Spring Rains Erode Brazil and Argentina Long-term Drought

Charts of the day: Recent rainfall and daily soil moisture anomalies.

Discussion: The wet pattern starting December 2024 is (mostly) across Argentina extending northward to Southern Brazil. North of the wet zone, most of Brazil is drier than normal. The daily soil moisture analysis reveals the effectiveness of spring rains at eroding both Argentina and Brazil long-term drought.

Week-2 Valid December 15-21, 2024: Southeast Brazil trend is drier.

Discussion: A dynamic upper air forecast features a trough southeast of Brazil and ridge over Central Brazil. The sensible weather is wet due to the low pressure area in East Brazil but dry on the subsidence side of that convective rain across Southeast Brazil. Central Brazil is normally wet and warmer than normal. Argentina trend is wetter.

Week-3 Valid December 22-28, 2024: Wet East Brazil.

Discussion: Weak upper trough delivers wet weather to much of East Brazil. Southeast Brazil stays on the drier side. Argentina is hotter and drier.

Week-4 Valid December 29, 2024-January 4, 2025: Drier Brazil Coast.

Discussion: Weak low pressure spawns a pattern possibly wetter than indicated especially in Brazil. High pressure may dry-out Coastal Brazil.