Understanding Long-Lead ENSO Predictions within the Framework of Recent ENSO Events.

A strong El Niño frequently precedes a La Niña. However, the remarkable duration and extent of the 2015/16 El Niño may have contributed to the demise of the 2016 La Niña. The strong El Niño appears to have introduced unexpected uncertainties into the seasonal forecasting of El Niño-Southern Oscillation (ENSO). Whiles the physical processes governing the evolution of both the 2015/16 El Niño and the 2016 La Niña are well understood, the frequent variations in the probability of recent ENSO events due to the changing behavior of ENSO remains an important area of research. The analysis presented is focused on using observational datasets and model simulations to understand the reasons for the changing behavior of recent ENSO events, as well as understanding ENSO behavior in the context of long-lead ENSO prediction potential and the various ENSO precursor patterns. One example is the North Pacific climate variability that involves the Pacific Meridional Mode and the Western North Pacific (WNP) mode, which have been shown to be skillful predictors for the development of ENSO a year in advance. Observational results suggest the predictive power of the PMM/WNP may have changed over time, particularly under the current global warming dispensation. Model diagnoses will be presented.