Model output discussion - deep cold inbound?

[sheikhy]

IF the gfs looks anything like icon am gona go sleep a very happy man!!!BUT we know gfs likes to prolong things a bit so wouldnt be surprised if it continues to do its own thing!!

[ICE COLD]

Icon is lovely at 120

[MATTWOLVES 3]

I feel its an improved icon 18z at 120 with the colder uppers much better placed than the 12z run..

Well then folks its im sure you would agree been a stressful day. And perhaps a drink could be called for.

Oh...and RIP Captain Tom Moore.. what an heroe that succumbed to the very illness he was raising so much money for..true legend...God bless.

[Daniel*]

Upgrades from ICON uppers 2°C colder than 12z all because that low is a bit further south and east amazing how much rests on it.

[Radiating Dendrite]

3 minutes ago, Paul_1978 said:

Portrait and landscape view. Sorry to ask for this diversion. 

Try it with night mode off. Your device is not rendering the tablet / desktop view. 

[sheikhy]

3 minutes ago, ICE COLD said:

Icon is lovely at 120

Are we gona get those beast from the east 850 charts out again for the 18z mate?!!

[Man With Beard]

30 minutes ago, snoangel said:

As someone with no training in understanding the weather or models, can any experienced posters help me out here...

... I *think* I’ve noticed in the past that models often correct the position of low pressure south very late in the day (T24/48 hrs) when low bumps into cold air.

My question is, is this real? As I live in the south east I’m wondering if that is simply sub conscious hopecasting rather than model flaws and physics!

Yes this often happens, though I think models are getting better handling it. The general rule of thumb - when lows are traveling alongside high pressure but slightly towards it, models will normally correct away from the high pressure. 

[chionomaniac]

We have seen such pendulum swings from the GFS previously, so wouldn’t rule out a swing back. GfS had been so keen on a strong easterly, and to see it being blocked by a stationary low is disappointing but no surprised to seasoned model watchers.. without cross model support I wouldn’t be surprised to see a nudge back for that pendulum - but probably no more than that. 

[NewEra21]

1 minute ago, Daniel* said:

Upgrades from ICON uppers 2°C colder than 12z all because that low is a bit further south and east amazing how much rests on it.

Exactly, we need to stop of all of this northerners and southerners squabbling. Because at the end of the day, the further south this low is the better. It allows a better overall pattern and colder 850s in for everyone!

[northwestsnow]

Icon leads the way!!

Expecting upgrades on 18z now   

[danm]

Just now, NewEra21 said:

Exactly, we need to stop of all of this northerners and southerners squabbling. Because at the end of the day, the further south this low is the better. It allows a better overall pattern and colder 850s in for everyone!

I don’t think there’s any squabbling, but it is absolutely true that the further south and east the pattern, the better it will be for all. 

[sheikhy]

Heres to ya 18z....

[WorldExplore]

Lovely Icon18z

Anyone else seeing the vortex Squirrel on the left and pingu on the right or is it just me watching too much weather porn last few days

[ICE COLD]

5 minutes ago, sheikhy said:

Are we gona get those beast from the east 850 charts out again for the 18z mate?!!

I will mate if the gfs stops being an idiot

[SqueakheartLW]

After some not so good GFS updates today it is time to go through the 12z models

12z GFS

Time for me to see if the GFS has continued to improve in terms of the average peak of the predicted cold spell. The average peak on this update is at 144 hours away

The 12z GFS still maintains an average easterly and that at least is something we can hold hope for. However it hasn't gone back to the nirvana lows it had up to the 00z yesterday before the downgrades started to happen. The 12z has an 850hpa average peak of -6.8 which is -3.5 below the long term mean and is a slight downgrade of 0.2 from the 06z but still better than the 00z was. The anomaly chart also has less deep blues than it did have. I haven't gone in with my usual top 3's then mild and cold charts and I will explain why at the end

12z GEM

The GEM has been the better model so far today but is the 12z going along the same lines as the 00z did or has it now decided to copy GFS and start backtracking too. Good news is that the GEM seems to be very much on a par with where the GFS was before the backtrack yesterday. The 12z GEM has an average 850hpa temperature at the peak of the cold spell at -9.0 which is -5.3 below the long term mean and is an upgrade of -0.4 compared with the 00z. The peak of the cold spell is at 150 hours away.

