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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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W. G. Blumberg, T. J. Wagner, D. D. Turner, and J. Correia Jr.

, while a change in the height of B min may be correctly detected with a probability of 50%–60%. This difference suggests that the AERI’s primary benefit when assessing destabilization may be identifying changes to the initial parcel properties rather than precise changes in the environment, such as the lifting of a capping inversion. This is useful given that some of the dramatic changes in parcel instability are associated with an increase in moisture of the low levels rather than a change in

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

orthogonally to enhance the frontal lifting of moisture. Thus, the weak frontal lifting allows air from the warm-sector NBL to experience conserved lifting of θ and q υ (i.e., “isentropic upglide”), which in turn primes the environment to help sustain the forming MCS. Fig . 2. South–north cross section through the stationary front at 0300 UTC using four soundings from MG1, MG3, MP4, and MP1 indicated by black dashed lines and labeled with the respective sounding unit. All panels have solid black

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Bart Geerts, David Parsons, Conrad L. Ziegler, Tammy M. Weckwerth, Michael I. Biggerstaff, Richard D. Clark, Michael C. Coniglio, Belay B. Demoz, Richard A. Ferrare, William A. Gallus Jr., Kevin Haghi, John M. Hanesiak, Petra M. Klein, Kevin R. Knupp, Karen Kosiba, Greg M. McFarquhar, James A. Moore, Amin R. Nehrir, Matthew D. Parker, James O. Pinto, Robert M. Rauber, Russ S. Schumacher, David D. Turner, Qing Wang, Xuguang Wang, Zhien Wang, and Joshua Wurman

stage, before its merger with the mainly internally driven MCS ( Fig. 7 ). The LASE water vapor profiles revealed a ∼200-km-wide region of high water vapor mixing ratio values in the southerly inflow region during the MCS developing stage, a few hours before the Fig. 4 map time. Surface dewpoints were as high as 22°–24°C under this moisture dome, which can be seen to grow deeper and more moist toward the incipient MCS ( Fig. 7 ). The LASE precipitable water over a depth with good-quality data

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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

. 1997 ), designed to measure water vapor and aerosols along their flight transects, and the Wyoming King Air with a compact Raman lidar. Time–height sections from the ground-based upward pointing profilers captured horizontal/vertical motion, moisture, and temperature. Pre- and postbore environments were sampled with atmospheric soundings and the Kansas Mesonet recorded changes in temperature, pressure, and winds. It required a lot of planning and a little luck, but the 10–11 July 2015 IOP and other

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David J. Bodine and Kristen L. Rasmussen

500-hPa flow in southern South Dakota compared to northern South Dakota. At 850 hPa, a strong low-level jet is evident across the Great Plains region collocated with the strong gradient in the 850-hPa heights ( Fig. 2b ). The low-level jet terminates along the 850-hPa cold front position, leading to strong convergence along an axis from northeast Colorado to eastern South Dakota. Precipitable water exceeds 40 mm in central and eastern South Dakota, indicating substantial availability of moisture

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Evgeni Fedorovich, Jeremy A. Gibbs, and Alan Shapiro

and moisture to regions eastward with a potential for convection initiation. In fact, a very similar evolution pattern of the flow velocity ( Fig. 9 ) was observed during one of the intensive observation periods of the recent Plains Elevated Convection at Night (PECAN) experiment ( Geerts et al. 2017 ) when convection was indeed observed later in the night. The observed velocity profiles show the same developmental tendencies as their simulated counterparts presented in Fig. 6 . Fig . 7. Height

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Matthew D. Flournoy and Michael C. Coniglio

Klemp 2008 ) using the Data Assimilation Research Testbed ( Anderson et al. 2009 ). The ensemble has 36 members that are created by using different parameterization schemes for longwave and shortwave radiation, the surface layer for heat, moisture, and momentum fluxes, and turbulent mixing in the planetary boundary layer (PBL), as well as by using the initial conditions provided by 18 members of the Global Ensemble Forecast System [GEFS; the configuration is the same as that detailed by Hitchcock

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Alan Shapiro, Evgeni Fedorovich, and Joshua G. Gebauer

.0.CO;2 Charba , J. , 1974 : Application of gravity current model to analysis of squall-line gust front . Mon. Wea. Rev. , 102 , 140 – 156 , https://doi.org/10.1175/1520-0493(1974)102<0140:AOGCMT>2.0.CO;2 . 10.1175/1520-0493(1974)102<0140:AOGCMT>2.0.CO;2 Chen , R. , and L. Tomassini , 2015 : The role of moisture in summertime low-level jet formation and associated rainfall over the East Asian monsoon region . J. Atmos. Sci. , 72 , 3871 – 3890 , https://doi.org/10.1175/JAS-D-15

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Thomas R. Parish

levels of the atmosphere. A strong LLJ is possible under such conditions. In contrast, if an extended period of cloud cover or excessive soil moisture exists, the terrain-induced temperature gradients associated with the sloping Great Plains terrain will be reduced. This will decrease the magnitude of the thermal wind within the lowest levels of the atmosphere and the low-level PGF. Further, if the 600-hPa geostrophic winds are from the north the terrain-induced temperature gradients and thus the

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