September 28, 2015: FB1-Seminar

11:00 h, Lecture Hall, Düsternbrooker Weg 20

Until recently, long-range forecast systems showed only modest levels of skill in predicting fluctuations in the North Atlantic Oscillation and surface winter climate around the Atlantic Basin at seasonal lead times. We describe new results from the Met Office Global Seasonal forecast system 5 which demonstrate high levels of prediction skill in retrospective forecasts of the surface North Atlantic Oscillation, and associated weather variables. We also show that this result is reproducible in independent sets of ensemble hindcasts and can be extended further back in time to at least the start of the satellite era. A substantial portion of the skill arises from teleconnections to tropical rainfall via Rossby wave induced teleconnections. Finally we present a new and potentially crucial paradox that emerges from these near term climate predictions: analysis of forecast ensembles suggests that while useful levels of seasonal forecast skill have now been achieved, signal to noise ratios are smaller than expected. One possible resolution is that the real world is more predictable than climate models suggest.

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