From record cold to rain: What’s causing the erratic weather?

After the coldest weekend in most of our lifetimes, a rapid temperature rise is on the way. As matter of fact, the difference between the subzero wind chill temperatures of Sunday morning and the high temperature tomorrow yields a nearly 90-degree swing! (Actual temperatures will show an over 60-degree turnaround in such a short period of time.)

Ahead of the mild air, a period of snow, sleet and freezing rain will create travel difficulties this evening, but should be mainly over by the morning commute Tuesday. Showers could be heavy at times on Tuesday and there is even the chance of a thunderstorm late in the day. From record cold to thunderstorms: what’s going on?


It can be tempting to start pointing fingers as to the cause of individual wild weather swings, but the atmosphere is very complex. There are, however, model simulations which do predict more arctic air spilling south into the mid-latitudes, such as here in New England, as the climate warms.

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Average snowfall increasing
Of course snowy and bitter cold weather often brings the standard joke about how a warming climate can produce more snow and cold. It seems counterintuitive to be snowier and colder, doesn’t it? During the past decade and a half, snowfall has increased along with large precipitation events.

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The chart below shows how much snow fell during every winter since 1999. Average snowfall in Boston is about 51 inches during this period, an increase of nearly 20 percent over the 140 year average. Why the increase? Many climatologists believe the added accumulation is because warmer air holds more moisture — and more moisture means more snow. Even an overall warmer planet won’t be hot enough for decades — or even a century — before yearly snowfall decreases.

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Snowfall has increased during the core winter months, but it has decreased on the margins in November, March and April. This makes some sense. As the earth warms, the first months to start losing snow would be those in the fall and spring. Eventually temperatures will warm further and we’ll get less snow December through February.

More cold snaps during the middle of winter

What about the cold weather? How can it be colder in a warmer world? First, remember that a warmer world still has a lot of cold at the top and bottom of it. Typically, the polar vortex spins around really fast and keeps much of the cold air locked in across the northern part of the planet. When the vortex weakens as it did last week, it allows the cold air to propel itself southward.


The loss of sea ice across the arctic is well documented. Again, researchers have found the loss of sea ice can dramatically influence the polar vortex which, in turn, influences climate variability.

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Less ice in the arctic impacts more than you’d think
The loss of sea ice is just one of many factors shaping the polar vortex. Snow cover across Eurasia, El Nino and Southern Oscillation and the fluctuation in solar activity all impact seasonal weather variability. How these variables interplay with shorter term changes, such as equatorial thunderstorms and pressure patterns in the Pacific and Atlantic, haven’t been systematically researched.

What’s become quite clear is that our highly erratic New England weather will continue, but the ride up and down is looking steeper and more inconsistent than ever recorded.

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