Model thread discussion - cold spell looming

[Tim Bland]

9 minutes ago, Notty said:

Will it though ...

Almost definitely..can you show a model that doesn’t have at a least a warmer interlude ? You will struggle to even find an ensemble member...

[chionomaniac]

4 minutes ago, Tim Bland said:

Almost definitely..can you show a model that doesn’t have at a least a warmer interlude ? You will struggle to even find an ensemble member...

Lol. P19?

Edited February 5, 2021 by chionomaniac

[Man With Beard]

18 minutes ago, chionomaniac said:

Fundamentally, a return to another easterly and round 2. These patterns do have a habit of repeating themselves. Remember the mini BFTE, that followed the BFTE a couple of years ago.

Absolutely in my thoughts right now. This Scandi high has come out of nowhere on the ECM, and it will take not very much at all to shift the cold back. If it were summer, and a plume was showing in tandem with a Scandi High at long range, I'd definitely be looking east.

[Don]

3 minutes ago, Tim Bland said:

Almost definitely..can you show a model that doesn’t have at a least a warmer interlude ? You will struggle to even find an ensemble member...

To be fair, those ensembles towards the end of next week could well change tomorrow.  Happened many a time before be it from to cold to mild and vice versa, so I think we need a few more days at least to see what happens?  However, a less cold/milder interlude is looking more likely.

[Snowman.]

GEM was so close, a little more SE under the developing high or even a shortwave and we're laughing!

[That ECM]

4 minutes ago, chionomaniac said:

Lol. P11?

Don’t think it’s 11 but there are a few of interest for sure.

Edited February 5, 2021 by That ECM

[Tim Bland]

2 minutes ago, chionomaniac said:

Lol. P19?

Presumable that’s one of the 2 that are cold at the end? Look at where they have come from...they have gone mild and trending down. Every single ensemble shows a warm up I’d agree there’s scope for the milder interlude to be short but very little chance of it being non existent ? As for the the talk of the UKMO sliding ...I’d bet my life that low isn’t going under at t144! It’s massive, bowling ball shaped and level with Scotland! 

[chionomaniac]

Just now, That ECM said:

Don’t think it’s 11 but there are a few of interest for sure.

I meant 19 and corrected myself immediately but obviously not in time for the sharpest.  P11 was a bus I used to catch!

[johnholmes]

Just now, Tim Bland said:

Presumable that’s one of the 2 that are cold at the end? Look at where they have come from...they have gone mild and trending down. Every single ensemble shows a warm up I’d agree there’s scope for the milder interlude to be short but very little chance of it being non existent ? As for the the talk of the UKMO sliding ...I’d bet my life that low isn’t going under at t144! It’s massive, bowling ball shaped and level with Scotland! 

You are correct it is a meteorological impossibility for it to 'undercut' as the phrase in here might suggest.

[CentralSouthernSnow]

2 minutes ago, johnholmes said:

You are correct it is a meteorological impossibility for it to 'undercut' as the phrase in here might suggest.

There’s still time for it to undercut... it’s very far out still. 

[Tim Bland]

2 minutes ago, chionomaniac said:

I meant 19 and corrected myself immediately but obviously not in time for the sharpest.  P11 was a bus I used to catch!

19 has uppers above freezing by Friday....

[nick sussex]

In these set ups there’s a tipping point in terms of energy either disrupting se or going ne. It’s best to look at the ensemble in full rather than just the 850 value to get at an idea if its past the point of no return in terms of disrupting the energy se wards or whether you use experience of past set ups to see whether that could easily switch to disrupting the energy favourably .

For example if you see a more negatively tilted low but the member still runs the energy ne wards or eastwards that goes down in the more likely to disrupt closer to the time category .

The reason here is we know historically that models do not like more complex set ups with juggling where the energy might go . In particular the GFS normally has a bigger problem with this type of set up.

[chionomaniac]

1 minute ago, Tim Bland said:

19 has uppers above freezing by Friday....

I was replying tongue in cheek, Tim! I expect a warm up first, that wasn’t an issue, moreso that a set up for a scandi high is a possibility following this

[feb1991blizzard]

14 minutes ago, Tim Bland said:

Almost definitely..can you show a model that doesn’t have at a least a warmer interlude ? You will struggle to even find an ensemble member...

No, but look at the GEFS now, going to be some stonkers in there at the end of the run.

[Cloud 10]

What is this? Pin the tail on the ensemble.

 

Lets start with 14.

 

[Scorcher]

15 minutes ago, Cold Winter Night said:

Two things:

1) The charts you are showing are mild at that timeframe, BUT they scream Major Cold Spell. Look through some of the most legendary cold spells of the past, and this setup was exactly the run up to that.

2) Like @chionomaniac said on one of the previous pages, will we even get to this point? A small tweak here and there, a slightly weaker low, a high just 200 miles farther NW and the cold doesn't even leave, before the new round of amplification hits. Because the models really are firming up on that second round.

Thanks for your reply but I was commenting on what the models are showing. What you've said is mostly speculation. Can you explain how the models 'scream major cold spell' and give some examples of these past cold spells?

I think a lot of you are looking at this with ice-covered spectacles. That energy being injected into the Atlantic has to go somewhere- and the smart money is on it cutting off the cold for the southern UK at least after midweek.

