Predictive diagnosis of El Niño based on empirical sea level anomaly forecasts

The aim of this paper is to present the skills of two statistical models in anticipating the development of El Niño based on sea level anomaly (SLA) forecasts with lead time up to 12 weeks. The models are: (1) the polynomial-harmonic model (PH) combined with the threshold autoregressive model (TAR), known as the PH+TAR, and (2) PH integrated with the multivariate autoregressive model (MAR), referred to as PH+MAR. Five powerful El Niño events are considered: 1997/1998, 2002/2003, 2006/2007, 2009/2010, 2015/2016. The performance of the prediction models is calculated in specific locations in the equatorial Pacific, i.e. centres of Niño 1+2, Niño 3, Niño 3.4 and Niño 4 regions. It is found that the SLA predictions hitting the El Niño peaks reveal different accuracy for dissimilar El Niño events, with the most skillful prognoses for El Niño 1997/1998. Two specific regions are identified in which the model performance fulfils the assumed accuracy limit of 5 cm, namely the Niño 1+2 and Niño 4 regions. In addition, the PH+MAR model performed better than the PH+TAR solution.