Synoptic Analysis of a Period with Above-normal Precipitation during the Dry Season in Southeastern Brazil

Abstract

This study presents an analysis of a period with positive precipitation anomalies and anomalous severe weather activity in parts of the Southeastern Brazil during the dry season (austral winter). The objective of this work is to identify the synoptic pattern associated with the severe episodes on August 2018. The analysis was based on observational data and the CFSR (Climate Forecast System Reanalysis). Standardized anomalies of the main meteorological variables were used in the analysis. An anomalous trough in the mid and upper troposphere and the associated low-level flow from the Amazon Basin to Southeastern Brazil provided high amount of precipitable water, and were the main responsible for the rainfall markedly above the climatology along with severe hail and strong winds. The atmospheric environment was conditionally unstable due to a stationary front. These type of analyzes should be taken into consideration at this time of year to improve weather forecasts and minimize impacts in such circumstances.