The severe thunderstorms that struck the United States from May 20 to the 27 will result in insured losses to residential, commercial, and industrial properties and their contents, and to automobiles of between $4 billion and $7 billion, according to catastrophe modeling firm AIR Worldwide.
“The month of May, normally the most active month for tornadoes, began quietly,” said Dr. Tim Doggett, principal scientist at AIR Worldwide. “For three weeks, only a handful of isolated tornadoes were reported.” But, Doggett noted, on May 20, severe thunderstorms in eastern Texas and parts of Arkansas and Oklahoma brought high winds, hail, and five reported tornadoes. Over the next seven days, there were more than 150 confirmed tornadoes across the heart of the country, from Lake Superior to central Texas and east through Missouri, Tennessee, Kentucky, Ohio, and to the East Coast, affecting more than 20 states in all. Thousands of buildings were damaged, hundreds more were completely destroyed, and more than a thousand people were injured, according to AIR.
None of the elements that gave rise to the outbreak of severe thunderstorms is unusual.
“Large, strong, jet stream disturbances happen occasionally; persistent low pressure frontal systems are common, especially in spring; and the storms that developed occurred where they are expected to occur at this time of year,” Doggett said.
But, he said, what is unusual is for all of the factors that contribute to the development of severe thunderstorms to have aligned themselves so optimally in the same place at an opportune time. “To get optimal intense instability, shear, and lift all in the same place for a long period of time is a relatively rare circumstance,” he said.
This outbreak of tornadoes coupled with the unusually high number of tornadoes in April has turned what began as an unremarkable year into a year that has so far produced almost twice as many preliminary tornado reports as the average since 2005, and that is on track to rival the very active 2008 season. Doggett said that 2011 will surpass 2008 in terms of insured losses from severe thunderstorm activity. The two major outbreaks of this year—the first in late April, the second in late May—are the costliest on record.
AIR’s insured loss estimates reflect insured physical damage to property (residential, commercial, industrial, auto), both structures and their contents; additional living expenses (ALE) for residential claims; business interruption losses; and effects of demand surge.
They do not reflect non-modeled losses, including loss adjustment expenses.
Damage by StateAccording to AIR, Minnesota suffered a moderate amount of significant damage across portions of the Twin Cities metropolitan area, where more than 100 houses and several commercial properties were damaged, and many trees and power lines were knocked down.
In Kansas, there were damaging winds and hail over much of the state, as well as 14 reported tornado touchdowns on May 21 alone. The city of Reading (population 231) was hardest hit, where 26 homes and ten commercial buildings were destroyed. The state capital, Topeka (population 127, 473 in 2010), suffered brief tornado touchdowns in its south and east sections, and hail as large as baseballs fell in some locations.
Texas was affected mainly in the north. Severe thunderstorms, funnel clouds, and hail the size of tennis balls bombarded the Dallas and Fort Worth areas through the early evening of May 24th, smashing car windows, and damaging roofs. Eight confirmed tornadoes touched ground in the state, one of them in the town of Denton, about 40 miles north of Dallas and Ft. Worth.
The severe thunderstorms affected Indiana mostly in the southern part of the state. In Bedford, a small town (14,000 population) near Bloomington, several homes were destroyed and much of the town sustained significant damage.
Missouri was most severely hit. The city of Joplin (population 49,000) lies in the southwestern corner of the state, just a few miles from the Kansas border. In the early evening of May 22nd, an extraordinarily violent tornado—later rated an EF5, the highest possible on the Enhanced Fujita Scale with winds of at least 200 mph—touched down just inside the Missouri border. It cut straight across Joplin, then continued to the east. Several other tornadoes also touched down in Missouri that day.
The tornado left a flattened path through Joplin three-quarters of a mile wide and 14 miles long. In nine minutes, more than 8,000 homes and apartment units, and more than 500 commercial properties were heavily damaged or destroyed. It was the deadliest tornado to hit the United States in more than half a century.