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Happy Birthday @C.A.P.E. I hope you are having an extended Happy Hour !!!!

This is crazy

@psuhoffman hearing some mets, including Webb talking about the first indications that the IOD may begin to weaken soon. HM stated it does not have go completely away, ( which is good because I know it will take a lot of time to do so ) but just not be as dominant. Webb feels it weakens month end, and we may start to reap the benefits as early as mid Jan as the focus of tropical forcing becomes more favorable. He stated if that happens it could have rather significant implications. Based on the context he stated his reply, I am rather sure he means cold and snow-wise.

For sure, this December presents many challenges and there are more diverse forecasts out there than typical. No one really knows for sure. Isotherm may be correct, as the month is only 3 days old.

Fits the recent theme of transient blocks and in and out cold during non-peak climo here. No real surprises. And, as some have mentioned, expect variability for a good portion of the month. We need a sustained -NAM to have real threats. I agree about the cutter outcome. However, things are progressing towards the cup being half filled.

Well, not everyone is optimistic about December, and the winter in general, regardless of the recent developments. Here is a very recent update from Isotherm. I brought this over from 33 if anyone is interested. from Isotherm: <<< [1] The recent storm largely behaved pursuant to expectations, favoring significance across the interior Northeast, with generally minor, 1-3" amounts along the I-95 corridor. The key dilemma was the relatively northerly location of the z700/850 and concomitant lows, which yield maximum felicitous forcing/lift and snow growth approximately 100 miles to the north; hence, the historical snowfall near Albany is not surprising. The boundary layer warmth was an issue for the coast, due in part to poor forcing, in concert with climatological issues [early season]; sporadic banding is insufficient to maintain the necessary evaporative cooling processes as well. [2] Pursuant to conversations hitherto, between myself and others such as @Bring Back 1962-63 and @Tamara, the negative NAO episode was quite ephemeral. The intraseasonally/extratropically forced perturbation yielded a transient diminution in the NAO from November 24th-November 30th, and both the AO and NAO are now strongly positive, in accordance with the base state forcing [and the variables underpinned in my NAO formula]. [3] Recent +EAMT episode will yield the ridge spike downstream, as evinced on medium range modelling; however, the underlying predilection will be for premature amplification and thus a continued propensity for hostile storm tracks for the East Coast/I-95 corridor. The aperiodic NPAC ridge spikes were highlighted in my outlook for December [and also repeated appearances during the winter], but the angular momentum transports will continue to promote circum-global sub-tropical ridging. FT has declined materially, and overall, the torque budget should remain near parity for the medium term, as GWO circuits again through the null. [4] Latest QBO value is slightly over +5 for November, again, pursuant to my expectations that this would be a slow descent of easterly shear stress. We have now fallen behind the pace of 2004, and it is unlikely to transition easterly until the end of January or later. This will have ramifications as far as persistently countervailing attempts at protracted blocking. [5] The pattern, from a sensible weather sense, should promote cold over the Mid-west/Plains, and surges of mild air pre-storm along the East Coast. The structures overall should be generally unpropitious/hostile to coastal significant snowfalls. [6] Recrudescence of lower geopotential heights near Alaska is expected following this EAMT induced ridge spike. Concomitantly, the NAM/NAO should remain generally positive throughout December. Hadley and walker cell behavior continues to operate in accordance with my initial thoughts several weeks ago. [7] Note, that the MJO was a largely minor component of my outlook, and the fact that it may be stationary over the IO for awhile does not impact the likelihood that December finishes warmer than normal. I still think the departure estimates set forth are reasonable. [8] Eventually, the MJO will regain coherency, as it propagates eastward [late December]. [9] Current ECMWF guidance indicates a fairly rapidly intensification of the stratospheric polar vortex in the medium term. Whether that happens or not --- is not dispositive as it pertains to the tropospheric structures. Summary: First, as a general caveat, to ensure to readers that I am not engaging in the very confirmation bias against which I impugn, here is what could enable to a faster transition into sustained winter pattern than I delineated in the outlook: Since it is unlikely to receive assistance from the QBO in a material way for awhile in my view, the earlier assistance must have provenance in the tropical troposphere. A very potent MJO circulation through 6-7 in late December, ideally in concert with highly anomalous EAMT, would engender a significant momentum induction and further elicit rossby wave propagation poleward. This would, a priori, disrupt momentum budgets enough, in tandem with material SPV disruption, to loosen the effects of the stronger than average tropospheric vortex. However, the likelihood of that occurring is currently low, and the present base state momentum transports and forcing backdrop should continue to promote a +AO/NAO in the means. Spasmodic NPAC ridge spikes should deliver bouts of arctic/polar air, but unfortunately, the storm track should continue to be unfavorable for coastal areas. And I do not see any indication of this tendency reversing for the foreseeable future. As seen with the recent storm, I believe this tendency will persist, re: favoring interior Northeast. All in all, everything appears to be on track, at least from the standpoints of myself and a few others who I know accord with these thoughts. I realize this is an unpopular interpretation, but it is my objective interpretation of the pattern, and no one can unequivocally claim they know what will transpire at this time. >>>>>

