Seasonal winter forecasts and the stratosphere

• Published in: Atmospheric Science Letters
• Main Authors: Scaife, AA, Karpechko, AY, Baldwin, MP, Brookshaw, A, Butler, AH, Eade, R, Gordon, M, Maclachlan, C, Martin, N, Dunstone, N, Smith, D
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley Open Access 2015
• Subjects: North Atlantic; North Atlantic oscillation
• Online Access: http://hdl.handle.net/10871/20937; https://doi.org/10.1002/asl.598

Published © 2016 Royal Meteorological Society. We investigate seasonal forecasts of the winter North Atlantic Oscillation (NAO) and their relationship with the stratosphere. Climatological frequencies of sudden stratospheric warming (SSW) and strong polar vortex (SPV) events are well represented and the predicted risk of events varies between 25 and 90% from winter to winter, indicating predictability beyond the deterministic range. The risk of SSW and SPV events relates to predicted NAO as expected, with NAO shifts of -6.5 and +4.8hPa in forecast members containing SSW and SPV events. Most striking of all is that forecast skill of the surface winter NAO vanishes from these hindcasts if members containing SSW events are excluded. This work was supported by the Joint DECC/Defra Met Office Hadley Centre Climate Programme (GA01101), the UK Public Weather Service research program and the European Union Framework 7 SPECS project. The contribution of AYK is funded by FMI’s tenure track program and the Academy of Finland under grant 286298.