Early run up to Winter 2020/2021 discussion

[Met4Cast 12,211]

I'm going for a milder & wetter than average winter again this year, unfortunately

This forecast is on the basis that there is no SSW this year. I'm not really seeing where the front-loaded winter is supposed to come from. The atmosphere hasn't thus far taken on much of a La Nina state, and given latest model outputs and intraseasonal models for December + the current state of the Stratospheric vortex, I'm not seeing a particularly interesting December, however I do think the highest risk of any potential cold could come through December > Mid January. Beyond that I think we'll see diminishing returns and an uptick in overall zonal/Atlantic activity.

[Catacol 18,319]

Not much good news yet. Very low heat flux - will only serve to pump up the vortex further....

Edited November 17, 2020 by Catacol

[damianslaw 14,743]

1 hour ago, mb018538 said:

Definitely. This year has shown us what we already know - anything is possible. Wettest February on record, a great April, sunniest May on record, the record breaking heatwave in summer. A cat 5 hurricane in November. Now winter is set against a backdrop of unprecedented arctic warmth, after seeing 38c at Verkhoyansk in the summer. Pattern matching and going against long term data is increasingly futile as the climate continues to change rapidly.

What I’d say is to just break things down into 10 day chunks, and go from there. The next 10 days (barring a brief dusting up north Thursday) are down the chute. It’s not even winter yet, and there’s 12 good weeks to use. Loads of time.

Nov 2009 was one of the mildest and wettest on record.

[Sunny76 986]

I’ve been wishing for a brutal cold spell after Christmas, or just after the new year, until the second week of January. Something similar to January 1987, or at the very least another late feb 2018 spell. Biting windchill and 3-5 days below 0c, even in London and the south. 
 

The only thing that makes me feel guilty about wanting something like this is, the fact that many people will be struggling to heat their homes, on top of not having enough food. Especially with the high unemployment during this coming year due to covid.

A mild winter would be more welcome by the general population. 

[Catacol 18,319]

32 minutes ago, Met4Cast said:

I'm not really seeing where the front-loaded winter is supposed to come from. The atmosphere hasn't thus far taken on much of a La Nina state, and given latest model outputs and intraseasonal models for December + the current state of the Stratospheric vortex, I'm not seeing a particularly interesting December, however I do think the highest risk of any potential cold could come through December > Mid January. Beyond that I think we'll see diminishing returns and an uptick in overall zonal/Atlantic activity.

Based on current output I agree. We have rising momentum once again, preventing what should be the Nina base state from coupling with the atmosphere, and the forecast for an Alaskan trough reinforces that view. So - a strangely Nino-esque pattern destructively interfering with the early season Nina projection continues, and all the while vortex temperatures at 30hpa are where they should be at the end of December and wind speeds are forecast to be high. There is still a chance of some cold shots in December, but the chances of anything sustained are fading by the day. Those hoping for snow from horizon to horizon may need to increasingly focus on developments in the stratosphere, and whether we can see a split reversal with accompanying roll of the dice in terms of outcomes. We learned in 2018 that such events can completely override any tropospheric forcings once in motion.

Incidentally - the question I have asked far more knowledgeable people than me is - how come the ocean and atmosphere can become decoupled in the first place? I'm yet to receive a satisfactory answer. I guess if it were possible to predict the match between the two each year then forecasting would become a hell of a lot easier. The fact that the climate system still confounds complete understanding is what gives us our uncertainty - despite the growing accuracy of tools such as glosea. 

Which I guess is grounds for hope and a never say die attitude....because that very failure to be able to accurately predict fundamental relationships such as the interaction between ocean forcings and atmospheric patterns means nothing is ever 100% set in stone. Things can change....

Edited November 17, 2020 by Catacol

[I remember Atlantic 252 7,326]

4 minutes ago, Sunny76 said:

I’ve been wishing for a brutal cold spell after Christmas, or just after the new year, until the second week of January. Something similar to January 1987, or at the very least another late feb 2018 spell. Biting windchill and 3-5 days below 0c, even in London and the south. 
 

