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Yun Lin, Jiwen Fan, Jong-Hoon Jeong, Yuwei Zhang, Cameron R. Homeyer, and Jingyu Wang

parameterizations are required for studying hail physics and aerosol effects on hail using model simulations ( Loftus and Cotton 2014a ; Ilotoviz et al. 2016 ). For aerosol–cloud interactions, typical bulk microphysical parameterizations have substantial limitations in their ability to simulate aerosol impacts on convective intensity, as documented in several studies ( Lebo et al. 2012 ; Khain et al. 2015 ; Fan et al. 2016 ). The objective of this study is to investigate how urbanization-induced land and

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Kevin R. Haghi, Bart Geerts, Hristo G. Chipilski, Aaron Johnson, Samuel Degelia, David Imy, David B. Parsons, Rebecca D. Adams-Selin, David D. Turner, and Xuguang Wang

a bore over the Gulf Coast. (c) “Morning Glory” seen from Virgin Australia flight (courtesy of Virgin Australia, @VirginAustralia). (d) GOES-16 water vapor channel (courtesy of NOAA). (e) Radar reflectivity images of an undular bore over Oklahoma, (courtesy of Noah Brauer, @NOAABrauer). (f) Images of a bore developed from a sea/land breeze interaction (courtesy of @Weatherology Twitter account). Disclaimer: data from GOES-16 data are preliminary. Past studies on organized convection captured

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Alan Shapiro, Evgeni Fedorovich, and Joshua G. Gebauer

://doi.org/10.1175/2010MWR3422.1 . 10.1175/2010MWR3422.1 McPherson , R. A. , 2007 : A review of vegetation-atmosphere interactions and their influences on mesoscale phenomena . Prog. Phys. Geogr. , 31 , 261 – 285 , https://doi.org/10.1177/0309133307079055 . 10.1177/0309133307079055 Means , L. L. , 1952 : On thunderstorm forecasting in the central United States . Mon. Wea. Rev. , 80 , 165 – 189 , https://doi.org/10.1175/1520-0493(1952)080<0165:OTFITC>2.0.CO;2 . 10

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David B. Parsons, Kevin R. Haghi, Kelton T. Halbert, Blake Elmer, and Junhong Wang

1. Introduction Haghi et al. (2017) recently showed that as the night progresses in the warm season over the Southern Great Plains, the interaction between convectively generated cold pools and the lower troposphere typically lies within a partially blocked flow regime, where bores will be generated. This study seeks to investigate the potential role of these bores in the initiation and maintenance of nocturnal convection. While high-resolution convection-permitting models show some promise

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

observed bore dissipation to the weakening of the wave duct in the near-surface stable layer. Blake et al. (2017) used the simulation to investigate the role of a bore in the maintenance of a nocturnal MCS. The basic theory of bores as hydraulic jumps in the depth of the stable layer, maintained by the ducting of vertically propagating wave energy, has been confirmed by numerous laboratory experiments and by analytically using a simple two-layer model of the atmosphere (e.g., Maxworthy 1980

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Aaron Johnson and Xuguang Wang

particular, at least one time–height cross section through each of the bores is available from an Atmospheric Emitted Radiance Interferometers (AERI; Turner and Löhnert 2014 ; Turner 2016 , 2017 ). In short, the AERI instrument uses downwelling infrared radiation at wavelengths ranging from 3.3 to 19.2 μ m to retrieve the vertical profile of temperature and water vapor in the lowest ~3 km of the atmosphere. While it can sometimes be challenging to distinguish bores from other features using only

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Aaron Johnson and Xuguang Wang

have demonstrated the sensitivity to features such as atmospheric bores, LLJs, elevated frontal zones, mesoscale regions of elevated ascent, and land–atmosphere interactions during the previous day. Therefore, the goal of this study is to determine the sensitivity of nocturnal convection forecasts to different aspects of the ensemble data assimilation (DA) and forecast system design in order to improve its configuration for the unique foci of PECAN. In particular, this paper will focus on the

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Stanley B. Trier, James W. Wilson, David A. Ahijevych, and Ryan A. Sobash

categories: 1) strong synoptic forcing associated with a cold front and a midtropospheric short wave ( Fig. 1b ), 2) interaction of a nocturnal LLJ with a quasi-stationary lower-tropospheric front ( Figs. 1a,d,e ), and 3) a nocturnal LLJ located immediately downstream from a midtropospheric ridge axis in the absence of a well-defined surface front ( Fig. 1c ). Fig . 1. Mean 500-hPa geopotential height and horizontal winds with 850-hPa wind speed (shaded) from DART ensemble analyses (see section 3c ) at

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Shushi Zhang, David B. Parsons, and Yuan Wang

and Roberts 2006 ; Koch et al. 2008a , b ; Tanamachi et al. 2008 ; Martin and Johnson 2008 ; Hartung et al. 2010 ; Marsham et al. 2011 ; Blake et al. 2017 ). These results are expected as Haghi et al. (2017) revealed that the interaction between the convectively generated cold pools and the SBL over this region typically resides in a partially blocked flow regime where bores will be generated ( Rottman and Simpson 1989 ). These bores will be long lived as the wave energy is typically

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Manda B. Chasteen, Steven E. Koch, and David B. Parsons

multiscale processes and environmental heterogeneity influenced the development and evolution of an initially elevated, nocturnal MCS that persisted into the following afternoon as a surface-based system. Section 2 overviews the MCS and the synoptic environment in which it developed, and section 3 details the early evolution of the observed convection. A description of the WRF-ARW simulation used in this study is presented in section 4 . Processes related to the LLJ and its interaction with

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