An El Nino climate is projected to develop during the second half of 2026 and continue into early 2027 across South America. The Climate Impact Company constructed analog (CIC-CA) climate forecasts for the next 4 seasons are based on the evolution of an El Nino climate plus influences on climate from the tropical South Atlantic SSTA regime and tendency for strong marine heatwaves off each coast.

Two marine heatwaves (MHW) are located off the U.S. and Baja California West Coast. MHW NEP25A reached record aerial coverage last autumn although weaker now while MHW NEP25B formed late last year, persisted all winter, and strengthened. Meanwhile, the Gulf of Mexico SSTA is +1.35C ranking in the top 1% warmest (since 1982).

Vigorous positive phase of the North Atlantic oscillation is the lead climate signal supporting the warm pattern across the U.S. during the past 14 days. The negative phase of the Pacific North America (-PNA) has dominated in recent weeks although under-performing as a wet/snowy weather maker in the Northwest/West U.S. while the attendant dry signal for the Southeast is strong.

A check on skill scores for North America medium range forecasts as meteorological winter closes. Using anomaly correlation provided by CWG/SVMW, the 6-10-day skill scores indicate AIFS ENS remains (routinely) the top model. ECM ENS typically ranks second to AIFS ENS and collectively, using both 30-day and 7-day skill scores, that ranking remains.