“If you don’t like the weather in New England, just wait a few minutes.” Few dead horses have been beaten more thoroughly than Mark Twain’s adage – beaten so often we’ve forgotten how true it is.
I had to live in South America for a year before Twain’s quote sank in. The temperature was in the 50s the first night I arrived in Quito, Ecuador, and the next day it rose into the mid 80s. That’s how it went for about a week, until, by chance, I read in a tourist guidebook that the daily temperature range in Quito is greater than the range of daily averages. Or, more succinctly, you experience more in the course of one day than you do over the course of the whole year.
Think about that for a second. If you’ve lived through one day in Quito, you’ve seen it all. There are neither heat waves nor deep freezes coming down the pike. A day in January is much like a day in June. If you haven’t worn your wool jacket by day’s end, you never will.
Now back to northern New England. A typical year around here will include a number of summer days hotter than 90 degrees and winter nights colder than -20 degrees. That’s a total annual spread of 110 degrees or so. Quito’s range, by contrast, is less than half of that: barely 50 degrees. We New Englanders can almost experience that in a single spring day.
Our annual temperature spread, in fact, is about as great as any populated place on earth. We’re almost equidistant between the equator and the North Pole, which puts us within reach of both tropical heat and arctic cold, and we’re situated on the eastern side of a large, continental land mass. Land tends to heat and cool much more extremely than the ocean does, so even though we’re perched on the edge of the Atlantic, our temperature is affected more by the continental interior because of our prevailing westerly winds. Few other locations on the globe have a similar combination of factors, though Vladivostok and eastern Siberia look promising.
Besides temperature extremes, New England is also situated at the intersection of three major storm tracks. Some storms form in the Gulf of Alaska and come straight to us across the continent – the so-called Alberta Clippers. Then there are the monsters that churn up the coast – the Nor’easters and hurricanes of lore and legend. And finally, there’s everything else – the storms that form in the central Pacific or Gulf of Mexico and come to us via the Ohio River valley.
The reason these storm tracks intersect here is that, from a meteorological perspective, New England is sandwiched in a deep valley between two high “mountain ranges” of air. The southern range, often called the Bermuda High, is a semi-permanent mountain of air that sits off the southeastern cost of North America. It’s semi-permanent in that it isn’t always there – atmospheric dynamics are far more complicated than terrestrial topography – but it usually is there, changing size and shape with the seasons and deflecting storms that would otherwise go out to sea down south up along the coast towards us.
In the summertime, the Bermuda High is often so big that it covers New England. You know those hazy, hot, humid summer days when the temperature is in the 90s, there’s not a breath of air, and the humidity is so high you often can’t see from one side of a valley to the other? That’s the Bermuda High.
The mountain of air to our north, though less stable than the Bermuda High and lacking its memorable moniker, performs a similar role by deflecting storms towards us that would otherwise head out to sea far to our north. When a Nor’easter crashes against the edge of this northern high, right over our heads, we get those epic winter storms whose names start with, “The Great Blizzard of….” Similarly, when we’re having one of those cold, still January nights when the stars appear no farther than arm’s length, we’re deep under the mountains of the northern high.
In the winter, as you might expect, the northern high is at its strongest and fiercest, while in the summer the roles are reversed and our weather has more in common with Bermuda than with Nunavut. In the spring and fall, however, the power struggle is at its peak, and our New England weather is at its wackiest and least predictable, making weather forecasters look bad and Mark Twain look good. That’s true most of all when the days and nights are of equal length and equal power, as they are this week. Happy spring equinox!