Wetter Pattern Change Heading for Central Brazil!

Fig. 1-2: Last week’s percent of normal rainfall and the deep layer soil moisture anomalies across South America.

Discussion: During Nov. 25-Dec. 2, 2023, the prevailing rainfall pattern across South America was drier than normal in much of Brazil while persistent rains were notable in Argentina (Fig. 1). The deep layer soil moisture anomalies are trending drier in much of Brazil signaling drought risk increase for the summer season ahead (Fig. 2). The latest 15-day percent of normal rainfall forecast utilizing the ECM/GFS/CMC mega-cluster ensemble is heavily reliant on ECM through 10 days and GFS in the 11-15-day period. Results indicate additional dryness in Central and East Brazil this week with wet focus on Uruguay and vicinity plus the North Coast of South America (Fig. 3). In the 6-10-day period, the trend is wetter in Brazil although heaviest rain is across Paraguay to Southeast Brazil (Fig. 4). In the 11-15-day period, an upper trough settles over Eastern Brazil and initiates a wetter pattern change (Fig. 5). In the extended period, the ECM week 3-4 forecast expands the Brazil rains across Central Brazil easing drought concern in that region (Fig. 6).

Fig. 3-5: Mega-cluster “most likely” 15-day percent of normal rainfall forecast across South America.

Fig. 6: ECM “weeklies” forecast a wetter pattern change across Central Brazil.