Currently, the AO is in a negative phase and is forecast to remain negative through at least the middle of December.
This will likely mean temperatures across the eastern United States will average below normal.
When the AO goes into a negative phase, the polar low pressure system (also known as the polar vortex) over the Arctic is weaker, which results in weaker upper level winds (the westerlies).
The result of the weaker westerlies is that cold, Arctic air is able to push farther south into the U.S., while the storm track also remains farther south.
SEE: 5-day forecast
The opposite is true when the AO is positive: the polar circulation is stronger, which forces cold air and storms to remain farther north.
The Arctic Oscillation often shares phase with the North Atlantic Oscillation and its phases directly correlate with the phases of the NAO concerning implications on weather across the U.S.
Currently, the AO is in a negative phase and is forecast to remain negative through at least the middle of December.
This will likely mean temperatures across the eastern United States will average below normal.
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