Two severe freezes in Brazil: precursors and synoptic evolution.

Abstract

Two freezes with repercussions on world coffee markets struck Brazil in recent years, one during FGGE in 1979, the other in 1981. Data from multiple sources including satellites and drifting buoys were analyzed for early warning signs and synoptic evolution of the freeze events. Two important precursors were found: a slowly moving long-wave pattern in the central South Pacific Ocean amplified greatly one to two days before frontogenesis in South America and four to five days before the freezes in Brazil; the long-wave ridge, when at maximum amplitude, was located near the southern Andes, and the next long-wave trough downstream was located in the South Atlantic at the longitude of Brazil. This configuration channeled subantarctic air northward entirely over land into subtropical latitudes. -from Authors