Seasonal Predictability of the East Atlantic Pattern in Late Autumn and Early Winter

• Published in: Geophysical research letters Vol. 50; no. 1
• Main Authors: Thornton, H. E., Smith, D. M., Scaife, A. A., Dunstone, N. J.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.01.2023; Wiley
• Subjects: Atmosphere; Atmospheric forcing; Atmospheric models; Atmospheric variability; Autumn; Climate; Climate models; Climate prediction; East Atlantic Pattern; El Nino; El Nino phenomena; Ensemble forecasting; ENSO; Evolution; Modelling; NAO; Noise prediction; North Atlantic Oscillation; Ocean models; Ocean-atmosphere system; Oceans; Precipitation; Precipitation variability; Rainfall; seasonal prediction; Teleconnections; Tropical climates; Variability; Weather patterns; Winter
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2022GL100712

The North Atlantic Oscillation (“NAO”) and the East Atlantic Pattern (“EAP”) dominate winter atmospheric variability over the North Atlantic. Unlike the NAO, seasonal predictability of the EAP has remained elusive. A multi‐model ensemble of seasonal predictions yields skillful forecasts of the EAP in late autumn and early winter, complementing NAO prediction skill in winter. The shift in prediction skill from EAP to NAO reflects the ability of the ensemble to forecast the evolving influence of the El Niño South Oscillation on the North Atlantic region. In early winter, the ensemble correctly forecasts the key tropical–extratropical teleconnections, resulting in skillful predictions of the EAP and western European temperatures and rainfall. However, the modeled tropical–extratropical teleconnections are weak compared to observations, contributing to a signal to noise error in predictions of the EAP. Improving the strength of such teleconnections would improve predictions of the EAP and associated surface climate. Plain Language Summary Predicting the most likely weather patterns ahead of the autumn and winter can be very useful for resilience planning. To date, skillful forecasts have only been possible for the most common pattern of winter atmospheric variability over the North Atlantic and European region, called the North Atlantic Oscillation (“NAO”), with no significant skill for the second pattern, called the East Atlantic Pattern (“EAP”). Using seasonal predictions from a range of coupled ocean—atmosphere models, we demonstrate significant skill in the EAP, in late autumn and early winter. The associated temperature and precipitation variability across western Europe is also skilfully predicted. We further show that skill shifts from the EAP to the NAO over the autumn to winter and reflects the evolving influence of the El Niño South Oscillation, a large‐scale atmosphere‐ocean feature of the tropical Pacific. However, climate models underestimate the magnitude of the predictable signal of the EAP, as found previously for the NAO. Resolving this error would further improve seasonal predictions of the late autumn and early winter period. Key Points Seasonal prediction skill of the East Atlantic Pattern and associated surface climate is demonstrated in late autumn and early winter A seasonal shift in prediction skill reflects the evolving influence of the El Niño Southern Oscillation on the North Atlantic region Modeled tropical–extratropical teleconnections are weak, contributing to a signal to noise error in East Atlantic Pattern predictions