Model output discussion - here comes the beast!

[Weather Wonder]

Just to clarify a couple of things, I have not called a failed easterly I simply stated that IF the watering down and arrival of the deep cold continued it would be a cause for concern.

Maybe I should have worded my post better but by easterly I mean deep cold arriving from the east for a period of more than 36-48hrs.

[Man With Beard]

1 hour ago, weirpig said:

Can anyone tell me when the clusters for the ecm come out please?.  or if they already have  Ta

Here are the clusters from T144 to T240:

        

They pick up brilliantly the move from the Scandi based High to a more Greenland based High.

Looking at how the op fits in with the clusters:

T144 & T168: Bearing in mind that the further north the 546mb line is, the further north the cold pool is into the UK (at these timeframes, not necessarily later!) - 39 ensembles have this line further north than the op, 5 ensembles have this line further south.

T192, T216 & T240: 21 runs close to the op at this point (potential snowstorm from the north), 19 runs see a direct hit from the cold pool (potential snowstorm from the east), 11 runs have us in a battleground situation between the cold pool and air coming up from the south (potential snowstorm from the south)

T264: Only one cluster which I have come to believe means the ECM computer was unable to spot clear enough patterns, so my advice is follow the mean chart. Here's the T300 mean chart - I think you'll see what I mean - no way there will be a great big nothingness over the UK at that time!!

So my interpretation (feel free to disagree!) is D6-D7 = emphasis on deep cold + convective snow, D8-D10 = emphasis on snow risk more widely with varying possibilities for cold, D11-D15 = wait and see

 

Edited February 21, 2018 by Man With Beard

[geordiekev]

34 minutes ago, Captain Shortwave said:

To set something straight here. I would suggest using the -8c isothern as the goal post as this has been a lot nore consistent in when it arrives. The ECM has pretty much suggested that this will arrive some time on Monday for instance.

Worth noting that whilst the coldest air initially mixes out, it more than compensates for this in terms of a widespread snow event.

Totally agree with yours and many comments trying to calm the negativity down. I think people have become obsessed with seeing purples on the T850 pressure charts, when the purples aren't required from a drier easterly direction which has lower dew points, unlike a warmer Atlantic.

Just because the lower temps are shown to reach us a bit later does not mean the cold and snow has been delayed. The purples just mean turn your hive up a bit more. Me I'm happy with the snow, the wind direction and the surprise disturbances that will pop up post Sunday and the longevity like we haven't seen in a long long time.

Let's just enjoy the rollercoaster and worry when the blocking starts to disappear which I can't see any sign of in the next 2 weeks.

Edited February 21, 2018 by geordiekev

[Weathizard]

The GEFS concern me having just looked at the panels, quite a few of them look like this at 144 with the cold pulse going south, heights flattened/squashed south by the Icelandic low pressure

Edited February 21, 2018 by Weathizard

[winterof79]

6 minutes ago, Weathizard said:

The GEFS concern me having just looked at the panels, quite a few of them look like this at 144 with the cold pulse going south, heights flattened/squashed south by the Icelandic low pressure

And the means are fine

[Chris101]

1 hour ago, Chris101 said:

Now i've probably looked at nowhere near as many past cold spells as some of you guys and i do try and remember little trends.

So my question.......Is it not representative of past cold spells to have a theme of cold pulse, trough/disturbance, another pulse of cold, trough/disturbance, pulse of colder air again and so on? 

Obviously as oppose to having a straight easterly going for days on end.

Thanks for the feedback guys, unfortunately any replies must have been lost in the 4 pages of bickering about charts that will look nothing like they do when they get to t0.

On aside note i must be easily pleased, i shall be very happy with -10 uppers heading across the country during Monday.

[frosty ground]

10 minutes ago, Weathizard said:

The GEFS concern me having just looked at the panels, quite a few of them look like this at 144 with the cold pulse going south, heights flattened/squashed south by the Icelandic low pressure

How many look like that?

[johnholmes]

59 minutes ago, Summer Sun said:

Some substantial snow on the 06z and that is without the potential for lake effect snow in the east!

If you or anyone believes that at the time scale shown then you must have fairies at the bottom of your garden. Ludicrous to have belief in that happening. To any newcomers ignore such posts.

[stodge]

Morning all

Another day, another set of shredded nerves it would seem. Will it snow ? Will it snow where I am ? How deep will the snow be ? Why isn't the cold coming sooner ? I want my -20 uppers back, I'm not settling for -15 because that'll b e like a summer's day.

Before the Mods get too perturbed, let's get right down to business with my daily look at the medium range output which today takes us to Saturday March 3rd:

Starting as always with the ECM 00Z at T+240:

The run ends with the British Isles under a light NE'ly flow between HP over Greenland and LP over Poland. -8 uppers have returned to northern and eastern areas with -4 uppers further south and west. With a small kink in the isobars over the south east you'd expect wintry showers with more settled conditions to the north and west.

