Model output discussion - cold spell approaching?

[PolarWarsaw]

Well, it's clear things are fickle at the moment.

It's also clear that things are changing for the worse this morning, once that happens it basically never reverses. We saw this around 10 days ago when the GEFS/EPC showed a clear rise towards mid month and even though it was against practically every strat forecast, it's not been cold enough for snow to fall for around a week now. 

If this morning charts are correct then we are heading towards flooding taking the headlines, nothing SSW or Cold related.

With that being said, there's a few opportunities for transient slushy snowfall, particularly the further north and over higher ground.

I think it's suffice to say at this point, that the initial chances of a traditional 'BFTE' response from the SSW, is all but gone. We are in the midst of another push back to beyond Day 10 for the coldest air and this is a pattern that has now repeated 6-8 times already this winter. It is beginning to feel like we may never get there in terms of a proper cold spell. 

Let's hope there's plenty of snow around.

Interested to see where the 12z goes and how long/any delay at all we are looking for. 

[damianslaw]

Staying quiet on current model output as fully expect lots of flip flopping as to be expected as they play around with after effects of SSW. In the very short term we are seeing sudden developments throwing spanner in the works, current front set to develop wave and cold air advancing from the east.. 

[Bricriu]

2 minutes ago, damianslaw said:

Staying quiet on current model output as fully expect lots of flip flopping as to be expected as they play around with after effects of SSW. In the very short term we are seeing sudden developments throwing spanner in the works, current front set to develop wave and cold air advancing from the east.. 

There maybe changes between runs, but the trend is the same: very cold air looks to remain out of reach for most, if not all of us. What we are left with is  where the boundary rests between competing airmasses. The UK Met Office looks to have made the correct call in their extended outlook in this regard. 

[Bricriu]

8 minutes ago, PolarWarsaw said:

I think it's suffice to say at this point, that the initial chances of a traditional 'BFTE' response from the SSW, is all but gone. We are in the midst of another push back to beyond Day 10 for the coldest air and this is a pattern that has now repeated 6-8 times already this winter. It is beginning to feel like we may never get there in terms of a proper cold spell. 

 

To be honest i was not confident of a BTFE  because they are rare, and we got a displaced vortex, rather than a split,  which ended up with a lobe of vortex in the wrong position. The MJO phase did not help matters either.

[throwoff]

I think there’s a lot of people really letting the models play them at the moment.

The weather is going to do what it is going to do, even the best models are nothing more than an educated guess.

The best thing to look at is pattern not run by run. The pattern is still for cold to come, don’t panic. 

[Rayth]

8 minutes ago, Bricriu said:

 and we got a displaced vortex, rather than a split,  which ended up with a lobe of vortex in the wrong position. 

A split in the middle to lower strat is forecast tomorrow , will be interesting to see how this now plays out with the models in the coming days 

[Daniel*]

I don’t think people notice we have already had one major wobble including ens and they tread back, the broad picture hasn’t changed fundamentally, it’s not like we have expected very cold easterlies only to end up with euro high and southwesterlies now that would be a kick in stomach. A lot unresolved, while I find this output this morning disappointing, if I lived up north I’d see much more in it, often for lord knows what reason 00z tends to disappoint and well GFS 06z was a slight improvement. I’d give it 36 hours before passing judgement. 

[Ali1977]

Most likely scenario according to the professionals, I expect a trend back colder on the 12zs

[Daniel*]

6 minutes ago, throwoff said:

I think there’s a lot of people really letting the models play them at the moment.

The weather is going to do what it is going to do, even the best models are nothing more than an educated guess.

The best thing to look at is pattern not run by run. The pattern is still for cold to come, don’t panic. 

Yep top post. Too many people let the models gain control over them it’s quite ridiculous. Just go with the flow, anything can happen, nothing is fixed particularly post SSW and the split of sorts in vortex later this week will further complicates matters, as N Atlantic segment is absorbed east into Russian segment. There’s good reason to believe blocking in Atlantic/Greenland area will not be going anywhere soon.

[IDO]

11 minutes ago, Scandinavian High. said:

I’m suspecting upgrades with models later met office updated there website no changes really chances of cold anywhere in uk there expecting north easterly next week colder weather from Scandinavia.

Yes, just seen the update video and they have two options, but favour the NE'ly flow over the SW'ly. TBH it would not take the modelling to be tweaked much for either to be the outcome. The trend from the gfs is the SW flow, but gfs has a bias for pushing the Atlantic through and we have seen with the slower push east the next few days that maybe the NE'ly option is in with a chance?

The ecm de bilt suggests that there is a def split has to how the pattern evolves post-d7:

The control probably goes the SW'ly route. Hopefully we can get some clarity as to what follows in the coming runs?

[frosty ground]

1 minute ago, IDO said:

Yes, just seen the update video and they have two options, but favour the NE'ly flow over the SW'ly. TBH it would not take the modelling to be tweaked much for either to be the outcome. The trend from the gfs is the SW flow, but gfs has a bias for pushing the Atlantic through and we have seen with the slower push east the next few days that maybe the NE'ly option is in with a chance?

The ecm de bilt suggests that there is a def split has to how the pattern evolves post-d7:

The control probably goes the SW'ly route. Hopefully we can get some clarity as to what follows in the coming runs?

