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

[nick sussex]

7 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!

Spot on.

The reason the high builds into Greenland is helped by that second warming which in turn helps to form the Omega block.

In that scenario a trough drops south into Scandi , what’s happened on tonight’s ECM run is an acceleration of the Omega block signal .

The GFS op doesn’t really have that signal yet, the best outcome is an eventual Omega block because that’s more likely to extend the cold and give further chances for more deep cold to drop sw from Scandi but a nice 36 hour delay to give the deep cold time to get into the UK.

 

[BlueHedgehog074]

34 minutes ago, The Eagle said:

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

Not again. Posting charts while I’m feeling tired from work maybe isn’t the best idea ? 

Then again, just noticed on Wetterzentrale that today’s 12Z NAVGEM charts seem to run from 0 hours to 132 hours, while the 12Z ones from yesterday run from 144 hours onwards. Which seems pretty confusing and what probably threw me off! 

(Don’t worry, I’m not trying to attention seek or anything, even though I made the same mistake twice with posting wrong/out-of-date charts, lol)

Edit: It’s good that tonight’s NAVGEM is an improvement though with the blocking high towards the end of the run extending itself further West through North-Eastern/Northern UK, so would agree that it seems good tonight

Edited February 18, 2018 by DiagonalRedLine

[ANYWEATHER]

Evening All , Easterly winds 98% probable ,only a 20% chance of deep cold for the uk.....Please don't take too much notice of projected bitter easterly winds at this time of year, from computer models . IE 1947 , saw a rare Easterly and how many times have we had a repeat of that??? It will happen again ,but when??? Anyway ,both ecm and gfs differ greatly at the ten day range which can be expected but Caution needed ;;;;;;;

 

 

Edited February 18, 2018 by Team Jo
Keeping relevant images

[Banbury]

40 minutes ago, The Eagle said:

Don't think so.

GEM

GFS

ICON

UKMO

 

Crucial time period for the evolution here. The differences are fairly significant.

I do

you move the hours on they get to a very similar evolution even ECM does ....trot them onto 144 . Block and cold pool to the NE very very similar , your looking far too early in the run for problems 

[nick sussex]

The De Bilt ECM extended ensembles are an upgrade in terms of longevity for cold.

The snow spikes also increasing. Looks like more deeper cold heads sw later.

 

Edited February 18, 2018 by nick sussex

[The Eagle]

4 minutes ago, Banbury said:

I do

you move the hours on they get to a very similar evolution even ECM does ....trot them onto 144 . Block and cold pool to the NE very very similar , your looking far too early in the run for problems 

The "problem", if there is one, is between 72 and 96 hrs. Feel free to disagree. 

Differing opinions are welcome to me.

[bluearmy]

9 minutes ago, ANYWEATHER said:

Evening All , Easterly winds 98% probable ,only a 20% chance of deep cold for the uk.....

What do you construe as deep cold ? 

[johnholmes]

14 minutes ago, ANYWEATHER said:

Evening All , Easterly winds 98% probable ,only a 20% chance of deep cold for the uk.....Please don't take too much notice of projected bitter easterly winds at this time of year, from computer models . IE 1947 , saw a rare Easterly and how many times have we had a repeat of that??? It will happen again ,but when??? Anyway ,both ecm and gfs differ greatly at the ten day range which can be expected but Caution needed ;;;;;;;

Hello to the Net Wx comic, I suppose it's not tea you are drinking A

Good to see you on form and markedly misunderstanding the models as usual

take care young fella

oh just to confirm that the flow is going to come from east not west from later this week and into March, below the links to the latest NOAA 500 mb anomaly charts. They have been consistent for several days now with what they show this evening. Just how cold and how much snow not even Anyweather has any real idea. The synoptic models will to and fro about this over then next 4-5 days. So really interesting model watching.

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

Edited February 18, 2018 by johnholmes
posting charts and comment on the outlook

[phil nw.]

