Model Output Discussion - Snow for some, but what else is in store?

[Vikos]

3 minutes ago, bluearmy said:

It’s just nonsense to say that there are no signs of the ssw in the trop modelling .... look how slow the Atlantic jet is at its normal northern arm latitude ...look at the anomalous cold across the USA and Siberia/n scandi  

 

 

The spread to the south is presumably where the trough is more suppressed 

You show a +246h chart. Serious?

Sorry, but that doesn't count for me as it is not resilient in that timeframe.

But ok, that is just my point of view. No need to get an anger about it

[bluearmy]

8 minutes ago, Vikos said:

Sorry, there are no outcomes yet wich I would consider as an effect of the SSW. So please show me wich ones you actually mean. Patterns are way to unsteady for any solid predictions. I am getting tired of repeating this.

   

it’s not rocket science vikos ..... it’s as clear as the nose on your face .....if you can’t see these charts screams reverse flow and downwelling wave then you aren’t understanding 

the fact that nw Europe and Germany aren’t going frigid is just unlucky .....you need to deal with that rather than getting upset that the output doesn’t fit what you were expecting ....

 

[bluearmy]

Just now, Vikos said:

You show a +246h chart. Serious?

Sorry, but that doesn't count for me as it is not resilient in that timeframe.

But ok, that is just my point of view. No need to get an anger about it

That’s a mean ens chart, not an op 

and you can see the onset of the reverse flow at day zero with anomalous unforecast upper ridges and an arctic high. A strongly negative AO/NAO combo 

Here you are at day zero ..... what more evidence do you want to see ?????.

[Weathizard]

Mildly interesting from the ICON 12z to 18z  

[IDO]

Just looking through Twitter to see what is going on. A lot of despondency there, it appears that the hype was exaggerated and feeds are full of puzzled punters. Canada has been above average all winter and the US not seeing much cold. Cohen doesn't have his usual cold focus, a reconstituted sPV showing up on GFS apparently, and maybe heading towards Canada by the end of January, nothing much to hype pre-then and that is what is showing in the models. Marco hinting at a slow recovery for the sPV after the next warming.

The new wave expectation of an SSWE seems to raise hopes and so far the coupling has been rather tame for many regions. People expecting the BFTE and weeks of locked in cold, this qtr has not delivered that at all. 

It is a learning curve for me as I suspect that we do not yet have enough data to be specific with these warming events. We will see how it fairs for the rest of the winter. Still no snow in my location and may just be too far west to see tomorrows!

[sebastiaan1973]

3 minutes ago, Mike Poole said:

Later to it today, but I can’t believe the negativity in here when nothing has gone wrong.  It hasn’t gone right either, but that is just because of massive uncertainty.  Illustrated perfectly by the clusters, here T72-T96

No point posting the later ones, they are a single cluster (the ens member closest to the mean, as if that means anything at all at late times), meaning they basically haven’t got a clue.  And neither have we.  We could be on the cusp of something special or nothing at all or anything in the middle.  But the current split vortex up top today might have a say in that even if it is only there for a short time.

The models are clueless beyond T96, so the interesting model watching period continues, but I think we are getting closer...

I hope so I find it hard to see that the models are clueless. I can imagine there is more temperature diversity in the plume.

[Bricriu]

10 minutes ago, Vikos said:

Sorry, there are no outcomes yet wich I would consider as an effect of the SSW. So please show me wich ones you actually mean. Patterns are way to unsteady for any solid predictions. I am getting tired of repeating this.

If you don't want to acknowledge that the SSW has clearly imprinted itself on the Northern Hemisphere profile there is not much i can do to persuade you otherwise at this stage.  We'll just have to agree to disagree.

[Vikos]

Just now, bluearmy said:

   

it’s not rocket science vikos ..... it’s as clear as the nose on your face .....if you can’t see these charts screams reverse flow and downwelling wave then you aren’t understanding 

the fact that nw Europe and Germany aren’t going frigid is just unlucky .....you need to deal with that rather than getting upset that the output doesn’t fit what you were expecting ....

 

And again... I am not in any way frustrated about any outcome here or elsewhere on the planet.

And again, you show charts in a "far" distance, also the first is a mean chart. You should do some research on mean or median in statistics. In lager timeframes they often tend to get very diffuse.

I get yout point. And you are right. But again, those things did not happend yet, so by now, we don't have a outcome of the SSW.

[MAF]

can we please adhere to the rules and not bicker or snipe. everyone is entitled to an opinion, either agree with it or disagree, but be polite and then carry on with your own views. constant sniping is tedious at best and down right annoying at worst.

 

[pyrotech]

Okay i am going to try to calm the nerves a bit.

