After a predominantly mild and wet December, it may be tempting to give up hope for the return of winter weather in Washington. As the image above (courtesy NOAA) indicates, temperatures across much of the eastern two-thirds of the United States have been running well above average the past thirty days. So what’s in store for the Washington Region over the next several weeks? Specifically, is a return to a colder weather pattern on the horizon? Meteorologists will look at variety of “teleconnections” or relationships between large-scale features in the mid to upper levels of the atmosphere that offer insights into the medium-range forecast. Four key teleconnections indicate that a significant pattern change may be in store for the eastern United States as we head into mid and late January.
1. The Madden-Julian Oscillation (MJO)
The Madden-Julian oscillation is a significant driver of the weather pattern and consists of eight phases, each impacting global weather by shifting the location of tropical convection in a relatively short period of time, generally during the course of several weeks. During the winter months, various phases of the MJO can signal heavy rainfall events along the west coast of the United States or even be a precursor to predicting arctic outbreaks east of the Rockies. The image below (courtesy NOAA) shows typical temperature anomalies (departure from average) across the United States associated with each phase of the MJO in the month of January.