This is the journal paper: https://journals.ametsoc.org/doi/10.1175/BAMS-D-18-0270.1 https://journals.ametsoc.org/doi/10.1175/BAMS-D-18-0270.1 It looks like t

This is the journal paper: https://journals.ametsoc.org/doi/10.1175/BAMS-D-18-0270.1 https://journals.ametsoc.org/doi/10.1175/BAMS-D-18-0270.1 It looks like they are focusing on "sources of predictability", i.e. weather phenomena on sub-seasonal scale that can be observed and then it can be predicted what will happen next. So the methodology works better in certain areas of the world where well-defined sub-seasonal oscillations in the weather are found. They have used an ensemble of different models, and have done predictions on several decades of weather data, as well as one year of "live" predictions and comparison to what actually happens. From what I can tell, it seems like the best predictions can explain ~16% of the observed variation in weather.