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

1. Introduction North and South America are home to two of the world’s largest mountain ranges: the Rocky and Andes Mountains. The elevation of these barriers, north–south orientation, and their position on the western side of the continents substantially influence the weather downstream because they modify midlatitude westerly and other associated flows. Interestingly, the regions east of the mountainous terrain in both continents are global hot spots for deep and organized convection, owing

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

subtropical South America (SSA) are deeper and more frequent than those east of the Rocky Mountains in North America ( Zipser et al. 2006 ; Houze et al. 2015 ). Specifically, the cloud shields associated with SSA mesoscale convective systems (MCSs) are approximately 60% larger than those occurring in the continental United States (CONUS; Velasco and Fritsch 1987 ) and their precipitation areas are larger and longer lived ( Durkee et al. 2009 ; Durkee and Mote 2010 ), contributing up to ~95% of warm

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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

subtropical South America is the South American low-level jet (e.g., Vera et al. 2006 ; Salio et al. 2007 ; Montini et al. 2019 ). During RELAMPAGO, a sounding site at Villa de María del Río Seco (hereinafter Villa de María), located approximately 175 km north of Córdoba ( Fig. 1a ), collected daily soundings at 0900 UTC, along with other times during IOPs, to monitor the SALLJ and its potential effects on convection. The objective criteria for identifying low-level jets first introduced by Bonner

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Zhixiao Zhang, Adam Varble, Zhe Feng, Joseph Hardin, and Edward Zipser

repository hosted by the NCAR Earth Observing Laboratory ( https://data.eol.ucar.edu/master_lists/generated/relampago ). Relevant radiosondes are available through the Atmospheric Radiation Measurement (ARM) archive ( https://adc.arm.gov/discovery/ ). Raw model output is available by contacting the authors. REFERENCES Benjamin , S. G. , and Coauthors , 2016 : A North American hourly assimilation and model forecast cycle: The Rapid Refresh . Mon. Wea. Rev. , 144 , 1669 – 1694 , https://doi.org/10

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

conducted in which the north–south model terrain (mimicking the Sierras de Córdoba in Argentina, South America) was altered by systematically varying maximum terrain height between 500 and 4500 m. The idealized numerical modeling simulations displayed systematic variations in DCI timing and location, as well as subsequent supercell intensity, updraft and downdraft structure, cold pool and rainfall characteristics, and upscale growth rates that varied with modified environmental characteristics caused by

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

) flow of all cases, while CI cases had the strongest. Due to the similarity in the terrain-perpendicular wind, there are no statistical differences in F n 8 for the CI, Fail, or Null events. Therefore, the differences in upslope flow do not appear to differentiate event types. Fig . 9. Mean terrain (SDC) relative low-level winds (lowest 100 hPa) for CI (green), Fail (blue), and Null (red) events, where the north–south line is terrain parallel and west–east is terrain perpendicular. Proximity

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Zachary S. Bruick, Kristen L. Rasmussen, Angela K. Rowe, and Lynn A. McMurdie

show why this region is highly favored for convective initiation and subsequent upscale growth. Convergence is maximized near the SDC due to the impingement of the South American low-level jet (SALLJ) from the north and ageostrophic midlevel flow from the south on the elevated terrain. Because of the descent of upper-level air in the lee of the Andes, a mechanical capping inversion exists over the region that inhibits convective initiation. Moisture is advected into subtropical South America from

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Zachary S. Bruick, Kristen L. Rasmussen, and Daniel J. Cecil

1. Introduction Hail in subtropical South America can be very large ( Rasmussen et al. 2014 ) and frequent (10–30 storms per year in central Argentina; Cecil and Blankenship 2012 ), and it causes significant impacts to property and the agricultural economy in this region. Hail has been studied for more than five decades, yet relatively little is known about the storms that produce hail or the environments that support hail-producing storms in subtropical South America. Hail research in the

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

.1175/JAMC-D-14-0114.1 . 10.1175/JAMC-D-14-0114.1 Ribeiro , B. Z. , and L. F. Bosart , 2018 : Elevated mixed layers and associated severe thunderstorm environments in South and North America . Mon. Wea. Rev. , 146 , 3 – 28 , https://doi.org/10.1175/MWR-D-17-0121.1 . 10.1175/MWR-D-17-0121.1 Romatschke , U. , and R. A. Houze Jr. , 2010 : Extreme summer convection in South America . J. Climate , 23 , 3761 – 3791 , https://doi.org/10.1175/2010JCLI3465.1 . 10.1175/2010JCLI3465.1 Salio

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Adam C. Varble, Stephen W. Nesbitt, Paola Salio, Joseph C. Hardin, Nitin Bharadwaj, Paloma Borque, Paul J. DeMott, Zhe Feng, Thomas C. J. Hill, James N. Marquis, Alyssa Matthews, Fan Mei, Rusen Öktem, Vagner Castro, Lexie Goldberger, Alexis Hunzinger, Kevin R. Barry, Sonia M. Kreidenweis, Greg M. McFarquhar, Lynn A. McMurdie, Mikhail Pekour, Heath Powers, David M. Romps, Celeste Saulo, Beat Schmid, Jason M. Tomlinson, Susan C. van den Heever, Alla Zelenyuk, Zhixiao Zhang, and Edward J. Zipser

Jr. , 2016 : Contribution of extreme convective storms to rainfall in South America . J. Hydrometeor. , 17 , 353 – 367 , https://doi.org/10.1175/JHM-D-15-0067.1 . Ribeiro , B. Z. , and L. F. Bosart , 2018 : Elevated mixed layers and associated severe thunderstorm environments in South and North America . Mon. Wea. Rev. , 146 , 3 – 28 , https://doi.org/10.1175/MWR-D-17-0121.1 . Romatschke , U. , and R. A. Houze Jr. , 2010 : Extreme summer convection in South America . J

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