(RNN) – As we’ve all probably heard by now, there have been three nor’easters in two weeks. Now a fourth could be on its way next week.
The storms have wreaked havoc on the northeast Atlantic coast – but just how unusual is the weather?
First, let’s get a handle on what exactly a “nor’easter” is. The Weather Channel defines it as “a strong area of low pressure along the East Coast of the United States that typically features winds from the northeast off the Atlantic Ocean – hence the term "nor'easter."
The storms usually develop between Georgia and New Jersey, 100 miles east or west of the coast, and generally move in a northeastward direction. They normally reach maximum intensity around New England or Canada, and they’re most frequent and at their strongest between September and April.
The contrast between cold temperatures over land and warm temperatures over the Atlantic are the primary forces that create a nor’easter, according to Weather.com.
Nor'easters are common this time of year, especially around March, said Greg Carbin, chief of forecast operations at the National Weather Service’s Weather Prediction Center.
“But it is pretty unusual to see three consecutive storms in two weeks,” Carbin said. “I think it’s fair to characterize the frequency as rare.”
A number of factors, including the position of the jet stream and a mass of high-pressure air over Greenland, have come together to cause the atmosphere to be stuck in a repeatable pattern, which has allowed for the quick succession of nor’easters.
So, while the storms themselves are not uncommon this time of year, the static pattern that allows them to develop every week and a half or so is uncommon, though not unprecedented, Carbin said.
In fact, it was just in 2015 that three nor’easters developed within 11 days, in the vicinity of the storms that recently hit, according to data from David Roph, forecaster for the Weather Prediction Center.
Storms occurred on Jan. 24, Jan. 27 and Feb. 2, 2015. Those storms were comparable to the recent storms in terms of wind and pressure, Roph said.
But what part does climate change play in the nor’easters we’ve been seeing lately? Well, since climate and weather aren’t the same thing, it would be irresponsible to pin the frequency of the storms in the past few weeks on climate change, Carbin said.
The major impacts of the recent storms have primarily been snowfall and coastal flooding.
The snowfall has been about normal for March storms in the Northeast region. The flooding, though, has been unusually high this year, which could possibly be attributed to rising sea levels, Carbin said.
There’s also some evidence that melting sea ice could contribute to a gradual change in the polar jet stream, which itself affects nor’easter patterns, Carbin said.
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