Model Output Discussion - Colder but how cold and for how long?

[Mike Poole]

ECM mean at T240:

Pretty good support for a signal of height rises into Scandi - unfortunately the clusters don’t help, just one between T192-T240, await the extended with interest.

[That ECM]

14 minutes ago, Tim Bland said:

So close to something special for southern areas. Still a chance if a few flurries looking at UKV. For most this has been an other snowless cold spell. Let’s hope feb delivers at least 1 measurable snowfall for all 

Wouldn’t be surprised to see some in the south west with a bit of elevation get some snow.

[steveinsussex]

14 minutes ago, Met4Cast said:

The GFS 12z deterministics idea of a Scandi high is a huge outlier amongst the ensembles.. but it’s an interesting one. 

It’d usually be rather easy to ignore given it’s an outlier but what it shows does fit with the background forcing that has been discussed to death in recent weeks. 

MJO progression east > +FT > +MT > Rising AAM tendency with the MJO eventually pushing into the Pacific, tropics & sub tropics then singing together for high latitude blocking. 

I wonder if the GFS Det is picking up on this signal but being too progressive with it? Evidently there’s zero support currently but it’s a very curious one. The next few days could be interesting. 

Trend setter 

[bluearmy]

11 minutes ago, Mike Poole said:

ECM mean at T240:

Pretty good support for a signal of height rises into Scandi - unfortunately the clusters don’t help, just one between T192-T240, await the extended with interest.

Too much upstream forcing for the time being but there must be a few members that aren’t far from the gfs op 

[Mike Poole]

ECM clusters T264+:

Cluster 2 shows the heights into Scandi evolution, 17 members, some leap still to turn that into a full Scandi high, but it’s a strong signal in that direction.  Cluster 1 heading the same way with a slower evolution.  Cluster 3 remains westerly.

[Jason M]

Just now, bluearmy said:

Too much upstream forcing for the time being but there must be a few members that aren’t far from the gfs op 

Its not the outlier that the 850s would suggest. There is support for something similar albeit the other GEFS are failures in terms of getting cold here. 

[ScottSnow]

16 minutes ago, Met4Cast said:

The GFS 12z deterministics idea of a Scandi high is a huge outlier amongst the ensembles.. but it’s an interesting one. 

It’d usually be rather easy to ignore given it’s an outlier but what it shows does fit with the background forcing that has been discussed to death in recent weeks. 

MJO progression east > +FT > +MT > Rising AAM tendency with the MJO eventually pushing into the Pacific, tropics & sub tropics then singing together for high latitude blocking. 

I wonder if the GFS Det is picking up on this signal but being too progressive with it? Evidently there’s zero support currently but it’s a very curious one. The next few days could be interesting. 

The GFS was showing mild outlier ops for next week that look like they will turn out to be true, so hopefully it’s picking up on something for a return to cold.

There were quite a few times last week where we heard that the op was on its own in the ensembles regarding the return to mild.

[TillyS]

Aside from a chase over the distant horizon, I see that the 12z UKMO is still pepping up the winds this Sunday:

 

Less potent on ECM and GFS, except in the far north of Scotland.

12z ECM:

 

12z GFS:

[Stuie]

After hunting around ALL models for tomorrow morning, unfortunately IMBY misses out a decent snowfall on the South Coast. That close you can almost see the 2 fingers.

Funny old game (EVERY year)

EDIT: If all the models have it slightly wrong, I will report.

Edited January 16 by Stuie

[Stuie]

Posted yesterday about the potential of the weekend storm trending North, ECM tonight making it much more a Northern Scotland affair rather than whole country affair. Could end up being nothing at all.

 

[Rain All Night]

7 hours ago, RainAllNight said:

A briefer collection of this morning's model runs...

Deterministic runs to day 7, Tue 23rd

A possibly disruptive low arriving on Sunday, and perhaps a second one looking like it could reach us around the middle of next week?

Ensemble means at day 10, Fri 26th

It seems there is a reasonable chance of a drier spell for the south later next week.

Ensemble means at day 13, Mon 29th

That's a long way southwest those isobars are reaching...

An overview of this afternoon's model outputs.

Deterministic runs to day 7, Tue 23rd

It seems we may be affected at least indirectly by storms on both Sunday and Wednesday.

Ensemble means at day 10, Fri 26th

Drier for many by the end of next week?

Ensemble means at day 13, Mon 29th

Any further progress into the following week looks very uncertain... but other posters here have pointed out that we have reasons to be optimistic about this.

Edited January 16 by RainAllNight

[feb1991blizzard]

1 hour ago, Scott Ingham said:

The musing about scandi heights started back on the 3rd of January buddy some 13days ago with yourself and Battleground Snow and I think even a week before that I discussed this evolution with Catacol so if the GDSM products can nail this period for a second time this winter around a month before it happens it just adds even more evidence to this ever growing meteorological science used for long time forecasting! The hard bit is getting the lag periods and timings right. The 15th was correct it’s a waiting game for the 29th. There’s been so much to learn this winter!

