A climatological study of convective cloudbands in northeastern Brazil Part I: preliminary analysis

This work analyses the role of convective cloudbands (CCBs), associated wit h low-level convergence zones on the northeast region of Brazil (NE). A pre liminary analysis of synoptic situations based on six years of meteorologic al satellite images and observed rainfall data for the region is presented. The results show two main patterns of CCBs. The first one classified as ty pe A has a NW-SE orientation. It is associated with convergence zones due t o cyclonic vortices or fronts, both rain-producing systems that reach mainl y the southern, central and western regions of the NE. The second pattern ( type S) results from interactions between frontal systems and upper-level c yclonic vortices over the Atlantic Ocean, to the east of the NE, as well as with the intertropical convergence zone (ITCZ). These frontal systems or c onvergence zones move northeastward and remain semistationary over the sout heast coast of Brazil. The north-south orientation of these CCBs seems to b e responsible for above average rainfall over the western and central parts of the NE. The type A cases are observed more frequently in October and No vember, while the type S cases are common in January, February and March. D ecember is considered to be a transition month.