This replaces simple persistence as a skill threshold. Multiple least squares regression is employed to test a total of fourteen possible predictors for the selection of the best predictors, based upon 1950-1994 developmental data. A range of zero to four predictors were chosen in developing twelve separate regression models, developed separately for each initial calendar month.
Predictors are the predictands themselves at earlier times.
Final skill estimates reflect levels comparable to those of more sophisticated statistical and dynamical models. 1a and Fig. These cold phase conditions may give way to warm ENSO conditions in the summer of 2000, with a distinct transition occurring in the spring 2000 time period. These forecasts are consistent with those made in March, June and September 1999. Lead 0 and Lead 1 forecasts continue to perform very well.