Stormy Pattern Ahead

The Madden Julian Oscillation (MJO) index is entering phase three – favoring an amplifying trough of low pressure to set up shop across the Mid-Atlantic and New England states.  This trough (broad dip in the jet stream) will produce cooler than average temperatures along with the potential for three major storm systems to impact our area.  In addition to some moderate to heavy rainfall and the potential for some stronger/severe thunderstorms, the Appalachian mountains could receive some heavy, wet snow.

The next image shows the temperature anomalies in April which correlate with the eight phases of the MJO (notice how cold phase 3 is in the next image).

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Major Pattern Change for Mid-Atlantic Next Weekend

The Madden Julian Oscillation (MJO) is finally moving out of phase 7 and back into phase 8 this weekend. The image above shows warmer than average temperature anomalies over the Eastern United States in phase 7 with cooler than average temperatures in phase 8. You need cold air for wintry weather and with a very active storm pattern continuing, things are looking very interesting this weekend and beyond.

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Four Key Teleconnections Indicate a Return of Winter to the Eastern United States

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.

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