Executive Summary: The Climate Impact Company month 1-3 outlook valid for quarter 1 of 2024 is updated. The outlook is based on a constructed analog utilizing regional SSTA regimes and their correlating influences on the atmosphere lead by a west shifting warm SSTA pattern in the equatorial East Pacific, a sign of mature stage El Nino. The prevailing upper air pattern for Q1/2024 features a strong subtropical high-pressure area across Central Brazil made more effective by a similarly intense low-pressure area east of Argentina. In this pattern, the western half of Brazil is drier and hotter than normal accelerating drought risk. Long-term drought in Argentina has ended. Fig. 1-2: Climate Impact Company JAN/FEB/MAR 2024 temperature and precipitation anomaly forecast for South America. Climate: El Nino 2023-24 appears to be approaching the mature stage as waters off the northwest coast of South America have cooled from almost +4C in September to just above +1C in late December. The warmest anomalies are in the Nino34 region where ENSO phase is calculated and that reading is steady near +2.0C. Interestingly, the much weaker El Nino climate (as defined by multivariate ENSO index) continues. The daily southern oscillation index (SOI) has averaged near -0.40 during the past 30 days which qualifies as neutral ENSO. The tropical South Atlantic (TSA) index was historically warm one month ago and has weakened slightly. The oceans southeast of Brazil have warmed in December while a marine heat wave stretching from the Southeast Coast of Brazil to West Africa Coast has weakened. The ENSO outlook for Q1/2024 is peaking El Nino in January followed by steady weakening to neutral phase later in Q2/2024. Consequently, weakening El Nino governs the outlook for FEB/MAR while peaking El Nino governs the outlook for JAN. The warm SSTA region in the equatorial East Pacific should shift westward and slowly weaken over the next several months although El Nino maintains a relatively robust warm signature in the SSTA pattern by April 1st. Warming southeast of Brazil while east of Brazil is cooling is a recent and interesting phenomenon and not well forecast by global SSTA models. The warming waters southeast of Brazil are related to a semi-permanent high-pressure area during early meteorological summer. If the warming SSTA continues, the upper ridge in this position may stall through summertime. Preliminary look at December 2023 forecast verification: During December 2023 (so far), an upper-level high pressure ridge was positioned east-southeast of Uruguay ridging northwestward to Paraguay. Beneath the ridge axis, Southwest Brazil to Northwest Argentina were hotter than normal with an average departure of +2C to +4C (Fig. 3). The upper ridge kept most of Brazil hotter than normal while an upper trough off the coast of Chile caused cooler than normal climate across the southern half of Argentina. Above normal rainfall was observed across Western and East-central Brazil plus Northeast Argentina and Uruguay. Dryness prevailed across southwestern Brazil to the interior east sections and Northern Brazil (Fig. 4). The Climate Impact Company DEC-23 temperature outlook was too cool across Northern Argentina and reasonably correct for most of Brazil (Fig. 5). The precipitation outlook was reasonable except for a forecast that was too dry across Northern Brazil (Fig. 6). Fig. 3-6: December 2023 temperature and precipitation anomalies (so far) compared to the Climate Impact Company forecast. January 2024: Resurgent dry and hot weather redevelops across Amazonia during mid-summer. The wet zone shifts to Northeast Brazil. Some of the northeastern Brazil rains can extend toward Mato Grosso in January. However, while drought concerns ease back in Northeast Brazil, they remain intact for Central Brazil. A drier than normal bias is forecast across parts of Southeast Brazil to the east of Paraguay but not as dry as previously indicated. The wet pattern forecast for Northeast Argentina is consistent. Anomalous heat dominates most of Brazil strongest east of Paraguay and near Amazonia. Fig. 7-8: Climate Impact Company January 2024 constructed analog temperature and precipitation anomaly forecast for South America. February 2024: The late meteorological summer 2023-24 outlook remains consistent. Indicated is widening drier than normal climate across Brazil. A major Central Brazil drought is indicated by this forecast for late summer. The dryness expands into East Brazil after a wet period in this zone during mid-summer. Anomalous heat continues to cover all of Brazil accelerating the effectiveness of a dry climate on soil moisture. Wet weather remains in the Northern Argentina forecast where long-term drought has collapsed. Central and South Argentina are markedly cool. Fig. 9-10: Climate Impact Company February 2024 constructed analog temperature and precipitation anomaly forecast for South America. March 2024: A dry and hot bias remains over most of the western half of Brazil. Wet climate returns to East Brazil. The forecast remains consistent. In Argentina, the outlook is less wet and temperate while southern sections are not as cool as previously indicated. Entering meteorological autumn, a large drought remains intact across Central Brazil. Fig. 11-12: Climate Impact Company March 2024 constructed analog temperature and precipitation anomaly forecast for South America.