If we look back to a recent cold spell 2018 we can see the inconsistency in the models and the nerves on the threads here on net-weather

I have added some images that were being shared at the time. I also include a post about the SSW and how they see it modelled.

The Met office remained quiet until quite late on, although hinted at some cold periods and snow showers.

I am in South Wales and was pretty much snowed in.

The models at the time hinted at times of the cold spell, but also all the models at longer range played with a variety of outcomes. The trend is your friend here.

What we should be looking at is two main things

1. Changes in right direction between a model at same roll out time

So the GFS 12z against GFS 12Z  and ECM 12z against ECM 12Z (ECM 00Z v ECM 00Z)

Then look for cross model agreement, especially for trends and direction of any change. Again models on same run only.

So here are images of posts and model output back then.

The rule has been look for cold first, then snow later, if cold is not widespread look for trends that enhance it. Plus it took longer than expected in 2018 and for along time just showed up in fi, which may sound familiar. It can mean the models are picking up  a trend but enhancing it too quick. This weeks models appear to be doing a very similar thing

 

[stodge]

Evening all

Am I going to see some snow tonight and tomorrow morning in lowland East London? A transient covering wouldn't surprise but those to higher ground will, as always, have a better chance for heavier and long-lasting snow. I'll leave that to others and concentrate on my evening look at the medium to longer term options.

Some miserable forum members this morning with some of the overnight output putting the UK (and especially the southern half) on the milder side of the street while the battleground might yield some positive outcomes for snow fans further north.

Let's see where this evening's out put takes us - last evening we had some common themes of Greenland heights and a complex trough over Scandinavia but persistent heights to the south threatened to push the jet back north and keep the south of the British Isles in a milder airflow.

12Z GEM: - the mildest of the options yesterday evening making little or nothing of the wedge of heights south from Greenland and not breaking the Atlantic trough. T+120 takes us to next Wednesday and the LP has drifted down to cover much of the British Isles but milder air hangs on in the south east under a cyclonic SW'ly. Heights persist over the far south east of Europe and a new Atlantic trough is heading towards north-west Europe. Southern and Eastern Britain has positive 850s (up to +4) but negative uppers have moved into Scotland and Northern Ireland behind the cold front which is moving south east. From there, the trough remains very much in charge with a series of secondary LP moving across the south while the main centre remains to the north and east over south-west Scandinavia. By T+180 colder air has finally filtered through to the Channel coast with -8 850s over northern parts. A new and deeper LP is approaching the English Channel from the south-west. Moving on and by T+240 clear signs of the jet heading back north as heights rise over south-west Iberia with a transient HP ridge about to cross the British isles ahead of the next Atlantic trough. 850s of -4 to -8 over the British Isles at this time but milder air is approaching from the south-west.  The plume of warner air vacates Greenland at T+168 and from there it's only a matter of time before the jet kicks back north.

 

A decent run for northern Britain but for the south very unsettled with a lot of rain and at the end of FI a clear sign of a return to milder conditions for all.

12Z GFS OP - a strong run for cold fans last evening. At T+120, a good example of how minor changes can have huge impacts. GFS has a slightly deeper LP and a smidgen further south so by T+120 the colder air has made more headway. The upstream profile differs in that, unlike GEM, there is a narrow but distinct gap between the Atlantic troughs - this may or may not be significant later. The push of milder air in the early part of the week has been largely replaced by colder PM air (except in the far south east). The break in the Atlantic trough doesn't last but it allows a small LP to head into the Mediterranean suppressing the heights and allowing a colder NNW'ly airflow down across the British Isles by T+180. Shortwave LPs have closed the ridge upstream. -4 to -8 850s across the British isles by this time with some colder air nearing northern Scotland. From here, however, the trough over Scandinavia remains in control until heights start to build from the south and by T+240 there's a SW'ly flow across the British Isles with an active Atlantic LP moving NE toward Iceland and the jet moving back north. Milder air is moving across Ireland and the far south-west but colder air hangs on further north and east for now.

GFS OP heads to the same place as GEM which suggests a theme and I suspect that's where Parallel will be heading.

12Z Parallel - we're starting to see some consistency in the T+120 output after a number of days of divergence. Parallel looks very close to OP at the same time. The milder air is still over southern and eastern England at T+120 but the colder air is pushing south and east. From there, a fairly familiar path but at T+180 the main LP is to the north so it's a slack airflow across the British isles with heights rising around the Canaries and new shallow LP coming east in the Atlantic trough as the warmer air vacates Greenland to the west. Uppers of -4 to -8 generally with colder air coming into Scotland by T+180. Moving on, the heights to the south play their role in pushing the jet back north and by T+240 Parallel joins the other output in having a SW'ly flow over the British Isles but do I see a hint of heights to the north east again? Milder air is marching north and east across the British Isles by this time.

