The NAO now: And the dark side of night

(Photo by Dion Ogust)

We’d all agree that late summer and early autumn have been very pleasant this year. But it may not last. That’s because of the North American Oscillation.

Meteorologists abbreviate that the NAO. You may never have heard of it. Other big weather-influencers like El Niño and La Niña have gotten far more press, so that most people know that El Niño is a warming of eastern Pacific tropical waters that creates far-reaching consequences for our weather. On a year like this one, without a pronounced El Niño (Pacific Ocean conditions are currently pretty neutral), we’d expect a normal winter, or maybe a slightly cold one.

The North American Oscillation hasn’t gotten general media coverage. But most weather experts now believe that it’s right up there with El Niño in influencing our winter weather, and determining whether we get hard or easy winters – or, more commonly, whether a particular period of time (several weeks in a row, or a couple of months) is warm or cold.


The NAO is simple to understand. A permanent high-pressure area pretty much sits over the Azores islands, west of Portugal. And a low-pressure area hovers over Greenland and Iceland, which gives them their chronic dismal weather.

But sometimes that Azores high is stronger at the same time that the Greenland low is deeper, and this is called a positive NAO. It tends to channel warm South Atlantic air up the East Coast to us, and gives us mild winter conditions. Such a positive NAO existed during some of our warmest, least-snowy winters.

But right now, a negative NAO has set up, and it’s predicted to last at least the next two months. This means that the Azores high is weak, and the Greenland low is weak, too. This setup typically lets cold polar air pour into the Northeast, and can set the stage for early snowstorms. So, whether you know it or not, you don’t like a negative NAO one bit. (It is good for the ski resorts, however.)

Nobody knows why this oscillation occurs – only that it steers our weather, and provides weeks of either agony or ecstasy. You can go on the web, look at the NOAA climate prediction center and see what meteorologists are saying about the current and projected changes to the NAO.

Meanwhile, this month of October also features the final few weeks of generally clear skies and abundant sunshine. For the past five months, our skies have averaged 66 percent cloud-free conditions, hence lots of sunlight. But climatologically, our region typically changes dramatically around November 1. From that week through April and much of May, our skies stay two-thirds cloudy. Combined with the annual minimum hours of daily sunlight during November to February, we are about to get a double whammy of cloudy skies and long nights. We will be starved for light.

About 15 percent of us suffer from Seasonal Affective Disorder, and go into significant depression due to the lack of light. Many more experience lesser effects of diminished joy. So be sure to step outdoors and get the antidote: sunshine, whenever it’s out. Expose your skin to the full extent possible. You might even talk to your doctor about purchasing a light box. Natural vitamin D is important, too, and (unlike the SAD antidote light) can’t be gained by sunlight through windows. You have to hang out in front of an open window, or outdoors. Maybe even maybe head south for a week or two if you can, during that November-to-February period.

But be aware of what’s about to happen. These are our final couple of weeks before the annual darkness overspreads our beloved region.

Want to know more? To read Bob’s previous columns, click here. Check out Bob’s podcast, Astounding Universe, co-hosted by Pulse of the Planet’s Jim Metzner.

There is one comment

  1. Johanna Hall

    Thank you for this! Bob Berman always explains the universe in the clearest, most felicitous way. The best teacher I’ve ever known.

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