December 2021

[snowman19]

31 minutes ago, bluewave said:

The extended EPS is -NAO/-EPO/-PNA from late December into January. 
 

Dec 20-27
 

 

Dec 27 to Jan 3

 

Jan 3 to Jan 10

 

@donsutherland1  They are all very persistent with the -PNA, also, some big questions on what actually happens with the MJO and if it actually gets into phase 8 or does then dies out. Allan explains: 

Also, the La Niña has now gone moderate, doesn’t appear to be going anywhere soon, it’s effects will certainly continue into January, February, March: 

 

[brooklynwx99]

There has been research on the MJO-QBO relationship, and it has been found that easterly QBOs often lead to slower, higher amplitude waves of convection, so I am not overly concerned with the MJO dying out in Phase 8:

"In summary, it has been found that the composite OLR anomaly shows a larger negative value and a slower eastward propagation with a prolonged period of active convection in the QBO easterly (QBOE) phase than in the QBO westerly (QBOW) phase."

https://journals.ametsoc.org/view/journals/clim/32/21/jcli-d-19-0013.1.xm

[donsutherland1]

24 minutes ago, snowman19 said:

@donsutherland1  They are all very persistent with the -PNA, also, some big questions on what actually happens with the MJO and if it actually gets into phase 8 or does then dies out. Allan explains: 

Also, the La Niña has now gone moderate, doesn’t appear to be going anywhere soon, it’s effects will certainly continue into January, February, March: 

 

I believe we will probably see a cooler period during the first 10 days of January given the atmospheric response to the MJO’s move into Phase 7 at a very high amplitude. I am not sure whether there will be severe cold nor whether such a pattern would persist more than 2 weeks. It’s possible most of the severe cold will remain confined to the west. 

[Allsnow]

37 minutes ago, bluewave said:

The extended EPS is -NAO/-EPO/-PNA from late December into January. 
 

Dec 20-27
 

 

Dec 27 to Jan 3

 

Jan 3 to Jan 10

 

Weeklies very blocky from xmass to the end January 

[MJO812]

10 minutes ago, Allsnow said:

Weeklies very blocky from xmass to the end January 

Primetime

[forkyfork]

get that stupid trough out of california plz

[EastonSN+]

1 hour ago, bluewave said:

The extended EPS is -NAO/-EPO/-PNA from late December into January. 
 

Dec 20-27
 

 

Dec 27 to Jan 3

 

Jan 3 to Jan 10

 

Are there any similar looks in the past to compare the upcoming patter to? I can't remember such a set-up.

[MJO812]

 

[EasternLI]

31 minutes ago, brooklynwx99 said:

There has been research on the MJO-QBO relationship, and it has been found that easterly QBOs often lead to slower, higher amplitude waves of convection, so I am not overly concerned with the MJO dying out in Phase 8:

"In summary, it has been found that the composite OLR anomaly shows a larger negative value and a slower eastward propagation with a prolonged period of active convection in the QBO easterly (QBOE) phase than in the QBO westerly (QBOW) phase."

https://journals.ametsoc.org/view/journals/clim/32/21/jcli-d-19-0013.1.xm

Yeah, recent research has really shown its a very important piece of the puzzle. Plus, this particular year, there's even more to that. La nina plus EQBO plus low solar (which lags ~3 years) cumulatively increases the North Atlantic response to said mjo. So the base state is primed to be very receptive. It's all a big part of the reason I got interested at the possible progression earlier this month. Now it's all about to get underway and I'm fascinated to see how this all goes.

https://journals.ametsoc.org/view/journals/clim/33/1/jcli-d-18-0811.1.xml?tab_body=fulltext-display

As shown by the spatial correlation resultsofFig. 10and the SLP/SAT diagnostic results ofFig. 11,composites for combined SMIN/cool ENSO, SMIN/QBOE, and SMIN/QBOE/cool ENSO conditions produce progressively stronger MJO modulations of meanSLP and SAT anomalies in the North Atlantic/Eurasiansector. These results are consistent with previous workshowing that the QBO interacts with other low-frequency stratospheric signals such as the 11-yr solarcycle

[brooklynwx99]

I continue to remain confident on a wholesale change to the 500mb pattern over the next 10 days... this is mainly due to the strong MJO wave propagating towards the dateline, which will provide the impetus for -EPO ridging, as well as the anomalous Scandinavian trough which will retrograde into the NAO domain. 

The MJO is currently in Phase 7, and looks to make a break for Phase 8 as well within the next 10 - 14 days, which is favorable for high-latitude blocking and cold air intrusions into the E/C US. Although there have been some murmurs about the -ENSO interfering with the propagation of the wave, having it die before reaching Phase 8 with high amplitude, the -QBO state often allows for stronger, slower waves. This should allow for the MJO to continue its propagation through favorable phases.

