Hundreds of Homes Destroyed by Midwest Tornado Outbreak: AIR

Hundreds of homes were flattened by the outbreak of intense late-season thunderstorms accompanied by high winds, quarter-to-baseball sized hail, and dozens of tornadoes that swept across the Midwest on Nov. 17, according to catastrophe modeling firm AIR Worldwide.

Tornadoes were sighted in several states, including Kentucky, Indiana, and Ohio, but the most damaging twisters occurred in central Illinois.

According to preliminary reports from the NOAA Storm Prediction Center (SPC), 80 tornadoes were produced by this severe thunderstorm outbreak, making it the second most active severe weather day of 2013 for the United States. However, the SPC cautioned that the preliminary figure may include double-counting of tornadoes and the total may therefore be revised over the next several days.

According to AIR, residential structures in the affected area typically comprise wood-frame construction, which are more vulnerable to high winds and windborne debris than masonry structures.

Commercial buildings are, on average, less vulnerable than residential structures or automobiles, but exhibit a broader damage distribution due to wide variations in construction practices and design. Light-metal structures are the most vulnerable to high winds and can suffer severe to complete damage from tornadoes categorized as EF-2 or higher.

“While the high winds and large hail associated with the severe thunderstorm outbreak damaged buildings across the affected region, the worst damage was inflicted by the dozens of tornadoes produced by the storm system, particularly in central Illinois,” said Scott Stransky, senior scientist at AIR Worldwide. “The worst damage occurred in Washington, Illinois, a town of 16,000 located in Tazewell County about 140 miles west of Chicago, where 250–500 homes were destroyed by a powerful tornado that has tentatively been assigned an EF-4 rating (peak winds of 190 mph).”

Leaving a path of destruction 34.5 miles long and 0.5 miles wide, the tornado leveled homes, and overturned cars, and injured more than 100 people, AIR Worldwide reported.

In addition, an EF-3 tornado touched down two miles east of and stayed on the ground for 24 miles, causing serious damage in the town of Gifford. The nearby towns of Beecher and Pekin also experienced severe damage. An additional EF-4 tornado was reported near New Minden, Ill. in Washington County, about 50 miles east of St. Louis, which caused significant damage to the town and surrounding farms.

November is usually one of the least active months for tornadoes, while May is the most active month, according to the Insurance Information Institute. The E-5 tornado that hit Moore, Okla., on May 20 of this year cost $1.6 billion in insured damages. Severe U.S. thunderstorms, including tornado events, cost $14.9 billion in insured losses in 2012, according to Munich Re.

The United States experiences more tornadoes than any other country in the world, according to a 2013 report by Lloyd’s of London.

The costliest U.S. catastrophe involving tornadoes occurred in April 2011 when twisters hit Tuscaloosa, Alabama, and other areas causing $7.4 billion in insured damages in 2012 dollars, the I.I.I. said. The second costliest U.S. catastrophe involving tornadoes struck Joplin, Mo., and other locations in May 2011. These storms struck multiple states causing $7 billion in insured losses in 2012 dollars.