An equation for each was developed using the 1950-1994 data which provided a sample of 43 hindcast data points. These were based on one to four predictors with most equations containing two to three predictors. The equations were tested in the hindcast mode on 1950-1994 data. The skill results through the lead 2 time period are rather encouraging, while forecasts at longer leads damp toward climatological values to minimize squared errors. The model does well through 2 seasons lead for all regions, with skill falling off to zero in and around the highly transient spring target period.
Minimal skill returns again at the longest leads.
The adjusted RMSE values are is also plotted as vertical bars, indicating the degree of uncertainty associated with each forecast. The warm phase is suggested to end by Jun-Aug 1998, remaining near neutral out to early 1999. For full details the code as well as the coefficients for this simple model are available upon request. The authors wish to thank William Gray, Tony Barnston, John Sheaffer, Dave Enfield Dennis Mayer, Barb Brumit, Amie Hedstrom, Bill Thorson 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.