Model output discussion - proper cold spell inbound?

[Ayrshire weather]

Will be fun for us in SW Scotland tomorrow morning... 

[ICE COLD]

17 minutes ago, bluearmy said:

I don’t believe JH was of the opinion that any outcome would verify! And certainly not a mild one !!

i suspect many in here are fed up of the chase and being disappointed- I urge you to get on board this time !!

 

I'm definitely on board BA . Just hope we don't get thrown off like the last 5years . ?

[alexisj9]

1 hour ago, karlos1983 said:

looking through the individual GEFS purbs at +276, an awful lot show an easterly of sorts, hardly any are what I would call mild! and some corkers in there too. I would expect a colder set of ens in graph format to follow. 

Here's the mean for the same time which is a pretty good representation after studying the set. 

 EDIT: Here they are

Fl moving closer, personally I would expect the scatter to move even closer in the next few days.

Edited February 12, 2018 by alexisj9

[Mike Poole]

GEFS 06z seem to show an evolution to a Greenland High via a UK High.  Taken as a set, plots below of probability of pressure >1030 mbar:

Leading to this mean at T+348:

[Jonathan Rhodri Roberts]

12 minutes ago, Ayrshire weather said:

Will be fun for us in SW Scotland tomorrow morning... 

Some very heavy snow showing for Wales on that chart but yet we've only got our usual wind & rain warning from MO for tomorrow morning. Something doesn't sound right 

Edited February 12, 2018 by Jonathan Rhodri Roberts

[Frosty.]

We are on the right track towards higher pressure next week with  overnight frosts, especially further south, it's an important stepping stone and the longer term cold / very cold signal is intact so coldies still have a lot to be optimistic about and eventually excited about once we reach late feb!

Edited February 12, 2018 by Frosty.

[Duane S.]

Another absolutely stunning ens set. This is becoming a very strong signal...

This whole QTR debate. It has become increasingly evident (IMO) that the MJO / projected AAM was skewing things on the output and the SSW wasn't ever really being factored in. Well it was, but I don't believe it was ever actually forecast to propogate down that quickly. A good call by the models by the looks of things. And 2 weeks is still a fairly QTR as well.

That said, a slight sub tropical nudge may be enough to get the MLB to turn into something a little more mouth watering, before the main event. All to play for. Fantastic model wathing days.

 

[Man With Beard]

GEFS and EPS starting to come together with the surface level Scandi High for D12-D14

  

Cold very near on GEFS (EPS a lot more scattered):

   

GEFS then sniffs out a Greenland/Scandi link up - look at those isobars running east to west all the way across the chart!

[Ice Day]

Just viewed the 6z ensemble and I think they are very much deserving of a wow. Scrolling through the various stamps at 228, 252, 300 etc, even the milder options have a mouth watering look about them regarding developing something colder down the line.  Best set for 'potential' (sorry) I've seen this winter.

Two things of note.  Firstly the Op was at the top of the mild end from day 7 onwards, also there are now several sub -10 options being seen out in FI which is an improvement versus previous sets.  I am eagerly awaiting the 12z's as I truly believe there's going to be a marked turnaround in output today / tomorrow.

[Jemma Croton]

I put out a tweet to Ian Ferguson. He’s replied they are looking around the 18th still to see effects. Plus this from MV gives hope 

[BLAST FROM THE PAST]

Jemma, I think Fromey posted Fergie’s response on the previous page,  Encouraging still.  

 

Looks like some are going to be lamp watching tonight.....alas just a serious soaking down here in Swansea.

 

BFTP

[Daniel*]

I’d definitely say over the last 24 hours things have taken a more positive turn. As above 1020mb mean +ve heights over Iceland by 20th this intensifies further to 1030mb in extreme FI. 

Something in modelling suggests something is afoot. Often Iceland low is indicative of a positive NAO indications is that it will probable go negative towards end of this month.

Edited February 12, 2018 by Daniel*

[supernova]

45 minutes ago, Ice Day said:

Just viewed the 6z ensemble and I think they are very much deserving of a wow. Scrolling through the various stamps at 228, 252, 300 etc, even the milder options have a mouth watering look about them regarding developing something colder down the line.  Best set for 'potential' (sorry) I've seen this winter.