That's 3-0 to the milder evolution by T+240 tonight - I don't expect ECM to do anything different if I'm being honest.

12Z ECM - no surprises at T+120. Cooler air with 850s of zero to -4 is gradually displacing the milder uppers by this time. By T+192 the colder snap has ended for southern parts as the Iberian HP is already building north east and pushing the jet back north. The brief push of colder air is being displaced by milder air from the south and west. It's not quite that simple as the LP to the north of Britain dives SE while a major Atlantic storm is heading north in the middle of the ocean. There's a residual LP to the west of Norway with heights persisting over Iberia and again just that hint of heights to the north east. The milder incursion is delayed but not I think for very long.

So, 4-0 to mild by T+240 but not a straightforward evolution perhaps and ECM teases by dropping the LP SE suggesting a hint of new heights to the north east which is also teased by GFS Parallel tonight (as it was yesterday in further FI).

Let's see if further FI plays this theme on either GFS OP or Parallel taking us towards month end:

One of them brings a raging PV back to Greenland/NE Canada and the other doesn't. Parallel indeed shows the jet heading back south at the end of FI and colder air returning to the far north. Control restores the PV into far FI but more over Canada so I'd be looking for height rises over Scandinavia into February.

10 HPA charts - all look the same - from the shattered PV a new lobe emerges at T+192 from the far east of Siberia and moves back over our side of the globe though much weaker than you would expect a this kind of year. I suspect this is the part of the reason for the end of the cold spell and reversion to something more Atlantic-driven.

Conclusion: it looks as though we will be transiting via a brief cold spell to a prolonged spell of Atlantic-driven weather which could be very wet and at times stormy in the last third of the month. I'm still looking to the north east for height rises in February but that's a very long way off at this time and it looks as though cold fans will by the early part of the week after next looking at a minimum 14 days of milder weather. A long long way from any notion of winter being "over" and it's fair to say we've had mild spells in most winters in the last few centuries so nothing unusual in that but it does look wet and that might cause some issues in the next 10-14 days.

 

[Griff]

49 minutes ago, sebastiaan1973 said:

Well. Some time ago, I posted the study by Domeisen et al. There are different types of effect of SSWs related to the regime five days before the SSW onset and five days after.

It is my guess, Cohen tweet points in that direction, we see a dipping effect of the 'European Blocking' type.  If this is true, we can expect more 'dipping' in february.

The role of North Atlantic–European weather regimes in the surface impact of sudden stratospheric warming events

WCD.COPERNICUS.ORG

---

<p><strong class="journal-contentHeaderColor">Abstract.</strong> Sudden stratospheric warming (SSW) events can significantly impact tropospheric weather for a period of several weeks, in...

 

 

7 minutes ago, Griff said:

 

 

1 hour ago, Hotspur62 said:

A very good point made from Vikos re the SSW.The effects are only just being felt and by 21st just using ECM as an example that is not a bad chart(UKMO AND GFS not too dissimilar).

The frustration is understandable as we are so close yet so far but if the Pacific ridge and Arctic ridge can start becoming more prominent then we can push this ruddy trough further south.Signs are this COULD happen but we will just have to wait and see.

Fascinating model watching and I think I have learnt a lot more on trying to read charts from the really good knowledgeable posters on here so thanks to all of you.

5FABCAF4-DF2A-4231-9080-0F73584CE5F6.webpFetching info...

 

53 minutes ago, sebastiaan1973 said:

There was no QTR in the charts.  Just people with their hope.

Effects of the SSW are typical after ten days. It can last (with breaks) up to two months.

There are different types of effects. My guess we have a dripping effect beloning with a European Blocking type.

The role of North Atlantic–European weather regimes in the surface impact of sudden stratospheric warming events

WCD.COPERNICUS.ORG

---

<p><strong class="journal-contentHeaderColor">Abstract.</strong> Sudden stratospheric warming (SSW) events can significantly impact tropospheric weather for a period of several weeks, in...

 

How Sudden Stratospheric Warming Affects the Whole Atmosphere - Eos

EOS.ORG

---

High above Earth’s surface, air temperatures occasionally increase suddenly, producing widespread effects on weather, air chemistry, and telecommunications.

 

So apologies if this is anecdotal but somehow it crosses threads and doesn't sit well or precisely in one thought... 

The best answer I've had so far is that the current warming event is technically classed as part of the original ssw, and the outcome is far from definitive and certainly not over. 

