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Abstract 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.
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Can Mountain Waves Contribute to Damaging Winds Far Away from the Lee Slope?
Abstract On 25 December 2016, a 984-hPa cyclone departed Colorado and moved onto the northern plains, drawing a nearby Arctic front into the circulation and wrapping it cyclonically around the equatorward side of the cyclone. A 130-km-wide and 850-km-long swath of surface winds exceeding 25 m s−1 originated underneath the comma head of the lee cyclone and followed the track of the Arctic front from Colorado to Minnesota. These strong winds formed in association with a downslope windstorm and mountain wave over Colorado and Wyoming, producing an elevated jet of strong winds. Central to the distribution of winds in this case is the Arctic air mass, which both shielded the elevated winds from surface friction behind the front and facilitated the mixing of the elevated jet down to the surface just behind the Arctic front, due to steep lapse rates associated with cold-air advection. The intense circulation south of the cyclone center transported the Arctic front and the elevated jet away from the mountains and out across Great Plains. This case is compared to an otherwise similar cyclone that occurred on 28–29 February 2012 in which a downslope windstorm occurred, but no surface mesoscale wind maximum formed due to the absence of a well-defined Arctic front and postfrontal stable layer. Despite the superficial similarities of this surface wind maximum to a sting jet (e.g., origin in the midtroposphere within the comma head of the cyclone, descent evaporating the comma head, acceleration to the top of the boundary layer, and an existence separate from the cold conveyor belt), this swath of winds was not caused by a sting jet.
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- Award ID(s):
- 1545927
- PAR ID:
- 10128164
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Weather and Forecasting
- Volume:
- 34
- Issue:
- 6
- ISSN:
- 0882-8156
- Page Range / eLocation ID:
- p. 2045-2065
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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