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

[Dunstable Snow]

1 hour ago, Seasonality said:

Look at @carinthian's post immediately above yours, his sources are sceptical of the ECM output. So yes, agree that only a fool would outright ignore the output, but it seems that some experts are not convinced of it offering the correct solution.

I very much doubt that any of the models has got this 100% right at this range, including the ECM.A blending of the options would provide a very good event for many parts of the country. I wouldn't get too hung up on any one output, either positive or negative at this stage as long as the trends remain broadly the same. As others have alluded too, including some of the most technically gifted on here, this is a very different situation to the norm so I would not be expecting normal outcomes for the UK from this forthcoming episode of weather.

I have in my post on Saturday morning nailed my flag to the mast in terms of what I think will be a likely outcome. Not a lot has changed in terms of my thinking. I therefore rather boldy in a senior managers meeting this morning warned my colleagues of the potential weather event and the disruption that it could have to our business. I gave the likelihood of severe disruption at around 40% ( we are based in the Chilterns) and recommended that we keep a very close eye on the situation and make sure we are prepared in terms of our staffing and customer communications, implementation of bad weather policy, plenty of grit etc. I hope the met office get it out there to businesses as soon as it is practical to do so. Not every business has a weather geek in their senior management team ! 

 

 

 

[Daniel*]

35 minutes ago, Jimmyh said:

it is interesting to read all of the comments on ECM and how if it shows something different it must be followed. I have to admit I am totally confused by this. Correct me if I am wrong but the ecm has flipped more than any other model going into this scenario starting at the weekend in Ernest. if there was a chance of this being delayed or reduced time scale, I very much doubt the super computers at Exeter would have released this statement, otherwise they would be left with egg on their faces, like the bbq summer as an example despite that being a long range forecast.....

Met largely go by MOGREPS we are none the wiser however @essexweather did post lately we used to have IF reveal snippets it’s superior guidance compared to ECM however it too is incorporated. We have a mean like this at day 6! If you’re from Southern England then it should make you ecstatic unless you’re knocks, severe cold looks odds on for south, snowy conditions more uncertain particularly the northern extent.

[The Eagle]

Anyone have the UKMO @ 168 hrs? 

[legritter]

Good afternoon fellow posters ,off topic but thank you all posters who have sent me messages of sympathy ,very heart warming .On to the Charts today ,Looking very good across all Models ,i am getting very excited ,and today at our local supermarket people are literally having a good stock up , the young girl at the check out asked me if i was buying soup because of the big Russian storm coming ,i did try explaining to her that its a week away and things could change .Fax charts will be very helpfull but remember at this range we can expect downgrades and upgrades from all weather predicting charts ,but my gut feeling is we will be visited by a very cold spell ,and yes snow is on the menu but on whoes plate it falls is still to be decided . AS i have said before ,any New members trying to understand upper air patterns Temperatures etc ,have a look at plane Contrails ,then read  ,The science of Contrails ,very interesting stuff ,small contrails long contrails ,different shape contrails etc etc ,if you log the plane you see you can look up on many sites and it will tell you its height etc ,UK AIRSPACE IS A GOOD SITE ,of course if its cloudy and snowing hard you will probably be glued to the snow radar ,or if its night you will be Curtain twitching ,or Lamp post watching .So very interesting period coming up lets hope we all get in on the action ,it will be interesting if we can get that 510 DAm line or lower ,Let the hunt begin Gang ,cheers STEllas all round .

[The Enigma]

Another tense set of runs coming up,  Arpege and ICON 06z's heading the right way (better ridging/Atlantic profile). 

Remember that regardless of whether or not the 12z's show what we all want (or don't) that this is unlikely to be set in stone this evening. S4lancia's post above is worth taking stock of- run to run variation happens every time. 

I have to say it's been some of the best model watching over the last few weeks,  watching the SSW being forecast and then coming to fruition with a devastating affect on the tropospheric vortex coming - pure synoptic heaven.  Hopefully this beast lands...  It's long overdue. 

[winterof79]

29 minutes ago, bluearmy said:

Looking at the gem ens mean (geps) for next Tuesday (taken from last Monday) and thinking this is a model we should be paying more attention to !!

Yes and as I posted earlier here is the mean for next Wednesday

  Just saying

[Deep Snow please]

We're definitely heading into twitchy toes time with the runs this afternoon, tonight and tomorrow. If we still have no clear pattern by tomorrow night I'd be concerned.

[ZK099]

I know we always say this but due to the high impact this cold spell could have and the fact we're less than a week out, this afternoon's ECM is huge- one of the most important I can think of. If it sings from the GFS hymn sheet, we can be fairly confident of the way this pattern will evolve and if we really will get snowmaggedon! I for one am nervous... 

