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10/18/2018, 7:42 am EDT

Early AG Wire: South America Update

Argentina dry persistence weighs more heavily than wetter operational forecasts. Models are much too wet in Argentina 30-day rainfall: Wetter-than-normal conditions have been present across Southeast Brazil to Uruguay and into eastern Paraguay the past 30 days (Fig. 1) while much of central and especially northwest Brazil has been quite dry. In Argentina dryness has dominated the north-central and northern tier (Fig. 2) the past 30 days. Fig. 1-2: Rainfall anomalies across Brazil and Argentina the past 30 days. Current satellite: A large plume of heavy thunderstorm activity is located across Sao Paulo with another area of heavy rain in southern Buenos Aires. A small but intense thunderstorm was located in northeast Argentina. Fig. 3: Current satellite/precipitation measurement across South America. Day 1-5 outlook: Both the GFS and ECM OP initiate their short-term model run(s) too wet across Paraguay to southeast Brazil today. While a large area of afternoon thunderstorm activity, similar to yesterday is likely across southeast and southwest Brazil into Paraguay the activity forecast over north/northwest Argentina looks to robust into the weekend. Similarly, due to a lack of synoptic trigger heavy thunderstorms into late weekend over northwest/north Argentina forecast by both models looks overdone especially given dry persistence. Day 6-10 outlook: A more vivid trigger to produce anomalous rainfall is indicated Paraguay to far Southeast Brazil early period lifting north into Interior Southeast Brazil later next week. This area has been wet in SEP/OCT and is likely to gain more significant rainfall. Argentina (correctly) trends drier. Day 11-15 outlook: GFS pushes the Brazilian rainfall farther north across areas that have been dry. The model may be too wet in Argentina where 2-3 plumes of thunderstorms are forecast. Climate: The Madden Julian oscillation is forecast to intensify in phase_1 during the 8-14/11-15 day period. Phase_1 increases the risk of significant rainfall in Brazil.