I feel this is great news. Regardless of the closet match, keep it going down. Hopefully this is another positive added to the mix for Jan through March. Some folks were concerned it might stall.

Reading from a met who stated some of those looks within a greater window of 30 days, not the date centered on 12/14 , so going towards and including 12/28 have produced some significant EC snow events, including significant over running snowfall producers going from the Tennessee Valley to the Northern Mid Atlantic. I am thinking he did a roll over from that CPC depiction, but not sure.

I will take an order of blizzard, a side of drifts and for dessert a gale or two.

Very true, he knows his stuff, but that does not give one the excuse to act like an ass to others . Being humble has advantages. Eating crow is on his menu today.

You know avoiding a massive and prolonged warm up in Canada, along with a loss of snow cover, similar to last December, in my opinion really ups the ante for severe arctic outbreaks here in our area. Snow cover to our North and Northwest is very impressive right now.

More on the possible NAO block from HM and his general thoughts about December. Great job so far Anthony ! Colder risks seem to be gaining traction lately.

Most excellent ! I totally agree, minute details in weather do matter, that is what makes this hobby so enjoyable. Next, I need snow, a lot of it please. I want to dust off the snowshoes.

Excellent animation by Hugo regarding the upcoming wave break in the North Atlantic. Gives more support to something near mid month. The evolution of any -NAO is still key to an any snow possibilities down our way. By this time we are deeper in December, will be interesting to see what transpires in the NAO domain the second and third weeks of December. Maybe the block times perfectly with some over-running moisture to our South, as signs are for an active STJ this month. Also, note the changes here beyond December 7 th : 00Z GEFS 1.0° 100 hPa 60°N tercile categories The tercile-category anomaly of the lower-stratospheric polar vortex, defined by the 100 hPa 60°N zonal-mean zonal wind, has been used as a diagnostic for the behaviour in the ‘coupling layer’ between the stratosphere and troposphere, i.e. the level in the stratosphere where circulation anomalies are important for influencing tropospheric weather regimes (e.g. Charlton-Perez et al. 2018, Lee et al. 2019). The chart below shows the percent of GEFS members in each tercile anomaly category, based on daily 1979-2018 ERA-5 climatology. Weak = lower tercile; neutral = middle tercile; strong = upper tercile.

A few interesting things to keep an eye on : The mid month period when there are signs of a drop in the AO along with a +PNA interval. Some favorable action too from the strat may work its way down to a degree. Meanwhile, interesting progressions with the warming as it transpires in terms of the Canadian vortex and trop / strat vortex over Siberia/Scandy , as mentioned by Hugo. Also, the elongation and the movement of the trop vortex has my interest as well, in a backdrop favorable to keep the vortex perturbed. Below are several relevant recent releases on the above.

