Model Output Discussion 01/09/17

[damianslaw]

Recurrent theme of the models in recent days, and continuing today is the signal for significant height rises over the Pole and into N Russia, with a rather stretched PV over N Canada. Excellent building blocks for something cold further down the line, but as others have stated, there are always fine margins when it comes to the UK, we can sit neatly on the cold/mild divide, so it remains to be seen how things might evolve, but certainly the models are painting very different synoptics to what we normally expect in mid November i.e. a dominant atlantic westerly pattern, now is the least likely time of year for strong heights to edge out the power of the atlantic, but there is no denying the fact that since mid October, the atlantic has gone into some slumber - mmm might be something to do with all the heat fluxed up from ex-tropical storm activity..

In the short-term, the models are suggesting a more potent northerly shot this weekend - indeed a long fetch northerly, shortlived yes, but come Sunday wintry showers could fall to quite low levels in the north, and it will be cold everywhere in the keen arctic wind. A classic toppler scenario, but pleasing to see all the same given we've a thread commenting on how rare such synoptics have been in recent years outside of the Spring/summer months at least.

Certainly some interesting model output in recent days, not your standard November fayre.

[ICE COLD]

14 minutes ago, snowray said:

Not always extreme solutions, the operational can be just as extreme at times, in fact might get one off those from the coming up 18z after this evenings ECM. The control is simply run at a lower resolution so is less accurate, generally speaking anyway.

Cheers snowray

[winterof79]

This shows the East veering North Easterly nicely

Edited November 8, 2017 by winterof79

[Jonan92]

It seems GFS will show us a Northerly this run

[Allseasons-Si]

I am more interested in the heights building  behind and in front of the trough,it def seems to sink more SE than the 12z,could go the ecm route.

 

Edited November 8, 2017 by Allseasons-si

[Cheshire Freeze]

7 minutes ago, Allseasons-si said:

I am more interested in the heights building  behind and in front of the trough,it def seems to sink more SE than the 12z,could go the ecm route.

 

Get a decently rigid block between Greenland and Scandi and the Atlantic is all but buggered for the foreseeable. 18z wants to try and give it a go

This is one of the most stunning charts you'll see in a UK winter...if it was January it would bring the UK to a standstill

Edited November 8, 2017 by CreweCold

[Man With Beard]

I've really enjoyed following the ECM ensemble clusters this last week as they have been excellent for following the trend. Here's tonight's for D10, D12 and D15

If you've been following the clusters this week, you'll see that the general trend keeps going here - heights building somewhere to our north (Greenland looking favoured tonight I dare say), which should promote a cold pattern for the UK, but that nagging fear that low pressure will not clear the UK resulting in the cold being too far west.

Interestingly the majority of clusters keep that low pressure more influential at D10 - but with the control and op in the same cluster, you'd have to take that a bit more seriously than usual for a third cluster (Though I'm sure Bluearmy said the control run was not similar to the op??).

The control run cluster at T300 looks particularly ripe for something very cold for the UK.

Above all, quite impressive to see the ECM show much consistency in the general pattern over a period of 7 days now.

 

[Jonan92]

Most of the North Pole taken by high pressure

[knocker]

Still going for the explosive cyclogenesis I see. Wouldn't want this to come to fruition

[feb1991blizzard]

2 minutes ago, CreweCold said:

Get a decently rigid block between Greenland and Scandi and the Atlantic is all but buggered for the foreseeable. 18z wants to try and give it a go

That's actually the favoured outcome in my opinion but there is a huge problem with it, just how do we get any decent uppers from there?, it wont require 1 bite at the cherry, it would require several pushes from the NE, this just shows you why 2010 style ends to Nov and beginnings to Dec are extremely rare.

[MattTarrant]

Just now, CreweCold said:

Get a decently rigid block between Greenland and Scandi and the Atlantic is all but buggered for the foreseeable. 18z wants to try and give it a go

As Knocker has recently mentioned frequently in the last day or so, the GFS has constantly been causing cyclogenesis in the later period of its runs. Caution required obviously all round, one positive is the higher resistance to the energy (Low Pressure) upstream which Nick mentioned would be critical to the process the ECM was trying earlier. 

[Allseasons-Si]

We are going to have a big bite at the apple soon not the cherry

[snowray]

Europe going into the Freezer at the end of the 18z, and whats that I can see...Heatwave in central USA moving up into Canada!

