Executive Summary: The Climate Impact Company season 1-4 ahead climate forecast for South America is updated. The forecast is based on a constructed analog correlating historical upper air patterns with prevailing ENSO conditions and SSTA regimes either side of the continent. Departing summer 2023-24, despite some late summer rains, Brazil soil moisture is mostly below normal, and drought is present for some areas. The 2020-23 Argentina drought eased due to El Nino rains. Looking ahead through 2024 toward the next warm season, climate forecasts favor regenerating drought in Central to East/Southeast Brazil and possibly parts of Argentina to the west and southwest of Uruguay for next spring and summer. The winter season ahead faces above normal risk of a cold surge into Southwest/Southeast Brazil during mid-winter. Climate discussion: Beginning in early 2023, soil moisture conditions featured an intense lengthy La Nina-inspired drought across far Southeast Brazil, Uruguay, and Northern Argentina. Soil moisture conditions have reversed one year later featuring a wet soil profile in Southeast Brazil with general dry soil conditions across the remainder of Brazil. Meanwhile, the long-term drought in Argentina has eroded. The soil moisture reversal is linked to evolution of the 2023-24 El Nino episode. The 2023-24 El Nino episode is unique in that oceanic El Nino (Nino34 SSTA) has been substantially stronger than the attendant reaction of the atmosphere (multivariate ENSO index). Interestingly, the opposite was true of the 2020-22 La Nina (Fig. 1). The explanation is related to the SST gradient between the equatorial region where ENSO phase is measured and the poleward subtropical ocean SSTA pattern. During El Nino, the lack of thermal gradient between the anomalous warm equatorial region and warm SSTA in the subtropics lead to diminished SST gradient correlated to a weaker El Nino climate. During La Nina, the cool equatorial waters vs. the warm subtropics created a large SST gradient correlated to a strong La Nina climate. In this regime, South America La Nina climate should be stronger than El Nino climate. Looking forward, El Nino 2023-24 is expected to weaken over the next few months. Recently, upper ocean heat in the equatorial Pacific diminished rapidly implying the robust El Nino signature at the surface will begin to fade soon. The speed of subsurface cooling increases the validity of the NCEP CFS V2 rapid transition from El Nino in early 2024 to a robust La Nina later this year (Fig. 2). If the NCEP CFS V2 prediction is correct, the Climate Impact Company constructed analog projects La Nina continuing to DEC/JAN/FEB 2025-26 (Fig. 3). In the northern hemisphere, an optimum climate normal (OCN) is used by Climate Impact Company accounting for the tendency of strong warming of the mid-latitude oceans and their influence on the prevailing climate pattern. In the southern hemisphere, this approach is used for the past 5 years (2019-23) due to the persistent robust warming of the ocean surface east of Argentina and the consistently strong marine heatwave (MHW) surrounding New Zealand extending westward toward Chile in recent years. The prevailing influence on the upper air pattern of the oceanic warming described is increased high pressure from west of South America to Brazil. Interestingly, the NMME global SSTA forecast indicates the warm SSTA pattern of the past 5 years is in retreat by the midpoint of 2024. The projections are a closer match to the 2014-18 less aggressive mid-latitude warming. Fig. 1: Oceanic (Nino34 SSTA) and atmospheric (multivariate ENSO index) ENSO conditions are compared for this decade so far. Fig. 2: The NCEP CFS V2 Nino34 SSTA forecast through October 2024. Fig. 3: The Climate Impact Company constructed analog Nino34 SSTA forecast through DEC/JAN/FEB 2025-26. Climate summary: El Nino is confidently forecast to shift into La Nina around or just after midyear. A lengthy La Nina is likely to follow lasting through next year. Unlike the past 5 years when prohibitive warming of the ocean surface on each side of South America occurred, a less robust warm pattern similar to the 2014-18 climatology is forecast through next year. Forecast methodology: A constructed analog based on past similar ENSO regimes combined with the 2014-18 OCN correlated to the atmospheric upper air pattern generates the seasonal forecasts beginning with meteorological spring 2024 and ending with meteorological winter 2025-26. Also considered are soil moisture conditions for the warm season outlooks. MAR/APR/MAY 2024: El Nino shifts to neutral phase. The El Nino climate may linger. Ocean temperatures are much warmer than normal in the South Atlantic tropics. However, waters on either side of the subtropical/mid-latitude coastlines cool to near normal. The projected prevailing upper air pattern for the period features an upper ridge over Brazil fueling a warmer and drier than normal autumn season. To compensate, an upper trough is semi-permanent across Southeast Brazil. The upper trough causes a wet autumn in Northeast Argentina to Southeast Brazil and a cooler than normal climate across Northern Argentina. In Brazil, dry soils regenerate during autumn and any lingering summer drought worsens. Fig. 4-5: The Climate Impact Company constructed analog forecast of temperature and precipitation anomalies valid for MAR/APR/MAY 2024. Previous forecast below. JUN/JUL/AUG 2024: Meteorological winter 2024 produces a semi-permanent upper-level ridge over Brazil while a large upper trough extends from near the Amundsen Sea off Antarctic to southwest of South America. If the Amundsen Sea trough extends to the southern half of South America during mid-to-late winter, risk of a cold outbreak reaching Southern Brazil occurs. Given the weakness in the upper air projection from southwest of South America to east of Uruguay, the risk of the cold scenario is above average. The prevailing winter climate features warmer than normal conditions across the northern half of Brazil and near normal temperature for Southern Brazil to Northern Argentina. Wetter than normal climate is projected for central continent while northern continent is dry. Fig. 6-7: The Climate Impact Company constructed analog forecast of temperature and precipitation anomalies valid for JUN/JUL/AUG 2024. SEP/OCT/NOV 2024: Meteorological spring 2024 features a stronger than normal subtropical ridge into East Brazil while a strong upper trough off the Southeast Brazil Coast occasionally extends across central continent to drive a wet climate pattern for Southwest Brazil and Paraguay. The upper ridge leaves Northern Brazil warmer than normal while East Brazil is mostly dry. Argentina is unusually cool during the spring season. Drought conditions are likely in Central to East Brazil with a marginal drought risk in Argentina to the west-southwest of Uruguay. Fig. 8-9: The Climate Impact Company constructed analog forecast of temperature and precipitation anomalies valid for SEP/OCT/NOV 2024. DEC/JAN/FEB 2024-25: Next summer season, an upper low is forecast to drop anchor much of the time over Uruguay. Consequently, wet weather is persistent across Southwest Brazil, Paraguay, and Northern Argentina. Just north, East Brazil is dry and hot. Drought conditions are likely to develop east of Paraguay toward the Brazil Coast and northwestward toward Central Brazil. An upper-level high pressure ridge heats Central Argentina where climate is likely drier than normal. The north coast of South America is wet in response to a La Nina climate pattern. Fig. 10-11: The Climate Impact Company constructed analog forecast of temperature and precipitation anomalies valid for DEC/JAN/FEB 2024-25. The year-2 ahead forecast is issued separately.