Cold, Stormy Signal Over North US In Long Range

ECMWF on left, GFS on right.

The GFS and ECMWF long range 500mb height anomaly forecasts are in, and both are showing a cold and stormy signal over the East US.

First, let's acknowledge what's going on over Greenland. See all that red? The more orange and red there is, the more indication there is that this is a ridge of high pressure, like the high pressure systems that bring sun after a cold front. This particular high pressure system is involved in a pattern called the North Atlantic Oscillation, or NAO. In a positive NAO, there is a strong low pressure system sitting over Greenland, not really moving. This, in turn creates a warm and dry situation over eastern portions of the US. In the negative NAO phase, one can find a ridge over Greenland. This ridge forces a cold and stormy pattern to set up over the East US. In the winter, this negative NAO can pave the way for big snowfalls, especially in the Northeast.

Both the ECMWF and GFS appear pretty confident on this negative NAO signal emerging over the next 8-10 days. This means that the eastern US should become much more stormy and cool in response. Notice the blues over the Northeast on both images. This means a stormy pattern, and is seen in response to the negative NAO expected.

In summary, if you live in the East US, get those heavy jackets at the ready, because the consensus at the moment is for a much wetter and cooler pattern to start up in about a week or so.

Andrew