A unique set of C-band meteorological radar echoes is analyzed. The data were obtained in Petrolina (9°24′S, 40°30′W), located in the semi-arid region of Northeast Brazil, from January to June 1985. The characteristics analyzed are echo areas, types and patterns. As in other tropical areas of the world, echoes with an area≤100 km2 dominated, making up 53% of the total number of echoes while echoes with 100 km2<area≤400 km2 accounted for 36% and the larger echoes, the remaining 11%. A linear correlation analysis between the parcel convective energy and the number of echoes within different classes of horizontal area resulted in a positive correlation for echoes with areas≤400 km2 only. The largest precipitation areas found in this study were shapeless, extensive, long-lasting stratiform rain areas covering about 35 000 km2. Satellite images and daily maxima surface rainfall rates give evidence that they are associated with mesoscale convective systems formed in the presence of an upper tropospheric high amplitude trough or cyclonic vortex. The echoes were classified following two criteria. The first classification is based on lifetimes and horizontal reflectivity gradients obtained from the Plan Position Indicator (PPI) and Range, Height Indicator (RHI) images, which allowed the identification of convective, stratiform and stratiform with embedded convection echoes, the last one being an intermediary class assigned to intense precipitation cells embedded within stratiform rain areas. The second classification is based on the apparent degree of organization observed on the PPI images, which allowed identification of five distinct patterns: scattered echoes, zone of echoes, line of echoes, strip of echoes and band of echoes. Results show convective echoes to account for 98.78% of the total number of echoes. They occurred throughout the period of study, being more frequent in the southeast quadrant of the radar coverage. A relatively high frequency of stratiform echoes (0.8%) occurred in January only. Scattered echoes and zones of echoes were observed during the entire period of study, being more frequent in March and April. Lines and strips of echoes were more frequent in March and April also. Bands of echoes occurred almost entirely in June. Preliminary analyses based on satellite images, surface maps and Petrolina surface and upper air data enable speculation that a system of frontal origin penetrating the radar area provided the dynamical forcing to form the bands in June. All five distinct patterns were more frequent in the southeast quadrant of the radar coverage. It is hypothesized that this preferential location may be explained, among other factors, by the interaction between the smooth relief and moisture advection by the southeasterly trade winds. Copyright © 2000 Royal Meteorological Society