Model output discussion - Post SSW - Will it turn cold?

[nick sussex]

6 minutes ago, Raythan said:

When you said you were going to pray this morning , you didn’t tell us it was to steal our uppers Mr @nick sussex

I feel like public enemy number one ! 

What you want is just a little delay in the evolution to the omega block , it’s the trough dropping into Scandi which then forces the deeper cold further south .

The thing is for locked in cold the ECM is better than the GFS, no high slippage to the se with heights remaining low there.

 

[The PIT]

Nothing is locked in yet. How many times have I heard phrases similar to that only for things to go tits up. The placement of the high is crucial and it still could end up in the wrong place for us.

[damianslaw]

Models showing variations of the same theme, one of an increasingly colder blocked set up as we move through the final part of the month and into March. 

A classic almost text book evolution to cold, azores heights ridging through the UK, warm air advection through the mid atlantic with heights blocking off any atlantic frontal attacks,enabling heights to build out of NW Russia and head SW, joining hands with the heights over the UK, creating a scandi high and thereafter a long drawn easterly, with signs of retrogression later on, and the end result a Greenland high, a true one as well, thanks to the impact of the secondary warming in the stratosphere infiltrating the PV.

The variations are to do with how the models play around with any shortwave activity getting in on the act over NE Scandi as we see the PV stretch and splinter. ECM suggesting shortwave features cutting off the elongated heights and causing cold air advection to surge more SW into C Europe allowing a quicker route to retrogression of the heights and perhaps more stable less convective easterly, whereas GFS isn't suggesting this and instead keeps the west-east aligned heights, so we end up with a very cold convective easterly over the UK, with heights then retrogressing a little later.

Greenland highs or at least northerly episodes do often surface in early March, think back to 2001, 2004, 2006. The arctic is at its coldest now, and SST values and with the increasing solar energy convection inland is much more likely to occur now than in the depths of winter.

 

[Banbury]

A couple of hundred miles North and no one would moan , 

[ScottishSnowStorm]

1 minute ago, The PIT said:

Nothing is locked in yet. How many times have I heard phrases similar to that only for things to go tits up. The placement of the high is crucial and it still could end up in the wrong place for us.

Even if the easterly is missed initially i can't say hieghts going into greenland is things going tits up especially when you would look at the whole PV coming round the top into siberia and if you look at the 850 charts all the deep cold would be coming round our side of the globe and even the ECM 240 chart shows a good pool of cold uppers moving south that would link up with the cold uppers going to the south of the UK

[Spah1]

 

[london-snow]

34 minutes ago, inghams85 said:

Agreed i believe you'll see the happier posts from out South East contingent it's not great for all the UK

Well we’ve missed out thus far bar a few brief wintry showers on a north westerly flow about time something to smile about,

Great op’s today ALL ROADS LEAD TO COLD ?

[Captain Shortwave]

At this point a large proportion of how things turn out depends pretty much on one area of low pressure and whether this becomes cut off or not and as such determines the depth of the Atlantic trough.

So here are the day 4 charts

ECM/UKMO/GFS

      

GEM/Arpege/ICON

      

The GEM/ECM and ICON all have that low becoming cut off which sees the jet running over the ridge as opposed to the digging south east in the Atlantic sheering the ridge and building the Scandi high further north. Given the models on each side, you could really call evens on how this will pan out.

Very few GEFs members take the ECM route, but that shouldn't really be of any relevance on making a judgement call at this point. I must admit to being slightly disappointed with the ECM tonight, mainly as it really wasn't far from the GEM at day 6/7 which was a bullseye strike for the UK, simply the ECM refused to complete the loop around of the jet around the high to push it north.

Edited February 18, 2018 by Captain Shortwave

[Cheshire Freeze]

The ultimate ECM outcome is decided in the 72-96 hr range (angle of WAA up western limb of developing block and interaction with Arctic HP)...so we shouldn't have long to wait to see if it is barking up the wrong tree!

[The PIT]

2 minutes ago, ScottishSnowStorm said:

Even if the easterly is missed initially i can't say hieghts going into greenland is things going tits up especially when you would look at the whole PV coming round the top into siberia and if you look at the 850 charts all the deep cold would be coming round our side of the globe and even the ECM 240 chart shows a good pool of cold uppers moving south that would link up with the cold uppers going to the south of the UK

We will know if the easterly is going tits up in the next few runs. No guarantee the high will end up favorably even now. It's case of wait and see and the next few runs are now very important.

[Team Jo]

I think some folks need to just step back from the frame by frame run by run panic. To a newcomer <waves at the 400+ folks reading> some of the comments in the last 30 minutes would make anyone think the whole thing is a bust. Think i'm being dramatic? take a look at some of the posts.

There does, and I mentioned it before, seem to be a fine line between those who relish in the 'poor chart' and like to give a 'dose of realism' - and only seem to post in these circumstances. It seems a bit sad that you'd only want to come on here just to enjoy other people's anxiety and disappointment.

It's one run. There's a lot of hours between now and next weekend. I have no doubt it'll swing to and fro a few more times before we get this cold in.

Play nice! 

 

 

 

[Daniel*]

Not to worry folks the Chinese model has got this in the bag.. 

nervously awaiting ECM ens mean imo it’s likely to not be with less support. However, Sod’s law.

