Rogue tornadoes ravage Las Vegas. An arctic blast hits the North as a steamy storm slams the South. All three forces collide over Chicago, resulting in a horrific superstorm that takes down the national power grid.
The dramatized disaster is the focus of a new two-day CBS miniseries, "Category 6: Day of Destruction," and its special effects echo those used on the big screen.
"When we used to do these kinds of things, you accepted that TV was going to be a different quality than people saw in the theater," said Bob Sertner, the program's executive producer. "But over the years, as the quality of feature effects rose and TV couldn't match it, it became harder to do this genre on TV. But now the visual-computer-effects world is accessible to everyone."
The show stars Brian Dennehy as a meteorologist tracking the devastating weather patterns.
"Brian was our first choice for the role," said Sertner. "And Dianne Wiest was the first choice as secretary of energy."
Even before the storms rain down, Wiest's character emphasizes the vulnerability of the national power grid, warning Chicago residents to conserve energy or risk leaving millions powerless.
Nancy McKeon portrays a local TV reporter covering the heat wave that is sauteing Chicago, and Randy Quaid stars as "Tornado Tommy," who flies adventure-seekers into the path of an Oklahoma tornado.
Craig Weiss, who supervised the film's special effects, said the scenes with Quaid were difficult to capture on film.
"When he's being chased by a twister, with all that weather destruction, that poses a challenge," Weiss said.
The show's weather sequences include both stock footage and computer-generated shots.
"We'd have the real footage side by side with the computerized shots, and you can see how the details match up," Sertner said.
The movie follows both major and minor characters as they cope with the havoc created by the wild weather paths. In an early scene, a Las Vegas bridal party sees its wedding chapel whisked away, and a hotel guest is pulled through a window by the twister's fury. An airplane flies into the eye of the storm. And Quaid's character watches helplessly as the famous St. Louis Arch crumbles.
Weiss said the use of 3-D storyboards, called animatics, "allow us to look at what a scene might look like before we shoot it. We have a digital actor, a virtual blueprint of the live action. Ninety percent of what we do is in the preplanning, because visual effects are like creating a puzzle: If you don't properly plan, you have trouble fitting it together."
The actors also faced challenges in shooting the scenes with special effects.
"Once upon a time, everything was done on a green-screen stage," said Sertner, referring to the technique of an actor standing before a blank green screen, with effects added when the film was edited. "Now we can track shots into the moving camera. We can design the shots. The environments they have to act in are much more real."
McKeon did do some green-screen work on the film, an experience she found "terrifically fun."
"You really have to use your imagination. It's a whole other way of working."
Being a TV reporter was an easy role for McKeon.
"I've been a news junkie for a very long time," she said. "I usually have MSNBC or Fox News Channel on. . . . I'm always trying to catch a sound bite here or there."
This year's series of hurricanes that slammed Florida resonated with the actors on the project, which was already in production, McKeon said.
"Our hearts went out to those who were going through the same stuff we were re-creating at the same time. I'd turn on the news, and there it was. It was an incredible thing."
Jay Bobbin of Zap2it contributed to this report.
Category 6: Day of Destruction
Sunday at 9 p.m. and Wednesday at 8 p.m. on CBS