[Singularity]

I'm increasingly of the impression that we may - for a change! - see a spell of high pressure next weekend, as the Atlantic trough stalls fully to our west.

A breakaway low may produce some frontal precipitation Thu-Fri in that scenario, which could be snow for a time. GEM 12z shows that as an example.

In that scenario, 850s will probably rise next weekend - perhaps even quite a bit - but if the flow is light enough, the surface cold may hang on with only a slow thaw of lying snow.

[Tim Bland]

UKMO precip charts below.   Re ensembles we can play this game all night lol..some end cold or are cold at some point but they ALL have a mild spell at some point ...p14 is mild end of next weekend 

Edited February 5, 2021 by Tim Bland

[chris55]

8 minutes ago, snowspotter said:

Hmmm. A certain person who used to post on here has tweeted ‘UKMO 144 is a boom time slider . Don’t let anyone tell you it won’t go under . Which post is correct  

This is a good point to pick up on. Neither post is correct.

It highlights how we need to interpret the charts rather than take them at face value when we get beyond around 96h, and especially in non zonal pattern.

I have said lots of times recently that the Atlantic low incoming Thursday looks like it "should" disrupt and edge south east as its coming up against the dense cold blocking air in situ. Lots of people disagree, and that's not a problem, we are all giving our own individual views on the runs.

Tonights UKMO didn't take that path and edged that Low north east, along with the GFS suite (which tends to be progressive anyway) the "trend" at that point was for the low to push in at an unfavourable angle and eventually usher in milder air.Hence my interpretation of the run.

I said "await ECM with interest" that was to see how that model dealt with it.

Since then we have had GEM with a slower evolution and next we will see what ECM shows.

So basically its not an exact science, take everyones interpretations and make your own judgments, that's a good way en joy the thread and all the conflicting opinions

 

[danthetan]

5 minutes ago, Singularity said:

I'm increasingly of the impression that we may - for a change! - see a spell of high pressure next weekend, as the Atlantic trough stalls fully to our west.

A breakaway low may produce some frontal precipitation Thu-Fri in that scenario, which could be snow for a time. GEM 12z shows that as an example.

In that scenario, 850s will probably rise next weekend - perhaps even quite a bit - but if the flow is light enough, the surface cold may hang on with only a slow thaw of lying snow.

Exactly what I thought, no way in this world that low is going under the block.  But if that weak scandi ridge get's far enough west then that Atlantic low will head back NW and like you say shear off some energy clipping the SW and the UK will remain under high pressure with a slack E flow best case scenario at present.

[icykev]

6 minutes ago, Snowman. said:

GEM was so close, a little more SE under the developing high or even a shortwave and we're laughing!

Like a game of chess, area interest to me is looking at the trough disrupting trying to push south west along the french german border down to croatia. If that can get into north west Italy then the low approaching from the west will go under the heights with amplitude gained due to the trough digging sw or stall in the atlantic with a ridge. I think it could make it a greatly lengthened cold period ❄ Will look into the ensembles to see areas of interest 

[nick sussex]

If someone just showed me the UKMO day 5 and said what happens next I wouldn’t have picked its day 6 .

I would have expected more trough disruption at day 6 . 

 

[Cold Winter Night]

4 minutes ago, Scorcher said:

Thanks for your reply but I was commenting on what the models are showing. What you've said is mostly speculation. Can you explain how the models 'scream major cold spell' and give some examples of these past cold spells?

I think a lot of you are looking at this with ice-covered spectacles. That energy being injected into the Atlantic has to go somewhere- and the smart money is on it cutting off the cold for the southern UK at least after midweek.

Well, I keep my feet on the ground. I prefer the cold winter nights of my screen name, but I won't proclaim cold if that is an impossibility.

That 'energy', the lows into the Atlantic will not push through if the high is strong enough.
Day to day comparisons show Northern heights increasing for the same timeframe, i.e. models underestimated them earlier. So that milder interlude might not be as pronounced.

The best example of a cold spell that developed like this, December 1962. January '47 isn't far off either.

 

[That ECM]

16 minutes ago, feb1991blizzard said:

No, but look at the GEFS now, going to be some stonkers in there at the end of the run.

 

[Derecho]

13 minutes ago, Singularity said:

I'm increasingly of the impression that we may - for a change! - see a spell of high pressure next weekend, as the Atlantic trough stalls fully to our west.

A breakaway low may produce some frontal precipitation Thu-Fri in that scenario, which could be snow for a time. GEM 12z shows that as an example.

In that scenario, 850s will probably rise next weekend - perhaps even quite a bit - but if the flow is light enough, the surface cold may hang on with only a slow thaw of lying snow.

It's certainly still a possibility. Getting the -10C uppers into southern England and northern France too by next wednesday would certainly be a big help. Would allow for incoming low pressure to disrupt more and give a better opportunity for pressure to build. On some of these runs uppers aren't that cold though this can be a little deceiving. With the air coming in off a cold continent, surface cold will still remain as you say.

A return to milder weather for next weekend is the most likely scenario at the moment but still a substantial probability of cold hanging on.

Edited February 5, 2021 by Quicksilver1989