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T. Connor Nelson, James Marquis, Adam Varble, and Katja Friedrich

environments supporting it with adequate spatial and temporal resolution, as well as an incomplete understanding of environment–cloud interactions supporting growing congestus (e.g., Crook 1996 ; Weckwerth and Parsons 2006 ; Houston and Niyogi 2007 ; Lock and Houston 2014 ; Rousseau-Rizzi et al. 2017 ; Weckwerth et al. 2019 ). For CI to occur, the atmosphere requires three fundamental ingredients: static instability, moisture, and a triggering mechanism (e.g., surface airmass boundaries, orographic

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Jeremiah O. Piersante, Kristen L. Rasmussen, Russ S. Schumacher, Angela K. Rowe, and Lynn A. McMurdie

; Zuluaga and Houze 2013 ; Houze et al. 2015 ). WCCs are primarily responsible for the regional maximum in high impact weather as they are much more numerous than DCCs in the La Plata basin (see Fig. 5 of Rasmussen and Houze 2011 ), and they maximize in size, intensity, and frequency in the region ( Romatschke and Houze 2010 ; Rasmussen and Houze 2011 ). Thus, the identification of WCC environments is the focus of the current study. To test the hypothesis that larger and thus more impactful WCCs are

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Jeremiah O. Piersante, Russ. S. Schumacher, and Kristen L. Rasmussen

months were included to highlight how precipitation forecast skill is lowest during the warm season; the change in error with season is discussed throughout the paper. All members were run via the Advanced Research version of the Weather and Forecasting (WRF) Model ( Skamarock et al. 2008 ) version 3.7.1 with RRTMG radiation ( Iacono et al. 2008 ), Noah land surface ( Tewari et al. 2004 ), 43 vertical levels, a 90-s time step, and GFS initial/lateral boundary conditions (except for one that uses GEFS

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Russ S. Schumacher, Deanna A. Hence, Stephen W. Nesbitt, Robert J. Trapp, Karen A. Kosiba, Joshua Wurman, Paola Salio, Martin Rugna, Adam C. Varble, and Nathan R. Kelly

located much higher than those typically observed in the United States, similar to the findings of Oliveira et al. (2018) . The diurnal cycle, spatial structure, and other aspects of SALLJ observations during RELAMPAGO-CACTI are a current area of active investigation (e.g., Sasaki et al. 2021 ). Fig . 6. Vertical profiles of the meridional wind component (m s −1 ) for soundings meeting the northerly LLJ-2 criteria (a wind speed maximum of 16 m s −1 below 3 km AGL and a decrease of 8 m s −1 above

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Robert J. Trapp, Karen A. Kosiba, James N. Marquis, Matthew R. Kumjian, Stephen W. Nesbitt, Joshua Wurman, Paola Salio, Maxwell A. Grover, Paul Robinson, and Deanna A. Hence

preparation for the Bulletin of the American Meteorological Society ; the current article will focus specifically on the IOP4 supercell. As we will show in section 3 , the IOP4 storm possessed a midlevel mesocyclone and a “hook echo” in radar reflectivity, and also exhibited a motion that deviated from the mean environmental wind. These are considered hallmarks of the supercell morphology (e.g., American Meteorological Society 2020 ). However, as confirmed by multiple-Doppler wind analyses, the

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Hernán Bechis, Paola Salio, and Juan José Ruiz

strongest moisture gradients is relatively small and shallow. There is a generalized low-level moistening, mostly explained by the previously discussed horizontal advection term ( Fig. 13b ). Midlevel drying is observed on the lee side of the Andes generating an area of dry air aloft (ADAA) ( Fig. 13a ). This drying is produced by subsidence over the lee of the Andes of air originated above the top of the Pacific Ocean maritime boundary layer ( Fig. 13c ). The ADAA is embedded in a westerly current that

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Sujan Pal, Francina Dominguez, María Eugenia Dillon, Javier Alvarez, Carlos Marcelo Garcia, Stephen W. Nesbitt, and David Gochis

measurements in the headwaters of the basin using acoustic Doppler current profiler (ADCP) and large-scale particle image velocimetry (LSPIV). The group measured the hydrologic response of three severe high-flow events during the IOP. The main objectives of the hydrometeorological observations were 1) to quantify the hydrological response associated to the extreme convective events simultaneously measured by the larger RELAMPAGO team, 2) to build suitable stage–discharge curves for the headwater rivers

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Jake P. Mulholland, Stephen W. Nesbitt, and Robert J. Trapp

(LLJ), and upper-level negative geostrophic potential vorticity (weak ambient inertial instability) all favored the most rapid transition of discrete convective cells into an MCS. Furthermore, Dial et al. (2010) found that for cases of convection initiation (CI) along a frontal or similar boundary, the potential for UCG increased when the cloud-layer wind and deep-layer vertical wind shear vectors were nearly parallel to the initiating boundary. Additionally, as the magnitude of low-level forcing

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Matthew R. Kumjian, Rachel Gutierrez, Joshua S. Soderholm, Stephen W. Nesbitt, Paula Maldonado, Lorena Medina Luna, James Marquis, Kevin A. Bowley, Milagros Alvarez Imaz, and Paola Salio

Hail can cause significant damage to property and agriculture, as well as injuries or even deaths; in part, the risk associated with hail increases with increasing hailstone size, which generally leads to greater impact kinetic energy. The current definitions for hail size based on the National Weather Service include “sub-severe,” “severe,” and “significantly severe” ( Table 1 ). In the scientific literature, some studies have also identified “giant” hail as those stones with maximum

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Jake P. Mulholland, Stephen W. Nesbitt, Robert J. Trapp, Kristen L. Rasmussen, and Paola V. Salio

. (2012) , have revealed that most tornado and large hail reports originate from supercellular convection, whereas damaging straight-line wind gusts predominantly occur with larger mesoscale convective systems. Similar studies have been largely absent across Argentina, however, as high spatiotemporal radar, surface, and upper-air observations are sparse, and a standard severe weather reporting procedure has not yet been implemented operationally at the time of this publication. The aim of the current

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