Two things of note.  Firstly the Op was at the top of the mild end from day 7 onwards, also there are now several sub -10 options being seen out in FI which is an improvement versus previous sets.  I am eagerly awaiting the 12z's as I truly believe there's going to be a marked turnaround in output today / tomorrow.

Well if not a wow then certainly cause for significant optimism, not least as the mean trends downward and both the op and control are at the mild end of the spectrum - noticeably so for the op with the control spiking milder later in the run. Also suggests FI starts Feb 18th looking at the scatter which fits in well with @fergieweather's earlier Tweet. Additionally, some of the well-informed comment on both the model and strat threads have consistently suggested we should look to see influential downwelling to the trop circa Feb 20 onwards. The days might be getting longer, more strength in the sun, blah blah blah but this SSW remains right on track for a record-breaking event and all previous data tells us it'll take more than ten minutes to see the effect at lower levels. All ensembles/means suggesting we're a week away from knowing whether we need to dust off the sledge or bring out the Pledge for an early spring clean!

Edited February 12, 2018 by supernova

[Man With Beard]

Oh and to answer the question "Why the sudden obsession with the D10-D15 ensemble means??" It's because historically they have been able to pick patterns when the anomaly is high. 

Couple of examples: 11th March 2013 - easterly for the UK picked by the D10 mean

  

Perhaps one of the best was November 2010. Just a small resemblance to the latest GEFS charts for D15.

[Nick F]

Looking at the 00z EPS clusters, although are 6 clusters as early as day 8, 3 clusters comprising over 60% of the ensemble point towards ridging building north from 18-20^th.

EPS clusters: http://brunnur.vedur.is/kort/ec-ens/2018/02/12/00/ec-ens_nat_z500scenarios.html

The more positive shift overnight by EPS to offer more blocking with Ely or NEly solutions developing in the last 8-10 days of the month could be related models perhaps not capturing correctly the likely impacts of the SSW prior to the event, but now the SSW has started happening, the models will start to adjust to showing more blocking in the NAO domain now they get a clearer picture through new/recent satellite data of the downwelling of the wind reversal.

06z GFS op was a warm outlier from the 18^th, so expect to see some colder operational runs popping up.

Given the enormity and duration of the stratospheric warming over the N Atlantic, it seem likely the warming will imprint in the troposphere over the far N Atlantic and areas bordering too, given the existing wave configuration in the NAO domain and that the trop PV will be pushed aside from Greenland.

And for those worried about how late it will be in winter if/when the cold Ely or NEly flow arrives, take a look through March over the years and spot those that were cold and snowy, a good few examples there, even fairly recent, that show you can get ice days and big snow falls that can stick around even in March:

http://www.trevorharley.com/weather_web_pages/british_weather_in_march.htm

[stodge]

Afternoon all

Well, it seems the SSW is now upon us and is likely to be of a considerable scale so that will have impacts. Fair to say a rollercoaster of emotion over the weekend with the Highs and Lows creating some highs and lows of their own.

On the basis we can see a 10-14 day between the SSW and any tropospheric response, it's entirely possible any response is still at the fringes of the model outputs. I'd also like to mention Tamara's excellent post last night offering an explanation of why continued La Nina forcing might yet blunt the QTR (Quick Tropospheric Response). It remains to be seen if the SSW will overwhelm that as some expect and I have to say looking at last night's ECM EPS there were plenty showing northern blocking late into the month.

So to today's outpourings which take us to Thursday February 22nd:

Starting with ECM 00Z at T+240:

ECM has stood four square against a QTR since the end of last week and continues this morning. The Azores HP ridges NE at the end of the week promising a sine and mild weekend but at this point there's little sign of a ridge into Scandinavia. Low heights over southern Europe are encouraging but the Atlantic still seems strong at this time though the PV does look elongated and under pressure. Fine conditions for many from this chart and just the hint of an E'ly for the south and Channel Islands. Strangely it's a chart that reminds me more of July than February.