Maybe we get lucky with some snow showers this week, but the way the current pattern looks, I think we need to wait a while. The various indices that are normally associated with accumulating snowfall in the Northern Mid-Atlantic our not in our favor moving forward. Yes, I know about scoring in flawed patterns, but with the time of the year, I have less confidence that happens this go around. The end of the month still seems to be uncertain, maybe we turn colder with opportunities later in the month.

I will gladly ride the BAMMWX train ......................where can I get my ticket ? By the way.....I still believe in snow and in holiday spirit. Hopefully, a nice time coming up for us soon for those who enjoy cold and winter scenes of snow covered fields and streets bounded with snow in a winter wonderland.

I admit there are some positives but as you know the GEFS is at times biased weak, at least so far this early season, while the EC has done better in strat verification forecasts. However, as you mention, we are talking under 7 days here with the GEFS, so that is a positive. Also, according to Simmon Lee the FV3 GFS has been doing better versus the GEFS. A quick note on the AO ensembles - seems the forecasted extreme positives, up to +5 or more, have been trimmed back down to about + 3, with several members taking the AO back negative shortly thereafter. As HM stated previously, the same processes causing the AO to rise will be responsible for the upcoming decline in the NAM state. Meanwhile, Matt is impressed by the potential down the road. We will also get an update soon regarding the QBO. There are some interesting evolution and progressions possible in mid- January if things work in our favor. This is of interest as well :

I understand your point.

Sorry, nothing is bogus here. Research is convincing that during this decade there has been impressive warming in the Indo-Pacific warm pool and changes in the behavior of the MJO. Since 2010 there has been a tendency for repetitive Fall patterns. If you don't agree with the data that is fine.

Do you follow Isotherm? I know he has spoken about the solar cycle and in various posts he has alluded to role the solar minimum has on potential impacts within the NAO domain. His seasonal prediction of the NAO has a very good record. I found some articles/research that seems to reveal a link between the years after the solar min, and the phase of the NAO. The interesting part is the lag effects. Seems it could take a year or two, maybe even longer for the impact to be reflected in the NAO domain. The link was SST based I believe.

I brought it up because it has been repeating lately in some form or fashion ( a 2010's weather theme, and you can read more about MJO study here ) https://www.nature.com/articles/s41586-019-1764-4 and this from @bluewave Yes, I just posted that in the climate change forum with all the charts included. The changes to the MJO have become a big part of our 2010’s weather patterns. It shows what we already figured out. The MJO has been spending more time in the Maritime Continent phases due to the rapid SST warming of the Indio-Pacific warm pool.

You believe we follow the same general progression this winter? I feel we will, but the colder risks will win out once past early Jan. Also, speculation on my part that we will deal with some significant phasing events and some very cold arctic intrusions. Simple guesswork reveals the best -EPO period/events in mid- Jan, and the best -NAO event in early to mid Feb and another opportunity in March. ( March to a degree dependent on the declining QBO and any SSW in late Jan. and early Feb) again just some thoughts there.

The much anticipated warm December is coming. Simply can not fight the deep tropics. The same concerns last year regarding the MJO that lasted in the warm phases for weeks on end may repeat again this December. The latest AO forecast do not look as good today, the NAO going up. Source regions are warming. The camp that predicted an overall warm December is a step closer to possibly being correct. Early December this year similar to last year, and then we warm. Whether it lasts two weeks or longer is still hard to pin down. The consistency of the last few years of the pronounced warm up post 12/20 is an increasing risk again this December. There is a repeating pattern of late.... warm Octobers , cold Novembers, Decembers turning warmer after the first week. There could be a delay this December with the cold winning out until the 10th, but still looking like we warm once past the 10th. I will also mention new research reinforces that the idea in which the MJO is spending more time in the warmer phases while racing through the cold phases. This is pronounced in the time period from 2010 forward.

There does seem to be some differences to last year at time, with possibly a bit less amplitude. Last year was agony though, with the slow progression through the warm phases, and that lasted well into Jan. if I recall correctly.