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Coltin Grasmick, Bart Geerts, David D. Turner, Zhien Wang, and T. M. Weckwerth

well-mixed, deep planetary boundary layer (PBL)—to elevated nocturnal convection, which typically organizes at larger scales as the nocturnal stable boundary layer (SBL) deepens, and a low-level jet (LLJ) develops above the SBL ( Corfidi et al. 2008 ; Carbone and Tuttle 2008 ; Reif and Bluestein 2017 ). Convective cells develop when a parcel of air is lofted to its level of free convection (LFC), becoming buoyant with respect to its surrounding environment. Convective cells often initiate in the

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Stacey M. Hitchcock, Russ S. Schumacher, Gregory R. Herman, Michael C. Coniglio, Matthew D. Parker, and Conrad L. Ziegler

. 2003 ; Clark et al. 2007 ; Johnson and Wang 2013 ; Johnson et al. 2013 ). MCSs span a distance of ~100 km or larger and can have a variety of organizational modes ( Parker and Johnson 2000 ; Houze 2004 ; Schumacher and Johnson 2005 ). They are often associated with a midlevel short-wave trough, a baroclinic zone (in the United States this is often a warm or stationary surface front), a statically stable boundary layer, a low-level jet (LLJ), and the associated advection of warm, moist, high θ

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Aaron Johnson, Xuguang Wang, Kevin R. Haghi, and David B. Parsons

in the Great Plains ( Haghi et al. 2017 ) due to the frequent occurrence of blocked or partially blocked flows and the presence of nocturnal low-level jets, which act to duct the bore energy. The common occurrence of bores and the relatively poor performance of NWP models in representing these nocturnal systems motivate our aim to investigate and quantify the uncertainties and errors in bore simulations of a well-observed case study. The purpose of this effort is to guide future work to improve

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David J. Bodine and Kristen L. Rasmussen

archetypes at different life cycle stages. Several factors affect MCS propagation including the environmental flow, internal storm processes related to cold pool development, and nearby convection and its interaction with the MCS. Corfidi et al. (1996) found that mesoscale convective complex motion was related to both the mean wind and propagation associated with new convection. The propagation component is similar in magnitude to the low-level jet vector, but in the opposite direction. These motion

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Samuel K. Degelia, Xuguang Wang, and David J. Stensrud

problematic for NWP forecasts (e.g., Johnson and Wang 2017 ; Johnson et al. 2017 ; Stelten and Gallus 2017 ; Johnson et al. 2018 ). Reif and Bluestein (2017) note that NWP models are often tuned specifically for features that initiate surface-based convection, whereas nocturnal CI tends to be initiated by features above the boundary layer ( Corfidi et al. 2008 ). For example, the nocturnal low-level jet (LLJ), defined as a wind maximum occurring within the lowest kilometer of the atmosphere after

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Dylan W. Reif and Howard B. Bluestein

downstream from a low-level jet (LLJ) maximum and in a later study ( Maddox 1983 ) showed that the LLJ is a common precursor to MCS development. Elevated convection, which is defined as convection whose source of lift is not rooted in the boundary layer, is common at night during the warm season ( Colman 1990a , b ). In his 5-yr study, the peak occurrence of elevated convection was in eastern Kansas and the majority of cases occurred 1°–2° latitude (approximately 100–200 km) north of a quasi

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J. W. Wilson, S. B. Trier, D. W. Reif, R. D. Roberts, and T. M. Weckwerth

1990 ; Bluestein 1993 ). The storm is classified as a supercell hailstorm based on a radar Doppler velocity mesocyclone, radar reflectivity (maximum 71 dB Z ), and an extensive flare echo (discussed later). There were no hail reports, likely because the storm occurred in a remote area during the night. Reif and Bluestein (2017) reported that for the occurrence of pristine NECI, important features include the nocturnal low-level jet, midtropospheric moisture maximum, and a midtropospheric warm

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Matthew D. Parker, Brett S. Borchardt, Rachel L. Miller, and Conrad L. Ziegler

environments often exhibit a shallow statically stable boundary layer (SBL) and substantial evolution of the near-ground wind profile, including a developing low-level jet (e.g., Stull 1988 ). Climatologies also reveal that nocturnal MCSs often occur on the cool side of warm or stationary fronts (e.g., Augustine and Caracena 1994 ; Laing and Fritsch 2000 ), locations that may have even deeper layers of strong stability. Given a SBL, it has often been presumed that most nocturnal MCSs comprise elevated

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David M. Loveless, Timothy J. Wagner, David D. Turner, Steven A. Ackerman, and Wayne F. Feltz

bores will change their characteristics over the course of their lifetimes. Koch et al. (2008) used a combination of observations and numerical simulations to identify changes in the turbulent nature of the bore over the course of its life cycle. They identified that the majority of turbulent kinetic energy is generated by the shear stress from the strong along-bore flow associated with the low-level jet (LLJ). Additionally, they found that early in the life cycle of the bore, in what they called

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Stacey M. Hitchcock and Russ S. Schumacher

several different methods of classification, but two distinct categories consistently emerge for events over the central Great Plains. In synoptic-type events, a strong midtropospheric trough and slow moving surface front lead to strong forcing for ascent in a region with southerly flow and associated moisture transport. During the warm season, isentropic ascent of warm, moist air transported by the nocturnal low-level jet (LLJ) can lift an air to saturation on the cool side of a stationary or warm

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