GEM 00Z OP at the same time:

 

An unstable NNW'ly flow across the British Isles at this time. HP over Greenland is countered by a complex trough centred over northern Italy with a secondary centre in the northern North Sea. -12 uppers remain in the south but slightly less cold air is filtering down from the NW in the slack flow. Wintry showers continue to eastern and northern coasts but generally cold and dry elsewhere.

GFS 00Z OP at the same time:

A light ESE'ly flow over the British Isles in the circulation of a complex trough with the main centre over the western Mediterranean and secondary centres to the east over the western Black Sea coast and to the north west over southern Ireland. IN the slack flow, heavy snow showers or longer spells of snow look likely with -12 uppers in the south and east and -8 uppers elsewhere. Further into FI the trough expands into the Atlantic though it remains a complex feature with multiple secondary centres keeping the weather very unsettled with rain or snow but the latter increasingly confined to the north and high ground as milder air moves in from the south west.

GFS 06Z OP at T+234:

Continues the theme of a developing and expanding European trough (MJO Phase 2 anyone ?) with main centres over Romania, the Channel and to the south of Iceland. The British Isles is in -12 uppers so snow for all especially in the south. As is often the case, the GFS is keen and progressive in FI to promote "normal service" so the trough splits and migrates to the Atlantic pulling up much milder air into western Europe albeit very unsettled with gales and rain at times. At the far end of FI, signs of new height rises over Scandinavia.

GFS 06Z Control at T+240:

 

The British Isles remains in a ENE'ly flow between the Greenland HP and a complex LP over Italy. -8 uppers continue over southern Britain with slightly warmer air further north. Further into FI, LP to the SW swings NE than NW to the west of Ireland bringing in rain, wind and much milder air but at the far end of FO heights are rising again over Scandinavia with indications the LP is set to return SE re-introducing colder air.

The GEFS from the 06Z at T+240:

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

Strong agreement on the development of a complex and large European trough - some members have it further north and east than the OP and others have a centre over the British Isles but the net effect is the same - a more unstable flow with the likelihood of snowfall for many.

In summary, there are clear signs of the next significant pattern development into the medium term. As the Scandinavian HP retrogresses to Greenland and sets up to the NW, heights fall over Europe leading to the establishment of a complex European trough with a number of centres. In the residual very cold air left from next week, this is likely to maintain the cold and wintry outlook with the likelihood of more snow for many though amounts and details are far from settled. ECM is perhaps the only model not wholly embracing the European trough at this stage keeping it more toward Scandinavia but heading south and west.

GFS seems determined to shunt the trough further west and pull in a much warmer air source further on and it's possible we may see a transient much milder spell in the second week of March but there are clear signs of heights returning to Scandinavia in far FI on GFS and these are worth keeping an eye on for mid March onwards.

 

[Weathizard]

2 minutes ago, winterof79 said:

And the means are fine

Yes the means look fine on the ecm also, doesn't make its OP run implausable... I'm only concerned by this as we've seen this before with easterlies.. they get squashed and the coldest unstable air floods into France.

 

If you take a look there's 5/6 ensembles at a quick glance that look to go this way or similar 

2 minutes ago, frosty ground said:

How many look like that?

Here have a look yourself, I count 5 at a glance that look similar

https://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=144

 

[Chris.R]

8 minutes ago, geordiekev said:

Totally agree with yours and many comments trying to calm the negativity down. I think people have become obsessed with seeing purples on the T850 pressure charts, when the purples aren't required from a drier easterly direction which has lower dew points, unlike a warmer Atlantic.

Just because the lower temps are shown to reach us a bit later does not mean the cold and snow has been delayed. The purples just mean turn your hive up a bit more. Me I'm happy with the snow, the wind direction and the surprise disturbances that will pop up post Sunday and the longevity like we haven't seen in a long long time.

Let's just enjoy the rollercoaster and worry when the blocking starts to disappear which I can't see any sign of in the next 2 weeks.

 

 Great post. Only last week I got snow with 850s of -1, 925s of -1 and freezing level of 1800 feet simply because the dewpoint was just below freezing. That was only with the slightest bit of surface cold.

[Deep Snow please]

 

28 minutes ago, Optimus Prime said:

People like technical terms, and as a narrative it certainly adds an essence of extremity to things. So whilst a 'polar low' sounds great in this case it is incorrect; can't get polar lows from an easterly.

It formed to the north of the UK though?

[Iceaxecrampon]

32 minutes ago, Optimus Prime said:

People like technical terms, and as a narrative it certainly adds an essence of extremity to things. So whilst a 'polar low' sounds great in this case it is incorrect; can't get polar lows from an easterly.

Looks like its from Scandanavia.

Let's call it a Scandanavian Low.

[bluearmy]

5 minutes ago, Weathizard said:

Yes the means look fine on the ecm also, doesn't make its OP run implausable... I'm only concerned by this as we've seen this before with easterlies.. they get squashed and the coldest unstable air floods into France.

