Storm System Could Spawn Destructive Wind, Tornadoes

Most of Maryland and nearby states are under a flash flood watch and severe thunderstorm watches through the morning and into the day.
That's as a major storm system that has forecasters predicting a possible tornado outbreak similar, or even worse, than the one that hit Maryland on Monday. 
The system stretches to the middle of the continent. 
In the small town of Belmond, Iowa, about 90 miles north of Des Moines, Duwayne Abel, owner of Cattleman's Steaks & Provisions restaurant, said a tornado swept through his business' parking lot and demolished part of the building. No one was in the restaurant at the time.
"I was, oh, eight miles west of town and I looked toward town and I could see a funnel cloud, having no idea it was exactly where our restaurant was," Abel said. His wife and an employee were able to get out of the restaurant and sought shelter in a basement.
Other small tornadoes were also reported in other parts of Iowa and in Illinois. In Iowa, at least two businesses and a home were "completely damaged," authorities said. A storm ripped through a farm in rural Alexander, destroying a motor home. Tens of thousands of people across the Upper Midwest lost power.
"We're just happy that we don't have reports of injuries or fatalities," said Stephanie Bond with Iowa Homeland Security and Emergency Management. "We just hope the extent of the damage is minimal."
In addition to tornadoes, lightning and large hail, meteorologists warned about the possibility of a weather event called a derecho (deh-RAY'-choh), which is a storm of strong straight-line winds spanning at least 240 miles.
By late Wednesday, a derecho hadn't developed, but conditions were still ripe for one, with more storms expected overnight, said Greg Carbin of the National Weather Service's Storm Prediction Center in Norman, Okla. But, he added, "with each hour that goes by, it's less likely."
Derechoes, with winds of at least 58 mph, occur about once a year in the Midwest. Rarer than tornadoes but with weaker winds, derechoes produce damage over a much wider area.
Tornadoes and a derecho can happen at the same time. Straight-line winds lack the rotation that twisters have, but they can still cause considerable damage as they blow down trees and other objects.
In Wisconsin, authorities said thunderstorms packing heavy rain and high winds caused a Walmart roof to partially collapse. Lake Delton Fire Chief Darren Jorgenson says two employees had minor injuries, but no customers were hurt. Street flooding was reported in parts of the village of Boscobel in Grant County.
Even before the storms moved through, officials postponed Wednesday night's Chicago White Sox game against the Toronto Blue Jays and canceled a symphony concert at the city's downtown Millennium Park. The Metra commuter rail system temporarily halted all inbound and outbound trains, and Northwestern University canceled classes and finals at its campuses in Chicago and suburban Evanston. Airlines canceled more than 120 flights at O'Hare International Airport.
In Indiana, the warnings prompted the Northern Indiana Public Service Co. to increase staff at its customer call center and to schedule extra work crews for any power outages. Golf-ball sized hail damaged some cars.
Pennsylvania Emergency Management Agency spokesman Cory Angell said a standby worker was added at the emergency operations center in Harrisburg and officials had ensured two National Guard helicopters were ready if needed for water rescues.
Last year, a derecho caused at least $1 billion in damage from Chicago to Washington, killing 13 people and leaving more than 4 million people without power, according to the weather service. Winds reached nearly 100 mph in some places and in addition to the 13 people who died from downed trees, an additional 34 people died from the heat wave that followed in areas without power.
For Washington, Philadelphia and parts of the Mid-Atlantic the big storm risk continues and even increases a bit Thursday, according to the weather service.
The term derecho was coined in 1888, said Ken Pryor, a research meteorologist at the Center for Satellite Applications and Research at the National Oceanic and Atmospheric Administration in College Park, Md. The word is Spanish for "straight ahead" or "direct," Pryor said.
The structure of a derecho-producing storm looks distinctive in radar and satellite imagery, Pryor said. "The systems are very large and have signatures that are very extreme," he said. "You get large areas of very cold cloud tops that you typically wouldn't see with an ordinary thunderstorm complex. The storms take on a comma or a bow shape that's very distinctive."

SOURCE : http://www.wbal.com/article/100511/2/template-story/Storm-System-Could-Spawn-Destructive-Wind-Tornadoes