Analysis of a Nonconvective Mesoscale Windstorm and Wildfire Outbreak in Kansas on 15 December 2021

A rapidly deepening extratropical cyclone moved across the central Great Plains on 15 December 2021 and resulted in simultaneous extreme weather events. A derecho developed at the cold front and moved from the eastern half of Kansas to Wisconsin. Simultaneously, a nonconvective mesoscale windstorm occurred on the southwest side of the cyclone and moved from western to central Kansas and is the focus of this study. The windstorm downed power lines and triggered a wildfire outbreak covering over 160 000 ac (650 km²) resulting in two fatalities, several injuries, and the loss of hundreds of cattle. Surface wind gusts exceeded 50 kt (26 m s^-1) over a large area in western Kansas with a peak gust of 87 kt (45 m s^-1) observed at Russell, Kansas, on the southeast flank of the largest wildfire in the region. The extratropical cyclone resembled the Shapiro–Keyser conceptual model with the mesoscale windstorm focused near the cloud head and southern tip of the bent-back front southwest of the cyclone center. The near-surface wind speeds were highest where three airstreams}one along the bent-back front and the other two at higher altitudes to the west of the cyclone}descended and accelerated in a higher horizontal pressure gradient region near the tip of the bent-back front and cloud head. While the nonconvective mesoscale windstorm did not meet the exact definition of a sting jet, it exhibited many of the same characteristics and physical mechanisms that drive sting jets with oceanic Shapiro–Keyser cyclones.