The Scandinavian ridge that's been talked about since the beginning of the month is now starting to form in the short range, and will reach +2.5 sigma:

This cutoff ridge will retrograde towards Greenland, providing stout -NAO blocking that will, in turn, lead to significant confluent flow over Nova Scotia. This should keep the SE ridge at bay even with the -PNA. There will also be a great cold feed into the US from the -EPO forced by the MJO, which is a complete 180 from what we've been seeing recently. Both of these drivers should lead to a coast-to-coast trough, which becomes more apparent towards each of these runs:

 

I've heard a lot of concerns about the -PNA, and I don't believe that they're totally founded. We will probably have to deal with the SE ridge before the blocking is fully established, but once the -NAO begins to retrograde, the compression of heights in SE Canada will ensue. This almost always crushes the SE ridge and allows for redevelopment of any systems that would try to cut. So it might be a problem towards the 20th, but the maturation of the blocking should allow for confluence to take over.

Anomalous -NAO blocks like this have the potential to completely overwhelm patterns, and this one looks to become more and more west-based over time, which is optimal. If anything, a +PNA here would likely lead to supression until the block eventually decays. The negative anomalies throughout the Atlantic also lead me to believe that this is a legitimate -NAO, as the flow in that region is completely backed up.

The high-latitude blocking will also lead to dramatic heat fluxes into the stratosphere, which look to constantly disrupt the SPV. I don't believe that the SPV will be able to consistently strengthen, and a weakening of the SPV may allow for prolonged blocking. A SSW isn't on the way as of now, but that would significantly disrupt -ENSO climo if it were to occur, and this would certainly be a step in the right direction. 

This December will almost certainly finish with a -NAO/-PNA combo. The Januaries that historically followed Decembers with a -NAO/-PNA featured favorable patterns for the E US with a significant west-based -NAO:

Overall, I am quite excited for the end of the month, as things get very interesting any time we see blocking of this magnitude. I expect the SE ridge to continue to correct weaker as the -NAO trends stronger with time (as hemispherically forced -NAOs usually do), allowing for a coast-to-coast trough look. This would be the "just cold enough" type pattern where waves roll under the block with good climo. Hopefully we continue to see these corrections as we endure a dismal pattern through the 20th.

[bluewave]

23 minutes ago, EastonSN+ said:

Are there any similar looks in the past to compare the upcoming patter to? I can't remember such a set-up.

No recent years going into January had anything close to that 500 mb pattern. The only January with such a prominent -EPO/-PNA/-NAO was 1969. FWIW,  NYC finished at 31.8°, 1.10” of precipitation, and only 1.0” of snow. It was a very dry month. The caveats are that the extended EPS is only just a snapshot of what it’s showing from the end of December into early January. Skill falls off beyond the 2nd week.

 

[EasternLI]

 

[MJO812]

Gfs coming in southeast with the 21 storm

[SnoSki14]

The -PNA will be costly unless the Atlantic blocking is very strong. 

As soon as ensembles back off on the blocking the SE ridge will rage.

You can try to put lipstick on a pig but things still look crappy.  MJO also showing signs of halting in phase 7. 

[donsutherland1]

Temperatures rose into the 50s today across most of the region. Similar warmth is likely tomorrow.

Parts of the Midwest could see daily and December-record temperatures. Des Moines has a shot at seeing its first ever 70° December day. Some of that warmth will affect the region late in the week before cooler air again returns.

No Arctic blasts appear likely for the foreseeable future. Overall, through December 20th, there will likely be only some relatively short-lived cool shots. Afterward, the AO could go negative, increasing the opportunity for colder outcomes.

In the Midwest, Chicago has yet to receive its first measurable snowfall through December 12. Only four prior years saw their first measurable snowfall on December 12 or later:

1. December 20, 2012
2. December 16, 1965
3. December 14, 2001
4. December 12, 1946

The base case is that the closing 10 days of December could turn cooler, though not necessarily cold. Since 1950, there have been 7 cases where the AO averaged +2.000 or above during the first week in December, as has been the case this year. The mean December 21-31 temperature in New York City was 40.2°. The median temperature was 41.5°. The coldest was 35.3° (1951) and the warmest was 44.0° (1979). In short, this historic experience would suggest that there will be no severe Arctic outbreaks in the East this month. It also suggests that New York City will likely have an average temperature of 40° or above this month.

Afterward, if the small sample of cases where the MJO moved into Phase 7 at a high amplitude (1.75 or above) during the December 10-20 period, as occurred this month, is representative, the first 10 days of January could see below to perhaps much below normal temperatures. Both the magnitude and duration of the cold is uncertain, but the potential pattern change as support on the latest EPS weekly guidance.

Following very wet July-September periods, winter (December-February) precipitation has typically been near or below normal. The most recent exception was winter 2018-19.

