Though the calendar now says spring, atmospheric gremlins are conspiring to make winter linger a bit longer.
Thanks to a blocking system over Alaska, the jet stream will take another deep dive from the North Pole to the eastern United States this weekend. That pattern will be locked in place throughout much of next week, plunging most of the eastern part of the country back into the deep freeze. Temperatures from Sunday to Thursday will be 10 to 25 degrees colder than long-term averages across most of the East, more fitting of mid-January than late March.
But the crown jewel of the wintery encore will be a major late-season nor’easter. Born of a combination of bitterly cold air and a core of rapidly intensifying low pressure, a big storm is increasingly likely to buzz the East Coast early next week.
The National Weather Service did not mince words in its headline of a technical discussion of the potential beast: “Nor’easter bomb indicated off the mid-Atlantic coast late Tuesday night.”
The scary-sounding descriptor “bomb” – also known as “explosive cyclogenesis” – is a technical word meteorologists use when low pressure centers deepen at a rate faster than 24 millibars in 24 hours, which happens in only the most intense storms.
“The East Coast cyclone has the potential to produce late-season heavy snowfall over a wide swath of real estate from Virginia to New England; that is a generality at this point,” the weather service continues. “Much remains in terms of refining the forecast state by state. Another high-impact factor will be the powerful winds generated by this sprawling, intense circulation, along with high seas, beach battery, coastal flooding, and so forth. Again, at this point, such sensible weather effects are simply attendant to the potential of such a storm.”
That’s a bold forecast, especially five days before the storm arrives.
In this case, however, forecasting an extreme storm next week is becoming an increasingly easy call. Weather models have been showing the possibility of a big storm for days now and are displaying the kind of consistency meteorologists look for before going out on a limb.
In fact, one particular model, the GFS – the best long-range model produced by the United States – is forecasting the storm to strengthen at more than twice the rate necessary for a bomb, from Tuesday evening off the North Carolina coast to Wednesday morning off Long Island, just 12 hours later. That same model is forecasting the storm to peak with sustained surface winds of hurricane force over the ocean by Wednesday afternoon. At that same time, in the jet stream well above the surface, winds are expected to top 170 mph – fueling the rapid growth of the storm and increasing its “bomb”-making potential.
The extremely strong jet stream will form a direct link between the Arctic and the East Coast, energizing the storm and turning it into a major snow producer.
While the weather service is understandably skittish about making snowfall predictions when the storm is still five days away, thanks to the wonders of technology, we can get a sneak peak of what the totals might be.
Another model, the GGEM, has a snow forecast that would rank as one of the biggest the New York City area has ever seen – more than two feet by Wednesday.
Now, the GGEM is likely wrong – the weather service’s New York office conservatively noted the double-barreled center the GGEM is currently showing is probably unrealistic – but barring big changes in the forecast, there’s an increasingly strong line of evidence that someone’s going to get walloped somewhere along the East Coast.