At first sight the ECM operational run might not look that great, but what strikes me on the T+240 500 mb chart is that great pool of deep cold air that is by then centred over northern Russia, as indicated by the deep blues and purples. That's well displaced from where you normally find it in winter, which is over or to the west of Greenland. If I'm right in thinking it represents the core of what is known as the Polar Vortex, then I'd have thought the set-up must favour the development of northerlies over Europe. Also the smaller than usual temperature differential from north to south over the NW Atlantic would make vigorous cyclonogenesis in that region less likely, meaning the North Atlantic would become quieter than usual.
That ensemble mean chart for T+240 shows a similar situation; though there's still a pool of cold air to the W of Greenland, the one over northern Russia is far more intense.
Originally Posted by: jhall