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. The authors wish to thank William Gray, Tony Barnston, John Sheaffer, Dave Enfield, Dennis Mayer, Barb Brumit, Amie Hedstrom, Bill Thorson and Rick and Rick Taft for all their help and comments concerning this work. The second author was funded through the 1995-96 NOAA Postdoctoral Program in Climate and Global Change. A search for short range climate productivity. Actual numerical forecast values for these times are shown on each plot along with estimated RMSE bars.