When will the pattern change to cold occur?

[earthlight]

In terms of December's expectations, I am okay with this occurring. I was thrown with how we would transition into December, but now it seems like we are back on track again. The mid-December warm spell was something that showed up during "winter outlook season" and this was especially true for the Plains. Many of the best analogs were warmest here and it also appeared like the sun would still be elevated enough for this along with the lingering +QBO. The classic Aleutian High-->RNA La Nina December pattern is on the way with no blocking, once the "EPO Ridge" retrogrades back to its classic position mid-month.

While wave activity will likely become more coherent in the next 10 days from Asia, the recent proton bursts into the stratosphere may counter them and keep the polar vortex stable and cold. Once clouds form, it becomes really hard to destroy the vortex early in the season. The +QBO and relative spike in solar activity has made for an exceptionally cold vortex again, just like last year. The new November solar data will be telling but my gut says January and February see a relative min in solar activity, possibly allowing for blocking to return again. The major question is: how will this manifest?

Will it be like 67-68 and both Jan and Feb are cold or will it be more like 56-57 where the stratospheric warming managed to downwell into the troposphere by Feb, but it still was a warm month (while January was cold).

Great post and discussion. Up to this point (not even met. winter yet), it seems as if we've seen a disconnect between the Pacfic and N Atlantic patterns as far as favorability goes. This makes sense given the very positive (near +4) AO values and the now-transitioning PNA and EPO State. Interestingly, the ridge over the Western US (+PNA spike) retrogrades very fast over a period of 3-5 days back to the Gulf of Alaska, and then on most ensemble plumes actually flattens over the Pacific.

With the above transpiring out west, and the lack of blocking in response to the classic Aleutian High/RNA December Pattern you mentioned (in fact a very broad field of moderate negative height anomalies over Greenland and the Davis Straight) model guidance is allowing the Southeast Ridge to flex its muscles once again near Days 7-10. It remains to be seen to what degree it does so -- which may have implications on any gradient pattern that may develop thereafter -- but it appears that the retrogression of that ridge out west will at the very least be detrimental to a wintry pattern from NYC and South.

[Weathergun]

Hard when the stratosphere is locked in a deep freeze

We are also running well below, than around this time last year. And well below the average for late Novembers, back to 1978:

[NaoPos]

Question then:

Have there been any instances of having a neutral/negative AO /NAO during solar peeks? Or is the direct correlation between solar peaks with the same intensity as ours ( which I was under the assumption was not "that" strong yet seeing that we're coming out of a solar min) and high latitude blocking that directly linked to each other? I'm no solar expert here...

I do know that the stratosphere can become quite warm during minimums as we had observed 09-10, and the 1st half of last winter.

[bluewave]

Question then:

Have there been any instances of having a neutral/negative AO /NAO during solar peeks? Or is the direct correlation between solar peaks with the same intensity as ours ( which I was under the assumption was not "that" strong yet seeing that we're coming out of a solar min) and high latitude blocking that directly linked to each other? I'm no solar expert here...

I do know that the stratosphere can become quite warm during minimums as we had observed 09-10, and the 1st half of last winter.

Sure, take a look at the late 70's early 80's and late 60's. But at other times the more active phases had less blocking like the late 80's and early 90's.

http://solarscience....ch/spot_num.txt

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/monthly.ao.index.b50.current.ascii.table

[Weathergun]

Great post and discussion. Up to this point (not even met. winter yet), it seems as if we've seen a disconnect between the Pacfic and N Atlantic patterns as far as favorability goes. This makes sense given the very positive (near +4) AO values and the now-transitioning PNA and EPO State. Interestingly, the ridge over the Western US (+PNA spike) retrogrades very fast over a period of 3-5 days back to the Gulf of Alaska, and then on most ensemble plumes actually flattens over the Pacific.

With the above transpiring out west, and the lack of blocking in response to the classic Aleutian High/RNA December Pattern you mentioned (in fact a very broad field of moderate negative height anomalies over Greenland and the Davis Straight) model guidance is allowing the Southeast Ridge to flex its muscles once again near Days 7-10. It remains to be seen to what degree it does so -- which may have implications on any gradient pattern that may develop thereafter -- but it appears that the retrogression of that ridge out west will at the very least be detrimental to a wintry pattern from NYC and South.

What might save us from all torch December. is that MJO impulse may not be strong enough support a strong ridge over the Alleutians, that would give us stronger SE ridge. I do think without any blocking a weak/modest SE ridge is likely between 12/10-20.

[earthlight]

What might save us from all torch December. is that MJO impulse may not be strong enough support a strong ridge over the Alleutians, that would give us stronger SE ridge. I do think without any blocking a weak/modest SE ridge is likely between 12/10-20.