The only thing that makes me feel guilty about wanting something like this is, the fact that many people will be struggling to heat their homes, on top of not having enough food. Especially with the high unemployment during this coming year due to covid.

A mild winter would be more welcome by the general population. 

Aye it would, still say the colder it is, the higher the R rate

[Jason T 2,296]

2 hours ago, Sunny76 said:

While I usually agree with that statement, I would say anything up until mid December is up in the air. A cold winter could still happen from that point on.

1984/85, 85/86 and 86/87 all had fairly mild spells during November and December, then the cold came during or after Christmas. 
 

2009, and 10, along with 12 and 17 winters did seem to produce some chilly weather before late November. 
 

 

Wow, checked I'm for winter..2009 I'm pretty sure from memory Mr Holmes comments we're, not much posting here, We have the Daddy of all easterlies about to begin..as for chilly.. Minus 12 plus, plenty of snow..Thames streamer..2010 alot of snow and sub zero.

[damianslaw 14,743]

Any reasons for why we have a Nino-esque state when La Nina is very high - it doesn't make sense at all... should La Nina at the level it is at be having a more dominant impact... 

Its all very confusing..

[blizzard81 6,560]

It is way too early to make any firm predictions about December at this stage, no matter how knowledgeable or experienced you may be. We are still two weeks away from the beginning of December. The met office are still second to none imo. Nowhere near perfect by any means but still the most accurate. They have been gunning for a fairly cold first half of December for a while now. I take great comfort from that. 

[damianslaw 14,743]

7 minutes ago, blizzard81 said:

It is way too early to make any firm predictions about December at this stage, no matter how knowledgeable or experienced you may be. We are still two weeks away from the beginning of December. The met office are still second to none imo. Nowhere near perfect by any means but still the most accurate. They have been gunning for a fairly cold first half of December for a while now. I take great comfort from that. 

Agree with that, many November forecasts have gone rather awry, don't recall seeing many calling for a very mild month, lots of signs end of October could be rather cold month.  Mind I remember Met Office suggesting average or rather cold start to November, then changed there mind when November started, and through the month have had to remove any reference to cold.

[Met4Cast 12,211]

29 minutes ago, Catacol said:

Based on current output I agree. We have rising momentum once again, preventing what should be the Nina base state from coupling with the atmosphere, and the forecast for an Alaskan trough reinforces that view. So - a strangely Nino-esque pattern destructively interfering with the early season Nina projection continues, and all the while vortex temperatures at 30hpa are where they should be at the end of December and wind speeds are forecast to be high. There is still a chance of some cold shots in December, but the chances of anything sustained are fading by the day. Those hoping for snow from horizon to horizon may need to increasingly focus on developments in the stratosphere, and whether we can see a split reversal with accompanying roll of the dice in terms of outcomes. We learned in 2018 that such events can completely override any tropospheric forcings once in motion.

It's a cruel irony really - The first half of this winter almost seemed "in the bag" for a while. The SPV was weak, La Nina was dominant adding confidence to the idea of a front loaded winter and now we find ourselves in an increasingly dire situation. You can bet your bottom dollar the atmosphere will move into a more La Nina state by January, just in time for more zonal. 

One possible wildcard for December is the lack of a true Strat/Trop coupling at the moment, if that continues then we could tap into some MJO led blocking assuming we see favourable developments there, at the moment though it's not looking ideal. 

I was hoping the Ural high/wave 2 activity we'd seen being forecasted in the past week or so would transpire, but that's all been dropped by models across the board in the last day or two. 

Edited November 17, 2020 by Met4Cast

[Alexis 491]

3 hours ago, daz_4 said:

Not sure if I agree with people saying "it's only middle of November, plenty of winter left." In my experience, the next four weeks will set the tone of the winter. Winters very rarely deliver (at least in Central Europe) if there is no cold spell from middle of November to middle of December. And based on today's runs we can probably write off at least the next ten days. Not that I'm surprised. I very much doubt this winter will be different from the last seven or so.

Other than 2010 I can't recall a single winter that got going before Christmas Day to be honest! 

