Climate Logic

The summer (JJA) of 2010 is forecast to be warmer than the summer of 2009 over the eastern United States, with temperatures above the 1971-2000 average. Colder than normal temperatures are expected in the Pacific Northwest and western Canada. The temperature anomaly pattern in June is likely to be similar to that established in May, with warmer than normal temperatures in the southeastern United States and negative anomalies in the western states. The July pattern will represent a tripole, with positive anomaly centers in the Southwest and British Columbia, and a negative anomaly center in between these region.  In August the highest CF for above normal temperatures are centered over the Great Lakes, that is the area that experience a very cold summer in 2009.

In the summer of 2010 mean seasonal temperatures in Europe are forecast to be close to their climatological (1971-2000) values, being slightly above normal in western Europe and near or below normal in eastern Europe. Even in western Europe, however, temperatures will likely be colder than in the summer of 2009. In terms of temperature anomalies, July will probably be the coldest month in comparison to June and August. Temperature conditions are expected to improve by the end of summer.

The winter of 2010 was anomalously cold in the contiguous United States. Mean seasonal temperatures in many southern and southeastern states were coldest since the late 1970s. At the same time, Canada experienced its warmest and driest winter on record. This temperature anomaly pattern is consistent with a combined effect of a strong El Niño event and extremely strong negative phase of the North Atlantic Oscillation. As usual during El Niño events frequent storms traveled along the southern United States, and many of those states experienced above normal precipitation. Major snowstorms were pounding the East Coast, particularly in February. In several eastern cities, February was the snowiest month on record.

The winter of 2010 in Europe was much colder than expected. In many places seasonal temperatures dropped to the values not seen in decades. This cold winter was associated with an exceptionally strong negative phase of the North Atlantic Oscillation. The roles of solar activity, quasi-biennial oscillation of the stratospheric winds and other factors are discussed. Interestingly, temperatures in the European Arctic Seas were well above normal; however, they cannot be explained simply by the negative phase of the Arctic Oscillation, as in the NSIDC report. The unusual behavior of the climate system in the winter of 2010 raises a question about a possibility of a climate regime shift.