 

[Rayth]

Think some balance is needed!  Iv only recently in the past couple of years took up this rollercoaster as a hobby and I have the thirst for knowledge ,and Iv never seen charts like this before ,

any cold fan would love to be in this position ,with a good hand at this table ,

if it doesn’t work out , cruel maybe , but then you get to learn why it didn’t work out ,

and if you get what you want , lucky us being around for something potentially historical ! 

Point being , we are messing with Mother Nature , she will give us what ‘she’ wants 

[Derecho]

Looking at the ECM it's a very subtle difference that causes the differences in the evolution later on. Westward movement of the cold pool into Europe is guaranteed now but minor changes show the butterfly effect on this run in classic fashion.

At T72 hours we can see the Scandi high and Russian highs are about to merge.

                       ECM                                                     GFS


At T96 we see the key difference.

 ECM
 GFS

This however just affects the timing of the cold spell. In the ECM we are unlucky because of how the high behaves when the cold pool is moving eastwards. A very minor tweak and it could be just the same as the GEM.

Hopefully the signal for a pressure rise isn't the start of a trend. I remember though I think it was on Friday the 00z ECM was way off the mark keeping us mild before reverting.

Still -13C uppers for the south! lol and perhaps more for other areas later when the high moves to Greenland.

Edited February 18, 2018 by Quicksilver1989

[nick sussex]

This is a bit surreal .

An Omega Block is like what we spend all winter hoping for and now unfortunately it’s come around too quickly which cuts off the easterly a bit too soon.

If the ECM is too quick with that evolution then it could work out well for the UK, easterly then northerly .

[Team Jo]

As mentioned in big letters a few pages back, this isn't the Countryfile/BBC/MetO broadcast autopsy thread. I'm sure we've got one somewhere - please use it, otherwise we just end up on a massive derailed tangent,

Thanks!

 

 

[stodge]

Evening all

Well, I'll be in the minority here and say if you want an extended cold spell the 12Z ECM is absolutely superb. If you want a snowy spell, I can appreciate your disappointment.

Let's look at GFS 12Z OP at T+240:

Yes, it's a wonderful snowy chart but the movement is south to north and the coldest of the 850s are going to be mixed out from the south so a short intense snowy spell before a thaw and plenty of rain under the trough and -4 uppers which in early March won't deliver to lower ground.

ECM doesn't "fail" because of what happens early but how the HP is modelled. At T+168 all looks fine:

You might expect or hope the HP would stay where it was or meander slightly west but the orientation and latitude are pretty much perfect to send the coldest air right across the British Isles but instead the HP moves SW through Scandinavia and to the NW of the British Isles:

At T+216 MSLP is 1040MB for most of us which equals dry albeit with -12 uppers across the south so hopefully brilliantly sunny days and cold frosty nights but obviously for snow fans poor. At T+240 the HP retrogresses to Greenland and the 850s are uninspiring:

The key though is the wind-flow is NE so no possibility of a mild breakdown from the south or west - the cold is with us and staying and with further retrogression wouldn't we see a renewed cold incursion from Scandinavia as the trough drops down there ? 

Frustrating of course for many if not most but here's where we may have the next trade off or stand off. On the one side, a short and intense snowy spell especially for the south but with milder conditions returning from the south or a protracted cold and dry spell. I know most on here would like to have their cake and eat it too and that's NOT off the table even with this one OP run.

Let's see how the HP is modelled on the morning output - I mentioned in my previous how a number of the ECM ENS had brought the HP further south into southern Norway and I suspect this OP may be reflecting that. 

At least we are talking about the probability of cold and the possibility of snow which puts us well ahead of where we normally are at this time.

[norfolksnow]

15 minutes ago, The PIT said:

Nothing is locked in yet. How many times have I heard phrases similar to that only for things to go tits up. The placement of the high is crucial and it still could end up in the wrong place for us.

Totally agree with this, the locked in posts re weather are so wrong.

Been here a hundred times and more only to see it all change in 24 hrs

jason 

[pad199207]

3 minutes ago, nick sussex said:

This is a bit surreal .

An Omega Block is like what we spend all winter hoping for and now unfortunately it’s come around too quickly which cuts off the easterly a bit too soon.

If the ECM is too quick with that evolution then it could work out well for the UK, easterly then northerly .

As we in Ireland always say each winter 'Whatever can go wrong will go wrong'.

[Daniel*]

Nothing has been said of ARPEGE it’s a good model. It’s in tune with GFS & UKMO.

 

[Summer Sun]

UKMO extended looks to have the low to our west closer to the UK than the other models?

[bluearmy]

Is the accelerated Greenland blocking a response to the second warming? The second largest eps cluster this morning kept the ridge too close so this shouldn’t be a shock. let’s see what the eps and the morning bring. Remember that yesterday mornings ec op was too far south but corrected next run. It is ultra consistent on timing though. 

[Stuie]

Well, looking at our little island friend model, the JMA, what an evolution this is. If you wanted a Scandi HP, here it is with the main cold on the doorstep.

Lovely.

Edited February 18, 2018 by Stuie W

[bluearmy]

1 minute ago, Summer Sun said:

UKMO extended looks to have the low to our west closer to the UK than the other models?

Which probably means the cold pool isn’t a bit further north than we would ideally want 

[Frostbite1980]

There have not been many op runs that show this evolution so lets just wait and see where the mean sits before people start reaching for the Prozac. To be fair even if there is a major shift in the mean it would seriously put doubt it my mind how reliable anything is model wise is this current period of teleconnections and background signals as they have been so steadfast up to this point.