November 19th, 2013

U.S. Severe Weather Outbreak, November 2013

Posted at 9:49 AM ET

severe-11-17-smallA late-season severe convective outbreak has affected a large portion of the Midwest, Ohio Valley, and Great Lakes including Southern Ontario. This widespread and violent outbreak has left absolute damage in communities such as Washington, Illinois. The outbreak occurred ahead of a strong cold front affecting the area. Numerous tornadoes have been reported, primarily in Indiana and Illinois, with some preliminary reports as high as an EF-4 rating on the Enhanced Fujita Scale. Reports of pea to quarter sized hail are more widespread, together with damaging winds.

Reports of roof damage with downed trees and powerlines are widespread over the affected area. More severe damage with violent tornadoes includes leveled communities, with extreme to absolute damage to homes of recent construction. At least eight fatalities have been reported as a preliminary estimate.

severe-11-17-big

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 www.i-axs.info for further information.

Meteorological Summary

This outbreak occurred along a powerful cold front cutting through the area on Sunday November 17. The enabling environment included warm, moist unstable air and wind shear (changing wind speed and direction with height). Initiation of severe thunderstorms in this environment occurred with the cold front (a boundary between cold-dry and warm-moist air) as it advanced through the affected area.

According to the U.S. Storm Prediction Center (SPC), this outbreak included 87 tornado reports, 559 straight-line wind reports (nontornadic) and 42 hail reports for the United States. At least one tornado was initially rated as an EF-4 on the Enhanced Fujita Scale, consistent with the complete devastation found in the Washington, Illinois area. Tornado activity was most frequent in Illinois and Indiana. Hail reports generally ranged from pea to quarter size, with isolated reports of golf ball sized hail, and one report of hail exceeding 3 inches in the Washington, Illinois area. Damaging wind reports were more widespread across the Great Lakes including Southern Ontario, and included measured gusts of 79 mph in Rock Falls, Illinois, 80 mph in Crown Point, Indiana and 85 mph in Bowling Green, Ohio. 

While late-season outbreaks of severe weather can and do occur, it is less frequent for such severe impacts to be rendered so far north at this time of year.

Impacts

Some communities such as Washington, Illinois have been absolutely leveled, consistent with the preliminary rating of an EF-4 tornado. Many others have sustained light to moderate roof damage together with downed trees and powerlines over a very large area from the Midwest to the Ohio Valley to the Great Lakes.

The full scope and severity of impacts is still being assessed by local emergency management agencies. Damage surveys are ongoing and it will take time to consolidate the results into confirmed tornado tracks and intensities.

Illinois

The State of Illinois experienced the worst of the severe weather outbreak, especially in the Town of Washington, which lies about 140 miles southwest of Chicago. Mayor Gary Manier estimated that 250 to 500 homes had been destroyed by the tornado. The National Weather Service gave the tornado a preliminary EF-4 rating, with estimated wind speeds in the range of 170 to 190 miles per hour. According to state police, the tornado affected an area about an eighth of a mile wide from one end of the town to the other. At least six confirmed fatalities have been reported in the state, and the number of injuries has been listed in the hundreds. Governor Pat Quinn has declared a disaster in seven counties, and the Illinois National Guard is currently assisting with search-and-recovery operations in the state. 

Michigan

The State of Michigan was affected by strong winds and rain, causing downed trees and powerlines over a wide area.  More than 530,000 homes and businesses were left without power.  At least two fatalities have been confirmed in the state.

Indiana

Widespread damage and injuries have been attributed to tornadoes and strong winds in the state. Governor Mike Pence stated that 12 counties reported tornadoes or storm damage. At least three dozen people were injured in the town of Kokomo due to what appears to have been a tornado. Tens of thousands of homes were without power. 

Ohio

Damage to buildings in a light industrial park attributed to the storms has been reported in an area just south of Columbus. The National Weather Service has deployed teams to the area to determine whether damage was caused by a tornado or straight-line winds. Tens of thousands of homes were without power.

Wisconsin

Reports of damaged buildings and downed trees were reported in Dodge County. The Milwaukee area experienced power outages due to high winds.

Kentucky

Tornadoes were spotted in at least eight counties, according to Kentucky Emergency Management. Reports of damage to homes and other structures have been confirmed, but the extent of the damage is unknown.

Missouri

Trees were uprooted in parts of St. Louis, and tens of thousands of homes were without power. The National Weather Service reported shingles being torn off roofs in St. Louis and St. Louis County.

Sources: National Weather Service (NOAA), U.S. Storm Prediction Center (NOAA), Associated Press, Reuters, Agence France Presse.

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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 CAT.i@guycarp.com 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 RISK.i@guycarp.com if you wish to be added to the free email distribution list.

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