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

[Daniel*]

Fanatastic I knew it was in all probability outside of spread the ECM op. Majority have blocking further north with the cold pool not slipping south as ECM later frames had it. 

[karlos1983]

2 minutes ago, Catacol said:

It is a definite shift to the south.

But only one run. With luck a bit further north tomorrow...

This has its benefits for the more southern areas of the uk! More margin for error! 

[Met4Cast]

ECM mean vs GFS mean at 96hrs

ECM

GFS

GFS perhaps very slightly better but otherwise there's not a great deal on it, ECM OP looks like it was off on one.

Edited February 18, 2018 by Daniel Smith

[BlueHedgehog074]

My bad, just realised accidentally included the 00Z NAVGEM charts in my previous post, rather than the 12Z ones. 

The 12Z NAVGEM actually has the pattern just a little bit further East compared with the 00Z run, with the colder 850 hPa temperatures making slower progress West next weekend ?

Even though there’s still a chance for a bitter, unstable, Easterly to become stamped out (but probably unlikely), I think I would be worried if I were you, Atlantic! The models seem to agree that the Scandinavian/Arctic High Pressure system will kick ya bum! ?

 

[karlos1983]

JMA at 192

bang tidy 

[The Eagle]

2 minutes ago, DiagonalRedLine said:

My bad, just realised accidentally included the 00Z NAVGEM charts in my previous post, rather than the 12Z ones. 

The 12Z NAVGEM actually has the pattern just a little bit further East compared with the 00Z run, with the colder 850 hPa temperatures making slower progress West next weekend ?

Even though there’s still a chance for a bitter, unstable, Easterly to become stamped out (but probably unlikely), I think I would be worried if I were you, Atlantic! The models seem to agree that the Scandinavian/Arctic High Pressure system will kick ya bum! ?

 

They are from yesterday. 12z is out on Meteociel (and it's good too) 

Edited February 18, 2018 by The Eagle

[mulzy]

Definite shift to the south in the eps but not as marked as the Det shift.  Extended eps similar to this morning - strong retrogression signal with cold UK 850s.

[chris55]

13 minutes ago, carinthian said:

Not sure what models the BBC World service use for their weather for the week a head. Yes cold established in most of Europe by mid week quite widely but from what I made of the graphics still had much of the British Isles in mild air mass for mid week and talk of gradually getting colder in SE by Thursday with a max of 9/c, hardly edge of the seat forecast. May be still some doubt of the extent of the cold advection west not yet shown in some of the main models. Just an observation of what I just watched. 

C

 

 

 

 

EC op for next Saturday, cold 850s still a way off, though cold at the surface. 

Ties in with the more tame TV forecast and tweets etc. The early onset of the proper cold looks to be the less likely option, its into Sunday and next week where the very cold air may avect west. 

And with the solid building blocks in place for a robust Scandinavian high we just need to hope things align favourably

 

[Purga]

31 minutes ago, chris55 said:

GEFS highlight the facts clearly.

Just look at the spread from 23rd!!

I know they can be easy to ignore but they are an important tool in deciphering the probability of the operational run, 

tight clustering = high confidence in outcome

large spread = low confidence in outcome

 

in laymans terms, until we see solid clustering on that cold pool smashing into the UK then nothing is guaranteed, and frankly ensemble data is the true forecast tool, taking operational runs in isolation can lead to a skewed view of probabilities and ultimately a misrepresented view of model performance.

That being said obviously we are still in with a massive chance of proper cold just that the spread on the ensembles highlight the other routes we could end up with.

There is spread of course but there is significant cold clustering around the -10 / -15 range whereas there is not wiith the minority of 'milder' runs

[The Eagle]

1 minute ago, Purga said:

There is spread of course but there is significant cold clustering around the -10 / -15 range whereas there is not wiith the minority of 'milder' runs

Also the average is distorted with the few runs that are 10 - 15c milder...in reality it would be lower when they are discarded.

[Chris101]

Can't find it now but Essex Weathers post from yesterday mentioned that the Meto were seeing some wobbles from the ECM caused by a shortwave around Denmark/Norway sending the cold air more into C.Europe but stated it was still 70% to be UK bound.

He also stated that Sunday was seen to be another wobble day and Mon/Tues would be starting to firm up more.

[nick sussex]

The issue with the ECM isn’t at the start .

It had the more progressive trough to the west for the previous runs.

Its after day 7 with the trough dropping se from Greenland which changes the shape of the block .

This evenings ECM was almost a carbon copy of the morning run upto day 7.

People  need to stop worrying about the earlier timeframe.

Amidst all the attention on the ECM the UKMO isn’t as great as it looks.

You don’t want the main block that far north.

 

[WalsallWeather123]

This run from an American model is the best of all. Would bring country wide snow and temps below freezing for all

[ITSY]

The EPS are clearly very encouraging, with the op a distinct mild outlier. Before the pub run comes along, it’s also worth noting that an op run that comes top or bottom of its pack doesn’t make it an outlier - only if it is way out on its own can you use the term. Otherwise it is simply part of the pack, at one end or anothrer. Anyway, the clusters make for positive reading in whatever terms you want! 

