Observational evidence of European summer weather patterns predictable from spring

Osso, A., Sutton, R. ORCID: https://orcid.org/0000-0001-8345-8583, Shaffrey, L. ORCID: https://orcid.org/0000-0003-2696-752X and Dong, B. ORCID: https://orcid.org/0000-0003-0809-7911 (2018) Observational evidence of European summer weather patterns predictable from spring. Proceedings of the National Academy of Sciences of the United States of America, 115 (1). pp. 59-63. ISSN 0027-8424 doi: 10.1073/pnas.1713146114

Abstract/Summary

Forecasts of summer weather patterns months in advance would be of great value for a wide range of applications. However, seasonal dynamical model forecasts for European summers have very little skill, particularly for rainfall. It has not been clear whether this low skill reflects inherent unpredictability of summer weather or, alternatively, is a consequence of weaknesses in current forecast systems. Here we analyze atmosphere and ocean observations and identify evidence that a specific pattern of summertime atmospheric circulation--the summer East Atlantic (SEA) pattern--is predictable from the previous spring. An index of North Atlantic sea-surface temperatures in March-April can predict the SEA pattern in July-August with a cross-validated correlation skill above 0.6. Our analyses show that the sea-surface temperatures influence atmospheric circulation and the position of the jet stream over the North Atlantic. The SEA pattern has a particularly strong influence on rainfall in the British Isles, which we find can also be predicted months ahead with a significant skill of 0.56. Our results have immediate application to empirical forecasts of summer rainfall for the United Kingdom, Ireland, and northern France and also suggest that current dynamical model forecast systems have large potential for improvement.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/74646
Identification Number/DOI	10.1073/pnas.1713146114
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Uncontrolled Keywords	climate variability, predictability, seasonal forecast, sea–air interactions
Publisher	National Academy of Sciences
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