Tornadoes, High Winds and Hail Delay Flights, Damage Buildings

Several tornadoes, high winds and hail brought down power lines and trees and damaged buildings across the U.S. Midwest, even as the chance of a massive rare storm dwindled, according to the U.S. Storm Prediction Center.

The threat of dangerous weather was reduced to moderate from high earlier in the day by the storm center, as various thunderstorms sweeping the region had failed to merge into a powerful wind storm known as a derecho.

Forecasters were “not as confident in the evolution of a long-lived derecho per earlier outlooks,” according to an outlook released last night by the center in Norman, Oklahoma. “If or when these storms ultimately evolve into a squall line, then the threat of damaging winds could increase markedly.”

The center has received at least 16 tornado reports in Iowa, Illinois and Ohio, along with 79 instances of hail from as far west as Wyoming and as far east as Virginia. There were also numerous reports of strong winds snapping trees, flipping boats and tearing off roofs, including a Wal-Mart in Lake Delton, Wisconsin.

At least 528 flights in and out of Chicago’s O’Hare International and Midway airports were canceled, according to FlightAware, a Houston-based airline tracking service.

At least 32,000 customers in Chicago and its suburbs were without power as of 9:30 p.m. local time, Commonwealth Edison Co. said on its website. An additional 34,500 outages were reported in Indiana, according to a statement from Northern Indiana Public Service Co. in Merrillville, Indiana.

Flood Warnings

As of 10 p.m. New York time yesterday, tornado watches stretched from Iowa to western Pennsylvania and Maryland, according to the National Weather Service. Flood watches and warnings reached from Iowa to Massachusetts because the larger storm system is expected to bring heavy rain storms along the U.S. East Coast.

New York may still receive 2.5 to 3.5 inches of rain, with some isolated areas getting as much as 5 inches, according to the weather service.

Ground already saturated by earlier rains could easily flood as more precipitation falls, according to a weather service flash flood watch issued for Washington.

A smaller area from central New Jersey to northern Virginia, including Philadelphia, Baltimore and Washington, has a 45 percent chance of high winds, hail and possibly tornadoes, according to a storm center forecast.

Cool Winds

New York and Boston will probably be spared the worst of the storms, said Tom Kines, a forecaster at AccuWeather Inc. in State College, Pennsylvania.

The New England states will benefit from cool onshore winds that will help stabilize the atmosphere, keeping the severe thunderstorms from forming, he said.

Forecasters had feared the thunderstorms would coalesce into a derecho, which is characterized by winds of at least 58 miles (93 kilometers) per hour, creating a line of damage at least 240 miles long. A derecho swept through the Midwest into the mid-Atlantic a year ago, knocking out power to 5 million people from Chicago to the District of Columbia and killing 22, according to government data.

Derechos are rare because they require a number of smaller storms “to work together,” said Russell Schneider, a director of the Storm Prediction Center. More than 75 percent of derechos occur from May to August, and they’re most likely to happen along an axis from the southern Great Lakes southwest into Texas, according to the storm center.

Severe thunderstorms and the tornadoes that sometimes accompany them caused $15 billion in insured losses in 2012 and $25 billion in 2011, according to the Insurance Information Institute in New York.

From 1992 to 2011, thunderstorms and tornadoes accounted for the second-highest amount of catastrophic loss in the U.S., $130.2 billion, topped only by hurricanes and tropical storms with $161.3 billion, the institute said.

To contact the reporter on this story: Brian K. Sullivan in Boston at bsullivan10@bloomberg.net

To contact the editor responsible for this story: Dan Stets at dstets@bloomberg.net

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