Estudos de dois casos extremos de precipitação sobre a costa leste do Nordeste do Brasil

Abstract

In this study, the genesis of two cases of extreme precipitation events on the East Coast of Northeast Brazil (NEB), which occurred during the period from October 1999 to September 2000, was analyzed, with the objective of improving knowledge about the meteorological systems involved and their consequences on this region. The analyses were made from daily precipitation recorded at rain gauge stations, satellite images and reanalysis data from the National Centers for Environmental Prediction (NCEP). The first case was of an Upper Tropospheric Cyclonic Vortex (ULCVO) formed over the Equatorial Atlantic Ocean in early January 2000, and intensified on the 4th and 5th, when one of its active branches was over the NEB. The positioning of the Bolivian High over the west coast of South America, the anticyclonic circulation associated with the vortex near the west coast of Africa, and the more equatorial position of the Northern Hemisphere (NH) subtropical jet appeared to be indispensable elements for the genesis, persistence and control of the VCAN displacements over the NEB. The second case studied, between July 31 and August 2, 2000, was generated by the confluence of two synoptic scale systems, a wave disturbance in the trade wind field, originating from E-SE, and remnants of a frontal system, whose low pressure center was located over the Atlantic Ocean. From this interaction, an intense convective complex developed over the East Coast of the NEB. The complex reached its maximum intensity in the early hours of August 1, when rainfall totals reached 300 min/day on the southern coast of Pernambuco. The following day, the convective complex moved northward, over the coast of Paraíba and Rio Grande do Norte, where rainfall totals were lower but significant, reaching approximately 100 mm/day.