Environmental Conditions Leading to Observed Convective Organization in Central Argentina

Deep convection frequently forms along the Sierras de Córdoba (SDC) mountain range, downstream of the Andes, and grows rapidly upscale, spatially aggregating into larger systems. The 2018-19 Remote Sensing of Electrification, Lightning, And Mesoscale/Microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaign collected detailed observations of convective systems and their environments, including periods of upscale growth near the SDC. In this study, we analyze two intensive observational periods (IOPs) where storms grew upscale with different rates and degrees of upscale growth. On 13-14 December 2018, strong synoptic forcing led to a Northwestern Argentina low with a cold front and an elevated South American Low-level Jet (SALLJ). Convection grew very rapidly upscale overnight behind the front where the northerly winds from the SALLJ encountered the front, leading to initially elevated convection. Strong deep-layer (0–6 km) wind shear was observed with a large front-parallel component and 2–6 km shear, which includes SALLJ peak winds, was oriented even more parallel to the low-level forcing produced by the front, favoring upscale growth. In contrast, weak synoptic forcing led to afternoon convection focused over the SDC on 5 December 2018. Convection grew upscale near the SDC but grew more slowly, had a lesser degree of organization, and was more spatially limited than on 13-14 December. These IOPs highlight how the alignment of favorable synoptic and localized environments connected to the SDC impacts upscale growth and emphasize the importance of accounting for varying SALLJ heights when choosing vertical layers over which to calculate relevant environmental parameters.