Edited November 8, 2017 by snowray

[summer blizzard]

2 minutes ago, feb1991blizzard said:

That's actually the favoured outcome in my opinion but there is a huge problem with it, just how do we get any decent uppers from there?, it wont require 1 bite at the cherry, it would require several pushes from the NE, this just shows you why 2010 style ends to Nov and beginnings to Dec are extremely rare.

At this time of year a strong high pressure should be able to cool its own uppers slowly albeit the floor is above -10 for uppers so although we'll struggle to generate ice days and the level of snow showers we saw in Nov 10 i'd not worry too much.  

[Man With Beard]

Just now, summer blizzard said:

At this time of year a strong high pressure should be able to cool its own uppers slowly albeit the floor is above -10 for uppers so although we'll struggle to generate ice days and the level of snow showers we saw in Nov 10 i'd not worry too much.  

With snow cover on the continent, uppers of even -1C may be enough on an ESE wind. But I'm not sure we'll have that luxury.

[Cheshire Freeze]

3 minutes ago, summer blizzard said:

At this time of year a strong high pressure should be able to cool its own uppers slowly albeit the floor is above -10 for uppers so although we'll struggle to generate ice days and the level of snow showers we saw in Nov 10 i'd not worry too much.  

Yes, in late November that is one thing that goes for us, unlike during the second half of February for example. You're on a timer past mid February, which is why cold early doors can be so much more rewarding.

[summer blizzard]

4 minutes ago, Man With Beard said:

With snow cover on the continent, uppers of even -1C may be enough on an ESE wind. But I'm not sure we'll have that luxury.

Yeah, that low that undercuts is interesting in that regard. Uppers look about -2/-3 so cold rain for the south but in that scenario some people around Birmingham and Sheffield (depending how far north the front got) would be looking with moist lips given the hills. 

The thing that may have been missed today though is that those height rises are now getting close to the reliable and are now seen at day 8..

[booferking]

Some crazy charts the past few days but this states in the freezer & Europe in the freezer.

Edited November 8, 2017 by booferking

[Jonan92]

The control run is similar to the main one

 

Europe in the freezer in this one

[ITSY]

Some of those ensembles are absolutely bonkers. That said, notes of caution:

1. Nothing is close to the reliable 

2. The lurking danger of a Westerly based -NAO is real if you look through the charts, which would no doubt leave many super frustrated 

3. Simultaneously, the prospect of raging easterlies with uppers of only -1 or -2 is equally real - several members show this. 

I think that if/when our first shot comes, it will have to be via a direct northerly flow if we are to get a short and snappy route to cold and snow. For optimism, the number of runs that show 1, 2, 3 or more chances for readjustment, new blocks, and new routes to cold are eyebrow raising at least. Therefore caveat my prior warning about a northerly with the notion that it may not matter....

final point - any run that sends Europe into the freezer should be welcome. It opens up our routes to cold exponentially, esp if northern blocking is on the cards. 

Edited November 8, 2017 by ITSY

[Mucka]

18z ensembles

mean 850's continue to slowly fall in FI run by run.

 

Not even close to hitting the -5 line yet though.

Once (If) we start to see it below that we can start thinking snow.

Edited November 8, 2017 by Mucka

[Snowy L]

If we do get a long-lasting block we probably will be looking at a week of cooling down before snow possibilities. November 2010 didnt happen overnight. The easterly formed on the 20th and most places did not see snow until the 27th. If we get the set up and it manages to last, sufficiently cold air from Russia/North Pole will reach us eventually. Tbf we shouldnt even be discussing this at great length because it is a hypothetical within another hypothetical. Get the block in place first then we can worry about these details.

[Daniel*]

So called ‘reversed zonality’ cold pattern locked in, by the day it will get colder and colder with an increasing chance of snow a long way from a south westerly flow on GFS 18z. A pleasure to view the models of late they’re behaving unusually well presently, no doubt they’ll be a few trip ups but the overall signal is very strong indeed. 

 

[andy_leics22]

I know it's wayyy into F.I but i've seen worse from the models for the end of November!

[Interitus]

2 hours ago, summer blizzard said:

At this time of year a strong high pressure should be able to cool its own uppers slowly albeit the floor is above -10 for uppers so although we'll struggle to generate ice days and the level of snow showers we saw in Nov 10 i'd not worry too much.  

Seems a slightly confused concept - a strong high pressure by definition involves the convergence of air - this increased mass of air is what raises the surface pressure. As the air converges it descends and warms, typically to the 850mb level or below. This is different to the cold surface high such as the Siberian which forms from the pooling of cold dense air forming a deepening inversion which extends above and cools the 850mb level to maybe around 500mb.