[feb1991blizzard 22,712]

41 minutes ago, damianslaw said:

Any reasons for why we have a Nino-esque state when La Nina is very high - it doesn't make sense at all... should La Nina at the level it is at be having a more dominant impact... 

Its all very confusing..

Its probably just lagging behind a bit, it will catch up, regardless of whether the nina unexpectedly weakens significantly or not

[Premier Neige 234]

3 hours ago, Sunny76 said:

While I usually agree with that statement, I would say anything up until mid December is up in the air. A cold winter could still happen from that point on.

1984/85, 85/86 and 86/87 all had fairly mild spells during November and December, then the cold came during or after Christmas. 
 

2009, and 10, along with 12 and 17 winters did seem to produce some chilly weather before late November. 
 

 

I'm not 100% but I'm pretty sure 1962 had a mild November as well. No, I'm not saying this will be a 1963 winter but it doesn't necessarily follow that you need a cold November to get a cold winter. 

[Catacol 18,319]

22 minutes ago, damianslaw said:

Any reasons for why we have a Nino-esque state when La Nina is very high - it doesn't make sense at all... should La Nina at the level it is at be having a more dominant impact... 

Its all very confusing..

It's a headscratcher isnt it? We know the ENSO state is a huge factor in determining momentum transport and the pattern of Rossby waves that roll around the hemispheres. The closest I have come to understanding disconnected states is that sometimes tropospheric weather systems can create spikes (or dips) in atmospheric momentum via mountain torque events in particular, and these can serve to counteract ENSO influence. Perhaps also wider ocean temperatures can upset expected impacts locally. We know that ocean temps in the atlantic can impact pressure patterns, and we have certainly seen a semi permanent north pacific ridge enhanced by warm waters for some years. 

But even the highest power computers are unable to get a full handle on these factors - look at the hopeless accuracy of MJO forecast year on year and the inability of models to consistently agree on MJO strength and passage. And therefore major torque events are often only seen at short ranges, and the potential for an SSW can equally be invisible until forecast patterns become accurate, usually at T + 240 approx. We can spy the broad driver direction because the ENSO state is visible and the MJO can be plotted - but variables that impact on it are much less easy to see.

So - we were able to watch Nina take hold, we knew what that OUGHT to mean as an early season driver of a north atlantic ridge...but along came a record breaking spike in AAM for a Nina in October (I dont have access to AAM plots at the moment so am a bit unsure of the origin - probably mountain torque) and this has thrown us into a more Nino orbit. We now have another rise in AAM. Nino orbit sustained. 

= ENSO trying to force up a mid atlantic ridge....but Nino atmosphere instead working to enhance the Euro high...and we have been given a big ScEuro positive anomaly instead. Warm instead of cold.

As Metcast just said - bet AAM falls and the Nina base state re engages just in time for the second half of the season when wavelengths shift and the atlantic ridge is replaced by a late winter atlantic trough. Or.....maybe it won't. If it stays disconnected for the long term then we might find the front loaded winter transformed into a back loaded one - as per Roger's forecast. And enhanced by an SSW? A semi permanent ScEuro high for the first half of winter would increase this chance.

Got to love the uncertainty.....

[damianslaw 14,743]

20 minutes ago, Met4Cast said:

It's a cruel irony really - The first half of this winter almost seemed "in the bag" for a while. The SPV was weak, La Nina was dominant adding confidence to the idea of a front loaded winter and now we find ourselves in an increasingly dire situation. You can bet your bottom dollar the atmosphere will move into a more La Nina state by January, just in time for more zonal. 

One possible wildcard for December is the lack of a true Strat/Trop coupling at the moment, if that continues then we could tap into some MJO led blocking assuming we see favourable developments there, at the moment though it's not looking ideal. 

I was hoping the Ural high/wave 2 activity we'd seen being forecasted in the past week or so would transpire, but that's all been dropped by models across the board in the last day or two. 

