Model output discussion 25th Jan - The final third of winter beckons..

[January Snowstorm]

11 minutes ago, Frosty. said:

Too many knee jerk reactions this evening, there is just as much support today on various output as there was yesterday plus a better ( colder ) MO update, at least for the east of the uk..let's wait and see what happens in the coming days..I'm seeing positive signs that we will see a cold block developing favourably for the uk during the next few weeks. 

Not so things have clearly been shoved back further into FI. As for the Meto update that was obviously based on last night's model runs.

Having said that the trend is still good but I think where frustration kicks in is we are on borrowed time once we get towards mid month

[SMU]

Evening All -

So So many discussion points this evening- where do we start? 

Ive skim read the MOD thread this evening  & lots of inputs with many differing angles of personal perspective - 

FWIW heres mine... In no particular order -

* Snow & snow cover in late feb / Early March is an odd discussion point cropping up today & in terms of the reason why snow doesnt fall or even doesnt lie or does / doesnt melt - The time whether it be early feb or late feb actually makes some difference-  but its not the important factor, & anyone really putting at ththe forefront of their worries need not be 'to' concerned-

If we consider a starting condition over say Milton keynes on Feb 1 then replicated the same atmospheric conditions on Mar 1 I would hazard a guess that the potential Maximum temperature would differ by 1/1.5c tops- 

So, the maximum temperature change across the month & slightly longer daylight hours would aid a longer period of sublimation  - maybe an hour more- pro rata- maybe another cm of snow V early feb ( if we had it lol )

Ahead of this though is other more crucial factors

* Soil / Ground temps pre snowfall are certainly indicitive of fast snow melt if very mild weather precluded snowfall

* dewpoints are critical when it comes to melt - you could lose a couple of cms in a sunny easterly with dewpoints sub zero or loose inches in mild +5c dewpoints from the SW - ( although mega low dewpoints do increase sublimation again- but we dont really get that !)

* Also weather type has an influence- rain will melt snow faster than sun !

So for the UK ^^ if we do finally even get snow in Winter one of the above usually isnt far behind ( or ahead ) to melt our snow no matter what time of year it is...

 

Onto the models tonight - On what appears a mixed bag however really I dont see to much divergence across the piste...

The strong positives are:

-To see Scandi High continually modelled in the same ( more or less location ) & not drifting south to become a sceuro High

- No SE Scandi shortwave spoiler becoming a limpet on the coast

- Importantly looking through the detail, the medium to long term looks very very blocked with the GFS keeping a continental flow from 168 all the way to day 16 & beyond

So whether we get the cold or deep cold straight away it appears that across the piste it should only be a matter of time behind we see some snow from this 'evolution'

The 'opportunities'

* I think we have gained real clarity tonight that cycle 1 as suspected would just be to much for the UK to hope to get into continental air - the western edge looks like it will land close to holland before holding in situ as cycle 2 works through the UK, I guess this isnt a negative so much as 'it was a bonus if it happened' so our real prospect of cold from the east / South East I would say increases post day 6 - With wednesday earmarked as the 'start' of cycle 2 ....

The UKMO / GFS blend here sees a very deep upper air cold pool in central europe by then, the uppers at the top end of the core -16, bottom end -24 depending on the original flow allignment out of the pole- 

Cycle 2 will throw the atlantic at us, we must expect this, we 'should' expect to the azores high throw a ridge NNE as thats the process- the key being what energy goes underneath as opposed to lifting out -

ECM is the most eastward solution @144 , this is because the upper air cold pool was poorly alligned at 120 to repel the atlantic push

-

Where as the UKMO was much better with the allignment allowing for cycle 2 to be almost a battleground-

ECM by 168 the atlantic is lifting out & energy is nicely split so the ECM then never allows the atlantic back in-

UKMO 168 is very similar by starting to pull back the Easterly flow as the atlantic 'lifts' out-

The GFS sits in the middle - a bit like the shortwave does over the UK !

I think FWIW the ECM is to progressive tonight - very much the same as it was x2 days ago before backtracking ...

UKMO looks spot on, although I think the upper air cold pool is to deep & the CAA we see over the continent at 120 is a bit fast & isobars to close- but overall UKMO looks again to be my run of the day in terms of a forecast-

In a nutshell, Cycle 1 throws the cold deep westwards into europe but doesnt make it, Cycle 2 spanning another 24-36 hours will really drive 'some' cold west but how much is the key & what allignment will the winds be...

