Model Output Discussion - Spring Has Sprung

[Harsh Climate]

Aprege also brings Thursday's snow much further South

  

[nick sussex]

It’s not just where the low centre tracks but how it develops .

So it’s a bit more complicated than the simple track .

Looking ahead the signal for blocking to the n ne continues . I know the UK has some bad luck but it would be incredibly unlucky to miss out on a decent cold spell once that blocking sets up .

Edited February 4 by nick sussex

[IDO]

 winterof79

Only said that as it is rare for the op to fall out of the standard deviation around D5-6. The EC is notorious for D8-10 outliers but rarely that early.

 MJB

Sorry, I meant for long-term higher latitude blocking. What comes later next week is not sustainable for snow or for it to remain (see GFS). However, if EC op is correct, then we may get lucky. For example, the GFS snow:

It comes and goes quickly. 

[CoventryWeather]

 bluearmy I personally didn't expect a drop that far tbh! Hopefully it can stay there - we haven't had a proper event in what feels like years! Great output this morning - all models pulling the low further south.. let's hope it gets someone other than France. 

[Nick F]

EPS mslp mean has the late week / early Saturday low running through the Channel!

Trend GIF over last 4 runs shows the slowing of the low moving NE/E and also further south track. Ending up in France?

[bluearmy]

 IDO

    
 

todays 00z                                                    Yesterdays 00z 

 

the three in between have shifted a little south each run 

at some point this southerly shift will stop.  The op is obvs the edge of the envelope and outside of 80% of the members. We reach the point beyond today where the ops should be more informative then the ens if they are consistent with their solution. Like you I think the ec op has gone too far south but it may be that a half way solution between the current mean and todays op is feasible 

Edited February 4 by bluearmy

[Cambrian]

What a great Sunday morning to be up early looking at the charts! Especially when there’s such interesting ones on show, even now for the end of the same week.

0z EPS day 6 is a cracker of a surprise with the low pressure tracking to the south of Ireland through Wales and southern England, many of us kept on the cold side, or quickly brought back into it in the wrap. Just a point about how low the heights are - this is a mean, probably the best mean we have, showing 525 dam heights    to the southwest and through southeast England at day 6. There could well be a lot of surprises in store with this one.

 

Thereafter, by day 8, we have the centre of the low heading into Europe but with a meaty bit of troughing hanging back through the southern UK, with some properly cold air entrained in the northeasterly flow of the departing low. 

 

The icing on the breakfast cake for me this morning though is how quickly and solidly the high pressure builds in from the west by day 10, a surface high extending from the UK and Ireland northeast to Scandinavia. 

 

This puts one of the best types of prospect on the table - some snow on the ground, with a high pressure quickly established to trap in the surface cold over the snow. Potential for a good winter spell.

At this stage, we’re still very much defining and re-measuring the envelope. But it’s actually now surprisingly a bigger envelope than yesterday, with many more of our addresses being considered for being written on the front. Mornings like this are what makes this hobby so enjoyable. 

[Ali1977]

 Nick F loving that update, this must be another headache for the METO 

[carinthian]

Morning all from a very mild Austrian Alps this morning. Still looks like a tricky forecast for The British Isles later this week. The various models differ with the position of the low as it comes up again the installed cold air up North.  GFS has it further north compared to latest ECM which has significantly changed with a correct southwards. So base your forecast on that ! However, I think the most encouraging chart offered this morning is from extended UKMO which shows a NWly jet digging well south. This will enforce a European trough with the British Isles on the cold side with possibly a good snow set up. Good news for the rest of the month if that turns out to develop. I think UKMO fax charts may be the one to watch over the coming days if your Met Guys have a correction southwards in mind. Snow prediction charts will be unreliable the moment, however the out parameters results show lots of potential this morning.

C

Edited February 4 by carinthian

[Anthony Burden]

Morning all,Fax 120 hrs show a very messy and complicated picture,I mentioned yesterday the position of the low looked somewhat south of the UK.latest Fax chart showing main low of the south west of Ireland with secondary low further north,going to be another 24/48 hrs before we hopefully find the correct progression but more complications if it hangs around which seem possible.Hopefully all will see some snow from this situation.

