Mechanisms for long-duration extreme winds in a WRF simulation of the 10 August 2020 derecho

The Weather Research and Forecast Model (WRF) was run using a 3-km horizontal grid with a 1-km inner nest to better understand mechanisms that might explain the extreme wind behavior. Simulations were sensitive to the microphysics used, with many schemes failing to produce a long-lived system in the area of the observed derecho.

However, an unusually realistic simulation was obtained using the Thompson scheme but only when the Kain-Fritsch convective scheme was used. That scheme prevented spurious nocturnal storms that dried the lower troposphere prior to derecho development, causing the derecho to dissipate in western Iowa.