A atuação de um ciclone explosivo próximo da costa sudoeste da América do Sul entre junho/julho de 2020 trouxe grandes prejuízos socioeconômicos para essa região. A previsibilidade limitada devido ao rápido aprofundamento da pressão em superfície, motivou o desenvolvimento deste trabalho, que tem como objetivo contribuir com informações que possam ser utilizadas para os setores de tomadas de decisão. A descrição sinótica foi feita através de dados de reanálise do European Centre for Mediun Range Weather Forecasts, as respostas observacionais de variáveis meteorológicas foram obtidas a partir das estações meteorológicas do Instituto Nacional de Meteorologia e imagens de satélite do GOES-16. A ciclogenêse foi observada as 11UTC do dia 29 de junho de 2020 e apresentou uma queda de pressão de 35hPa nas primeiras 16 horas, com taxa de decaimento de 2,2 hPa/h, chegando ao valor de 969 hPa no centro do ciclone. Nas horas seguintes, foi observado um aumento no valor da pressão em 3 hPa, chegando ao valor de 972 hPa em 24h. O ambiente pré-ciclogenético contribuiu para a formação de uma intensa linha de estabilidade na região centro-norte do Rio Grande do Sul, e no decorrer de todo o dia se propagou por toda a área de Santa Catarina e Paraná e por parte de Mato Grosso do Sul e São Paulo; causando rajadas de vento que ultrapassaram 100 km/h. As principais características relacionadas a ciclogênese e rápida intensificação foram um intenso escoamento do Jato de Baixos Níveis, intensa convecção, gradiente de temperatura e difluência em altos níveis em toda a região de atuação do ciclone explosivo. O sistema provocou intensas rajadas de vento na costa da região sul do Brasil, que ultrapassaram 116 km/h, além de grandes acumulados de precipitação.Palavras-chave: Ciclone extratropical, estudo de caso, América do Sul, ciclone bomba Description of atmospheric conditions associated with an explosive cyclone observed in Southeast South America in June / July 2020 A B S T R A C TThe action of an explosive cyclone near the southwest coast of South America between June/July 2020 has brought great socioeconomic damage to this region. The limited predictability due to the rapid deepening of pressure and surface, motivated the development of this work, which aims to contribute with information that can be used for the decision-making sectors. The synoptic description was made through reanalysis data from the European Centre for Medium Range Weather Forecasts, the observational responses of meteorological variables were obtained from the meteorological stations of the National Institute of Meteorology, atmospheric sounding and satellite images of GOES-16. The cyclogenesis observed at 11UTC on June 29, 2020 and showed a pressure drop of 35 hPa in the first 16 hours, with a decay rate of 2.2 hPa/h, reaching the value of 969 hPa in the center of the cyclone. In the following hours, an increase in the pressure value was observed in 3 hPa, reaching the value of 972 hPa in 24h. The pre-cyclogenetic environment contributed to the formation of an intense instability line in the north-central region of Rio Grande do Sul, and throughout the day it displaced throughout the area of Santa Catarina and Paraná and by Mato Grosso do Sul and São Paulo; causing wind gusts that exceeded 100 km/h.  The main characteristics related to cyclogenesis and rapid intensification were an intense flow of the Low Levels Jet, intense convection, temperature gradient and difluence at high levels throughout the explosive cyclone." The system caused intense wind gusts off the coast of southern Brazil, which exceeded 116km/h, as well as large accumulated precipitation. The main characteristics related to cyclogenesis and rapid intensification were an intense flow of the Low Levels Jet, intense convection, temperature gradient and difluence at high levels in acting region the explosive cyclone. The system caused intense wind gusts off the coast of southern Brazil, which exceeded 116km/h, as well as afinal large acumullated precipitation.Keywords: Extratropical cyclone, case study, South America, cyclone bomb

Weather and climate conditions directly influence the occurrence and dynamics of forest fires. And when they occur in environmental preservation regions, they have impacts on biodiversity loss, climate change and water security. This study identified the synotic patterns favorable to the occurrence of hotspot in the Ecological Station Region of the Taim and Campos Neutrais, both located in the extreme south of Brazil. In the study region, humidity deficits are more important than high temperatures, differing from what is described in the literature. Three synoptic patterns were identified: the first presenting negative anomalies of temperature and humidity, established after the passage of a cold front, which has as main contribution to generate a postfrontal stability, associated with the displacement of a high pressure system.  The second and third pattern (64% of wildfire) correspond to the most intense and long-lasting events, which occur in the presence of the South Atlantic Convergence Zone and Humidity Convergence Zone, respectively, and act on the northwest-southeast region of Brazil. These systems favor the slow displacement of a high pressure system over the study region, which contributes to the intensification of a stable environment, favoring moisture deficit and positive temperature anomalies in the study region. The results of this study provide an understanding of how the atmosphere influences the occurrence of wildfire in the study region, and will help in planning the minimization of the impact they can cause in an environmental preservation region