If anyone thinks they know they're better clued up or more confident at least than Simon Lee - mods please feel free to deposit this where you see fit, ta

Edited January 15, 2021 by Griff

[Battleground Snow]

3 minutes ago, Weathizard said:

Mildly interesting from the ICON 12z to 18z  

Indeed, may not change much long term but certainly different

[sundog]

1 hour ago, Vikos said:

You show me the effects, please! Show some major (!) outcomes anywhere on the globe today wich are due the effects of that SSW with its long lasting reversal of 10hPa winds. Than we can talk.

Very good point.  I was thinking the same that as of yet no place seems to have gotten anything out of the ssw . So perhaps this is not the end of the story.............we just need more time to see how things unfold.

[Vikos]

6 minutes ago, Bricriu said:

If you don't want to acknowledge that the SSW has clearly imprinted itself on the Northern Hemisphere profile there is not much i can do to persuade you otherwise at this stage.  We'll just have to agree to disagree.

People don't always have to find a conclusion. That is called a discussion. That is what forums are made for

Let's just end it here and go on with the 18z runs

A virtual pint from me to those who discussed with me. Cheers!

[Mike Poole]

2 minutes ago, Griff said:

 

 

 

So apologies if this is anecdotal but somehow it crosses threads and doesn't sit well or precisely in one thought... 

The best answer I've had so far is that the current warming evening is technically classed as part of the original ssw, and the outcome is far from definitive and certainly not over. 

If anyone thinks they know they're better clued up or more confident at least than Simon Lee - mods please feel free to deposit this where you see fit, ta

Yes, it isn’t classed as another SSW if within a certain number of days of the first one, can’t remember how many, think it might be a couple of weeks?  Anyone know for sure?  But in my view it is irrelevant - the whole saga, from late December through the SSW 5/1/21 to what’s going on now is part of one unique weather event that we will learn from, they don’t come along very often...

[Man With Beard]

Right enough complaining from me - time to make an actual forecast. Looking through the ECM ensembles for D8, its clear most are keen on secondary lows running into the base of the primary low, and a great number of them have a snow event on the northern flank. That means, next Friday/Saturday, look out for a snow event 100-150 miles from the northern extent to the southern extent. The question will be: where? South of the M4? M4 to Birmingham? North midlands? Lancs/Yorks? Or even in the channel? A nail biter. But the ensembles are quite keen.

[bluearmy]

- anyone got the verification stats for January thus far ??  Based on what many say, I would expect them to be poor ....

[IDO]

9 minutes ago, bluearmy said:

   

it’s not rocket science vikos ..... it’s as clear as the nose on your face .....if you can’t see these charts screams reverse flow and downwelling wave then you aren’t understanding 

the fact that nw Europe and Germany aren’t going frigid is just unlucky .....you need to deal with that rather than getting upset that the output doesn’t fit what you were expecting ....

 

I noticed that reverse flow at latitudes north of us when you mentioned it a couple of day ago and have to admit to not seeing that before! To get the HP and LP systems to align like that is def not trop driven! Just a shame that this is keeps the cold too far north and allows the undercutting westerly flow. To get a mean to run with this at d8 onward's means it is def a strong imprint.

How long will this pattern persist is what we should be asking (usual caveats and disclaimers)?

[Griff]

Just now, Mike Poole said:

Yes, it isn’t classed as another SSW if within a certain number of days of the first one, can’t remember how many, think it might be a couple of weeks?  Anyone know for sure?  But in my view it is irrelevant - the whole saga, from late December through the SSW 5/1/21 to what’s going on now is part of one unique weather event that we will learn from, they don’t come along very often...

Exactly "it’s not really a canonical one either" 

[Mike Poole]

1 minute ago, bluearmy said:

- anyone got the verification stats for January thus far ??  Based on what many say, I would expect them to be poor ....

T120:

T240:

I’m posting both reliable and FI so as not to put any spin on it.

[bluearmy]

2 minutes ago, Mike Poole said:

T120:

T240:

I’m posting both reliable and FI so as not to put any spin on it.

Day 5 interesting ....

day 10 surprisingly normal but then we aren’t ten days past the ssw yet so maybe not surprising 

maybe best to look again in a week 

[IDO]

4 minutes ago, bluearmy said:

- anyone got the verification stats for January thus far ??  Based on what many say, I would expect them to be poor ....

Looking at the d5 and d6 verifictions we can see the trend in the most recent runs:

Def a drop in performance. Not really showing at d8 or d10 but when they do, they will be bad due to them being poor earlier.

[Johnp]

Slightly improved icon?

[Mike Poole]

Just now, bluearmy said:

Day 5 interesting ....

day 10 surprisingly normal but then we aren’t ten days past the ssw yet so maybe not surprising 

maybe best to look again in a week 

Yes, you can see the drop off on the day 5.  Models struggling for sure!