I'm sensing quite a bit of frustration given the earlier projections of possible cold end to Autumn and start to December - we are not in December yet, so remains to be seen, but the way November has paned out has got people questioning why are things not going to 'plan' so to speak, but as ever with our weather it is never that straightforward and there will always be things that catch us out. Last year it was the IOD.. keeps us all guessing. 

SSW events are the same, never quite know what the impacts might be. Always therefore best to expect the unexpected especially given we seem to be constantly entering 'uncharted territory' so more so we should expect things not to go to plan as perhaps expected based on previous situations.

One feature of our weather that has become always a resident one in recent winters in the main is the Aluetian ridge/N Pacific high and downstream NW Canada trough, that does seem to fire the jet and put pressure on any ridge development, so we have become more reliant on changes in the upper layers of the atmosphere for something other than typical atlantic conditions in our winters. 

[Hotspur62 1,548]

All fascinating stuff atm with regards to winter.The drama of that GFS gave hope to those with a “cold” inclination but as quick as  it appeared it has disappeared just as quickly.I don’t have the knowledge about the possible implications of a strong La Niña be it Central Based or East Based but the perception I get is it is such fine margins of how strong it becomes determines how mild the winter becomes in The UK.A Strong La Niña and it seems very unlikely cold spells will develop,much like a strong El Niño means the same for the UK.it seems we are jinxed whatever occurs.Then you have an Eqbw or Wqbw and they never seem to play ball either!!In some ways it would be great if we could get a proper cold spell in the UK When so many factors seem to be transpiring against us-clutching at straws and with GW,yes I probably am,but  it would be nice if Mother Nature just put a spanner in the works and gave the vast majority on here some Winter wonderland landscapes and a Day 10 chart just for once turned into reality👍

[Rollo 485]

15 minutes ago, Premier Neige said:

I'm not 100% but I'm pretty sure 1962 had a mild November as well. No, I'm not saying this will be a 1963 winter but it doesn't necessarily follow that you need a cold November to get a cold winter. 

There was a pretty cold spell mid November with snow  to low levels, we had snow cover in Sunderland and in “Weather”  magazine it showed a picture from York station all covered in the white stuff, to the best of my memory  the spell lasted 3-4 days.y6

 

[Brucie 36]

I seem to recall that the developing La Nina did not couple with the atmospheric state in the summer. Is this right?

Whatever,  we are in a 'new norm' where nothing goes as planned. Mind, I suppose there's always been chaos theory regarding the weather. 

[Tony47 60]

Re the influence of Novembers on the succeeding winters, well, I was a 15 yr old during Nov '62, living in Birmingham at the time and we had a northerly three days mid month,  with three inches of snow on the ground, with a cold foggy end to the month.November 1946 was one of the mildest months on record. And both were followed by fantastic winters (from a coldies perspective that is).

[cheeky_monkey 3,990]

1 hour ago, Brucie said:

I seem to recall that the developing La Nina did not couple with the atmospheric state in the summer. Is this right?

Whatever,  we are in a 'new norm' where nothing goes as planned. Mind, I suppose there's always been chaos theory regarding the weather. 

It did here ..we had a classic La Nina summer cool and wet to start turned warmer and drier as we got past mid July ending with a dry August and September ..exactly the same thing happened in 2010 and 2011 both La Nina summers

[MattHugo 3,298]

Hi. Just briefly dipping into this thread, as a one off, to perhaps provide some further insight here...

The spike in AAM in Oct was, of course, directly related to the eastward movement of the MJO and that created a surge in AAM, clearly at a time when seasonal wavelengths would still have supported the Atlantic ridge and downstream trough, which clearly dominated all of summer. That is definitely the annoyance, on a more short-term, as we had to put up with relentless -ve AAM trends all summer that repeatedly brought about the Atlantic ridge - downstream trough. However, the key aspect here, which can be mis-understood or forgotten is that what happens with AAM through the summer doesn't mean it is the same for winter, and we are now at a point where seasonal wavelengths actually mean something of the opposite. Looking forward we do actually want and need +ve AAM to develop through the tropics to counterbalance the broader La Nina background. We are moving out of the period now when getting -ve AAM and getting an all round La Nina profile won't actually help in bringing blocking patterns. 