[K9]

3 minutes ago, Deep Snow please said:

We're definitely heading into twitchy toes time with the runs this afternoon, tonight and tomorrow. If we still have no clear pattern by tomorrow night I'd be concerned.

Mmmmm.....possibly, however, most folks are posting charts that are still 7 to 10 days out ( and ramping them up IMO...not there's anything wrong with that...i love a decent cold chart !! )....i'd give it a few more days before you allow your toes to twitch !!

[shaky]

1 minute ago, ZK099 said:

I know we always say this but due to the high impact this cold spell could have and the fact we're less than a week out, this afternoon's ECM is huge- one of the most important I can think of. If it sings from the GFS hymn sheet, we can be fairly confident of the way this pattern will evolve and if we really will get snowmaggedon! I for one am nervous... 

Firstly we need gfs to stick to its current output lol as that comes out first!!!if it continues with the wintry output on the 12z then i expect ecm to look better this evening!!if not then i expexct madness in this forum and paul is gona have a big job on his hands lol!!

[stodge]

Afternoon all

Late to the discussion party today as I have a life beyond forecast charts, model output and the like.

Last evening, on a rare weekend foray into the thread, I opined we might face a stand-off or trade-off in terms of medium term evolution (I'll leave the agonising over T+72 - T+96 to others) between a short, intense, very cold snowy spell followed by a substantial thaw from the south and a more extended colder but drier period.

The positioning of the controlling Scandinavian HP is vital - too far north and the immediate chances of snow and cold increase but leave us more vulnerable to the Atlantic from the west and south and especially so if we move to a west-based negative NAO. Too far south and while the longevity of cold is likely especially via retrogression to Greenland, there's less chance of snow which is after all what most here want.

So it's a fine balancing act if you want both snow and an extended period of cold making sure we are on the cold side of the east-west trough.

Some extraordinary output over the weekend, any single example of which would have reduced the forum to meltdown in the past four years. As it is, if the uppers are less than -12 it's a downgrade. Incredible.

So where are we going into March with the charts of the first day of spring (allegedly) - starting with ECM 00Z at T+240:

The HP has retrogressed but maintains a strong SE'ly ridge right down to the Bay of Biscay. A light NE'ly flow covers the British Isles with a small disturbance over Holland. 850s of -4 to -8 suggest some wintry precipitation to high ground but the far north west dry and fine. There is colder air to the NE again but the extent to which this can push SW remains to be seen.

GEM 00Z OP at the same time:

An intense HP over SE Greenland controls the weather with a ridge ESE across the Faeroes to Scandinavia. LP is over Iberia and in between the British Isles is in a strong E or ENE'ly flow. 850s are -12 over southern England with -16 uppers over Northern France. Any precipitation would be of snow with drifting in the strong winds and a pronounced wind-chill. Much drier over northern Scotland and Ulster though with severe overnight frosts.

GFS 00Z OP at T+240:

A large anticyclone over Greenland ridges SE toward the British Isles. Between that and LP over the Adriatic and Scandinavia a NNE'ly flow covers the British Isles. 850s generally between -4 and -8 as the coldest air departs south. Some wintry showers to southern and eastern coasts but drier further north and west. The cold weather is on its way out as a ridge pushes up from the south and very soon "normal service" is resumed with a westerly flow and much milder air.

GFS 06Z OP at T+234:

LP is over the Channel and an ESE'ly flow covers the British isles. Cold air remains to the north and west but much milder air is in to the SE but, I suspect, with plenty of rain and showers with snow further north as a transitional frontal band moves north and north-west. Further into FI a broadly Easterly flow remains in place with signs of as renewed pressure rise over Scandinavia at the very end of FI.

GFS 06Z Control at T+240:

Signs of a west-based negative NAO and a small LP has spun up from the SW and while currently over the SE of England is going to swing up the east coast with much milder air on its eastern flank while very cold air (850s of -8 to -12) remains to the west over the bulk of England and Wales. Further into FI and it turns milder for all briefly before the winds swing back NE'ly and a new plunge of very cold air looms.

Looking at the T+240 GEFS:

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

Some seem to want to bring milder Atlantic air from the SW via the west-based negative NAO, others go for an attack from the south but a lot of members are still very cold at this time. Going further into FI and I note a growing tendency for the GEFS to indicate a flow from the N or NE returning some very cold air across the British Isles.

In summary, another day of extraordinary chart output but little is resolved. GFS seems keen to promote a breakdown at the T+240 stage but they may just be playing the progressive card and indeed signs even within the GEFS suite any milder spell could be quite short-lived. No such issues with ECM and GEM which keep Britain firmly in the cold - both promote retrogression but fans of snow will prefer GEM which has more possibilities than ECM which keeps the stronger anticyclonic influence.

