May 22nd, 2013

U.S. Severe Weather Outbreak

Posted at 6:06 PM ET

moore-smallSevere weather hit the central United States over the last several days, spawning several tornadoes, large hail and damaging straight-line winds. The town of Moore, Oklahoma experienced the worst of the outbreak. A rare EF5 tornado, the most powerful ranking on the Enhanced Fujita Scale, obliterated scores of buildings and killed at least 24 people, 9 of them children. The tornado was reported to be 1.3 miles wide and spent 40 minutes on the ground, leaving a 17 mile trail of destruction. According to AIR Worldwide, the estimated value at risk from the EF5 is between USD2 billion and USD6 billion. Oklahoma’s Insurance Commissioner, John Doak, stated that insured losses could exceed the cost of the 2011 Joplin tornado, which was nearly USD3 billion.

Highly unstable atmospheric conditions produced the severe weather outbreak that spawned the EF5 tornado on May 20. While the Moore, Oklahoma tornado was the most damaging, the severe weather system produced 22 tornadoes in total that day. The majority of these occurred in Oklahoma. However, Kansas, Arkansas, Colorado and Texas also had reports of tornadoes. Large hail was another factor across the Central Plains, with Missouri experiencing quarter-size hail and Osage County, Oklahoma experiencing baseball-size hail. Damaging winds were reported over a wide area of the plains, the Mississippi Valley and into the Canadian Great Lakes.  A suspected derecho was reported in Michigan. 


Hazard data illustrated in the CAT-i map was taken from i-aXs®, Guy Carpenter’s web-based risk management platform. i-aXs users can view impacted areas on any map as well as see how their portfolios were affected. Please contact your broker or GC Analytics®   representative for assistance or go to for further information.

The National Weather Service (NWS) initially reported the Moore, Oklahoma tornado as an EF4, however, damage assessment teams on the ground determined that winds had exceeded 200 miles per hour, classifying the tornado as an EF5. The winds were so powerful that most of the debris consisted of wood splinters no more than 12 inches long. More than 2,400 homes were damaged or obliterated according to Oklahoma Emergency Management. Two elementary schools were leveled, and a hospital was severely damaged by the tornado.  

According to Oklahoma Governor Mary Fallin, at least 24 people perished from the storm and more than 300 were injured. Nine children were among the dead, most of them from an elementary school that took a direct hit by the tornado. While the human toll has affected the community of Moore, Oklahoma, officials and residents are thankful that the death toll remained relatively low given the extent of the devastation. Officials credit early warning from meteorologists as part of the reason why so many lives were spared. Others also credited the increase in storm safe shelters in the community after the devastation from an EF5 tornado in 1999 that packed some of the strongest wind speeds in history and destroyed more than 8,000 homes.

Six adults are still unaccounted for, according to the Oklahoma Office of Emergency Management. While rescuers are still combing through the rubble, rescue efforts will slowly transition to recovery and clean up efforts.

The severe weather threat has moved to the east, where the NWS Storm Prediction Center is forecasting a risk of severe thunderstorms Wednesday afternoon and evening across parts of the Tennessee Valley to the lower Great Lakes and into New England. The primary threats are damaging winds and large hail, especially across the lower Great Lakes region.

Sources: National Weather Service Storm Prediction Center (SPC), Associated Press, BBC News, Reuters, Agence France Presse, CNN, AIR Worldwide.

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Guy Carpenter publishes CAT-i reports for major natural catastrophes worldwide. These reports cover catastrophes including worldwide tropical cyclones, earthquakes, major UK and European floods and any other natural event that is likely to incur a significant loss to the (re)insurance industry. Please email if you wish to be added to the free email distribution list.

Guy Carpenter compiles RISK-i reports for major technological or man-made events worldwide. These reports cover risks to property, transport and life including explosions, fires, crashes, engineering disasters and terrorist attacks that are likely to incur a significant loss to the (re)insurance industry. Please email if you wish to be added to the free email distribution list.

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