The reason, is as follows...

In winter extra +AAM momentum at around 50N (under La Nina setup we have this year) is inhibitive to the creation of stable higher latitude blocking under a +AO regime and it is +AAM transport from the tropics poleward that creates the mechanisms to slow the polar jet and bifurcate the tropopause/stratosphere layers. But once this has happened, its quite often a low angular momentum regime that can lock in the pattern as the usual polar jet flow that prevents blocking cannot penetrate the blocked tropopause layers once it has been set up  and is forced to loop around the pole instead. The looping of the polar jet into the pole, rather than straight across on a flat jet at mid latitudes, propagates even further warm air advection into the pole and this in turn prolongs the duration of the blocking. While this is subject to some 'give and take' as a general guide Nino phases are better for cold spells in winter and warm spells in summer.

There had been examples of this recently, especially through late Oct, in association with the +ve AAM spike, but this coming at the wrong time, again destructively interferring with the broader Nina background. As the recent AAM plot below highlights, there has been some attempted northward movement of -AAM anomalies (which we need) but that has, unfortunately, recently stopped as the trades have returned. Within the last few days there is a clear evidence for a robost +AAM anomaly at, surprise, surprise, around 50N, as circled. So no wonder no GFS blocking has come off and only minor amplification between systems from the W will dominate the next 7 to 10 days...

Also, using earlier in the year as another example, look at the AAM profile from between late Dec and through the whole of last winter. It was locked within a profile that had +AAM around 40-60N, driven by the extremely strong polar vortex as well, with any -ve AAM anomalies around 30-40N. If you look at reanalysis plots of this same time frame, you'll actually see a 'ring' of high pressure circulating the globe at around 30-40N, this propping up a robust W'ly and strong polar jet stream. It wasn't until April and May when those -ve AAM anomalies finally move to a more N'ly latitude and, surprise, surprise, look at the weather we had in April and May!...

There were some tweets on this a few days back, the link to those are below. Looking forward, what is needed is additional eastward movement of the MJO, to increase +AAM through the tropics which in turn will help to propagate -ve AAM anomalies further north, out of the sub-tropics. Total AAM, relative AAM etc etc sort of all fall second-string to the most important variable now for the coming 3 months and that is AAM transports, which links back in to what was discussed above. So don't hope for a La Nina reset now, that time has been and gone, seasonal wavelengths have altered the 'goal posts' on that. However, we are very finely balanced once again this year because the strat vortex is so strong, there's some residence from an E'ly QBO regime acting as a lid, but AAM isn't playing ball either. We could very easily end up where we were 12 months ago within the next 4 weeks, which does seem likely and hence why the mid-winter period is likely to be +NAO and why, most of Dec still provides the potential for amplification. Also, as a hint, keep an eye out for an EAMT within 10 days too, that could tip the balance for blocking, for a time, into the first half of December...

Hope, this is of some interest...

 

[Hotspur62 1,548]

Thank you MVH for the above post which has really helped me understand more on this subject.👍As you say don’t expect anything cold for next 10 days but after that there is hope.Shall be watching with great interest at beginning of December to see if things can fall into place which may give us some blocking.

[summer blizzard 7,180]

10 hours ago, Brucie said:

I seem to recall that the developing La Nina did not couple with the atmospheric state in the summer. Is this right?

Whatever,  we are in a 'new norm' where nothing goes as planned. Mind, I suppose there's always been chaos theory regarding the weather. 

We've basically seen 2.5 phases so far. 

Since May we have seen a largely -AAM regime however AAM has spiked during August and November within that. This is fairly normal as things are rarely uniform and we will see disruption early in the event especially. 

Edited November 18, 2020 by summer blizzard

[philglossop 570]

Well following on from this hurricane season- could we be looking at February again for the coldest snap of the winter- aka like 2005? Remember that cold snap very clearly, the signs in the Peak District were clear about a week before it hit at the end very end of the month. November this year has felt like November 2004 that year. 

Edited November 18, 2020 by philglossop