Analysis of a hailstorm in the south of Minas Gerais state on October 13, 2020

Abstract

On October 13th, 2020, at approximately 1940 UTC, a hailstorm struck the city of Itajubá, located in the south of the Minas Gerais state, Brazil. This hailstorm produced hail with a diameter of 5 cm causing damages in roofs of houses and shelters. In this sense, the objective of this study is to describe the synoptic-scale environment that lead to the “ingredients” necessary for the mesoscale development of the storm, and to provide a description of cloud microphysical and lightning properties. Several data sources were used in this study as: surface observations, reanalysis data, and atmospheric remote sensing information. The synoptic-scale environment conducive to storm formation was associated with an inverted trough at surface and a shortwave trough at upper-level levels, which were important to organize upward movements in the atmosphere. High reflectivity (> 60 dBZ) was registered in the convective cell from 1940 to 2010 UTC, according to the São Roque radar data, indicating the presence of large raindrops and/or hail on the ground. The total lightning rates increased from the beginning of the storm, reaching ~ 80 lightning/5 min around 20 min before the hail precipitation, which occurred at 1920 UTC. This study highlights the importance of associating synoptic and physical information for understanding the environment and the main features of hailstorms. It also emphasizes the significance of producing information that can aid in nowcasting tools.