On then to GEM 00Z at the same time:

A very different evolution though from a similar start. GEM sends the Azores HP across the British Isles and into Scandinavia and then moves back slightly westward so we have twin centres over the Faeroes and southern Norway. The Atlantic is weaker with the northern arm running to the far NE and there's an E'ly across the far south though with the coldest air passing over France. Could it correct further north ? Who knows ? With -8 850s clipping the SE it won't be warm but could be quite pleasant over Scotland and Ireland.

GFS 00Z OP at T+240:

A taste of spring with a S'ly feed over the British Isles  The Azores HP tries to ridge into Scandinavia but topples into Europe instead with the Atlantic held at bay. The HP is oriented north-south over Eastern Europe so the cold air is sent far to the east and most of Western Europe enjoys/endures (delete as preferential) a warmer feed from north Africa. Further into FI and slightly counter-intuitively, the HP heads north into Scandinavia and builds a ridge further west toward Greenland. The airflow switches to a SE with a sharp contrast between colder air approaching from the east and milder air over the British Isles and to the west.

GFS 06Z OP at T+234:

Subtle differences as you might expect. The HP is oriented more NW-SE so a SE'ly flow with a stronger jet profile to the NE. Further into FI, HP is never far away and while the synoptics are confusing, one thing is clear - there's no Atlantic dominance.

GFS 06Z Control at T+240:

Anticyclonic though it's worth noting Scandinavia is more dominated by LP. An E'ly across the south but is retrogression the name of the game here ? Not quite but the tune is firmly anticyclonic with a SE'ly ruling the roost though, it has to be said, not especially cold.

On then to the GEFS at T+240:

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240

Have to say the ECM evolution looks in a minority as GFS is looking at disrupting the Atlantic and strongly promoting HP but where ? There are any number of options and the placement and orientation of the HP will be crucial in determining whether we get a final blast of winter or a first blast of spring.

To conclude, after a final unsettled spell in the early part of the week, the models are agreed on a push of HP from the Azores at the end of the week but whether that ends up as a blip or something more substantial is far from resolved.

 

[Frosty.]

Looking at the GEFS 6z mean, temps recover somewhat later this week and the current unsettled weather gradually becomes more restricted to northern britain as high pressure builds in from the southwest. During next week it becomes generally settled nationwide under high pressure with widespread night frosts and crisp bright days with maxima struggling in low single digits celsius, the trend thereafter is colder and very blocked with strong height rises to the NW around iceland / greenland and height rises to the NE across scandinavia.

Edited February 12, 2018 by Frosty.

[bluearmy]

noted that the AO tanked earlier again on the 06z gefs. Probably a good idea to see if the 12z repeats the trick. I would also note that the NAO has been far more consistent in being modelled negative, even on the less enthusiastic eps suites. Without a convincing neg AO, this neg NAO should still take nw Europe cold but the neg AO would help to bring very cold uppers into the flow. 

[karlos1983]

De Bilt starting to get some colder members towards the end of the run now!

[bluearmy]

Anyone who knows the gem model and it’s temp bias for w Europe will be interested in this mean chart for T2 day 16

[Daniel*]

8 minutes ago, karlos1983 said:

De Bilt starting to get some colder members towards the end of the run now!

The ECM op was at the top of the spread a rather big mild outlier from 20th. Probably signalling MLB isn’t as influential and further north allowing colder continental air to pull in.

Edited February 12, 2018 by Daniel*

[bluearmy]

4 minutes ago, biggreyface said:

Obviously fergie still lurks in on this forum  because @tiets has been highlighting the 18th of February as a day to watch for over a week now .

Ignoring the satirical nature of the post (which I liked btw), dave has highlighted 20th as the point beyond which he felt it could turn wintry. He won’t be far away. I think fergie is highlighting the 18th as the point where the trop could well begin to show HLB beginning to show its hand. 

[karlos1983]

Looking at the ENS, its not surprising that the 18th is highlighted, as the spread after that date increases significantly!

 

[Daniel*]

CFSv2 is following along too week 2 seems to be when the cogs in ‘machine’ all work together.

[ALL ABOARD]

Icon first out of the blocks.

 

Nice steady start compared to its 6z output.   

 

By the 18th we have heights reaching up towards the pole. 

 

 

Edited February 12, 2018 by ALL ABOARD