11/17/2022, 5:15 am EST

South America Month 1-4 Outlook: Summer outlook emphasizes heat, dryness, and drought in Argentina. Brazil drought concerns mostly confined to the far southeast.

Executive Summary: The Climate Impact Company month 1-4 ahead climate outlook for South America valid through the entire warm season emphasizes anomalous heat and dry risk for Argentina where a major drought and possibly flash drought is expected. Highest risk is in the north/northeast portion of the nation/ The dry risk reaches northward into Paraguay and far southeast Brazil. However, to the north, the remainder of Brazil should avoid a major drought during upcoming summer. Climate: During the past several months, the upper air pattern across South America has featured an upper-level low-pressure trough centered on Southeast Brazil (Fig. 1). Consequently, a wet zone formed stretching from Paraguay to Interior Southeast Brazil (Fig. 2). Soil moisture conditions identify the wet conditions across this stretch (Fig. 3). The upper low shifts slightly east-northeast the remainder of November (Fig. 4) and maintains a wet pattern across East and Northeast Brazil while just the opposite regime is not far to the west, dryness for Argentina into Southwest Brazil (Fig. 5). The implication is the dryness dominating much of Argentina expands northward into Southwest to far southeastern Brazil and similar too last year. An upper-level high-pressure ridge is present across the marine heat wave (MHW) to the east of Argentina. During November, the high-pressure area is unusually amplified and helping to maintain dry-to-drought conditions in Argentina. Where the upper low and high migrate during summer 2022-23 is the driving force behind where drought may emerge. La Nina remains intact and the atmospheric La Nina is quite strong. A La Nina climate is certain to last through summer 2022-23 despite any weakening of oceanic La Nina in 2-3 months (Fig. 6). The tropical South Atlantic (TSA) index is in the warm phase and a catalyst for wet climate in north/east Brazil. However, NMME global SSTA forecasts ease the +TSA regime during the summer season (Fig. 7). Fig. 1-2: The upper air pattern across South America since Aug. 1st and the attendant rainfall anomaly pattern. Fig. 3-4: South America soil moisture anomalies and the upper air pattern projected for the remainder of November. Fig. 5-6: The percent of normal rainfall for the next 15 days across South America according to ECM ENS and the 2023 IRI/LDEO Nino34 SSTA probability forecast. Fig. 7: The IMME global SSTA forecast for February 2023. Methodology: The monthly climate forecasts for December 2022 through March 2023 is based on a constructed analog featuring La Nina, strong presence of the marine heat wave east of Argentina, weakening warm phase of the tropical South Atlantic index and distant presence of the Amundsen Sea upper trough. December 2022: The first month of meteorological summer is expected to maintain an upper trough on the Southeast Coast of Brazil while subtropical high-pressure ridging stretches across Southern Argentina. The precipitation pattern generated by the upper air features dryness across the Argentina drought region extending north into Southeast Brazil. In Brazil, the western part of the nation is very wet while East-central Brazil also receives above normal rainfall. In December, Central Argentina is somewhat hotter than normal while the East/Southeast Coast of Brazil is less hot than normal. Fig. 8-9: Climate Impact Company December 2022 constructed analog temperature and precipitation anomaly forecast for South America.  January 2023: In mid-summer, the upper trough stubbornly remains anchored over Southeast Brazil while the core of the subtropical ridge is highly amplified east of Argentina. The sensible weather pattern offers above normal cloudiness and wet weather risk which suppresses mid-summer heat beneath the upper trough in Southeast Brazil. In Argentina, anomalous heat and dryness accelerates drought. Northeast Brazil trends drier as the tropical South Atlantic cools to near normal. Paraguay is also wetter than normal due to thunderstorms during January. The forecast trend is hotter/drier in Argentina and wetter/cooler Southeast Brazil. Fig. 10-11: Climate Impact Company January 2023 constructed analog temperature and precipitation anomaly forecast for South America. February 2023: Late summer produces expansion of the upper trough over the Amundsen Sea well southwest of South America toward the south coast while the subtropical high weakens and shifts east of Argentina. A weak upper trough persists across northwestern South America. The upper trough may be in response to the expected breakdown of La Nina. The sensible weather stays hot across Argentina and Northern Argentina is drier than normal. Southeast Brazil shifts into a drier pattern and wet weather becomes established over Northwest and North Brazil. The forecast trend is emphasis on dryness for Southeast Brazil to North Argentina and maintaining the hot summer of 2022-23 in Argentina.   Fig. 12-13: Climate Impact Company February 2023 constructed analog temperature and precipitation anomaly forecast for South America. March 2023: As summer shifts to autumn, dryness, and anomalous warmth shift northward across the eastern half of Brazil. In Argentina, anomalous heat and dryness persists. The northwest continent is where the heavy rain gathers for the end of the warm season. Fig. 14-15: Climate Impact Company March 2023 constructed analog temperature and precipitation anomaly forecast for South America. Summary: The Climate Impact Company constructed analog (CIC-CA) climate forecast for South America during meteorological summer 2022-23 indicates persistent anomalous heat and dryness in Argentina where flash drought is quite possible (Fig. 22-23). The dryness extends to Southeast Brazil although less consistent. Far Southeast Brazil has a drought risk for summer 2022-23. The remainder of Brazil Crop Areas is normally wet with diminished drought risk. The CIC-CA forecast is generally consistent with climate probability outlooks issued by IRI (Fig. 24-25). Fig. 16-17: Climate Impact Company DEC/JAN/FEB 2022-23 constructed analog temperature and precipitation anomaly forecast for South America. Fig. 18-19: The International Research Institute for Climate and Society DEC/JAN/FEB 2022-23 temperature and precipitation probability forecast for South America.