Weather Talk: A positive North Atlantic Oscillation

The fall season (September through November) has been unusually mild. There has been very little cold weather and no visitation at all of air from the Arctic. During fall, there has been a lot of talk about the very strong El Nino and the likelihood that it would help bring a mild winter to our region. It is likely that the El Nino was a significant influence on our weather pattern in November. However, it is unlikely that the El Nino had much to do with our mild weather in September and October. A semi-permanent low pressure region near Iceland has been quite strong during the past few months. This is the positive phase of the North Atlantic Oscillation. A positive NAO usually brings wet weather to Europe but limits Arctic air from dropping into the United States. Also, there is a large blob of anomalously warm water off the coast of the Pacific Northwest. So our fall was a mild one, but for a number of reasons; not just El Nino.