For those interested my winter forecast this year was way out. A prediction of a mean of 4.7C was 2.3C too low. The chief culprit for the 7th mildest winter back to 1797 was most probably the strong polar vortex which has often been at record strength over the past three months.
Rainfall prediction was also over 100mm too low. The wettest winter for 25 years with 248.1mm recorded places it 13th in wettest winters. The only crumb of comfort I can take is that the stats indicated an uptick in precipitation in February! The 90.8mm recorded made it the wettest February for 10 years, just short of 2010. Before that you have to go back to 1951 to find a wetter February. It places 9th in wettest Februaries since 1797.
Over the past months I have looked into the method of seasonal prediction and found some interesting results. For example, the winter of 1989/90 – a winter that was very similar to this one – led to a prediction that was 2.7C too low. Similarly the winter of 2013/14 was predicted 2C too low.
Rainfall looks to be far more random. Though it is obvious that we are now in a wetter than average spell experience shows that it is impossible to tell how long this will last.
Pattern matching and singuarities can be helpful in long distance forecasting. The spanner in the works, however, can be a sharply positive or negative ENSO (El Nino / La Nina) or, as in this year, a very strong polar vortex.
You can find the original forecast here.