Previsão por conjunto e características sinóticas de um evento de chuva intensa na região Sul do Brasil

Abstract

The period between 23 and 30 June 2014 was marked by heavy rainfalls and floods in Southern Region of Brazil. The goals of this study is analyze the atmospheric conditions that make this event possible and verify if it was possible to forecast this event using ensemble GFS model and forecasts based in different physical parametrization of WRF. In addition, the cost-benefit relationship between GFS and WRF ensemble forecasts was evaluated. It was observed a transition of a cold front and the formation of two low pressure areas on the region. Both ensembles forecasts showed accumulated rain closer to the observed in the days 23, 24 and 25 with a highlight to the ensemble of the WRF with initialization 24 hours before the beginning of the event showing a better accuracy. Besides that, it was verified more uncertainty between the members of the GFS ensemble, since only 40% of the members indicated rainfall probability equal or more than 40 mm, while 80% of the members of WRF ensemble, with initialization of 24 hours before the beginning of the event, indicated rainfall for the same threshold. The ensemble made with WRF showed a better performance in respect with the occurrence of the event, in relation with that of GFS.