An enjoyable period of model watching, probably the best since 2013 !!- 

S

 

 

 

 

 

 

Edited February 1, 2017 by Steve Murr

[Man With Beard]

Guys, when you consider that 48 hours ago the ECM was showing this:

And now it's showing this

don't you think it's a bit premature to write off the easterly?

People talking about upgrades/downgrades are missing the point. There's no point considering the models as gospel beyond D5 when there's a block like that to the east. It's all about the set-up - is it one that COULD allow an easterly in the D6-D14 timeframe? And the answer tonight is the same as this morning, and all of yesterday - YES!!! 

Model variation is absolutely normal on this set-up. Are there heights on the northern tip of Scandi? Has the Atlantic stalled and is it splitting against the block in any position to the west of the North Sea? If "yes", then it's a good run for cold. And then, wait to see if the easterly reaches us at D5/D6. It still may never happen, but it's hopeless to make a detailed prediction before then with an easterly. I still haven't given up hope on wave 1 yet, let alone wave 2!!!

[Purga]

Just a bit of advice to watch taking chart outputs so literally and focus more on the bigger picture. Notably we have negative tilt lows, a southern jet stream and height rises over Scandanavia.whch have developed from the Siberian / Arctic High pressure which is NORTH of the jetstream rather than having evolved as a displaced Azores High having drifted somewhat NE and would be SOUTH of the jetstream. The latter scenario is what we have experienced in the recent coldish spell. The former is much, much better for proper cold evolution.

Best to focus on the 500hpa heights at this range, and do not take 850hpa temperatures or SLP forecasts too seriously. 500hpa heights are a much better tool for the 'bigger picture' and actually have higher verification stats at longer range.

Plenty of fun and interesting model watching folks and a huge upgrade on what we thought only last week when we were dreading the Atlantic onslaught seemingly setting in for weeks to come - enjoy whatever the outcome.

Edited February 1, 2017 by Purga

[Ali1977]

De Bilt ENS on the 06z run and now the latest 18z. Similar amount go cold as this morning, but the Op now in the middle 

I'd actually say tonights ENS are better as less mild runs and a more distinct drop off in temps and less spread - for de Bilt anyway.

Edited February 1, 2017 by Ali1977

[Man With Beard]

Must add this one to the discussion. Thoughts @knocker @johnholmes?

[That ECM]

10 minutes ago, Man With Beard said:

Must add this one to the discussion. Thoughts @knocker @johnholmes?

Very blocked. 

Still looking interesting from mid month, looking forward to seeing this unfold.

[bluearmy]

We are close to something special but something is just missing for me - just not convinced that the Atlantic trough will get close enough to the continental cold to force an undercut of cold into the precipitation and that leaves us in either a slack continental cold feed or cold rain (possibilities for higher ground Midlands north) 

[feb1991blizzard]

4 minutes ago, bluearmy said:

We are close to something special but something is just missing for me - just not convinced that the Atlantic trough will get close enough to the continental cold to force an undercut of cold into the precipitation and that leaves us in either a slack continental cold feed or cold rain (possibilities for higher ground Midlands north) 

I take it you mean in the first part of Feb?, you have to think there will be more opportunities down the line, that high doesn't look like its going anywhere fast, even with some of the most Atlantic influenced GEFS members, the high is within reach.

Edited February 1, 2017 by feb1991blizzard

[blizzard81]

3 minutes ago, bluearmy said:

We are close to something special but something is just missing for me - just not convinced that the Atlantic trough will get close enough to the continental cold to force an undercut of cold into the precipitation and that leaves us in either a slack continental cold feed or cold rain (possibilities for higher ground Midlands north) 

This is what I am seeing and neither of those options would be welcome after the virtually snowless winter thus far. I have been quite pessimistic so far this evening. However, I do not rule out the possibility of quite major upgrades on tomorrow morning's runs. I would only put this at around a 20% chance though.

[Stuie]

Quick read this before it get`s deleted, Steve Murr, shoots from the hip and tells it how it is in layman`s terms. Great post Steve.

[The Weather Dragon]

The models are struggling to pin down the track of fridays low - also possibilities of a potential storm for Sunday. 

