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Stacey M. Hitchcock and Russ S. Schumacher

front ( Schumacher 2017 , and citations therein). In both cases, cloud layer winds can lead to cell motion parallel to the boundary and training/back-building. Corfidi et al. (1996) developed a technique to forecast the instances of back-building or quasi-stationary convection using the mean cloud layer wind and the (negative of) the LLJ. This was expanded to forecast forward propagation in Corfidi (2003) . In a conceptual model in Corfidi (2003) , the gust front is thought to elongate in the

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Hristo G. Chipilski, Xuguang Wang, and David B. Parsons

algorithm framework, this paper also highlights a spectrum of additional algorithm applications relevant for bore research and operational forecasting of nocturnal storms. Generally speaking, these algorithm applications can be utilized in two different ways. The first pertains to the verification of numerically simulated convective outflow boundaries. With the advance of convection-allowing NWP models, object-based verification techniques like the Method for Object-Based Diagnostic Evaluation (MODE

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

, https://doi.org/10.5065/D64M92RG . 10.5065/D64M92RG Wei , M. , Z. Toth , R. Wobus , and Y. Zhu , 2008 : Initial perturbations based on the ensemble transform (ET) technique in the NCEP global operational forecast system . Tellus , 60A , 62 – 79 , https://doi.org/10.1111/j.1600-0870.2007.00273.x . 10.1111/j.1600-0870.2007.00273.x Weisman , M. L. , C. Davis , W. Wang , K. W. Manning , and J. B. Klemp , 2008 : Experiences with 0–36-h explicit convective forecasts with the

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

different initialization times before bore formation, but to a lesser degree than compared to an initialization after bore formation. Recent studies have begun to use dual-resolution ensemble data assimilation techniques to provide a higher-resolution single analysis than the resolution of the ensemble members ( Wang and Wang 2017 ; Lu et al. 2017 ). Short-term forecasts initialized after bore formation may require such a data assimilation system in order to efficiently provide a higher

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Matthew D. Flournoy and Michael C. Coniglio

of kilometers and minutes, and can develop very quickly within QLCSs ( Mahale et al. 2012 ; Newman and Heinselman 2012 ). Because of this, forecasting severe wind associated with mesovortices is a difficult problem, and the study of both (i) synoptic conditions conducive for the development of mesovortices and (ii) mechanisms forcing mesovortex genesis in QLCSs remain active areas of research. Given favorable thermodynamic conditions, 15–20 m s −1 of line-normal vertical wind shear in the

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

: Observation of dual slantwise circulations above a cool undercurrent in a mesoscale convective system . Quart. J. Roy. Meteor. Soc. , 136 , 354 – 373 , https://doi.org/10.1002/qj.582 . 10.1002/qj.582 Bunkers , M. J. , B. A. Klimowski , J. W. Zeitler , R. L. Thompson , and M. L. Weisman , 2000 : Predicting supercell motion using a new hodograph technique . Wea. Forecasting , 15 , 61 – 79 , https://doi.org/10.1175/1520-0434(2000)015<0061:PSMUAN>2.0.CO;2 . 10

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Rachel L. Miller, Conrad L. Ziegler, and Michael I. Biggerstaff

2013 ). Nocturnal MCSs contribute to the well-established nocturnal precipitation maximum over the central United States during the summer months ( Maddox 1980 ; Carbone and Tuttle 2008 ; Wallace 1975 ). Achieving broad improvements in human and numerical forecasts of the formation, evolution, and intensity of nocturnal MCSs (e.g., as discussed by Ziegler 1999 ) continues to present considerable challenges, although there has been substantial recent progress in observing and modeling MCSs

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

1. Introduction Mesoscale convective systems (MCSs) play a critical role in the warm season nocturnal precipitation maximum over the U.S. Great Plains region (e.g., Wallace 1975 ; Maddox 1980 ; Fritsch et al. 1986 ; Carbone et al. 2002 ). These systems provide essential rainfall, but are often associated with severe weather ( Jirak et al. 2003 ; Maddox 1980 ). Despite its frequency and importance, nocturnal convection is not particularly well forecast in numerical models ( Davis et al

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

kt (1 kt ≈ 0.5144 m s −1 ), or ≈26 m s −1 ] in northeastern Kansas and western Missouri, including several estimated gusts exceeding 30 m s −1 ( Fig. 1 ). Horgan et al. (2007) discussed the substantial challenges of severe wind forecasting in this scenario. One testable hypothesis is that the 25–26 June MCS remained elevated and lacked a substantial surface cold pool. In such a case, severe winds might result either from the lifting and subsequent descent of air parcels within the near

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

. 2017 ) field campaign took place from 1 June to 15 July 2015 in the central United States. The designated PECAN domain was northern Oklahoma, Kansas, and southern Nebraska, but observations were taken as far north as South Dakota and as far east as Indiana. PECAN was designed to advance the scientific understanding and forecast skill of the processes that initiate and maintain elevated nocturnal convection in the Great Plains, and one of the focal points of the campaign was gaining a better

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