Havent had the chance to check for an update today, but yesterday's MJO from CPC was developing a moderate impulse around 130-140 E. Not quite as robust as the impulse in mid-late October, but we have seen the ensemble plumes respond the last several days. Recall the GEFS bringing the MJO to very weak -- they have since adjusted. It remains to be seen how far this impulse takes it, but let's hope the ECMWF plumes from yesterday aren't correct. They bring the MJO into Phase 6 and then kill the wave completely.

[Isotherm]

In terms of December's expectations, I am okay with this occurring. I was thrown with how we would transition into December, but now it seems like we are back on track again. The mid-December warm spell was something that showed up during "winter outlook season" and this was especially true for the Plains. Many of the best analogs were warmest here and it also appeared like the sun would still be elevated enough for this along with the lingering +QBO. The classic Aleutian High-->RNA La Nina December pattern is on the way with no blocking, once the "EPO Ridge" retrogrades back to its classic position mid-month.

While wave activity will likely become more coherent in the next 10 days from Asia, the recent proton bursts into the stratosphere may counter them and keep the polar vortex stable and cold. Once clouds form, it becomes really hard to destroy the vortex early in the season. The +QBO and relative spike in solar activity has made for an exceptionally cold vortex again, just like last year. The new November solar data will be telling but my gut says January and February see a relative min in solar activity, possibly allowing for blocking to return again. The major question is: how will this manifest?

Will it be like 67-68 and both Jan and Feb are cold or will it be more like 56-57 where the stratospheric warming managed to downwell into the troposphere by Feb, but it still was a warm month (while January was cold).

Good post HM.

Re solar, to add onto your post, the geomagnetic field has become temporarily unsettled, but overall the month of November was not as active as October in terms of Ap and K values. I think this is just a blurp in the overall solar pattern right now, and we should see values begin to decrease over the coming weeks. I also would not be surprised if February is a much colder month than expected by most, given a number of factors.

Hopefully we can get some accum in the Dec 5-12 period, otherwise we're probably going to be waiting until near the end of the month.

[earthlight]

Here is the MJO impulse I was discussing earlier. You can see the very robust October impulse there as well on the timeline. Unfortunately, almost all of the ensemble plumes are now taking this MJO impulse to moderate strength, and then weakening it into very weak/nonexistent before it can reach the more favorable stages. This, combined with the lack of solar or teleconnector help to promote blocking in the North Atlantic, could lead to a delay in the pattern change and a continuation of overall above normal temperatures for the next two to three weeks.

[Stormlover74]

Perhaps the thread should just be titled "will the pattern change to cold"

[Weathergun]

The new Euro ensembles are also out for the month. Most of them have a weak or modest MJO moving into phases 4-6 before collapsing. That would mean we would left at least a weak/modest SE ridge, until the end of December:

[NJwinter23]

Thanks john....pretty much had all our snow in one week that month.....if my memory serves me correct we had a postal hugger to end it all.....started that morning in the single digits, only to be raining by 9pm

The first 10 days had the 3 events, first 2 favored southern/coastal NJ. The Dec. 9th event was a 4 hour THUMP that dropped like 5 - 10 inches in the area and then did this insanity in Massachusetts

[ORH_wxman]

The new Euro ensembles are also out for the month. Most of them have a weak or modest MJO moving into phases 4-6 before collapsing. That would mean we would left at least a weak/modest SE ridge, until the end of December:

I'm thinking this MJO activity will promote a pretty solid SE ridge...and having it going into the COD before phases 6/7 is a bad sign...this will probably ensure that we keep a robust +AO/NAO through the end of December and possibly beyond.

I think the best hope to do a 180 in the arctic is a SSW that HM has hinted at in January. All data points that we won't get any help before that potential time. The periodic EPO ridges should help with cold in Canada and the extreme northern tier of the CONUS...so hopefully it won't be an all out torch across the CONUS, but this is a terrible pattern for the Mid-Atlantic. Even New England is teetering on the edge of disaster in this type of pattern.

[Isotherm]

I'm thinking this MJO activity will promote a pretty solid SE ridge...and having it going into the COD before phases 6/7 is a bad sign...this will probably ensure that we keep a robust +AO/NAO through the end of December and possibly beyond.

I think the best hope to do a 180 in the arctic is a SSW that HM has hinted at in January. All data points that we won't get any help before that potential time. The periodic EPO ridges should help with cold in Canada and the extreme northern tier of the CONUS...so hopefully it won't be an all out torch across the CONUS, but this is a terrible pattern for the Mid-Atlantic. Even New England is teetering on the edge of disaster in this type of pattern.

Yeah if those MJO forecasts are accurate, it's not looking too promising for a more favorable pattern in late dec. However, all MJO guidance has been pretty poor out past 7 days, so I'm not yet convinced we head into the COD after p4-6.