Model Output Discussion - Spring Has Sprung

[AO-]

Does anybody know if this has anything to do with downwelling and the SSW? In that case the battle is on and I know where to put my money. 

[bluearmy]

 Lukesluckybunch ec46 looks in line with weeks one and two when comparing to 7 day gefs mean. But it damn well should!  It’s only a tool to use for weeks 3 and 4. And the ec op at day 10 tells you nothing re that timescale 

[blizzard81]

Relying on a huge Siberian High to retrogress westwards does wonders for the frustration levels. I've been known to call it the shyest beast there is. 

[bluearmy]

2 minutes ago, AO- said:

Does anybody know if this has anything to do with downwelling and the SSW? In that case the battle is on and I know where to put my money. 

Too early for a response from the upcoming one (won’t have happened by 16th)

could be to do with events last month - clearly we have a neg AO ongoing and getting more negative 

[Cold Winter Night]

 Lukesluckybunch

Let's see, here's EC46 from two weeks ago:

NAO+ until February 10, then a few transition days to an attributed Scandinavian Blocking regime February 16 onwards.

Now watch EC 12z again, that's exactly what it shows.
EC 240h anomaly fits the Scandinavian Blocking regime:

The problem is thinking that "Blocking = Immediately Very Cold and Snowy IMBY," like 1+1=2, but that's not the way it works.

[Froze were the Days]

 blizzard81 Last time that happened other than the induced SSW of 2018 was back in Feb 2012 and even then the real cold only got to the east of London and a stalled front from the Atlantic dumped a bit, I think we're really clutching at straws and even then we'd probably get a short wave develop over the Norwegian Sea or something which usually crops up to put the Siberian Express on the buffers.

[bluearmy]

The op cluster days 8/10 is the non scandi ridge cluster (in that the Atlantic trough  is too far east on that cluster). The larger two clusters (80%) have a solid scandi/scrussian ridge with easterly flow 

we need to find a mechanism to leave some low uppers over Eastern Europe 

Edited February 6 by bluearmy

[Mike Poole]

 bluearmy T192-T240 charts to back up your comment:

T264+:

Clusters 1,2,3 all build a Greenland block formed by retrogression.  On cluster 1 it is a monster stretching into the pole, cluster 2 retains some higher heights to our NE.  On cluster 3, a white hole anomaly over Greenland results.  Clusters 1 and 3 look cold for the UK, with 28 members in total.  Cluster 4 is rather different with a westerly to the UK and Russian high.

So, another day, and still jam the week after next.  But the models really struggle in these setups that promise UK cold and then fail to deliver it…

[topo]

 

[Mike Poole]

ECM 46 zonal winds:

Noteworthy chart because it shows a reversal on the mean.  So it does now look like we’re getting another SSW.  This one has a good chance of being a significant reversal.  Will only add to the uncertainty…

Except, I’m not sure I need the likes of ECM or GFS to work out how this is going to pan out.  Oh, no!  It’s perfectly clear that no sooner than longer daylight means that a decent snow event is no longer possible, the perfect cold synoptics will miraculously present themselves in time to ruin spring!

[Frosty.]

The cfs shows some interest further ahead.. and even further ahead too! …that’s why I love  the cfs, it gives false hope at a safe distance, however, I do believe there will be some hot spells during the summer!  

[WYorksWeather]

Right, here we go again. Let's try to untangle this mess. I'll show UKV again for the short range.

In three hour intervals, here's UKV 15z from 3am Thursday:

I'll leave it there at 3am Friday - the rest is only snow into usual mountainous spots and the rest rain only. Nothing here to change my view from yesterday that we're looking at a snow to rain event on low ground, at best. Of course, disruptive levels of snowfall quite possible across higher ground. By Friday morning, 850hPa temperatures compatible with snowfall have been washed away almost everywhere except Scotland. Similar story with dew points.

You can see this on the snow depth charts as well - there's a move from a more widespread dusting of snow on Thursday evening to significant accumulations at altitude across the UK, and possibly in Scotland to slightly lower levels, and almost nothing anywhere else.

In short, this event looks like being a bust for most, and even if you do get some snow, it's going to be very transient. Out to T+120, beyond this, UKV also shows nothing but rain away from the usual prone spots.

So, next is the medium term outlook (12z GFS only, as ECM 12z is not out yet).

Again, it's not a very inspiring picture. Even further north, there are almost no ensembles showing deep cold. As we've seen, getting the 850s down to -5C probably doesn't cut it for low level snow at this time of year, we need those -8Cs and lower in most cases.

Worse yet, the mean is becoming more bullish about above average temperatures. You don't need to be a genius to recognise that the OP run tonight was a bit of a mild outlier, but it's not entirely without support, and the mean just looks very much like standard fare for this time of year. Temperatures a little above average. Most crucially, very few ensemble members getting the surface temperatures down to 0C, and the mean is going for not only a snow-free but a largely frost-free period for the next couple of weeks.

