A new index for more accurate winter predictions

Seasonal climate prediction remains a challenge. During Northern Hemisphere (NH) winter the large‐scale teleconnection pattern the Arctic Oscillation (AO) explains the largest fraction of temperature variance of any other known climate mode. However the Arctic Oscillation is considered to be a result of intrinsic atmospheric dynamics or chaotic behavior and therefore is unpredictable. Here we develop a snow advance index (SAI) derived from antecedent observed snow cover that explains a large fraction of the variance of the winter AO. The high correlation between the SAI and the winter AO demonstrates that the AO is most likely predictable and that this index can be exploited for skillful seasonal climate predictions. Key Points We develop a new snow index that measures the rate of change rather than extent This new index is much more highly correlated with the AO than previous indices This index shows great potential to improve winter climate forecasts