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

This work analyses the role of convective cloudbands (CCBs), associated with low-level convergence zones on the northeast region of Brazil (NE). A preliminary analysis of synoptic situations based on six years of meteorological satellite images and observed rainfall data for the region is presented. The results show two main patterns of CCBs. The first one classified as type A has a NW-SE orientation. It is associated with convergence zones due to cyclonic vortices or fronts, both rain-producing systems that reach mainly the southern, central and western regions of the NE. The second pattern (type S) results from interactions between frontal systems and upper-level cyclonic vortices over the Atlantic Ocean, to the east of the NE, as well as with the intertropical convergence zone (ITCZ). These frontal systems or convergence zones move northeastward and remain semistationary over the southeast coast of Brazil. The north-south orientation of these CCBs seems to be 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 November, while the type S cases are common in January, February and March. December is considered to be a transition month.