It is well established that the rainfall over central Brazil gradually decreases during the month of April. The observed rainfall over most parts of Brazil was less than normal, as was the case in the previous month. Above normal rains were registered only in South Brazil and northwestern Northeast Brazil.

Reduced rainfall over the large river basins such as Rio Grande, Rio Parnaíba, Rio Paraná and Rio São Francisco resulted in the reduction of volume of water in the reservoirs of the major hydroelectrics projects of the country. In Northeast Brazil the Sobradinho reservoir in the state of Bahia registered a discharge 66% less than normal during this month. The volume of water in the reservoir was only 39% of its capacity due to reduced rainfall and excess and uncontroled consuption of electric power during the previous months. This situation led the authorities and the population to be alert and to introduce measures for possible rationing of electric power in the country. In South Brazil, however, the water levels remained higher than normal.

The Intertropical Convergence Zone (ITCZ) was active during April near the coasts of Pará, Maranhão and Ceará causing the formation of instability lines near the north coast of Brazil which were responsible for above normal rainfall in northern Pará and Maranhão. In the eastern parts of Northeast Brazil the rains were less than normal. Cold air incursions from the south caused moderate fall of temperature in South Brazil.

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