Analysis of the Atmospheric Environment associated with the Extratropical Cyclone that formed in Rio Grande do Sul – July 2023

Abstract

This study aims to describe and identify the synoptic-scale atmospheric environment associated with the extratropical cyclone that hit the state of Rio Grande do Sul on July 12 and 13, 2023. The passage of the cyclone affected 82 municipalities, affecting 5,889,672 people, of which 55,912 were directly impacted, with 620 displaced, 7,504 houses unroofed, and 58 houses destroyed. To analyze the event, images from the infrared channel of the GOES16 satellite and reanalysis data from ERA5 were used to obtain the meteorological fields. The synoptic analysis demonstrated the formation of the already intense system still over the continent, and that dynamic and thermal factors contributed to its occurrence. The dynamic forcing was the advection of cyclonic vorticity due to the presence of a mid-level trough (500hPa) upstream, and the thermal related to the transport of heat and moisture from the north, which contributed to the intensification of the system. The origin of the low pressure system began over the interior of the continent, the so-called Northwestern Argentinean Low (NAL), intensified by a strong convergence of the moisture flux at low levels, with the presence of the low-level jet and diffluent flow at high levels.