Inter-tropical convergence zone (ITCZ) is a region where the northeast and southeast trade winds converge. This convergence results in the uplift of moist air and leads to the formation of cumulonimbus clouds, thunderstorms, and cyclones.

In the South Atlantic and southeastern Pacific regions, the ITCZ seldom occurs. This is because these regions are located in the subtropical high-pressure belt, where the air is descending and dry. As a result, there is very little uplift of moist air, which is necessary for the formation of cyclones.

Sea surface temperatures in these regions are warm enough to support the formation of cyclones. The Coriolis force is also strong enough to initiate the rotation of the cyclones. However, without the uplift of moist air in the ITCZ, the formation of cyclones is unlikely.