20 May 2013 Moore, Oklahoma, Tornado: Damage Survey and Analysis

The tornado that affected Moore, Oklahoma, and the surrounding area on 20 May 2013 was an extreme event. It traveled 23 km and damage was up to 1.7 km wide. The tornado killed 24 people, injured over 200 others, and damaged many structures. A team of surveyors from the Norman, Oklahoma, National Weather Center and two private companies performed a detailed survey (all objects/structures) of the tornado to provide better documentation than is normally done, in part to aid future studies of the event. The team began surveying tornado damage on the morning of 21 May and continued the survey process for the next several weeks. Extensive ground surveys were performed. The surveys were aided by use of high-resolution aerial and satellite imagery. The survey process utilized the enhanced Fujita (EF) scale and was facilitated by use of a National Weather Service (NWS) software package: the Damage Assessment Toolkit (DAT). The survey team defined a "well built" house that qualified for an EF5 rating. Survey results document 4253 objects damaged by the tornado, 4222 of them EF-scale damage indicators (DIs). Of the total DIs, about 50% were associated with EFO ratings. Excluding EFO damage, 38% were associated with EF1, 24% with EF2, 21% with EF3, 17% with EF4, and only 0.4% associated with EF5. For the strongest level of damage (EF5), only nine homes were found. Survey results are similar to other documented tornadoes, but the amount of EF1 damage is greater than in other cases. Also discussed is the use of non-DI objects that are damaged and ways in which to improve future surveys.