Upper tropospheric cyclonic vortices in the tropical South Atlantic

An analysis of subtropical 200 mb cyclones is made for the South Atlantic. The cyclones are observed to occur primarily during the summer months and generally form near the axes of the mid-oceanic troughs. The relationship between cyclone formation and the presence of 200 mb anticyclones over the continental areas is discussed. Proposed mechanisms for cyclone formation are considered. The cyclones are characterized by a cold core and a direct thermal circulation–the cold air sinking and warm air on the periphery rising. The cloud pattern associated with the cyclones is found to depend on the direct thermal circulation, the vortex location and its direction of movement. The effects of South Atlantic 200 mb cyclonic vortices on Brazilian weather are discussed.