Condições de tempo severo e formação de tornados em Brasília-DF: um estudo de caso.

Abstract

The frequency of tornado formation in Central-West Brazil is low. A tornado observed in Brasília-DF on 01 October 2014 highligths the importance of using methods that allow a better understanding of the various atmospheric mechanisms that dominate in severe weather episodes, and the monitoring of this meteorological phenomenon with high destructive potential. The aim in this study was to analyze the vertical structure of the atmosphere that dominated the development of adverse atmospheric conditions and to identify convective parameters that are adequate for determining atmospheric patterns that favor severe weather development. The statistic technique Principal Component Analysis (PCA), instability indices and meteorological radar images were the main analysis methods employed. The results show that the combination of high degree of atmospheric instability, high temperatures and intense wind with gusts was determinant for tornado development. However, values of the instability indices differ from those normally used as indicators of tornado formation. Arc-shaped squall lines (“bow echoes”) detected by radar during the period of intense rainfall with damages at the surface are the strongest evidence of the tornado that hit the region. Photos of power lines, roofs, trees and cars damaged by the winds (95km/h) are presented also.