[ZK099]

Just now, K9 said:

Mmmmm.....possibly, however, most folks are posting charts that are still 7 to 10 days out ( and ramping them up IMO...not there's anything wrong with that...i love a decent cold chart !! )....i'd give it a few more days before you allow your toes to twitch !!

Well I think everyone is pretty confident on the synoptic pattern that is about to evolve. The only question is where the high will sit. If the ECM corrects northwards on the next two/three runs I think we can get excited

[bluearmy]

21 minutes ago, winterof79 said:

Yes and as I posted earlier here is the mean for next Wednesday

  Just saying

They’re controls ??

from memory the mean is like ec mean 

[K9]

1 minute ago, ZK099 said:

Well I think everyone is pretty confident on the synoptic pattern that is about to evolve. The only question is where the high will sit. If the ECM corrects northwards on the next two/three runs I think we can get excited

Fair point...i just like to get to around +96 before i allow a smile to break out...seen far too many 'garden paths' since the olden days of the 'BBC Forum' where it all crashed and burned ( even at +48 TBH !! ) at the last minute....great model outputs though courtesy of the SSW...eyes down for a full house over the next few days !!

[winterof79]

1 minute ago, bluearmy said:

They’re controls ??

from memory the mean is like ec mean 

Forgive me you are correct GEM slightly better.

[Summer Sun]

1 hour ago, The Eagle said:

Anyone have the UKMO @ 168 hrs? 

I posted it this morning here it is for anyone who's missed it and a comparison with ECM

 

Edited February 19, 2018 by Summer Sun

[winterof79]

9 minutes ago, Summer Sun said:

I posted it this morning here it is for anyone who's missed it and a comparison with ECM

 

Does anyone know what the FV3 models output on there is about. I thought they were experimental models to replace FIM AND NOGAPS but not at all sure?

https://ruc.noaa.gov/hfip/tcgen/

They do show similarities to GFS and GEM but I think they may be linked to GFS 

Edited February 19, 2018 by winterof79

[winterof79]

10 minutes ago, Summer Sun said:

I posted it this morning here it is for anyone who's missed it and a comparison with ECM

 

I think you have posted FV3 NCP instead of ECM ?

It pains me to say that the ECM is closer

[pages]

Icon rolling 

at 42hr looks like that shortwave off the NE  Norwegian coast is taking more energy with it and by 6ohr heading more SE than SEE in last run. think the block will end up further West than last run. earlier easterly coming up

Edited February 19, 2018 by pages

[bluearmy]

1 minute ago, pages said:

Icon rolling 

at 42hr looks like that shortwave off the NE  Norwegian coast is taking more energy with it and by 6ohr heading more SE than SEE in last run. think the block will end up further West than last run. earlier easterly coming up

brave call at T42 !

[Weathizard]

Early days but the ICON is much better at day 4, better alignment and angle. Looks a lot more like the GFS from this morning than the earlier ICON.

[Decemberof2010]

I'm eagerly awaiting the GFS 12z and hoping for another nice run. Also nervous about the 12z ECM. So much in fact that because my sofa is pretty small I've gone in the garden shed

[SMU]

3 hours ago, Danielvn said:

 

yep IKON nearly 85-90% back to the GFS now

[winterof79]

Just a quick observation  as  the MET update mentions an area of snow moving N/E next week presumably from the s/w and the earlier GFS shows a disturbance moving up from the south. This could change on the link as the 12z rolls out.

"There is also the risk of more significant snow pushing northeastwards across southern and some central areas." 

No sign on ECM which makes me side with GFS more so.

 

Edited February 19, 2018 by winterof79

[Catacol]

47 minutes ago, Deep Snow please said:

We're definitely heading into twitchy toes time with the runs this afternoon, tonight and tomorrow. If we still have no clear pattern by tomorrow night I'd be concerned.

Actually I think the pattern is set. No doubt about that. We are going to be in an easterly air flow, and its going to get damned cold. The twitchy bit now.... and it is going to be a very twitchy few days, is resolving the microscale detail. In the end I don't think we have a useful template to follow in this regard: with a standard westerly flow we know from experience that ECM can be overly amplified... that GFS has a tendency to overmodel low pressure intensity... etc.

But for an easterly flow in the context of a major SSW? I don't think a roadmap exists. The fact that GEM is doing rather well at present since the SSW began is probably a fair sign that all models are going to be equally challenged by what is transpiring.

Which isn't really any help at all. Experience may not count for very much... and if we are honest any "gut" instinct will simply be based on hope.

So - truly twitchy times ahead. We could end up cold and buried.... or just cold. And to me this will be the hardest period of the whole event: I felt pretty confident 10 days or more ago as to the direction of travel. But now that the finishing tape is in sight I'm suddenly nervous.

Friday/Saturday cant come quick enough - by then the start of the main event will/should be within 72 hours and we can be better prepared for what is to come.