Model Output Discussion - Spring Has Sprung

[bluearmy]

7 minutes ago, Frigid said:

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.

[Eagle Eye]

 Singularity

Problem with the major SSW is that if it does happen, most of the runs appear to be wave-1 displacement driven with most of the vortex over Europe so favourable surface responses at the moment are looking a bit meh. So I'm not really thinking those March's are likely at the moment but we'll see. 

I really would warn people here getting excited over the modelled SSW, no matter the strength it's really not looking the best, arguably the worst scenario considering some runs saying about - 15ms zonal mean zonal winds. Most of the deterministic runs have been displacement type for a while. I'm still hanging onto hope but this feels like it's not going to end up well. 

[Frigid]

 bluearmy The no of members going for a reversal has increased significantly today, of course it can revert back to previous showings but I'd like to think this trend will continue. Positive signs..

[Mike Poole]

 damianslaw It is really weird.  I am sure the models did have it heading SE a few days ago!  Then the GFS got the idea of it heading NE, and now, particularly the GFS and GEM have it heading north or even NW.  

The thing is, it’s put a major diversion in the route to longer term cold.  

[blizzard81]

 Mike Poole Icon moving more towards what one would expect?

[blizzard81]

Icon 'looked' like it was an improvement then it let go unfortunately. 

[bluearmy]

 Frigid yes the 46 has committed to reversal today which I guess is expected since the eps did the same on its 00z run. 
my point was that this hasn’t just come out of the blue - the usual pattern with warmings and reversals (whether tech ssw or higher up)  is that the gfs op picks it up at 2 weeks range and it either disappears as time ticks down or it slowly picks up momentum in the ens and at some point they go all in.   The 46 with 100 members is having its first winter so new for us to see.  So far this winter, we’ve seen the first swift decline in flow picked up well by the model but thereafter, the Jan one and now this one were spotted around two weeks out. The actual ssw in jan wasn’t picked up at  more than a week out by any model. 

[E17boy]

This is not the time we wanted to see these trends appearing especially when time is ticking and sooner than later we will be clutching any straw to find a last saloon rescue for this season. I am a bit puzzled with this evenings output something does not seem right. I am puzzled as many of you why is all the energy heading north despite blocking. Either something has triggered this or the output will be completely different come tomorrow. The chase is beginning to take its toll now we need some changes soon to come and rescue us coldies. 

[bluearmy]

 Mike Poole I’ve been watching the AI models and they’ve consistently been keen to trend the lows north. Given that they are based on historic patterns, it’s surprising that we’re surprised! 

 

[WYorksWeather]

ECM 12z ensemble is much the same as the GFS. Less of a trend maybe, but still slightly on the mild side.

 

[blizzard81]

If that low just to the south of Iceland could dive south eastwards, that really could help that Siberian beast come out of it's shell and venture west. 

[Mike Poole]

 blizzard81 Let’s try and work this out, using the ICON run as an example.  My thoughts are, is the whole thing behaving like one big complex low system?  Here at T48 is our low:

Then at T72, T96, T117 - does it make more sense if it is the system I’ve drawn in yellow?

[Sweatyman]

 blizzard81 it's always things by Iceland that scuppers things it seems. Dam it

[blizzard81]

 Mike Poole I could be wrong but the low to the north at 117hrs looks like it spawns just east/north east of Iceland at circa 105hrs. Tbh mate, the more I look at the output for the next 72 to 96 hours time period, the more convinced I become of some major twists and turns at very short notice and dare I say it...... In our favour!

 Sweatyman Indeed mate. Very common. Also just off the coast of Norway is another favourite lol. 

[minus10]

 Mike Poole It was interesting watching the met deep dive earlier where Aidan stated that the sudden change in the modelling of the low from taking it southeast to stalling it over the uk/ moving it north was resulted from a small increase in the modelled development of the low way back in the Atlantic which then resulted in it becoming larger and extending its influence of mild air thus displacing the cold air further north...again minute changes upstream resulting in huge changes downstream..thus effecting the surrounding synoptic response too...have to say that the gfs saw this a few days before the ec/ ukmo...is it better at picking up developments in the Atlantic...really shows how complex and sensitive the weather processes are...

[blizzard81]

 minus10 Yep. Just that bit too much energy in the atlantic this winter. This goes down as a very wet and stormy winter in my book. These rarely deliver the cold goods. 

[bluearmy]

 minus10 gfs is better at picking up progressive changes to mild. IGiven that we tend to suffer these being at the eastern side of a warm ocean, it seems to do well.   I’m guessing we have a better opinion of gfs here than the netweather USA would. 

[Daniel*]

2 hours ago, Froze were the Days said:

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.

Not true..

 

[Cheshire Freeze]

 Mike Poole March has been showing as blocked (Greenland) on the seasonals for months…moreso than any other month. It was always going to head that way.

[bluearmy]

still worth waiting for …..

  

Edited February 6 by bluearmy

[CoventryWeather]

 Mike Poole so that small shortwave pulls the whole low northwards? For me that just defies physics. 

Unless there's a kink in the jet stream that moves it north.. I suspect its model bias. 

[Ice Day]

13 minutes ago, bluearmy said:

still worth waiting for …..

I've just run through all 51 at 300hrs..... it's an absolutely remarkable set!

[damianslaw]

 Mike Poole Still leaves me puzzled and what is the detached low to the SW doing there? Where is the high pressure inbetween. Some of the oddest synoptics I've seen. 

[frosty ground]

 CoventryWeather looks to me that its following the law of physics 

 

[Rain All Night]

10 hours ago, Rain All Night said:

0z deterministic runs, Tue 6th to Tue 13th (day 7)

The second Atlantic low struggles east and pushes the mess left behind by the first low (the nature of this mess is still unclear, a mixture of weak low and weak high pressure) up over us. ICON is now showing the mild southwesterly air flow at the end of the run that GFS was showing yesterday afternoon, but the ensembles shown further down this post suggest to me that this will not verify.

0z ensemble means, Tue 6th to Wed 21st (day 15)

The models still agree that the second Atlantic low will not reach the UK. Mid-run, the highest mean pressure on the surface has reverted to being over Scandinavia rather than the UK, although a cold air flow into the UK is not suggested. In the later stages, the mean heights in these runs are noticeably lower than they were last night, especially on the GFS and GEM where an Atlantic return is looking imminent by 21st February, and the signal for high pressure migrating to Greenland looks significantly diminished.

12z deterministic runs, Wed 7th to Tue 13th (day 7)

I'm not sure what I'd been expecting to see next from the deterministic model runs, but it wasn't this. First we had the GFS start unexpectedly sending our low north and the other models then following suit, and now we have the GFS begin following this up with mild southwesterlies only for some of the other models to start showing that too. If deterministic runs out to day 7 were the only output you could see, and you'd not seen any longer-range ensemble or seasonal output or heard any professional or amateur teleconnections-based forecasts, then I don't think you would look at these charts and think that significant high- or even mid-latitude blocking is what's coming next. And yet it still could be, which is why we keep watching!

12z ensemble means, Wed 7th to Wed 21st (day 15)

After initially looking like they may be going nowhere, these ensemble means do, between them, just about manage to deliver the signals for Scandinavian and then Greenland blocking that we've become accustomed to seeing over the past few days, with ECM the most convincing. The Atlantic trough seems to be looking more and more menacing with each new set of runs, though it is nonetheless impressive for us still to get to day 15 without it taking over on these mean charts.