Having been away for a while it's good to return to my favourite hobby and see that the much anticipated cold period is getting close now in modeling terms.

By Thursday-day 4 the change to an easterly flow is showing across the 3 main operationals.

All have a similar evolution of an Azores high moving ne across the UK by Tuesday and then towards Scandinavia so by T96hrs when we see this across the models.

so starting to feel colder as that wind picks up but this is just the starter.

I like the follow up period after this on the mean charts this evening.

On those It looks like the following 2/3 days will see the Canadian vortex taking a hit as it recoils back west under further warm air advection.The high then orientates more favourable and we start to see the reverse flow underneath as deeper cold comes west into the UK around day 8

This further pulse of warmth into that Canadian vortex is key as it sees the high establish to the north in the following days and ensures any Atlantic attacks can only go to the south of the UK.

See by day 10- on the means charts again- the end result

BY this time bitter cold across Europe and into the UK on a stiff easterly flow.The Upper cold pool across the se and near continent would surely create snow chances quite widely.

Something along these lines would bring a classic easterly setup rarely seen these days.  

[ScottishSnowStorm]

4 minutes ago, The Eagle said:

The "problem", if there is one, is between 72 and 96 hrs. Feel free to disagree. 

Differing opinions are welcome to me.

To me it looks later as well the problems are in the run the ens seem pretty solid with the mean up till the point the high sets for the easterly and then it goes to the mild side of the ens

I am in fife the scottish central belt 

[SMU]

shall we clarify 

-10 to -12 deep cold

sub -12 severe cold ???? 

there is of course no technical definition!

good correction west on the IKON of the atlantic shortwave interferring less on the block

c

 

Edited February 18, 2018 by Steve Murr

[Hotspur62]

Great to see this thread buzzing.There will be so many variations atm the  next 48hrs will i am sure show some more.Latest ECM doesn't give UK snomageddon in medium term but with retrogression extends cold spell and would very likely give more snow opportunities down the line.Being greedy i would like latest ECM being about 2-300 miles further north giving UK probable snow events.more so in Eastern and Central parts and then the High move West towards greenland hopefully giving us an Omega Block and then some Northerly/North Easterly winds which would give those that may miss out initially on snow time to join in the fun and games.This is a possible outcome as some evolutions show and would't it be great just for once if the UK could hit the Jackpot and have a double 6!!

This thread aint going to be for the faint hearted this week lol!!

[Banbury]

16 minutes ago, The Eagle said:

The "problem", if there is one, is between 72 and 96 hrs. Feel free to disagree. 

Differing opinions are welcome to me.

Cheers and welcomed 

if there is one BUT I haven’t seen the fax chart or isobar chart on the Beeb change so to 120 hours I would say .....’safe’ but who really knows ?

Edited February 18, 2018 by Banbury

[bluearmy]

2 minutes ago, Steve Murr said:

shall we clarify 

-10 to -12 deep cold

sub -12 severe cold ???? 

there is of course no technical definition

 

Well if it’s sub -10c then

eps: 70% T204/T240

gefs: 70% T192/T252

thats a tad larger than 20% ...............

and this is a dry continental source, not cold zonal across the Atlantic. 

[pureasthedriven]

2 minutes ago, bluearmy said:

Well if it’s sub -10c then

eps: 70% T204/T240

gefs: 70% T192/T252

thats a tad larger than 20% ...............

and this is a dry continental source, not cold zonal across the Atlantic. 

With the continental source and thus lower dew points, we’re probably not going to ‘need’ sub tens for snow are we (notwithstanding the chicken and egg of lower 850s helping convection et al)? I’ll take ‘em, because this has been the winter of marginal down here. But what do you think might do ‘the job’? I know - how long’s a piece of string, right...? 