[bluearmy]

14 minutes ago, feb1991blizzard said:

I take it you mean in the first part of Feb?, you have to think there will be more opportunities down the line, that high doesn't look like its going anywhere fast, even with some of the most Atlantic influenced GEFS members, the high is within reach.

Yes - next 10/12 days, beyond that, no decent indication of how things will pan out. 

[EML Network]

Well it didn't take long for another interesting week of model watching to appear,  at least this winter has given us massive amounts of eye candy...shame that so far none of them have really produced anything noteworthy in terms of snow. 

What concerns me from a cold lovers perspective, is that even if we do get this Easterly or ESE feed coming in, there is a distinct lack of cold uppers associated with it/ 

Case in point...

GFS Control @ 300 looks like this on the 12z run

On the face of it, that looks like some serious cold, but look at the uppers for the same time frame..

A thin slither of -8 uppers just about reaching the UK

 

There are numerous other runs on the 12z that show something similar....

That run looks to be loaded with cold...but again the uppers for the same timeframe..

 

If we really do get charts that look anything like this in 2 weeks time and we get uppers not dipping below -5 then we might as well give up hope of ever getting a decent snowy spell of weather

There's loads of other runs that look very similar...great looking charts but no real cold uppers.

Story of this winter is that we've had some fantastic HLB BUT ALWAYS SEEM TO BE ON THE WRONG SIDE OF THINGS.

 

I think that for once we are going to see some great looking charts, but alas IMO that the associated uppers will be far too mild and we'll all be sitting scratching our heads wondering what the hell went wrong.

 

 

[Ali1977]

Easterly quadrant flow favoured by day 10 - but not a done deal by any means. 

Edited February 1, 2017 by Ali1977

[Captain Shortwave]

I think todays output is a case of good new and bad news.

The bad is that the quick route to cold won't happen (within the next 7 days). We needed the perfect set up to allow this to happen anyway so as others have said this was a bonus anyway.

So the good news.

ECM ens

      

The block is a real beast and will prevent westerlies getting any further than the west of the UK at best with approaching systems likely to disrupt against this block. Also the Canadian lobe does appear to recede somewhat backing west meaning the low heights are less pronounced over Greenland.

GEFs

      

Good support from the GEFs as well. So can we get a proper cold easterly going or will we be on the boundary of milder/unsettled south to south westerlies and cold/dry south easterlies. 

GEFs later on lose the signal somewhat with various options on the table.

 

[Nouska]

1 hour ago, Ali1977 said:

Easterly quadrant flow favoured by day 10 - but not a done deal by any means. 

The wind direction from SW Holland (closer to SE UK than De bilt) sector tells that story. Rapid swings as the storms rush through, hit the block, then the flatlining in an easterly. Too much scatter for complete confidence but I don't see any other definitive cluster apart from the easterly one.

 

Edited February 1, 2017 by Nouska

[nick sussex]

I think theres a danger of assuming the ECM op is correct and that its evolution will verify. Theres still no agreement even with the block in its early stages at T96hrs so whether any of the big 3 currently have the correct solution is open to debate.

Aswell as this its not a case of just a narrow window of opportunity so as much as I'm known for the odd tantrum in here I've decided not to subject other members to this for the timebeing.

We do have the MJO on side and recent strat warmings so at least have cause for some optimism.

 

[Wilxy]

At just 84 hours!

[Dennis]

setup for some big ....Febr winter is possible

[MattTarrant]

1 minute ago, tomjwlx said:

At just 84 hours!

I know a remarkable difference in what is considered a reliable timeframe, this will probably lead to less undercutting of the 'block' which would likely not help advection of cold air west once the Scandi high has developed sufficiently. 

[I remember Atlantic 252]

Yes, hopefully 18Z has right idea, leaning towards ECM for Sunday, washout low gone? but is it correct, it could be back

Edited February 1, 2017 by I remember Atlantic 252

[Weathizard]

Looks like the pattern is even further east at t120 unfortunately...

[blizzard81]

Oh dear! The scandi high gets a battering on this run. Bad trends so early in the run.

Edited February 1, 2017 by blizzard81

[ACCOUNT DELETED]

Sunday's low much shallower on GFS 18z 

Plenty of cape with slightly negative lifted values around the south & west and over much of Ireland though by the afternoon so heavy, thundery showers might get blown inland on the breeze especially near the coasts where cape remains the highest from Saturday evening onwards.