[SMU]

having reviewed the ECM its quite progressive with that shortwave SE of Iceland - which I think I highlighted earlier on the IKON run-

That said the operational ECM has been volatile lately - the run in to this evolution is a typical example before correcting back to the more amplified pattern

plus the GFS / ECM mean looks a lot more healthy- even the ECM op is progressive on the retrograde so what you see at day 10 ECM is more likely to be the day 12 or 13 solution...

best

s

[Eastnorthwest]

Just now, DiagonalRedLine said:

My bad, just realised accidentally included the 00Z NAVGEM charts in my previous post, rather than the 12Z ones. 

The 12Z NAVGEM actually has the pattern just a little bit further East compared with the 00Z run, with the colder 850 hPa temperatures making slower progress West next weekend ?

Even though there’s still a chance for a bitter, unstable, Easterly to become stamped out (but probably unlikely), I think I would be worried if I were you, Atlantic! The models seem to agree that the Scandinavian/Arctic High Pressure system will kick ya bum! ?

 

Yes indeed ,no atlantic influence after the next 72 hours for minimum 2 weeks 

What do most want ?the perfect b easterly

What will we get beyond a few days time? Many possibly outcomes from the north to the southeast with either severe cold to not so encroaching up from the Mediterranean area as the models keep hinting

Let's hope the former will win out and we all see at least a foot of snow before the month is out

[chris55]

5 minutes ago, Purga said:

There is spread of course but there is significant cold clustering around the -10 / -15 range whereas there is not wiith the minority of 'milder' runs

There is a trend to cold/very cold and yes many members go cold very cold, but I was highlighting how until we see solid tight clustering (as we see up to the 23rd) on the pattern then we can not be truly confident of the outcome.

[Nick F]

Don't panic, the deep cold pool coming west over Europe next weekend on 12z EPS mean is not really much further south than the 00z EPS mean, best to stick to the ensemble means rather than worry about changes (for the worse) on the more volatile operational runs.

 

[Big Snow]

Hi all, just a question for someone more knowlegable than me (that'll be most of you...)

Regarding the colder air potentially slipping south, would that be caused by high pressure building from Greenland over the UK, as a result of a second bout of stratospheric warming, deflecting the colder air away from us?

Might be way off the mark with that but trying to learn as I go!

[Purga]

1 minute ago, chris55 said:

There is a trend to cold/very cold and yes many members go cold very cold, but I was highlighting how until we see solid tight clustering (as we see up to the 23rd) on the pattern then we can not be truly confident of the outcome.

Sure I understand your point, 'back in the day' I can remember, even within 24 / 36hrs of an incoming easterly, experienced forecasters unsure as to whether we would get a cold snowy NEly or a very cold dry Ely! We are looking 7-10 days ahead...

[Kentish Snowman in Yorks]

15 minutes ago, nick sussex said:

The issue with the ECM isn’t at the start .

It had the more progressive trough to the west for the previous runs.

Its after day 7 with the trough dropping se from Greenland which changes the shape of the block .

This evenings ECM was almost a carbon copy of the morning run upto day 7.

People  need to stop worrying about the earlier timeframe.

Amidst all the attention on the ECM the UKMO isn’t as great as it looks.

You don’t want the main block that far north.

 

So the ECM has the block too far South and the UKMO has it too far North?!

I will gladly take the usual middle ground solution then!  

I think there have been some overly pessimistic posts in here this evening following that ECM run.  If uppers circa -10 to -13 for much of Britain is a dreadful run then we must be in a pretty damn good position!

All roads appear to lead to cold it's just how cold and how snowy that remains open to question.

I am very relaxed about where we are presently.  

There is zero chance of the Atlantic getting in at the last minute a la 2012 so lets just enjoy the ride!  

Edited February 18, 2018 by Kentish Snowman

[Man With Beard]

EPS similar to GFS from D8-D10

Edited February 18, 2018 by Man With Beard

[Frosty.]

Tonight's Ecm 12z ensemble mean suggests a nationwide very cold spell is on the way for week 2 with bitterly cold easterly winds originating in russia so basically it's a freeze, I would expect ❄❄❄❄❄❄❄!!

As for the week ahead, starting mild with the uk in a warm front sector tomorrow with some ☔ but then trending colder and more settled as high pressure builds in with ?by day and frost overnight..then things will hopefully take a turn for the severe!!

[bluearmy]

Comparing the day 10 jet forecast for the cold pool from 00z and 12z 

 

 

Southeast by 150 miles ? 

No doubt that the slp means are also shunted south a bit but that’s nothing more than intra run variance. Of course the op being further south means we must be watching in the morning for further indications on this.  

The eps spreads and clusters seem to show a correction back north on the next run is most likely 

in the longer term, the retrogression of the block way to the northwest allowing the realignment of the vortex inducing a cold broad  sceuro trough. Given the time of year, a decent blanket of snow would be very helpful before the retrogression to enable the solar input to be reflected and daytime temps to remain suppressed. 

To those who asked a week ago how the Canadian vortex could survive the  predicted warming......... it clearly wont ! 

[Mike Poole]

11 minutes ago, Big Snow said:

Hi all, just a question for someone more knowlegable than me (that'll be most of you...)

Regarding the colder air potentially slipping south, would that be caused by high pressure building from Greenland over the UK, as a result of a second bout of stratospheric warming, deflecting the colder air away from us?

Might be way off the mark with that but trying to learn as I go!

Hi Big Snow, The high pressure is first building towards the UK and then north as a result of the first SSW, only then does it look like heading to Greenland probably forced by the second warming.

Sooner it gets it's skates on the better, for this upcoming cold spell to really count.