What is the North Atlantic Oscillation and how does it affect our weather?

November 14, 2017 11:34 AM

Let’s discuss a large scale feature of meteorology that has a very local and direct impact on our area here in Rochester.

That is the North Atlantic Oscillation. I know big word it sounds confusing but it’s basically a seesaw in the weather pattern over the North Atlantic and it is what drives these Jet Stream graphics we like to use.

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The thing you should remember is the difference between Positive and Negative phases in the oscillation. When it is positive we get a strong high over the Atlantic and a strong low over Iceland. This speeds up the Jet stream, kind of like a river flowing down a mountain stream. It flows fast and straight. So most weather systems move through our area quickly and we stay under some relatively milder weather.

But when it turns Negative these pressure systems weaken and the overall Jet stream pattern slows like a meandering stream. Once that happens we start to see storms build up and cold polar air escape south.

Now as far as forecasting this you can take a look at the pattern and see where it’s trending plus use models. Now this looks back and you can see in this dip here we had a slight negative phase. That allowed our cold shot of air and snow on Friday. Now look at the extended outlook and how far negative this goes based on this model compared to what we seen last week. And as I mentioned a moment ago the stronger the Negative phase the more the Jet will meander and the more cold air will escape south thus fueling our storm systems here in Rochester.


Robert Speta

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