Wednesday, December 6, 2017

Winter In Vermont: Now A Lot Warmer, And Oddly, A Lot Snowier

Who knows what this winter will bring, but in general,
Vermont winters  have gotten much warmer and snowier
in recent decades. Here's a street scene in Burlington
Vermont after a two-foot snowstorm in March, 2011.
As we prepare to go into winter, with a series of cold fronts due starting now and going into next week to bring us to near normal December temperatures and weather, here's some contradictory long term trends in Vermont winters:  

We are much warmer than we used to be decades ago. But also snowier.

According to Climate Central, Burlington, Vermont is the American city with the fastest warming winter, up about 7 degrees since 1970.

Though most of this is definitely real warming, a bit of it might be a function of the start date of this study, which is 1970.

That year was unusually cold here in Vermont. In fact, we had the coldest January on record that year.

Still, all data points to the fact that winters are warmer than they used to be in the northern tier of states, including Vermont as global warming has taken hold.

As always, the trend is uneven, with cold winters interspersed with warm ones. It's just the warm ones have gotten more frequent. And the winter heat waves have gotten more intense. Witness the unprecedented near 70 degree warmth on Christmas Eve 2015 and the previously unheard of 70 degree weather in late February this year.

There's no telling whether this winter will be cold or warm or all over the place. Stay tuned on that one.

It seems odd, but as Vermont has warmed, it has gotten snowier. Too bad the warmth does not allow the snow to accumulate all that much, or stay around for all that long.

The snow stats are striking. Five of the top 10 snowiest years in Burlington have occured since 1992. Seven of the top 10 occured since 1970.  Fourteen of the past 17 winters have had more than the average annual snowfall for Burlington.  Snowfall so far in this young winter is running a little behind normal, but the season is still extremely young, and that could change.

The big snows seem in large part to come from bigger individual snowstorms. Records in Burlington go back to the 1880s. But four of the top five biggest snowstorms have occured since 2007. Of the 20 biggest snowstorms on record, 13 of them have happened since 1993.

This all makes sense in a strange sort of way. Storms in a warmer atmosphere can draw in more moisture, and drop heavier precipitation that they could in a cooler world. If the temperature remains below freezing, storms in general now have the power to drop more snow than they could in the past.

As far as this winter goes, we'll just have to wait and see.


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