With you all the way but think 29th a little early, looks to me based on the ens suites it will have a go at scandi around 29th, not quite make it but retrogression to Griceland around 5th feb

[Scott Ingham]

6 minutes ago, feb1991blizzard said:

With you all the way but think 29th a little early, looks to me based on the ens suites it will have a go at scandi around 29th, not quite make it but retrogression to Griceland around 5th feb

It could very well be early mate in all honesty. The date is just an educated guess that has more chance of being wrong than right for the start of a pattern change to one conducive to high lat blocking near scandi or Iceland. I do feel fairly confident of us being in a favourable pattern however by mid Feb at the very latest. Your opinion based on the ens suites at this moment in time is well founded. Evidence would suggest at this moment in time that your timings are more likely to be correct pal

Edited January 16 by Scott Ingham

[blizzard81]

15 minutes ago, Scott Ingham said:

It could very well be early mate in all honesty. The date is just an educated guess that has more chance of being wrong than right for the start of a pattern change to one conducive to high lat blocking near scandi or Iceland. I do feel fairly confident of us being in a favourable pattern however by mid Feb at the very latest. Your opinion based on the ens suites at this moment in time is well founded. Evidence would suggest at this moment in time that your timings are more likely to be correct pal

I will add a bit of a curve ball to this. It could well be the ensembles in particular are underestimating the start of the amplification in around 9 days time - that's the 25th Jan. I say this because we have the gfs op and control and also the ecm control smelling the amplification route significantly today. It could well be one of those great ocassions when, if anything, the momentum could speed up and things brought forward a day or two. Quite the opposite to the present cold spell where the chase seemed to go on forever. 

Edited January 16 by blizzard81

[Scott Ingham]

4 minutes ago, blizzard81 said:

I will add a bit of a curve ball to this. It could well be the ensembles in particular are underestimating the start of the amplification in around 9 days time - that's the 25th Jan. I say this because we have the gfs op and control and also the ecm control smelling the amplification route significantly today. It could well be one of those great ocassions when, if anything, the momentum could speed up and things brought forward a day or two. Quite the opposite to the present cold spell where the chase seemed to go on forever. 

Yeah that’s also an option, models won’t have a grasp on this period, won’t have a full grasp on the momentum budget and consequently the level of poleward amplification. The next 5 days are a watching brief. Better to know we have a ticket to the raffle than no ticket at all. It will be another interesting period of model watching to come. As of now the evidence points to Febs analysis on dates but it doesn’t mean it’s right yet we’ll just have to watch for the trends and ensembles around the 25th as you suggest

[blizzard81]

6 minutes ago, Scott Ingham said:

Yeah that’s also an option, models won’t have a grasp on this period, won’t have a full grasp on the momentum budget and consequently the level of poleward amplification. The next 5 days are a watching brief. Better to know we have a ticket to the raffle than no ticket at all. It will be another interesting period of model watching to come. As of now the evidence points to Febs analysis on dates but it doesn’t mean it’s right yet we’ll just have to watch for the trends and ensembles around the 25th as you suggest

Just to clarify. I'm not saying the start of any cold spell on the 25th. Rather more ridging by this date than what is being modelled at the moment - This then leading to a more rapid descent into cold. 

Edited January 16 by blizzard81

[Scott Ingham]

1 minute ago, blizzard81 said:

Just to clarify. I'm not saying the start of any cold spell on the 25th. Rather more ridging by this date than what is being modelled at the moment - This then leading to a more rapid decent into cold. 

Yeah I thought that’s what you meant my own opinion is similar to yours ridging 25th leading to easterly winds by the 29th or a day or 2 after. All said and done if the broad evolution came off I couldn’t care less if the dates are before or after. The satisfaction comes from seeing the pattern play out so you know that you’re moving in the right direction as far as knowledge is concerned and interpreting the signals correctly and if not then not. Where did we go wrong and what can we learn from it for next time.

[blizzard81]

1 minute ago, Scott Ingham said:

Yeah I thought that’s what you meant my own opinion is similar to yours ridging 25th leading to easterly winds by the 29th or a day or 2 after. All said and done if the broad evolution came off I couldn’t care less if the dates are before or after. The satisfaction comes from seeing the pattern play out so you know that you’re moving in the right direction as far as knowledge is concerned and interpreting the signals correctly and if not then not. Where did we go wrong and what can we learn from it for next time.

Let's hope it comes off - I think we both feel like it could well be the main course if it does

[Scott Ingham]

3 minutes ago, blizzard81 said:

Let's hope it comes off - I think we both feel like it could well be the main course if it does

Absolutely! Will stop this winter from being one of “Great Potential and Disappointing Achievement!!” sounds like one of my old school reports…..