 

If you take a look there's 5/6 ensembles at a quick glance that look to go this way or similar 

Here have a look yourself, I count 5 at a glance that look similar

https://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=144

 

You are right to point this out and it continues the uncertainty of how we go from easterly to greeny ridge. Plenty of conundrums affecting next week. 

[winterof79]

5 minutes ago, Weathizard said:

Yes the means look fine on the ecm also, doesn't make its OP run implausable... I'm only concerned by this as we've seen this before with easterlies.. they get squashed and the coldest unstable air floods into France.

 

If you take a look there's 5/6 ensembles at a quick glance that look to go this way or similar 

Here have a look yourself, I count 5 at a glance that look similar

https://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=144

 

The mean at 180z so the 25% you quote Are the minority and there is too much looking into scenarios that WILL change once the deep cold is here

[chris78]

9 minutes ago, johnholmes said:

If you or anyone believes that at the time scale shown then you must have fairies at the bottom of your garden. Ludicrous to have belief in that happening. To any newcomers ignore such posts.

Brilliant John, Thankyou!   Thats the sort of consistency I was hoping for, and will make the thread a much more useful tool (as it is in summer)

[North Norfolk coast]

41 minutes ago, Nick F said:

00z EC op was at the warm end of the spread after the 28th looking at the London T2m, this is when the flow backs to a less cold NLy. 

Wow loving those ensembles.Looking very cold ..

[Doctor96]

Whilst I agree we should not moan if we get a 850 air at -15c rather than -19 , it does worry me if we get -8 rather -12 . In my experience the -8 gives us wet snow ,sleet at this time of year . We must not see the real cold slip into France , hoping next model runs don’t follow the gfs 0z run . 

Edited February 21, 2018 by Doctor96

[bobbydog]

well... the 06z shows over a week of deep cold weather, with the ENTIRE british isles getting snow at some point. (even camborne...)

many places are shown having CONTINUAL heavy snowfall for several days, add to that, we have professional meteorologists telling us that models often underplay the amounts of precipitation, meaning there could be even more than is shown in these few snapshots from the GFS-

yet for some people this is not good enough??

were you penguins in a former life?

[festivalking]

Just now, Doctor96 said:

Whilst I agree we should not moan of we get a 850 air at -15c rather than -19 , it does worry me if we get -8 rather -12 . In my experience the -8 gives us wet snow ,sleet at this time of year . We must not see the real cold slip into France , hoping next model runs don’t follow the gfs 0z run . 

Mind you on an easterley dry continental flow there will be more leeway compared to a damp cold norwester.

 

[Weather of Mass Disruption]

16 minutes ago, johnholmes said:

If you or anyone believes that at the time scale shown then you must have fairies at the bottom of your garden. Ludicrous to have belief in that happening. To any newcomers ignore such posts.

Surely such a chart would have as much of a chance of verifying as it does of not doing so? 

[Southender]

3 minutes ago, Doctor96 said:

Whilst I agree we should not moan of we get a 850 air at -15c rather than -19 , it does worry me if we get -8 rather -12 . In my experience the -8 gives us wet snow ,sleet at this time of year . We must not see the real cold slip into France , hoping next model runs don’t follow the gfs 0z run . 

Run through this....

http://www.meteociel.fr/modeles/gfs/royaume-uni/point-de-rosee/3h.htm

NOT an issue.

If we were getting a flow from the Atlantic perhaps it would be an issue. But we aren't.

[Doctor96]

Bobbydog 

 know what you mean and those charts suit me as I live exactly where the hit with maximum snow , but I was hoping to make up for the last 20 yrs of poor winters , with a monumental event . Happy if this stays as modelled just worry a trend shows a slip to less than -8 uppers 

[Timmytour]

16 minutes ago, johnholmes said:

If you or anyone believes that at the time scale shown then you must have fairies at the bottom of your garden. Ludicrous to have belief in that happening. To any newcomers ignore such posts.

While 99% of the time those are wise words JH, to be fair it is a comment on what a model is showing (which makes it stand out a bit at the moment!)

And I've never seen such an array of model runs look as close at T96 to what they were showing at T330 in some cases!

While t's not something I would have flagged up for the reasons you have put, I don't pretend this chart has any more chance of  becoming reality than any other FI chart but it does lead me to ask this question from the many of here who are much more knowledgeable than me.....

In these conditions evolving, with "reverse zonality", once the models have got to grip with it, is FI modelling a little easier for them to get right as opposed to all the possibilities that the weather coming from the Atlantic can offer?

[bobbydog]

Just now, Doctor96 said:

Bobbydog 

 know what you mean and those charts suit me as I live exactly where the hit with maximum snow , but I was hoping to make up for the last 20 yrs of poor winters , with a monumental event . Happy if this stays as modelled just worry a trend shows a slip to less than -8 uppers 

i shouldn't worry about the uppers too much, as long as we have very low dewpoints it should be fine.