporters across the area measure hail­stones as they try to keep their balance in heavy winds.

DRC/Al Key

On April 17, this wall cloud west of Sanger tried its best to drop a funnel near Sam Bass Road. Tornado sirens went off in Sanger at the time but no tornado ever formed. The ominous storm did bring torrential rain and quite a hailstorm with it, though.

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Are the city’s warning sirens sounding? Should they be?

Some area cities seem to blare theirs needlessly. Though there is no tornado, those cities have been sounding their sirens “as a precaution,” weathercasters say. Plano didn’t set off its sirens April 10, and even though there was no tornado, officials later apologized.

Denton’s sirens didn’t sound that night, said Emergency Manager Mike Penaluna, because the city’s weather conditions never quite reached the criteria for activating them. He said he sets off the sirens in several cases:

* when the National Weather Service issues a tornado warning for Denton,

* when storm spotters see rotation and lowering in the clouds over Denton,

* when the weather service issues a severe thunderstorm warning and predicts that winds could reach more than 73 mph, or

* when the storm produces hail 2 inches in diameter or larger.

“On April 10, we never quite got there,” Penaluna said.

The sirens can be frightening and confusing, officials say. And they never were meant to alert people inside their homes. They’re a warning for people outdoors to take cover, Penaluna said. Denton has 16 sirens, and they’re placed near locations like ball fields, schools and other places where people might be outdoors.

“They mean ‘take cover,’” he said. “In our insulated homes, we’re not going to hear them anyway.”

Penaluna has applied for grants for four more sirens to better cover the rapidly expanding city. Meanwhile, there’s a new system that is more precise to warn Denton residents — something meant for indoors. People who sign up for the Code Red telephone warning system will re­ceive a call no matter what time of day or night if their home lies in the path of a dangerous storm.

“I’m very excited,” Penaluna said. “This is one of the greatest breakthroughs I’ve ever seen. It’s another tool for us to use, and it’s a good one.”

The Code Red system calls only when warnings are issued and only if your address is in the path of the storm. Currently, only Denton, the Argyle Fire District and Sanger offer it in Denton County.

Penaluna said the Code Red system is a geographical-based notification system that uses  street addresses to select which phone numbers will receive emergency notification calls in any given situation.

“The system works fine for cellphones, too, but we have to have a street address,” he said.

Denton is fortunate that it has a strong ham radio operator group that works directly with the National Weather Service when a storm is forecast, he said.

Storm spotters are assigned to the areas most likely to produce dangerous conditions. They re­port directly to the weather service in Fort Worth via their ham radios. That’s how the weather service can be so precise about what is happening where.

Penaluna opens the city’s Emer­gency Operations Center at the Central Fire Station with a ham operator beside him to monitor the radios. There is a weather station on top of the fire station and one at the airport. So he is ready when conditions deteriorate to alert the public.

The first criterion for the sirens is a dangerous thunderstorm or tornado warning from the weather service. Dan Shoemaker, a meteorologist with the weather service in Fort Worth, said a tornado watch is issued if conditions are favorable for tornadic activity to occur. It is to inform people to be alert.

“We issue a warning if a tornado is imminent or occurring,” he said. “It means you need to take action.”

Television weather programming can be a bit alarming, Shoe­maker said. But television stations operate in a competitive market, and the showmanship is meant to get viewers’ attention.

“And we need for viewers to at least watch the weather crawls across the bottom of the screen,” he said.

Penaluna said people can stay well informed by buying a weather radio. These radios broadcast reports from the National Wea­ther Service and issue a loud warning noise if a warning is de­clared.

“Just like everyone needs a smoke detector, everyone needs a weather radio,” he said.

They are relatively inexpensive and are available where electronics are sold.

He encourages residents to sign up for the Code Red alerts as well.

“This is the most exciting development in my career as an emergency manager,” Penaluna said.

DONNA FIELDER can be reached at 940-566-6885. Her e-mail address is dfielder@dentonrc.com.