Índices de instabilidade na ocorrência de Distúrbio Ondulatório de Leste no Nordeste do Brasil.

Abstract

The Brazilian Northeast has a very large variety of weather with long periods of lack of rain and rainy quarter with big spatial variation. At least three meteorogical phenomena influence the rainfall of the region. These phenomena were determined by using the technique of main data and the weather data from 1961 to 1990. In the eastern of the region there are "Easterly Waves Disturb" (EWD) that cause a large amount of rain, most of the time, over 22.0mm/day. These weather systems in tropical atmosphere amidst disturbances in the pressure field from east to west and get the Brazilian Northeast coast, what makes difficult to have a precise weather forecast, since the known theories do not adjust well to this region. The index of atmospheric instability are empirical, but very useful at high latitudes, although their values depend very much on where they are applied. They were studied to determine values that can be used as indicators of the EWDs occurence. With this purpose we used radiosonde data and model analysis to find out and determine characteristic values of 10 indices to the occurence of 126 cases that reach the east Brazilian coast from 2009 to 2012. Weather forecast for 72 hours were also obtained from the forecast model BRAMs with the purpose of comparison with the forecast observed data and infer how the atmospheric indicator can be used from the model that can produce a tool that helps as predictor of EWDs. The results show that some indices obtained from radiosonde or models have characteristics values that can be good indicators of these systems. It will be given to support the makingdecision organs to contribute to the reduction of damage to population in case of heavy rain, since the east of Brazilian Northeast is the most populous area in this region.