This replaces simple persistence as a skill threshold. 14 candidate predictors are made available for the selection, based on the 1950-1994 period. Zero to four predictors were chosen for regression models for each of the calendar months.
Predictors are the predictands themselves at earlier times.
Final skill estimates reflect levels comparable to those of more sophisticated statistical and dynamical models. For the short leads these forecasts are almost solely based on the persistence of initial conditions. While they underestimated the intensity of the 1997 warming, they did predict warming. The strength of the warm forecast has increased in parallel with the increas-es in the observed initial state. In addition, ENSO CLI-PER has been, since June 1997, consistently predicting the rapid cooling expected to occur in spring 1998.