Greg Laden's Blog

The Polar Vortex hurt. We who lived in it, through it, with it, are like farm animals that got zapped by the electric fence a couple of times … notice all that long grass growing by the fence. Stay away. It hurt! So we are worried that this will happen again.

It is a reasonable worry, from a scientific point of view. The Polar Vortex visitation last winter was the result of changes to trade winds and jet streams that has characterized our weather for the last few years. One of the big questions on my mind is this: Are wavy jet streams and corresponding changes in the distribution of excessive rainfall and drought likely to become spatially patterned? In other words, is it likely that when the Polar Vortex wanders that it will tend to wander to the same small set of locations, like Siberia or North America? So far this seems to be at least partly true. The drought in California has not been maintained because of a lack of rainfall at that latitude, but rather, a lack of certain seasonal precipitation (winter snows) at that longitude, because of the oft-cited “ridiculously resilient ridge” which is actually one of several standing waves in the polar jet stream that shunts wet air around California, to places the Midwest. It is conceivable that the Polar Vortex, as part of the climate change induced “new normal,” will wanter off-pole and onto a landmass (either Eurasia or North America) often-ish, from now on, or until continued global warming results in some other pattern which we’ll probably call “New Normal 2.0”.

This is a question I’ve asked various scientists who are working on this problem. The answer I’ve gotten so far has been, paraphrased, “Yeah, I don’t know, maybe, we’re thinking about that. Get back to you later.”

But there is hope. I’ve put links to three places you can go for more discussion and information below. Here’s the tl;dr. The National Weather Service does a very good job of predicting what winter will be like in North America, but the accuracy of that prediction, unsurprisingly, drops off month by month. So the current prediction is probably pretty good for November/December, but as January and February come along, what is predicted now may be off. With that caveat, these are the salient predictions:

1) There will not be a Polar Vortex excursion into North America. Probably. The thing is, if this is a recent phenomenon and increasing in likelihood, the predictions may be off, but there are good reasons to believe they are not. Don’t assume the Polar Vortex will visit us, but don’t sell your wool pants at that last garage sale of the year.

2) California may actually get some rasonable precipitation this winter. It is hard to say if it will be drought-breaking rain, but it may help.

3) Although winter seems to be starting early this year (with many inches of snow having fallen or about to fall on the Front Range, the Dakotas, etc.) the overall prediction is a somewhat warmer than average winter for most of North America.

4) The Southwest, California, Texas, North-Central Mexico will have a bit more moisture than average, but other than Pacific coastal Mexico, not a lot more. That won’t translate into huge snowfalls except at high elevations. The middle of the country, from Montana to western Ohio and Michigan, south to a line running from southern Idaho across to Florida, including the Southeast, will have average precip. So, Minnesotans may see early snow if it remains cool, but this will not be an exceptionally snowy winter. Less than usual moisture is predicted for Kentucky, Ohio, western Pensylvaina, parts of New York and most of New England. But, this is only a small amount, so don’t sell your snow blower at that garage sale.

Parts of the Pacific Northwest and inland across to western Montana may be a bit dryer than usual.

Overall, temperature wise, no region is expected to be especially cold, mostly somewhat warm. The regions of Canada and Alaska along the Arctic Circle will be very warm (relatively … so many degrees below zero instead of many more degrees below zero) as we would expect with “Arctic Amplification.” Moisture levels, overall, are not going to be extreme in either direction anywhere, though the dry in the Northwest may be noticeable.

In other words, the average person’s perception of weather, which varies from reality a great deal, will include the actual realized variation, if the predictions hold up.

The NWS predictions can be found via this page.

Eric Holthaus has a discussion of the coming winter here.

Paul Douglas of Weather Nation has more here, with a lot of other info relevant to Minnesota.

Comments

  1. #2 Greg Laden
    September 18, 2014

    Normally I don’t allow links to Dorothy of Oz on this site, but in this case I’ll make an exception because it is a classic example of cherry picking.

  2. #3 Robert Clark
    Philadelphia, PA
    September 18, 2014

    I wonder if the polar vortex is connected to the rebound in the arctic ice level the last two years. In that case we should expect another instance of the polar vortex this Winter.

    Bob Clark

  3. #4 anonymous
    September 18, 2014

    In the Midwest, we have large caterpillars called woolly bears that are seen in large numbers poking across country roads in fall. They are normally brown at both ends with a central black stripe, and according to lore, the broader the black stripe, the earlier or harder the winter will be. This year, I saw a bunch of them before the end of August. All were solid black end to end. Shamefully un-Scientific, perhaps, but anyone who grew up where I did knows you disregard the woolly bears at your peril. 🙂

  4. #5 Greg Laden
    September 18, 2014

    Uh uh.

    “Even though it is widely believed that the woolly bear caterpillar can predict the upcoming winter’s severity, the truth is that this caterpillar can’t predict what Old Man Winter has in store for us in the upcoming winter. The woolly bear caterpillar’s coloring is based on how long caterpillar has been feeding, its age, and species. The better the growing season is the bigger it will grow. This results in narrower red-orange bands in its middle. Thus, the width of the banding is an indicator of the current or past season’s growth rather than an indicator of the severity of the upcoming winter. Also, the coloring indicates the age of the woolly bear caterpillar. The caterpillars shed their skins or molt six times before reaching adult size. With each successive molt, their colors change, becoming less black and more reddish. In addition, there are approximately 260 species of tiger moths (the adult of the woolly bear caterpillar) in North America, and each species has slightly different color patterns and hair coverings. As a result, some of the color and hair variations that we see each fall are a result of these different species.

    From NOAA: http://www.crh.noaa.gov/arx/?n=woollybear

  5. #6 anonymous
    September 19, 2014

    Oops, I misspoke – yes, of course, the central band is brown. And maybe I saw a new species moving into an area that always before had a different species. I’m not convinced, though, that a NASA page without citations completely debunks the legend. It would surprise me if there was no correlation between one growing season’s climate and that of the following winter.

  6. #7 Greg Laden
    September 19, 2014

    If there was, wouldn’t you think we would know there was, use that to predict winter, and instead of dismissing wooly bears NOAA would make the connection?

  7. #8 anonymous
    September 22, 2014

    Well, no, because modern ways of predicting weather are (under relatively stable conditions, and presuming that the associated infrastructure is maintained) so much more precise that there’s no need to use crude old-fashioned methods anymore, so no point in testing them. Why bother to prove or remind people that a “red sky at morning” statistically increases the chance of rain or storms if we will continue to get our daily forecast from the Doppler radar? But that doesn’t mean nothing in the old almanacs had any validity whatsoever or will ever have any use again. I’m not ready to count the woolly bears out just yet!

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