The big surprise

How much all cold fans on here would want a true winter fantasy nirvana situation to unfold over the next 384 hours. Well here is something you can feast your eyes on coldies. First I will show you the 12z GFS ensembles chart with a small modification

Notice that thicker orange line joining up all the points of the coldest ensemble members or points where they reach their coldest point. That is my fantasy ensemble member 31 which they should include on the GFS every time in the winter. Now below I have posted charts from those coldest points to create an imaginary fantasy cold run.

Member 7     +6 hours     850hpa temp 0.3

We begin as we know with milder air attempting to push in from the SW and this is bumping into the colder air in the north that is very stubborn and is resulting in persistent snow across Scotland and further pulses of rain are moving up through the rest of the UK into this colder air and reinforcing the snow already over Scotland

Member 21     +30 hours     850hpa temp -2.7

Things are already beginning to cool back down over England and Wales by this stage. The cold air is still in place over Scotland and the snow is still falling here and is really piling up over the high ground especially

Member 24     +60 hours     850hpa temp -2.9

Finally it looks like the low pressure is pulling away southwards and this is allowing the colder air to dig back into the rest of the UK once more. The rain is turning back to snow again from the north as easterly winds begin to set in and start bringing much colder air with them

Member 24     +84 hours     850hpa temp -10.5

What follows after this is a rapid decrease in temperatures as uppers below -10 work their way in but even colder weather is yet to come. Snow showers are now piling in from off the North Sea.

Member 21     +108 hours     850hpa temp -11.4

Even colder air is now in place and snow showers continue in the north. Further south an area of low pressure is attempting to push north and bring milder air with it but the cold air is very stubborn and persistent snow is falling across parts of England and Wales with the fronts associated with the area of low pressure.

Member 24     +120 hours     850hpa temp -12.3

That area of low pressure finally pulls away to the east leaving the UK in the cold air which is even colder now than it was. Snow showers resume their nationwide coverage once more

Member 27     +144 hours     850hpa temp -13.7

We finally reach the peak of the cold spell, at least in terms of the 850hpa temperatures that is. A straight run of easterlies here with frequent snow showers being driven in from off the North Sea. Sub zero temperatures both by day and night at this stage as the cold air is really established now.

Member 14     +216 hours     850hpa temp -11.6

We continue in similar fashion with easterlies but over time the pressure pattern slackens off somewhat so the snow shower risk in western areas decreases and the theme shifts somewhat from snow to frost with increasingly colder nights due to the lighter winds overall. Double digit negative minimums commonplace away from eastern coastal regions.

Member 15     +270 hours     850hpa temp -10.2

We generally continue with this slacker flow for some time with occasional snow showers in the east but the main focus is on the very cold days but especially the nights where some areas are getting below -20C at night.

Member 14     +300 hours     850hpa temp -11.6

High pressure has now finally collapsed over the UK so the snow shower risk is eliminated. However this is where the coldest minimums are set with records in some areas being set. The record of -27 in Braemar is also under threat here due to the established cold and snow cover which has allowed significant cold to build up in favoured frost hollows and other sheltered regions. Also out in the Atlantic there are signs that a pattern change is being attempted with milder air starting to ride up the area of high pressure.

Member 18     +342 hours     850hpa temp -11.4

The attempt by the milder air simply fails here but all this does is causes low pressure to sit both to our west and a new one dives down into Scandinavia to our east. The UK simply just sits under an increasingly weak area of high pressure with a lot of colder air still in the area. This keeps the cold days and very cold nights going.

