A multiscale analysis of the tornadoes of 30–31 May 2019 in south-central Chile

Abstract

Abstract On 30 and 31 May 2019, tornadoes occurred in the cities of Los Angeles and Talcahuano/Concepcion in south-central Chile, in a region where tornado activity is not common. The main goal of this study was to analyze these tornadoes across multiple scales: synoptic, mesoscale, and subseasonal. On the synoptic scale, the tornadoes were associated with an anomalous 500-hPa trough and associated surface cyclone to the west of Chile. A strong (20+ m s−1) low-level jet accompanied this trough, potentially enhanced by flow blocking by the Andes. A relatively warm and saturated surface layer combined with cold upper-level temperatures in the trough to yield 200–500 J kg−1 of CAPE on both days. This CAPE was accompanied by high levels of both deep-layer and low-level shear. Storm motions inferred by lightning swaths and GOES-IR imagery, along with estimates of storm motion and updraft helicity from a high-resolution WRF simulation, suggested this CAPE-shear combination was sufficient for the tornadic thunderstorms to be supercells. Finally, anomalies of sea level pressure, 500-hPa height, and surface dew point temperature from 27 to 31 May 2019 resembled long-term composite anomalies for MJO phases 1 and 2, suggesting a subseasonal link between the extreme event in Chile and convection in the tropics.