Performance of Residences and Shelters in the Oklahoma Tornadoes

An outbreak of 22 tornadoes occurred in central Oklahoma on May 24, 2011. One tornado traveled from Hinton to Guthrie, a total of 104 km and was rated EF-5. Two EF-4 tornadoes traveled from Chickasha to Newcastle (52 km) and from Bradley to Goldsby (37 km). This paper will present the results of our damage survey from these three tornadoes including how the EF-scale was utilized in rating the damage. Many rural homes were completely destroyed. However, the low number of fatalities (11) was attributed to excellent advanced warnings, people reacting properly to such warnings, and the use of tornado shelters. Examples will be presented where people survived in above-ground or below-ground shelters. However, tornado shelters were not without problems. All shelters had a single entry door (no second escape door) and some doors were blocked with debris trapping the people inside. Also, some shelter doors blew open as people forgot to secure the doors properly. New shelter design criteria by the ICC (International Code Congress) mandates that all shelters have a second escape door with at least three latches.