[BLAST FROM THE PAST]

56 minutes ago, Scott Ingham said:

It could very well be early mate in all honesty. The date is just an educated guess that has more chance of being wrong than right for the start of a pattern change to one conducive to high lat blocking near scandi or Iceland. I do feel fairly confident of us being in a favourable pattern however by mid Feb at the very latest. Your opinion based on the ens suites at this moment in time is well founded. Evidence would suggest at this moment in time that your timings are more likely to be correct pal

10-14 Feb at earliest, could have a lot of HP ‘domination’ in Feb prior.  Can’t see a cold signal appearing before then

 BFTP

[Scott Ingham]

4 minutes ago, BLAST FROM THE PAST said:

10-14 Feb at earliest, could have a lot of HP ‘domination’ in Feb prior.  Can’t see a cold signal appearing before then

 BFTP

Really? That’s feels a little late as far as the change to +AAM is concerned but if the new momentum cycle has a weak +FT and +EAMT then that scenario might play out as we don’t hit MJO phase 7 until the end of the month with a 10 day lag there after. I see scandi end of month and Greenland second week in Feb

[WYorksWeather]

So, quick update on two things. First, we now have the first storm system just about into range on UKV. Sunday afternoon looks highly unpleasant to say the least. Still a lot to be nailed down as far as the track goes, but if you have anything you're afraid to lose, maybe you should be nailing your stuff down, and not worrying about the models! I also think it'd be the perfect afternoon to be on an Irish sea ferry 

In all seriousness, this has the potential to be damaging if it hits with this intensity, wherever it hits. I think warnings will probably go up in the next day or two once the track is better constrained.

Next is my look at the potential for a daily record to go around the 22nd-24th, as I've been mentioning for a couple of days.

Modelling seems to be firming up on the 23rd as the mildest day. The target is 15.2C to beat. As previously mentioned, I am calling that anything above 13C on these ensembles is more likely than not to break the daily record, given typical under-reading and the fact that London may not be the absolute warmest spot. The mean is currently around the 11.0C to 11.5C range, but anything in the top quarter of the ensemble would be above 13C and probably get us there in practice.

Here's the 12z ECM mean:

 

Even this gets us widespread double digits, and 12C clipping the south-west in raw figures. It must also be noted that the mean is skewed downwards by cold outliers - the median would be a degree or so higher.

Strictly just for fun, but here's the most extreme solution, P39 of the 12z ECM:

This map includes a raw 15.5C in London, quite possibly 16-17C in practice, which is extraordinary. Very unlikely to happen of course, since it is at the top of the ensemble.

On to the longer term, unfortunately there's nothing I'm seeing the ECM meteograms that really backs up the rogue GFS run from earlier. I've posted Reading first, then Newcastle (since it would be quite exposed to an easterly if it came off):

Even at the very end of the run, right out to the 30th, the median is well above average by day and night, and even the 10th percentile is only average. I agree with other posters that there is still the possibility that we see the building blocks for a February cold spell start to assemble themselves later in the month, but I'm going to somewhat go against the grain of the other posters here and say that I think temperatures will remain above average right to the end of the month, even if the broader picture becomes supportive of cold - I think once lag effects are taken into account early February is more realistic.

 

[Battleground Snow]

5 minutes ago, Scott Ingham said:

Really? That’s feels a little late as far as the change to +AAM is concerned but if the new momentum cycle has a weak +FT and +EAMT then that scenario might play out as we don’t hit MJO phase 7 until the end of the month with a 10 day lag there after. I see scandi end of month and Greenland second week in Feb

I can only see the signal accelerating, similar to how the zonal spell got brought forward.

Doesn't mean the orientation will give us deep cold straight away, but it will definitely be an option at least.

Maybe a holding pattern of chilly weather in the final days of January, followed by something more substantial into the first week of February?

[Scott Ingham]

Just now, Battleground Snow said:

I can only see the signal accelerating, similar to how the zonal spell got brought forward.

Doesn't mean the orientation will give us deep cold straight away, but it will definitely be an option at least.

Maybe a holding pattern of chilly weather in the final days of January, followed by something more substantial into the first week of February?

We’re at a decent base state in GWO already. For me because of that once we get a boost in AAM from the +FT and +MT it could be enough poleward momentum to create high lat blocking but in Iceland/Scandi where both the Strat and Trop look better places for a high lat block to set up. The last piece in the budget jigsaw will be the MJO on the 30th of Jan. This will do two things. Strengthen northern blocking and act as a retrogressive signal to Greenland around the 10th with lag. There is a scenario where without the MJO we don’t see enough rise in +AAM and we go with a mid lat block around the UK then retrogressing to Greenland. For me they are the two scenarios on the table. A quicker and longer lasting spell or one that starts around the 10th from Greenland after a UK high

[Mike Poole]

Here we go!  Pub run T222:

You can see the amplification first with the trough in the Atlantic.