Member 5     +384 hours     850hpa temp -11.4

Eventually by the end of my fantasy cold run we find that the low pressure to our east continues to dive southwards and pressure builds over Scandinavia once more and this is causing a renew push from the east once more. This keeps us very much in the freezer and as a result the attention turns away from record minimums and back towards the threat of snow showers once again

[Man With Beard]

Looked closely at ECM individual ensembles for an underlying trend at D5 and D6, but I couldn't really separate between runs that bring a clean easterly, runs that scupper the easterly for southern areas through low pressure of the SE coast, and runs that were a bit of both. 

My gut feeling is that the clean easterly has gone for the south - once disturbances are picked up D4/D5, they rarely correct back to the clean version. But the heavy frontal snow option, that's still well on the cards. I see similarities with Feb 2009 here where many got heavy snow but the extreme SE got rain - it was touch and go until T0.

Northerners though, put your feet up, relax, and count up the snow falling/snow laying days. You'll need plenty of ink!

[kold weather]

7 minutes ago, chionomaniac said:

We have seen such pendulum swings from the GFS previously, so wouldn’t rule out a swing back. GfS had been so keen on a strong easterly, and to see it being blocked by a stationary low is disappointing but no surprised to seasoned model watchers.. without cross model support I wouldn’t be surprised to see a nudge back for that pendulum - but probably no more than that. 

I think something has to give on the GFS, it is starting to shift its dealing with the Iberian low a little but its still very different with how its handling all three low pressure areas. Even if one of them becomes more favourable it will show via an upgrade.

I can't imagine all the rest of the models being wrong this close in now regarding at least the broad pattern evolution, which as has been pointed out, is still very different on the GFS vs all other models, which are now near total agreement on the evolution, just not exact location.

[Timmytour]

Low looks a fraction west so far....hope it shifts east...

[feb1991blizzard]

1 minute ago, Man Without Beard said:

Looked closely at ECM individual ensembles for an underlying trend at D5 and D6, but I couldn't really separate between runs that bring a clean easterly, runs that scupper the easterly for southern areas through low pressure of the SE coast, and runs that were a bit of both. 

My gut feeling is that the clean easterly has gone for the south - once disturbances are picked up D4/D5, they rarely correct back to the clean version. But the heavy frontal snow option, that's still well on the cards. I see similarities with Feb 2009 here where many got heavy snow but the extreme SE got rain - it was touch and go until T0.

Northerners though, put your feet up, relax, and count up the snow falling/snow laying days. You'll need plenty of ink!

Would just say though not for all Northerners, Pennines Eastwards - yes, but no huge dumpings for many places West of the Pennines have been modelled on any run yet.

[goosey007]

 

Icon good for me ...imby

[Kentspur]

25 minutes ago, Mike Poole said:

Hi KW, I was thinking more of the longer term evolution than snow at this point!!  You can see the difference at T114, T120 on 12z for comparison:

Our problem low is already on its way and trough disruption on the next one and it will go under.  Good run, wish we could see it further.

Slightly lower heights towards Italy/ pattern a tad further southeast on this run,  

Edited February 2, 2021 by Kentspur

[DogToffee]

41 minutes ago, Timmytour said:

30 hours ago we were drooling over this 12z run from GFS  (for Sunday evening) and what it subsequently delivered

Thereafter things were not so good....starting with a pub run which rudely interrupted the delight being shown over a generally excellent 12z suite.....

Thereafter a further three runs underwhelmed.....

 

The pub run turned it round last night......it needs to turn it round again, but this time in favour of something that has us smiling at its outcome!

This is one of the best sets of charts I've seen in years!

[Kiwi]

 

[Kentspur]

1 minute ago, goosey007 said:

 

Icon good for me ...imby

Intruguing bearing in mind we've an easterly and all the snow ends up in Wales

[chionomaniac]

I wonder who can resist posting til day 4/5 comes up lol.  May stop the confusion often generated on here with these scenarios.