Brooks said the conditions have been ripe in recent weeks for just such a catastrophe. Cold, dry air aloft, powered by the jet stream, blows in from the west, meeting the low-level, warm, moist air moving northward from the Gulf of Mexico. If the cold fronts are strong enough, they’ll suppress tornado formation. But if they’re weak, the result can be a deadly compromise between the colliding air masses: The warm air at ground level will be moving in a different direction from the air higher up. That’s a recipe for the rotational energy that spawns a full-blown tornado.
At the nuclear plant
The storms shut down the three nuclear reactors at the Browns Ferry power plant 30 miles west of Huntsville, Ala., a plant of similar design to the severely damaged Fukushima Daiichi power plant in Japan. But unlike Fukushima Daiichi, when Browns Ferry lost primary power, the plant’s diesel generators kicked in as designed to keep the reactors cool, said Barbara Martocci, a spokeswoman for the Tennessee Valley Authority, which operates the 3,274-megawatt facility. “The plant is shut down safely,” she said, meaning that control rods dropped into the reactors when power went offline, stopping nuclear fission.
The plant’s cooling systems can run indefinitely on diesel generators as crews work to restore external power, Martocci said. The facility will not begin producing electricity again until “we have a full damage assessment of our entire transmission system,” Martocci added.
In Virginia, five people died — three in the small town of Glade Spring — in Washington and Halifax counties, when twisters roared through overnight, officials said.
A truck stop on Interstate 81 and a new factory were destroyed, according to Christy Parker, assistant administrator in Washington County, in southwest Virginia.
Tractor trailers “were flipped and thrown about the interstate like toys,” she said Thursday.
Pokey Harris, Washington County’s director of emergency management, said late Thursday: “We have multiple injuries . . . broken bones, crush injuries. We have a tremendous amount of devastation. A lot of buildings are destroyed.”
Most of the Virginia fatalities occurred when what appeared to be a tornado hit a mobile home park, the truck stop and an apartment complex, Virginia Department of Emergency Management officials said. Storms ripped through a subdivision in Shenandoah County, damaging several homes. Virginia Gov. Robert F. McDonnell (R) declared a state of emergency, authorizing state agencies to assist local governments in responding to the impact of the weather.
Severe storms and possible tornadoes also struck Goochland County, officials said. Fifty people were injured statewide.
Tornado warnings were issued across the D.C. suburbs early Thursday morning. Fast-moving bands of storms packed high winds and torrential rains. A funnel cloud formed over Point of Rocks in Frederick County shortly before 7 a.m., according to the National Weather Service.
There were widespread reports of damaged trees, including one that fell across Route 109 in Barnesville and another that landed on an electric line in Middleburg, according to the weather service. Fauquier County schools were delayed by two hours, and Prince William County schools canceled outdoor activities.
The storms caused flight delays of up to 90 minutes at Reagan National and Dulles International airports.
O’Keefe and Branigin reported from Washington. Staff writers Joel Achenbach, Michael Bolden, Michael E. Ruane, Jason Samenow, Krissah Thompson, Brian Vastag and Erin Williams and researcher Madonna Lebling in Washington contributed to this report.