New England has been battered in the last month or so by two massive Nor’Easters and the forecast is for another big storm coming mid week next week. Why has it been so relentless this winter?
This winter has been dominated by a long waved pattern. Frequency is lower if waves are longer, which is to say that the pattern slows way down when waves are longer. The wave in reference here is the upper level jet stream, which is analyzed here:
There is a lot of action on this map, which might make one believe that the pattern should be much more active, and there are indeed a few areas to watch (The Rockies, and the lower Mississippi Valley, for example) in the next couple of days, before we return our attention to New England.
The problem is that pink, stronger jet streak running from the Great Lakes to the north Atlantic. That is tied to a broader trough that is more easily identified when you look from the North Pole.
Here, you can see the north to south jet off the west coast. Over time, the jet streaks over the North American continent have or will continue to dissipate, leaving a broad trough over the US, with a strong exit region along the East Coast, wherein the exit region is the most conducive for cyclonic development.
Compounding things is a strengthening ridge in the north Atlantic, which will threaten to maintain the wave over North America for even longer. This is a summer or winter like pattern, but as we head towards spring, the differential heating across the planet will ease this logjam, and New England will start to come up for air.