We're at the point where some significant changes are needed in the next week or two on the modelling, otherwise I'll look for an early spring. We probably get one more shot for something to happen in the second half of February, plus a remote chance of something turning up in the first couple of weeks of March, but I'm not holding my breath, frankly. If we start seeing properly mild and spring-like charts instead, I'll probably jump ship over to warmth hunting.

I will compare with the ECM ensemble later. 

 

Edited February 6 by WYorksWeather
Removed unintentional extra chart.

[AO-]

Let's see where EC leeft ús with the 2m temperature for next week. A simple conclusion can be drawn and that is that the cold had been postponed by two days more again. Well, cold, more like average for the time of year. Despite the biggest chance of a Northeasterly apparently it is not very cold up north. 

 

 

[Scandinavian High.]

What a massive block to the north east I wonder if we can start to tap into into something much colder from east next few weeks

Edited February 6 by Scandinavian High.

[damianslaw]

 Daniel* Agree, the jet is southerly, and I'm bamboozled why the models want to move it north. It just seems odd. 

[Singularity]

33 minutes ago, Mike Poole said:

T192-T240 charts to back up your comment:

My main takeaway from these is that the deterministic run probably overdid the firing up of the subtropical jet stream days 8-10. A big deal considering it still managed to disrupt the trough.

Things do seem unnecessarily messy this weekend into next week. How much of that is down to genuine issues rather than modelling mishaps remains to be seen.

If we look past GFS frequently doing its usual thing when faced with an Atlantic trough versus Scandi/Russia blocking high setup, the broad scale signal for a large blocking feature retrogressing toward Greenland during 3rd week Feb has been pretty steady for several days now. I view that as the wood that we're trying to see through the trees, so to speak.

It bugs me that we look to be headed for the first true major SSW of the season with some potential for a split polar vortex to result. Bearing in mind the substantial snow events that happened in the Marches of 2018 and 2013 in the wake of a favourable MJO progression and major SSW, I fear spring may have some serious trouble getting off the mark. Of those two years, only 2018 managed to put down lying snow here... though it remains to this day the deepest level snow I've witnessed in my local area (18 cm on 1st March).

On the flipside, this SSW could still be early enough that the polar vortex can recover in its wake and drive a +AO by around mid-April. The blocking signal then refocuses more toward the mid-latitudes which can produce some very fine runs of weather indeed. Again, 2018 comes to mind. Ah, what a year.

[Frigid]

 Mike Poole The best chart I've seen all day, perhaps it's not all bad. That really is a sharp decrease in zonal winds, especially since a few days ago it was showing nothing like it. GFS also playing with the idea of a reversal, many members dipping to -15m/s. Seems like it'll be a lot more notable than the one we had in mid January.. question is will it deliver the goods or another mild borefest. Still got hope we'll see something special this month.

[blizzard81]

 Frigid I wonder what has caused this sudden turnaround?

[Singularity]

4 minutes ago, damianslaw said:

 Agree, the jet is southerly, and I'm bamboozled why the models want to move it north. It just seems odd. 

I know what you mean, it doesn't feel right. I've never had a greater sense of 'the models have totally lost it' clashing with 'but surely they can't get it that wrong at 3-4 days lead time?'.

It's especially peculiar how we initially had much more credible looking outcomes from UKM & ECM. Evidently, something very unusual has been picked up on, however well or not its impacts are being resolved.

[blizzard81]

 Singularity I wonder what? 

[Ice Day]

The ECM mean for day 10 is as strong a signal as you'd wish to see at that range.

 

How it develops thereafter will keep us on our toes, but it won't be a quick route to cold (when is it ever in the UK!).

[bluearmy]

 blizzard81 it’s not sudden

the model picked up on a marked slowdown about a week ago and the gfs ops began to show an appetite for a reversal ever since it was at day 16.   the gefs have slowly caught up and began to show mean reversal on and off for the past couple days. The eps since this morning. 

[damianslaw]

 Singularity Those who have more detailed knowledge may be able to explain why the models are shunting it north instead of east.. I keep looking at the models and scratching my head why this is the case, especially with heights building to the north as well.. it should in theory head SE.. answers welcomed.

[WYorksWeather]

As others have said, if we are going to get a BFTE setup similar to 2018 - a late cold spell that is going to rescue winter, the building blocks have to be in place. Just an example, but to show the differences.

Here are the 850hPa profiles, compared to the same date in 2018. For this year I'm using the GFS 12z mean.

11th February:

 

16th February (day 10):

 

Look at the spatial extent of the blues by comparison - no prizes for guessing which chart is from this year, and which chart is from 2018. This was before the actual synoptic that produced the BFTE in late February, and just shows how much more of a possibility there was in 2018. Easiest way is to pick something like the deep blue -8C contour and compare the area. In 2018 there are extra blobs of -8C well outside the locations where you'd expect them. This year, almost all of Europe, with the sole exception of Scandinavia, is mild.

And the culprit, I would suggest, is this.

I checked, and in 2018, the entire North Atlantic was half a degree cooler. That's a massive teleconnection if ever there were one, and it doesn't get mentioned enough.

[JimBob]

Now looking like a one day cold snap for most of the country on Thursday with rain and snow for some, the far south may not even turn cold until next week now.