At Large: Winter weather – it is what it is

At Large: Winter weather – it is what it is

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In late fall, when the long-range forecasts of winter weather began to appear, they ran the gamut from cold and snowy to variable and moderate overall. These contradictory outlooks do not generally occur in the same forecast. Most forecasters stake out one or the other end of the seesaw, although each adds a discrete qualifier — namely, that conditions may change.

As exhilarating as it may be for the weather wizards to declare themselves on the question of what’s next and to wind themselves up in advance of “weather events” they feverishly anticipate — like the Friday-Saturday northeaster beginning tomorrow that could bring a foot of snow after a mostly snowless winter so far in southeastern Massachusetts, or not — for weather consumers consternation is the common reaction. Sampling some estimates for the winter we’re now experiencing, I’d forecast a high degree of puzzlement.

“Last year we had mostly a single, northern jet stream track most of the year,” Peter Miller of National Geographic wrote, explaining his winter 2012-2013 forecast. “This year we’re seeing two strong jet streams setting up — a northern jet bringing polar air to the Eastern U.S. and a southern jet bringing moisture from the southeast Pacific and the Gulf of Mexico. It’s just a matter of time before these two come together along the East Coast. Combined with water temperatures running warmer than normal in the Atlantic, that could lead to a couple of big events — and more frequent events — in the snow category, especially as we get into January.”

Actually, we got into and through January, and the coming together Mr. Miller anticipates didn’t happen, but the forecast for this weekend suggests he may have been just a week or so off.

“For the coming season, we’re predicting that winter will return to some — but not all — areas,” Caleb Weatherbee offers in the Old Farmer’s Almanac. “We think it will be a winter of contraries, as if Old Man Winter were cutting the country in half. The eastern half of the country will see plenty of cold and snow. The western half will experience relatively warm and dry conditions. In other words, as in the political arena, the climate this winter will render us a nation divided. We predict that real winter weather will return to areas from the Great Lakes into the Northeast. Most eastern states –— as far south as the Gulf Coast — will see snowier than normal conditions and cooler temperatures. We are ‘red flagging’ February 12–15 and March 20–23 for major coastal storms along the Atlantic seaboard; storms bringing strong winds and heavy precipitation.” Don’t mean to be snide, but if you’re in the weather business, and you’re trying to predict when the coldest, snowiest weather is likely, “red flagging” February wouldn’t be a bad idea.

You’re probably wondering, as you read this, why you left your Ouija Board at home today, when it’s just what you need to divine in practical terms what’s actually going to happen. Don’t fret. Just when you need the straight dope, here it is.

“You’re likely to hear a lot about El Nino in the coming months, and your local TV weather guru may show graphics indicating that you will have a warmer/colder/drier/snowier winter as a result. Don’t believe it, (at least hook, line and sinker) because it may very well turn out to be wrong. There are a lot of factors that will play a role on the upcoming winter in the Northern Hemisphere, and El Nino is just one of many.” That’s from Dan Satterfield of the American Geophysical Union, and his heartwarming ambivalence very likely correlates very well with your own bewilderment. This, you might very well conclude, is the bedrock truth of weather and climate forecasting.

But there are other indices you might use. For instance, “I am curious if you have ever (in the fall) looked at persimmon seeds for a fun way to see what kind of winter we will have,” a questioner asked the Weather Advance Storm Center. The inquiry got no replies, which is too bad, because the condition of persimmon seeds may be as helpful a metric as any other to plot the course of a Vineyard winter.

But perhaps we’d be better off to put our money on this explanation for the nutty mix of mild days and frigid snowless ones we’ve had this winter. But first, a warning: it will require paying close attention and some significant head scratching. Jeff Weber is a climatologist and atmospheric scientist at the University Corporation for Atmospheric Research in Boulder, Colorado. He told NPR host Ira Flatow how it all works. The culprit — perhaps you’ve already guessed — is sudden stratospheric warming.

“Yes, the stratosphere and the troposphere are two layers of our atmosphere, and they’re kind of inversely related. So as the stratosphere warms, the troposphere can cool. The real dynamics of this situation, though, is that as the stratosphere has gone through this sudden stratospheric warming event, as the stratosphere warms, it tries to then, in the air in the stratosphere, it descends back into what we call the polar vortex, which is where all of the cold air over the Arctic kind of usually kind of polls up and sits during the winter months.

“Now, as that bubble of stratospheric air comes down and descends into the polar vortex, it disrupts the circulation, and all that very cold Arctic air is then able to spill out from the Arctic down into the lower 48 or into Europe.”

That makes sense, of course, but perhaps the most sensible reaction to seasonal weather forecasting is to say, thanks, but we’ll wait and see.