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Bluewave, any thoughts regarding progression of the +IOD / standing wave this month? In the short-term, as in this month, do you envision any weakening of the standing wave and a weakening in the general record +IOD. Eric Webb mentioned maybe later this month it starts to weaken. I believe it is typical as well to see the seasonal change over there and the eventual decline in the +IOD as we go through Jan and Feb.

I see a noticeable AO ensemble change with today's forecast, a decent majority of the members take the AO to neutral to even negative by mid-month. This is a rather big change in the last 24 hours.

I guess, but one never knows. Just because we were lucky so far does not mean it will last. I agree we have more than often verified seasonal to cold and avoided a torch period, so far. I however, can not shake Isotherm's view and a couple in his clan regarding tropical forcing/glamm/MT /AAM/ a stubborn PV, an ineffective QBO, etc. If correct, ( Tom ) we end this month warm and start Jan warm as well, with likely little snow. Yeah, Ok, it is December but if his view is correct it will take weeks to get to a better pattern. The -EPO not looking as good, AO and NAO not looking good, etc. Again two camps, seasonal December maybe a little below normal , and the other whom if correct with their insights, we warm as the HL turn to crud and we run the warm MJO phases or simply stagnant in the warm phase(s) along with possible consequences from the standing wave yet again.

Don S seems to think the talk about this potential split is talked about incorrectly by some on social media. I assume based on his post that he does not agree with BAMMWX, since they only focused on 50 mb. He also mentions a continuation of a +AO regime by the GEFS. . I bring you his post over from 33. from Don: << Bad information about an imminent polar vortex split is circulating on Social Media. Even at the 50 mb level there is no split. Further, a true split happens at more than a single layer of the stratosphere. Not surprisingly, the GEFS forecasts the continuation of a general AO+ regime.

I am not sure the outcome, but this will in some form be a player, whether though elongation of the vortex, displacement, etc. As we near hour mark 360 in fantasy land you can see the configuration may be a conducive one. This is also what HM mentioned two days ago, and it is still in the forecast currently moving forward.

If, this "colder" risk does indeed verify, it would go counter the recent warm-ups after 12/20 and potentially make many snow weenies happy. The storm threats look to continue, the more there are the higher the odds we eventually score especially if what Bob mentioned above continues to progress as well. Maybe we eventually progress to a Northern Mid Atlantic SECS pattern.

@poolz1 keep an eye on this in the week or two ahead via BAMM , as well as what HM mentioned about the near splitting vortex, further down. Low chance but still of interest. Also seems like a bit of a spread with "maybe" an improving AO towards mid month and beyond.

I don't recall the exact specifics, ( coffee still kicking in ) but reading over a post at 33 someone noted a similar evolution that did happen and triggered a negative NAO which was one factor responsible for the Jan 2016 miracle that trended from a rain event many days prior to your victory of the winter. Is that all true ?

Awesome stuff here. Love it !

I hope the "weaklies" are wrong.

Interesting, wonder what will happen when the record +IOD starts to weaken or the Eastern region 1.2 becomes colder. I believe 1.2 is expected to get colder again later this month. Also, signs down the road the MJO starts to improve. This may coincide with the next attempt of a - NAO , later in the month, or early in Jan. So, there is hope that both the Pac and the Atlantic may both become favorable for a time.

@Bob Chill your call about the +PDO seems to be happening in real time. The November figure was positive. Of course we might improve on that this month. If this oceanic researcher is correct with his formula calculation, then the PDO should rapidly increase in the + range later this month and in Jan.

Thanks for taking the time to post that psu ! And, this is not as bad as I would have thought: Since 1950 the January/February months following a +AO December were 12 negative AO, 16 Neutral AO, 20 positive AO.

To me he talks mostly of pattern drivers and such. I would think that benefits a large area.

I hope HM's hand remains hot at the table.

Bob, am I correct that it will be three more days until the shortwave comes onto the California Coast ? The particular latitude may be a player as well. If so, more changes are a coming no doubt.

I was really hoping once the AO peaked recently we would not have another attempt at a + 3 SD or higher. It appears another run up is possibly on the way. The image below is from the 12/4 , but if you looked today it is much higher. Could not get that to post correctly. Having the AO drop down in November was great, but I believe you can not gather that decline as a proxy to what the upcoming winter may have in store regarding NAM state. Another deep dive in December I would speculate has more relevant meaning for the months ahead such as Jan. and Feb., maybe even March, versus a November dive down. I am sure there is research on this somewhere. I could almost speculate that possibly the drop in November was more an outcome of the combination of typhoon involvement, and early season mechanics. So, I guess more a head fake versus a real signal. @Isotherm , Benchmark or even HM might be able to answer that possibility.