The ENSO Region 1+2 anomaly was -1.4°C and the Region 3.4 anomaly was -1.1°C for the week centered around December 8. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.00°C and the ENSO Region 3.4 anomaly has averaged -0.92°C. La Niña conditions will likely persist into at least late winter.

The SOI was +12.92 today.

The preliminary Arctic Oscillation (AO) figure was +0.395 today.

On December 11 the MJO was in Phase 7 at an amplitude of 2.411 (RMM). The December 10-adjusted amplitude was 2.425 (RMM).

Based on sensitivity analysis applied to the latest guidance, there is an implied 87% probability that New York City will have a warmer than normal December (1991-2020 normal). December will likely finish with a mean temperature near 42.4° (3.3° above normal).

 

[snowman19]

30 minutes ago, bluewave said:

No recent years going into January had anything close to that 500 mb pattern. The only January with such a prominent -EPO/-PNA/-NAO was 1969. FWIW,  NYC finished at 31.8°, 1.10” of precipitation, and only 1.0” of snow. It was a very dry month. The caveats are that the extended EPS is only just a snapshot of what it’s showing from the end of December into early January. Skill falls off beyond the 2nd week.

 

All the people who wrote off the La Niña as “dead” back in October were dead wrong. It just went moderate, peaking in December. Time to start praying for a major SSW to disrupt the normal Niña progression for mid-late January and February, especially given the severely -PDO/coupled Niña or the pattern is going to torch big time once the tropical convective forcing moves back to the maritime continent as per normal Niña climo, this isn’t last year where the Niña never coupled….

 

[rclab]

9 minutes ago, SnoSki14 said:

The -PNA will be costly unless the Atlantic blocking is very strong. 

As soon as ensembles back off on the blocking the SE ridge will rage.

You can try to put lipstick on a pig but things still look crappy.  MJO also showing signs of halting in phase 7. 

Good evening SS14. Oh I don’t know…. In my, just developing, much younger days, at least to my eyes, the lipstick, seemed to work quite well. As always …..

[MJO812]

16 minutes ago, SnoSki14 said:

The -PNA will be costly unless the Atlantic blocking is very strong. 

As soon as ensembles back off on the blocking the SE ridge will rage.

You can try to put lipstick on a pig but things still look crappy.  MJO also showing signs of halting in phase 7. 

How do you know the ensembles will back off ? These posts are useless without reasoning.

[WeatherFox]

Fyi

“La Niña is anticipated to affect temperature and precipitation across the United States during the upcoming months (the 3-month seasonal temperature and precipitation outlooks will be updated on Thurs. Dec. 16th) by NOAA”

[RippleEffect]

48 minutes ago, MJO812 said:

Gfs coming in southeast with the 21 storm

GFS looks perfect wish that low over the great lakes would come in later so it doesn't interfere with warm air because we already have a good high positioned around east of Montreal. the GFS track is perfect if you want a big snowstorm. still so early! good improvement though. GFS is not trustworthy though!

[Allsnow]

Weeklies finally picking up on the mjo progression into the colder phases. It’s also nice to see substance forming in the base state we have had this past fall.

[EasternLI]

Given the la nina went east based, coupled with a -PDO, favors -NAO. I posted the paper earlier in the thread about this. 

 

Not sure why people should have a problem with a weak or moderate Niña to begin with. Only weak Niño would be more preferred.

[SnowGoose69]

1 hour ago, snowman19 said:

All the people who wrote off the La Niña as “dead” back in October were dead wrong. It just went moderate, peaking in December. Time to start praying for a major SSW to disrupt the normal Niña progression for mid-late January and February, especially given the severely -PDO/coupled Niña or the pattern is going to torch big time once the tropical convective forcing moves back to the maritime continent as per normal Niña climo, this isn’t last year where the Niña never coupled….

 

 

There are usually 2 types of bad La Ninas in this area.  The one where Dec is cold and Jan/Feb torch, the other where Dec/Feb torch and Jan is cold..this year may be more or less the latter.

[Allsnow]

 

[EasternLI]

This is a bit.... different. Buried under the 12z EPS mean, HR's 192(bottom)- 240(top). Half of all the members did this.

[Rjay]

23 hours ago, MJO812 said:

You will be singing a different tune once the models adjust to the change.

 

2 hours ago, MJO812 said:

How do you know the ensembles will back off ? These posts are useless without reasoning.

 

[MJO812]

4 minutes ago, Rjay said:

 

 

So the models never adjusted to a pattern change ?  Come on Ray.

[Allsnow]

[NEG NAO]

46 minutes ago, Allsnow said:

I'm dreaming of a White  New Years..........Overrunning scenerios ? Miller B's ?  Plenty of blocking...........

 

[Rjay]

Just now, NEG NAO said:

I'm dreaming of a White  New Years..........Overrunning scenerios ? Miller B's ?  Plenty of blocking...........

 

Only 16 more days to go!