The distribution of rainfall is related to the regime of winds and air masses. In most of the tropical region east of the Andes, winds blowing from the northeast, east and southeast carry moisture from the Atlantic, causing abundant rainfall. However, due to a consistently strong wind shear and a weak Intertropical Convergence Zone, tropical cyclones are practically unknown in the South Atlantic. In the Orinoco lhanos and in the Guianas plateau, the precipitation levels go from moderate to high. The Pacific coast of Colombia and northern Ecuador are rainy regions. The Atacama Desert, along this stretch of coast, is one of the driest regions in the world. The central and southern parts of Chile are subject to extratropical cyclones, and most of the Argentine Patagonia is desert. In the pampas of Argentina, Uruguay and South of Brazil the rainfall is moderate, with rains well distributed during the year. The moderately dry conditions of the Chaco oppose the intense rainfall of the eastern region of Paraguay. In the semiarid coast of the Brazilian Northeast the rains are linked to a monsoon regime.