Can anyone confirm these maps were just released ? The Euro Seasonal . Seems new to me, and they look sort of blah with a 2 meter temp signal indicating ridging too far off the West Coast and a slight signal for a SE ridge. Bottom row indicates active storms and precip, but maybe on the rainy solutions along the East Coast ? Same issue as last year possibly with a lack of HL blocking, as I already mentioned earlier today. Looking at this output form the Euro seems it would be similar to last year in terms of the best winter target zone, the upper Midwest and Northern Plains. Can the Euro seasonal be wrong, of course, but balancing things out this continues the theme of high uncertainty regarding the winter. I mean last winter's seasonal from the Euro were so so bullish for snow and cold and then looked what happened. I continue to balance expectations.

The same old story with Decembers and the NAO. Seems no break in this pattern. According to bluewave this goes back to 2013. (see below ) I know there was talk of a wave break and possible interval of a -NAO during mid-month, but I don't see it. Those calling for a -NAO in December of any magnitude might need to reconsider. ( The caveat is no one really can be confident in the outcomes of the NAO far into the future so, my comment is geared to the next couple of weeks ) Bringing up the common seasonal idea is that the most robust - NAO is in Feb and the most robust -EPO is in Jan. However, starting to wonder whether HL blocking shows up eventually, and whether we get a -AO averaged winter. Reading some folks whom tie in the tropics with the HL, they state tropical forcing including AAM and GLAAM are lacking in terms of promoting the mechanisms needed to achieve durable HL blocking, They also state HL blocking precursors will be fading starting now and may last for a while. An additional concern is the warming in the Eastern ENSO region. So make of that as you may, it appears as others have stated, a high probability of not knowing what is going to happen along with a roller coaster of temps here in the East in the coming three weeks.

I am not really sure about what HM is focusing on in regards to the vulnerability of the vortex. When I read Isotherm and a couple others whom really focus on the strat they paint a not so rosy picture. Little to be hopeful about for a while. Even the QBO is not going to be a player until maybe Feb. from some sources. Regardless of whether the QBO is following the linear progression of 2002 most closely, this fall does not have the feel of 2002 and certainly the Nino aspects are not the same. Enter a recent warmer backdrop globally, that comparison losses value, as we are talking 17 years ago. Even though the GFS has short-term skill and is predicting wave 1 attacks on the vortex, the result seems to be more movement of the vortex, displacements if you may, versus a real weakening trend versus what was happening, or starting to happen last year at this time, as Simon mentioned that this morning. This development more closely matches what Isotherm was looking for I believe for the mid month period.

I will get excited when the highest snow amounts in the ensembles are South of us. Seems like the last 2 years the ensembles paint a rosy picture of 4 to 6 inch amounts ( several times in the season ) and they never happen. Worse yet, the 46 day snow total off the ECM, that also seems never to work out. I cringe when I see folks like JB or even Maue post these sometimes. I admit it is entertaining, but hardly ever works out.

Seems that the EPS and the GEFS are worlds apart in the eventual outcome. But, as mentioned already, without any significant help from the NAO or the AO regions any storm will simply cut despite how cold it is close to the event.

I had to read it twice until I realized it was Ji who wrote it . Very philosophical.

@Maestrobjwa I know you have an interest in this, I bring you a couple short posts from 33, one from a very informed member, the other from a met. From Bring-Back 1962-63 Low solar "can" be associated with colder winters. More often the coldest winters tend to be just after the solar minimum. We are right at the minimum right now. There is usually a run of 3 winters which "can" be influenced and any combo of 0, 1, 2 or all 3 can see colder patterns. The last minimum was in 2009 and there was a triple hit. In the UK (and Western Europe) we had a cold winter in 2008/9, 2009/10 and the coldest Dec since 1890 in 2010/11 (although the 2nd half of that winter was mild). From Analog96 DT was talking about that ( this might be a protracted min ) and how it could impact NEXT winter, as well. Now, I just want to point out one thing. Being in a solar minimum does NOT guarantee cold winters. HOWEVER, it biases everything toward colder. Atmospheric indices/teleconnections, etc, still rule the atmospheric response. BUT in a solar minimum, cold teleconnections will verify colder than otherwise, and warm teleconnections would verify "less" warm. Teleconnections that favor average temperatures would probably result in a bit cooler than average.

I don't think the WDI has any real value, whether by chaos or statistical merit. Too short a reference period as well. If you look way back there are periods when many years pass without any real significant snow.