Is it not more likely that we will get a mix of both?

IMHO Large snowfalls are likely over the next few weeks with milder weather in-between.

[Cold Winter Night]

6 minutes ago, IDO said:

Yes, just seen the update video and they have two options, but favour the NE'ly flow over the SW'ly. TBH it would not take the modelling to be tweaked much for either to be the outcome. The trend from the gfs is the SW flow, but gfs has a bias for pushing the Atlantic through and we have seen with the slower push east the next few days that maybe the NE'ly option is in with a chance?

The ecm de bilt suggests that there is a def split has to how the pattern evolves post-d7:

The control probably goes the SW'ly route. Hopefully we can get some clarity as to what follows in the coming runs?

That same page also shows the wind directions. The control is indeed mostly SW (225 degr), as is the majority of members. Just a handful that goes NE (45 degr), those must be the same ones that still show a minor grouping of ice days in De Bilt later on.

[IDO]

4 minutes ago, frosty ground said:

Is it not more likely that we will get a mix of both?

IMHO Large snowfalls are likely over the next few weeks with milder weather in-between.

I noticed that what you mention was the gem mean take! So, another option as you say. 

[frosty ground]

8 minutes ago, IDO said:

I noticed that what you mention was the gem mean take! So, another option as you say. 

You don't need the mean to see what could happen?, I'm not sure the mean at such time frames will even pick up on such events either.

Very cold air to the north and north east, southern tracking jet that will drag in this air from time to time equals large snow falls at some point at some location over the UK.

Will a day 10 mean pick up such an event? probably not.

[northwestsnow]

28 minutes ago, Ali1977 said:

Most likely scenario according to the professionals, I expect a trend back colder on the 12zs

Hope so Ali my friend.

We really do need upgrades...

In particular UKMO ...

Let's hope the 12zs swing back...

 

[IDO]

3 minutes ago, frosty ground said:

You don't need the mean to see what could happen?, I'm not sure the mean at such time frames will even pick up on such events either.

Very cold air to the north and north east, southern tracking jet that will drag in this air from time to time equals large snow falls at some point at some location over the UK.

Will a day 10 mean pick up such an event? probably not.

The mean 850's ebbs and flow from the SW then from the NE. That could mean a split in options, but looking at the Gt Yarmouth pressure ens, there is sine wave activity on many members suggesting the ebb and flow as you mention:

I would not be as optimistic as the Met is!

[phil nw.]

A weaker trend has shown in the 00z runs in trying to bring the cold in and that's certainly disappointing. I viewed one model to see what might have changed since the previous 24hrs.

Looking at the 00z ecm runs today and yesterday around the pole on the 500 chart,There is different modeling of the low heights there. The Arctic high is still shown but the movement of the pv segments around it are somewhat changed.

Yesterday we saw a more direct flow of the Siberian side,although by all means not perfect ,but today we see that flow warmed out over Scandinavia.(first image) 

The vortex chunk above Siberia is diverted west across towards Greenland.We then see less amplitude of ridging into Greenland,This impinges on the Atlantic pattern around the Uk as the rest of the Scandi.trough drops down further west of the UK,disrupting earlier and delaying the cold coming south.Of course all this does is mixes out more of the coldest air,hence milder uppers.

I haven't studied the other models but these are the type of changes over the Arctic that can happen especially in the current situation of a ssw downwelling.It's probably the area most difficult for modeling accuracy anyway.

The basic ideas of a ridge towards Greenland and lower heights around Scandinavia are there but the latter has now morphed into a broad disrupted feature as it comes south.

It's a wait and see now whether this path to cold resurges with better ridging to our north west and a more direct feed from the north east or indeed the set up reshuffles into another trend.

[WINTRY WALES]

46 minutes ago, Ali1977 said:

Most likely scenario according to the professionals, I expect a trend back colder on the 12zs

Is this a recent forecast off today’s models?? Sorry in work cannot access it

[Ali1977]

10 minutes ago, WINTRY WALES said:

Is this a recent forecast off today’s models?? Sorry in work cannot access it

An earlier tweet 

[Day_9]

Vile chart for a coldie but the models are not forecasts, they just generate multiple scenarios that people use to make a forecast.

 

As a total newb to this im just sticking to one chart - the 850s gfs ens.   And what that chart shows us in black and white is that beyond day 4/5 most models are useless.  (Circled red)
 

what I do know though is that whilst they might be not very specific and very sensitive to variables in their inputs, trend is how you make sense and the trend has been and remains cold...... on we go!

[Daniel]

Icon not as deep with the low. I think I am right in thinking this is better. Please correct me if I'm wrong 

[Battleground Snow]

2 minutes ago, Daniel said:

Icon not as deep with the low. I think I am right in thinking this is better. Please correct me if I'm wrong 

It's needs not to "pop out* out later into the run... If it's shallower it may track further south

[Tim Bland]

Icon showing a risk of snow right down to the south east as temps fall away tomorrow. Could be close to 0c in many areas late in the afternoon..

[mushymanrob]

Make of this what you will

 

[Ben Sainsbury]

Big improvement on the UKV 12z compared to its UKV 9z run for tomorrow's snow event:

 

Edited January 13, 2021 by Ben Sainsbury