Mesoscale environments of tornadoes in Chile and along the U.S. west coast

Despite a surge of interest following the May 2019 outbreak, many mesoscale details of tornadic environments in Chile remain unknown. In this study, we extend our understanding of tornadic environments in Chile and update our knowledge of environments during tornadoes along the U.S. west coast. To do so, the convective available potential energy derived from the most unstable parcel (MUCAPE), the effective bulk wind shear using the most unstable parcel (EBSMU), the storm-relative helicity in the 0–500-m layer (SRH500m), and two composite parameters, the Severe Hazards in Environments with Reduced Buoyancy (using wind shear over the effective inflow layer, SHERBE) and the Significant Tornado Parameter (STP), were analyzed during tornadoes from 1980–2023. Tornadoes in Chile tend to form in environments with lower MUCAPE than those along the U.S. west coast. However, EBSMU, SRH500m, SHERBE, and STP tend to be larger during tornadoes in Chile. This results in 50% of tornadoes in Chile, but only 25%–38% of tornadoes along the U.S. west coast, forming in high-shear, low CAPE (HSLC) environments. A cool, saturated boundary layer, low-level moisture fluxes, low cloud bases, and curved hodographs characterize the tornadic environments in all regions. Lightning activity is observed in at least 65% of tornadic storms in each region, but the largest flash density occurs during tornadoes in northern California. These results represent a significant advance in our understanding of the mesoscale conditions during tornadoes in Chile and along the U.S. west coast.