On a modified definition of a derecho. Part II: An updated spatial climatology of derechos across the contiguous United States

Abstract

Abstract Derechos are known as widespread severe windstorms that accompany extra-tropical MCSs. However, questions remain whether the term derecho should apply to widespread windstorms from all linear storm structures, or just MCSs that evolve from a progressive cold pool, which support concentrated swaths of damaging winds. Part I of this manuscript focused the derecho definition to windstorms with hurricane-force gusts that originate from cold-pool-driven MCSs. While Part I modified the derecho definition and formulated quantitative criteria for identifying future events, a derecho spatial climatology across the contiguous U.S. was derived for 2000-2022 using this more focused definition in Part II. The derecho climatology was created from cases identified with the same algorithm employed in Part I of this manuscript, which ingested a combination of datasets to objectively detect derechos. For the 2000-2022 climatology, derechos were found to be primarily warm-season events, with corridors of derecho occurrence noted across the Midwest and Southern Plains, in agreement with earlier studies, as well as the Northern Plains. 70 derechos were identified over a period of 23 years. Derechos occur, on average, three times per year nationally, and once every 1-2 years at given points within the Plains and Midwest corridors, with greater frequencies noted in earlier studies, likely due to stricter criteria requiring hurricane-force gusts and supporting cold-pool-driven MCS structures in the present study. Derechos frequently form in the afternoon and dissipate later at night, but peak in intensity just a few hours after development.