A Case Study of Atmospheric Dynamics and Thermodynamics in Derechos and the Societal Impacts

The word “derecho” is used to differentiate a storm having straight‐line winds as opposed to rotational, tornadic winds. Although the term “derecho” is relatively old, derechos were not readily recognized by the general public until recent outbreaks caused significant widespread damage and associated fatalities. Most notably, the 2012 Mid‐Atlantic Derecho in the USA brought these types of storms to the public's attention as a variety of societal impacts including infrastructural damage, power outages, and fatalities occurred over an extensive area from outside of Chicago to Washington, DC The associated damage can be more widespread than tornadoes, and the number of fatalities is comparable to those found in medium‐intensity tornadoes. This study investigated the importance of the dynamics and thermodynamics in maintaining the intensity of derechos. Key meteorological parameters were measured over six stations where the 2012 Mid‐Atlantic Derecho passed. Low‐ to mid‐level wind shear, as well as the Convective Available Potential Energy (CAPE) and Most Unstable Convective Available Potential Energy (MUCAPE), was found to be significantly higher at the time of passage, which allowed the system to intensify and propagate down‐ stream.