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Brian J. Carroll, Belay B. Demoz, David D. Turner, and Ruben Delgado

and wind lidars over Europe (without an LLJ) to evaluate ECMWF forecast model performance, showing a model wet bias of 17%. Passive ground-based sensors such as the atmospheric emitted radiance interferometer (AERI; Turner and Löhnert 2014 ) have also contributed to studies of LLJ thermodynamics and interactions with the stable boundary layer ( Bonin et al. 2015 ; Toms et al. 2017 ; Johnson et al. 2018 ; Lin et al. 2019 ). These observational studies have been complemented by modeling studies

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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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Aaron Johnson and Xuguang Wang

configuration of the cycled ensemble Kalman filter (EnKF) radar DA (i.e., number of cycles, interval between cycles, and total length of DA) and the physics configuration of the DA and forecast ensembles. This paper presents the first work specifically focused on a systematic evaluation of convection-permitting modeling system configurations specifically for nocturnal convection. This evaluation of retrospective forecasts from 2014 focuses on morning (i.e., 1300 UTC) initialized forecasts for consistency

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Jonathan E. Thielen and William A. Gallus Jr.

then evaluate the performance of the model simulations of these nocturnal MCSs using comparisons of mode distributions and a quantitative accuracy score. Section 2 explains the types of cases, morphology classification scheme, scores, and model configurations used in the study. Analysis and results then follow in section 3 , with section 4 presenting the conclusions, summary, and directions for future work. 2. Methodology An initial sample of five nocturnal MCS events with Type-A LLJs present

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Aaron Johnson, Xuguang Wang, and Samuel Degelia

; French and Parker 2010 ; Marsham et al. 2011 ). The model predictability of the nocturnal LLJ is therefore also an important component of nocturnal convection to consider. The purpose of this paper is to document the details of the real-time GSI-based multiscale ensemble DA and forecast system that was implemented during PECAN and to evaluate the performance of the system within the context of the above PECAN foci. The system configuration and forecast products are described in section 2 and

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Aaron Johnson and Xuguang Wang

2015 PECAN intensive observing period (IOP) to investigate the role of model physics configurations in the performance of model predictions of the observed bore, but did not consider the influence of model resolution. Since the cold pool strength and depth are strongly sensitive to the microphysics parameterization, it was shown that this sensitivity carries over to the bore prediction with the WRF single-moment 6-class microphysics scheme (WSM6; Hong and Lim 2006 ) providing the best prediction

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Sean Stelten and William A. Gallus Jr.

performance at predicting PNCI. LLJ-driven PNCI types (1 and 2) appeared to be better predicted in location than types 3 and 4. Since type 3 is completely dependent on the location of the parent MCS, correct prediction of type 3 initiation can only occur if the parent MCS is also correctly predicted, which increases the challenge in forecasting. Subsequently, type 4 PNCI is likely to be less predictable because this type occurs without obvious forcing mechanisms. To further examine the model handling of

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Thomas R. Parish and Richard D. Clark

since scale analysis of the equations of motion show that boundary currents in the ocean are not comparable to the LLJ. Parish and Oolman (2010) note that observations and modeling do not support the Wexler (1961) contention that the North American Cordillera acts as a barrier to the air moving about the Bermuda high. Theories proposed by Blackadar (1957) and Holton (1967) continue to be discussed as forcing mechanisms for the LLJ. Work has attempted to evaluate the LLJ in terms of these two

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

convection induced by the urban land effect. This also shows the importance of evaluating model simulations before further investigation. A possible reason for the better performance of MYJ here because MYJ is the best PBL scheme to simulate the boundary layer jet and other PBL structure on clear days based on Wang et al. (2017) , and the studied storm was initiated in the clear-sky condition and heavily relied on boundary layer jet transport. The urban land effects on storm initiation and diverting

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Guo Lin, Coltin Grasmick, Bart Geerts, Zhien Wang, and Min Deng

proximity of the colliding boundaries and to place the UWKA flight track in the context of the MCS, cold front, outflow boundaries, and the bore. The Meteorological Assimilation Data Ingest System (MADIS) is a fine-scale grid of interpolated surface meteorological observations ( UCAR/NCAR–Earth Observing Laboratory 2011 ), used to initialize and evaluate weather and climate models, provided by the National Oceanic and Atmospheric Administration (NOAA). MADIS combines NOAA data sources with non-NOAA data

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