[Harsh Climate]

Right I'm going to put a lot of this, it won't be cold enough for snow apart from hills to bed,  if the ECM was to be correct.

Check out these charts JAN/14/2021, who would have believed this would have dropped close to 10" just NW leeds on low ground! 

  

The snow fell and fully settled with the 850s between -1 and -4... With evaporative cooling from heavy precipitation and even with green (modest) 500s, that is all that's needed. Thursday's event is progged to have light/dark blue 500s which is better and really will pull the cold air down from high up dowwn to 2m level in heavy precipitation. Like I've been saying for days somewhere is getting clobbered on Thursday!  

 

 

[sheikhy]

 Harsh Climate yes and bear in mind arpege has had that low further south than any other model!so credit goes to the arpege and no other model if it does prove to be correct in the end!!

[IDO]

The difference between the EC op and mean at D6:

The op has the LP system tracking east whilst the mean (and GFS, GEFS, and GEM) take it E/NE, delaying the cold front. Also, the EC LP is less complicated than the mean and other models, including the fax chart with no satellite low(s). If it is correct, then one for the EC.

[sheikhy]

My thoughts are ecm lost the plot which it has done a lot recently for some reason!!gfs shall be correct!!!

[Snowyowl9]

It was GFS yesterdays 0z showing a foot of snow..

Swapped around now its ECM..Knife edge week coming up..

Edited February 4 by Snowyowl9

[winterof79]

 Harsh Climate

Thursday 06Z

ECM

Arpege

GFS

[frosty ground]

 IDO that chart you have used to determine if it’s an outlier or not has been proven to be unreliable, you should know this from the last time you tried using it.

use the full ensemble output then determine if it’s an outlier or not

[Lukesluckybunch]

ICON takes it ever so slightly south

[bluearmy]

 Anthony Burden that’s based on yesterday’s Ukmo 12z run Anthony. It could be that today’s 00z run is the same. 

looking at posts this morning, there are two events to keep an eye on initially.

the first is Thursday and another follows at the weekend.  If we aren’t specific then it’s going to get confusing in here! 

of course there is a relation between the two because if the first low disrupts more and tracks further south then likely the second is similar. 

[Harsh Climate]

 winterof79

Yeah Miles away from Northern Scotland wich looked possible Yesterday. 

IMBY I'm just hoping for baby steps further south, any big ones and this could end up Midlands/South afair lol.

Edited February 4 by Harsh Climate

[winterof79]

Strat in big trouble (Today and Mid Feb)

PV split

Moyenne trying to split too

Happy days.

Edited February 4 by winterof79

[CoventryWeather]

 winterof79 the Arpege isn't a model used much here but has consistently been going for a southerly low.

Think only once yesterday it went north before pushing south on the 18z run again. 

[Singularity]

What turns Thu-Fri into a more interesting setup for southern UK is a more west-east elongated trough, which limits the wraparound of milder air from the southeast while increasing the cold near surface inflow of air from the E/NE.

The latest two ‘main’ ECM det runs have made substantial strides in that direction & the ensemble is starting to follow suit.

On the other hand UKM hasn’t adjusted as far & GFS even less so. Yet again we find ourselves looking at a snowy frontal zone in 5-6 days time that could well be anywhere from northern England to northern France. A reminder that the models still have considerable limitations in certain setups.

[northwestsnow]

Would love to hear from @MattH referencing the lows ...

 

[IDO]

 frosty ground

I am talking about "statistical outliers" not whether a member has the lowest or highest data in a set.

You can have more than one outlier in a data set, as pre-agreed measures determine the outlier(s). The other outlier members are not plotted as they are irrelevant as we focus on one important member, the op. The op is a statistical outlier as it is outside the agreed standard deviation, along with other members that are ignored as irrelevant, for the same reason. The other graph showing all members does not show standard deviation, so it is moot for determining what is an outlier.

Saying all this, I hope EC has spotted something and it will be correct, but best to treat with extreme caution as it is rare that we see an EC op an outlier so early in a run.