Fig. 1-3: ECM ENS 15-day temperature and precipitation anomaly forecast for South America and the corresponding upper air pattern.
Summary: A difficult South America forecast yields a regenerating upper-level high-pressure ridge pattern across the marine heat wave east of Argentina during the medium-range. However, the compensating upper-level low-pressure trough located over Southeast Brazil for much of the last several months is likely to persist. Consequently, dynamics to generate significant rain remain intact in much of Brazil and just on the back side of that wet regime, Argentina is mostly dry. The pattern is similar to last summer except adjusted slightly farther southwestward. In the drier climate zone, the tendency is for hotter than normal temperature while Brazil rains suppress temperature (Fig. 1-2). The 15-day upper air forecast reveals a strong influence of the upper trough this week and during the medium-range the trough shifts westward to Southeast Brazil (Fig. 3). The proximity of the trough to Argentina can, at times, generate surprise rains as observed last week and indicated by one model (GFS) in the 11-15-day period. The bottom line? Argentina drought continues but a super drought or flash drought is less likely given the current upper air pattern forecast. Later this summer, the upper trough is forecast to shift east and northeast allowing some drying into Southeast Brazil.