[SMU]

2 minutes ago, pureasthedriven said:

With the continental source and thus lower dew points, we’re probably not going to ‘need’ sub tens for snow are we (notwithstanding the chicken and egg of lower 850s helping convection et al)? I’ll take ‘em, because this has been the winter of marginal down here. But what do you think might do ‘the job’? I know - how long’s a piece of string, right...? 

-12 for ice days. ( maybe -11 ) with no snowcover to start with...

[Deep Snow please]

3 minutes ago, pureasthedriven said:

With the continental source and thus lower dew points, we’re probably not going to ‘need’ sub tens for snow are we (notwithstanding the chicken and egg of lower 850s helping convection et al)? I’ll take ‘em, because this has been the winter of marginal down here. But what do you think might do ‘the job’? I know - how long’s a piece of string, right...? 

Doesn't that depending on what the job is? Up here with the current synoptics I'd be disappointed at less than 6 inches to a foot, I'm sure many down south would be satisfied with 3-4 inches, it's all relative to our standard winter experiences since the last big ones at the start of the decade.

The colder the uppers the better, the convective issue is naturally an important one so I'd say -12 to -20's would be more useful for us, but -8s and -10s would produce snow.

 

[Allseasons-Si]

27 minutes ago, johnholmes said:

Hello to the Net Wx comic, I suppose it's not tea you are drinking A

Good to see you on form and markedly misunderstanding the models as usual

take care young fella

oh just to confirm that the flow is going to come from east not west from later this week and into March, below the links to the latest NOAA 500 mb anomaly charts. They have been consistent for several days now with what they show this evening. Just how cold and how much snow not even Anyweather has any real idea. The synoptic models will to and fro about this over then next 4-5 days. So really interesting model watching.

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

And further more from that,you can clearly see the retrogression west into Greenland on the 8-14 day chart

The ecm and gefs means show this too out to 240 hrs and are quiet similar in that respect

temps and height anomly's

De-built temps,dewpoint and wind direction

if no one is happy with them charts ^,you need to go to.....

 

Edited February 18, 2018 by Allseasons-si

[abruzzi spur]

39 minutes ago, ANYWEATHER said:

Evening All , Easterly winds 98% probable ,only a 20% chance of deep cold for the uk.....Please don't take too much notice of projected bitter easterly winds at this time of year, from computer models . IE 1947 , saw a rare Easterly and how many times have we had a repeat of that??? It will happen again ,but when??? Anyway ,both ecm and gfs differ greatly at the ten day range which can be expected but Caution needed ;;;;;;;

Just curious why you often post the same chocolate teapot picture on the model output thread.  Do you think the models are as useful as one?  In which case why post on the thread at all?

[WalsallWeather123]

CFS at T240. Majority agreement between most models including the lesser known ones.

[weirpig]

Well icon at 120  shows very cold uppers in Europe quite a Little further west compared to its last run 

[Wilxy]

Can someone explain how reliable the ICON model is as reading on here people keep mentioning it but as far as i'm aware I thought most people followed the GFS, ECM, UKMO and GEM?

[Allseasons-Si]

5 minutes ago, weirpig said:

Well icon at 120  shows very cold uppers in Europe quite a Little further west compared to its last run 

Yes was just looking at that as you posted

120 18z v 123 12z

Edited February 18, 2018 by Allseasons-si

[Mike Poole]

18z rolling now - what do we want, I mean a repeat of last night's pub run would be unlikely, I'd suggest, trousers still damp from that one!!

I'd take a run that doesn't follow the GFS 0z, or the ECM 12z model output.  Anything else is fine.

Edited February 18, 2018 by Mike Poole

[Deep Snow please]

1 minute ago, Mike Poole said:

18z rolling now - what do we want, I mean a repeat of last night's pub run would be unlikely, I would suggest.   

I'd take a run that doesn't follow the GFS 0z, or the ECM 12z model output.  Anything else is fine.

We're looking for a continuation of the earlier theme this week of bringing cold uppers into the UK and having some form of snow machine; either low pressure/north sea based.