23STUDENT "The Black Derecho": A Case Study of May 12, 2022

A derecho is defined by the National Weather Service as a widespread windstorm commonly found in the Great Plains, Midwest, and sometimes the southeastern United States. In an environment of sufficient instability, deep convection is one of the key signatures of the storm structure of a derecho. Typically ahead of the gust front is another key signature, an intense wind field stretching for over 60 miles (also known as the rear-inflow jet). The intensity of these features allows derechos to become more than capable of producing dust storms (aka haboobs). These dust storms occur out ahead of their gust fronts due to the strength of their unidirectional atmospheric winds, sometimes miles ahead of their deep convection. Due to the premature season of agriculture and the lack of rainfall prior, the "black derecho" of May 12, 2022, was capable of kicking up an extensive haboob, a dark feature that spread for over 100 miles and lifted dirt/dust/bugs thousands of feet as observed from the dual-polarization and Doppler products of KFSD NEXRAD radar data. Locals defined this event to be a "black derecho" due to the skies turning a dark brown-black color in the late afternoon of around 2230Z, causing near-zero visibility. Between hurricane-force winds and over 150 damaging wind reports, this event was listed by the National Centers for Environmental Information as a billion-dollar disaster event.

Phenomena like this can be dangerous and fatal due to the violent wind damage and irritating dust that could bring acute respiratory symptoms to the public, as this case was of no exception. While a derecho is not defined until after it has met certain criteria of wind reports and damage, the analysis of radar data can aid in the assessment of an MCS’s characteristics to find key signatures of a derecho as the system itself grows and evolves. Because this derecho swept across the Northern Great Plains at a direct angle towards the city of Sioux Falls, an analysis from the KFSD NEXRAD radar captured a detailed view of some of the derecho's key signatures: a strong gust front, a tall dirt/debris signature kicked up by the intensity of the gust front, bowing line of deep convection, and the rear-inflow jet surging forward in the bowing line. As a result, this case study utilized the clear point-of-view of KFSD to study what characteristics this "black derecho" possessed.