Year 2 ENSO Predictability is Highly State Dependent

The El Niño-Southern Oscillation (ENSO) is the dominant source of subseasonal, seasonal, and multi-year climate variability and theoretical predictability. Forecast skill at leads greater than 12 months has been found in a variety of forecast systems, but the underlying dynamical states leading to long-lead predictability have not been investigated in depth. This lack of investigation is in large part due to the cost of running dynamical model predictions. In this study, we create enormous, multi-model hindcasts experiments totaling 10,000s of forecasts using model analog climate forecasts and show that multi-year ENSO predictability is predominantly due to high multi-year skill following strong El Niño events.