One of the culprits for our warm winter

6:21 PM, Feb 16, 2012   |    comments
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GOLDEN VALLEY, Minn. - The increased number of cars falling through the ice and out-of-season grass fires the Twin Cities have seen recently can ultimately be blamed on less arctic air travelling southward.

What meteorologists call the arctic oscillation controls that colder air and refers to a semi-permanent low pressure system that sits over the north pole. We classify the oscillation as either positive or negative. Currently, we're in a positive phase.

That means we have deep low over the North Pole that creates a strong wind force around the pole. Because the winds are stronger, they can hold in the cold air and keep it near the pole. This pattern also tracks storms through Canada rather than down through the United States.

The opposite happens when the oscillation is in a negative phase. The winds circulating around the pole are weak and they allow the cold air to escape and travel down to the U.S., giving us colder and snowier winters, like last year.

While the arctic oscillation is one major player in our game of winter, it's not the only one. Most of us have heard of La Nina; that plays a factor, as do a few other circulation patterns in the atmosphere and the oceans.

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