Supplemental Damage Indicators Discovered in Recent Strong Tornadoes

As part of an effort to improve the understanding of near-surface winds in tornadoes, surveys of tornado damage were conducted following a few major tornado events that have occurred since 2010. In addition to assessing a wide range of standard EF-scale damage indicators (DIs), a few non-standard or supplemental DIs were identified, including:

Parking stops (Joplin, MO)

Manhole covers (Joplin, MO)

Storm grates (Joplin, MO)

Transmission line tower (Bowdle, SD)

Grain Bins (Mapleton, IA)

Antique-style light poles (Joplin, MO)

Documentation of each bulleted DI will be provided. Additionally, the track-relative locations of each DI were identified and compared to the EF-ratings of nearby standard EF-scale DIs, where possible. An estimation of minimum wind speed necessary to produce the observed degree of damage (DOD) was made, where possible, by using the weight and cross-sectional area of the DI as well as the estimated pressure coefficient as induced by the atmospheric pressure drop inside the tornado (using laboratory vortex measurements). For example, preliminary analysis of lofted parking stops offers support for the assigned EF-5 rating in the Joplin tornado. Additionally, the transmission line tower's observed DOD (collapsed and removed from original location) in the Bowdle, SD tornado exceeded the highest DOD provided in the EF-scale (collapsed tower). Recommendations for how to implement these supplemental DIs in the EF-scale will be provided.