There is no reason to start this post with anything other than the three words which you will hear least out of most forecasters in the professional field: We were wrong. No sugar coating, no half-way statements, no "what if"s or "maybe if"'s. We were wrong with most of our long range forecasts beginning in October and moving forward through early to mid December as well. There are several things which have gone wrong (even with the most recent forecast for a late-January flip to cold/snowy) which will be covered in this post. But the fact of the matter is...the change in the hemispheric pattern that we, and many other forecasters including professional meteorologists were expecting..has not happened at all. Pictured right: GFS AO forecasts and bias from the past month or more of forecasts. See the third paragraph for details.

To this point, this winter has been unique in more than one sense. Plenty of people on these forums and throughout the community have extended their reach and shown knowledge of different atmospheric processes...stratospheric warming talk almost became a social trend in our community for example. But things have become way too complicated and people are looking in the wrong places for the right things. For example you will not find high latitude blocking on a GEFS NAO graph. You will not find accurate medium range pattern predictions through the GFS or Euro AO or NAO forecasts. In fact...the GFS has been particularly bad in forecasting these things at a relatively moderate lead.
The image to the above shows the GFS AO or Arctic Oscillation forecasts...for each 4 runs throughout the day...and the observed value which is indicated by a solid blue line. This image does not take much analysis and does not even take much meteorological skill to understand.  We will put it to you this way...this is an absolutely horrendous display of model skill. And while this graph doesn't necessarily dictate the actual "skill" of the model...what it should tell you is that we have seen 3 or more false starts to this pattern change...in AO forecasts alone.

There are still several forecasters who are still pushing talk about a pattern change occurring when in fact the "pattern change" has already occurred...but the hemispheric change to one more favorable for snow and cold in the east has not.

To this point -- the general talk about a "pattern change" in the meteorological community is becoming absolutely incessant and, to be honest, quite misinterpreted. The misinterpretation lies in the specific forecasters definition of a "pattern change" and the public perception of it as well. If you talk to someone in the Pacific NW they will tell you, you're damn right the pattern has changed in the last 20 days. But for the majority of posters here..the pattern has not changed to be more favorable for what they want which is cold and snow. This is where the problem arises...forecasters are not differentiating between a pattern change and a hemispheric/pattern change which is favorable for cold/snow in the east.


These are the newest GEFS ensemble mean height anomalies at 84 hours. This is fairly current and the skill at this time is moderately accurate. If you can look at that map and say  that the pattern has not changed from December until now...you either need to clear your cache or need to take a better look. However...this does not mean that the "new" pattern is favorable for our area. There is still a very anomalous Alaskan Vortex in place. That's the first thing that jumps out at me because if you want winter weather on the east coast it is one of the worst things you could see. Also notice the high latitude ridging...it is on the wrong side of the pole for our area at the present time...but it is there and it is quite anomalous in it's own respect. Finally...and this is an interesting point to drive home...there is a large trough/negative height anomalies associated with an upper level low over the Pacific. A friend of mine Dave Tolleris made a terrific post about a week ago about the importance of a large 500mb trough or upper level low in the Sea of Japan as it was modeled by the ECMWF ensembles at that time. Such a development teleconnects very well with not only the development of a more favorable Pacific...but processes to drive the Polar Vortex and associated air towards Eastern Canada in a very favorable position for us. The label on the above image reads "Too far east"...because not only is it too far east..but it never developed in the Sea of Japan at all...effectively canning the favorable changes which the Euro ensemble mean were hinting at. The next image shows the results.


We are now moved forward past 180 hours and the end result of the hemispheric ongoing changes is fairly obvious. Not only has the high latitude ridging maintained itself over Russia...but the vortex over Alaska remains in place and has become more anomalous. This is the GEFS showing the Polar Vortex becoming well established over the Pacific end of the Arctic. There is nothing remotely favorable about this development. You can also see the "channel" of arctic/polar air which takes the Arctic air from the Pacific through Central Canada and right over Baffin Island into Greenland (also known as + NAO).

In this pattern the amplification of the PNA or a ridge out west becomes our only chance for trough amplification in the east which could possibly make things favorable for snow. You'll notice on the 180 hr image above that the minute the west coast US ridge becomes less amplified..the Southeast Ridge on the East Coast rises and we see an area of positive height anomalies emerge. These are the facts. These are things that we cannot deny -- it is the hemispheric pattern which is developing in front of us. However as weather enthusiasts and in some cases professionals we are left to ask ourselves a question we've asked in our own heads thousands of times in various situations. If it's broken, will it get fixed? Where can we start and what needs to happen?

The answer, really...is that we need to see the movement of the Polar Vortex from the Pacific side of the Arctic Circle towards Canada and into a more favorable position. Yes...we could use some high latitude blocking. But the ensemble forecasts are very consistent in developing this vortex over Alaska and the Pacific side..which is no doubt the first thing that needs to change. The MJO does not look very favorable on most ensemble guidance with decent agreement on the impacts of Phase 6 (see the h5 and 2m temp anomalies for that phase...more of the same). That being said...the MJO forecasts have been incredibly inconsistent this season as well which brings a tremendous lack of certainty to their forecasts.

Synoptically, we can look for amplification on the Pacific side as a saving grace in the mean time. Any Greenland or  Davis Straight blocking that has been forecast to develop on all medium range guidance has not developed at all....and at this point I would not be banking on it to develop any time soon. The development of +PNA in the longer term could certainly support the potential for a storm...so long as the NAO region has not completely broken down into another +NAO state. The way it is now..and the way it is forecast to be through the term...is generally neutral...which could give the PNA some extra drive in the pattern.

For example, there may be the potential for trough amplification in the east on Super Bowl weekend. Most ideas haven't worked out so far this meteorological winter when trying to analyze pattern specifics in the medium range...but we are beginning to see most ensemble means indicate a favorably positioned +PNA with a ridge axis near Boise.

----- However..until things change on the Pacific side with the positioning of the vortex over Alaska and the Pac side of the Arctic Circle...or until we see a decently established -NAO block...nothing will change with the pattern we experience here. We will continue to see above normal temperature departures on average...with brief shots of below normal cold air bookended by warmth.

Before ending the post...I think it is important for us to break it down for a second and stop any confusion before it can even begin. This post was not meant to call for the end of winter...it was not meant to say that we won't see any more snow. What it was meant to do was summarize the past few weeks and look ahead to the near future..and make a point as to how the pattern has not cooperated until now and doesn't look to be doing so through the medium range either. All of this said...if you're looking for cold/snow...keep your head up. Things can change -- and although it doesn't look to be coming immediately, we still have just shy of two months of winter left to go.