Model Output Discussion - Staying cold into the new year

[kold weather]

5 minutes ago, Griff said:

GFSP is taking the very long route to the real cold... 

As per @kold weather

The big fear is we end up basically in a repeat of this week set-up, but less favourable thickness/500mbs temperatures to go along with it (which might be balanced out by cooler SSTs and surface temperatures mind you).

The GFS para looks a little too cold for a low coming down from that angle in my experience, and has often ran a little too cold deeper in its run, a flaw it shares with its OG in its earlier days.

Both the em/Para show a similar evolution as well, so it'd be foolish to not take it seriously as a possibility. It'd also put us in a dangerous position should the NAO become too west based.

 

Edited December 30, 2020 by kold weather

[northwestsnow]

18z is an absolute snowfest later on...

Trendsetter !!

[Stu_London]

Just now, Scott Ingham said:

Yeah they tend to go from absolute model chaos to counting down like clockwork once the models get set on the right path

what is remarkable as well is that a week or so ago, the long ensembles were as tight as I can ever remember them. And to be fair the last fortnight has been modelled pretty well .

[ALL ABOARD]

3 minutes ago, kold weather said:

A west based -ve NAO doesn't have to necessarily be a disaster, alot really depends on just how active the Atlantic is and the start of the southerly running jet.

The patter is very devoid of any major activity so its just a case of hoping that there isn't a poorly timed strong LP out in the atlantic. If its jut a weak wave train we will probably get away with a west based -ve NAO for a time.

I don't see where the jet would get any sort of energy from? 

No raging strat PV 

No raging trop PV 

No strong thermal gradient across America. 

[The Enforcer]

12 minutes ago, radiohead said:

That's a snow chart

Isn't this another easterly sourced from south-eastern Europe? Where are those dew point charts?

[sheikhy]

Gfs mean looks brilliant❄

[SMU]

Split vortex late on

 

Undepinning the potential for blocking 4-5 weeks

[BLAST FROM THE PAST]

18z run is just a monster, and one has to think it’s the upgrade story unfolding.  
Either billion pound models and investment are useless or there’s something really in the air.  
 

BFTP

[Allseasons-Si]

Just now, northwestsnow said:

18z is an absolute snowfest later on...

Trendsetter !!

It's stunning to see isn't it NWS

i mean,...you don't see charts like this every winter do you,i know we are a fair way from this but it is stunning.

[northwestsnow]

1 minute ago, Steve Murr said:

Split vortex late on

 

Undepinning the potential for blocking 4-5 weeks

God I hope its right Steve 

[blizzard81]

9 minutes ago, Steve Murr said:

Not always .... 

Im coming the evolution with UKMO

The good news here is the PV is broken & the jet will be non existent so that greenland high is looking very likely...

Hard to ignore the fact that the parallel has support from tonight's ecm op though. 

[Stu_London]

Still no nailed on widespread snow event 

Suspect some will fall next week and there will be accumulations in places but uppers and dewpoints remain the main issue. 

[kold weather]

Just now, ALL ABOARD said:

I don't see where the jet would get any sort of energy from? 

No raging strat PV 

No raging trop PV 

No strong thermal gradient across America. 

We are basically in a summer pattern which in itself is interesting. However even in the depths of summer you can still end up with large 980-990mbs low in the mid atlantic. 

It'd be somewhat bad luck, but it definately could happen, indeed the phase 3-4 progression of the MJO would suggest thats a real possiblity as well. 

Lets hope though that we maintain enough of a structual block and keep that LP to our SE that we need not worry about it.

[Tim Bland]

B-E-A utifull run ! GFSp not too bad either.

[sukayuonsensnow]

1 minute ago, kold weather said:

The big fear is we end up basically in a repeat of this week set-up, but less favourable thickness/500mbs temperatures to go along with it (which might be balanced out by cooler SSTs and surface temperatures mind you).

The GFS para looks a little too cold for a low coming down from that angle in my experience, and has often ran a little too cold deeper in its run, a flaw it shares with its OG in its earlier days.

 

Yup. I'm also watching the temperature forecasts for the pink snow on the model over much of the UK. If its 2c or more I'm not buying it at this stage, unless you get a heavier burst of precipitation or you are on higher ground.

The potential is there but until those temperatures go down a bit (or we get a lengthier spell of heavier precipitation) it is essentially a similar setup to this week.

Nevertheless some interesting model watching indeed.

[Eskimo]

I think what gives me so much confidence is that not even the GFS wants to bring the Atlantic back. I think for me that's the take-home message...not even the model that regularly has fantasies of mild, wet Atlantic-driven dross wants to bring any of that back. 

[Griff]

Just now, Tim Bland said:

B-E-A utifull run ! GFSp not too bad either.

GFSP is great for Greenland, shame we aren't getting the goodies... 

Now I understand west based concerns, very well demonstrated on 18z.

 

 

[Stu_London]

1 minute ago, Allseasons-si said:

It's stunning to see isn't it NWS

i mean,...you don't see charts like this every winter do you,i know we are a fair way from this but it is stunning.

Must be close to Greenland highest ever pressure on that chart, albeit surface only without any proper heights.

[damianslaw]

Not looked at the models much today, just the latest runs. Short term, northerly flow remains intact, wintry precipitation for northern parts, mix of rain/sleet and snow. Frost for many and possible freezing fog. A cold end to 2020 and start to 2021. 

By the end of the weekend heights to the NW begin to advect NE and we pull in an easterly feed, but as others have said this will not be from a particularly cold source, SE Europe, temps back to near average, rain or sleet showers rather than snow on low ground at least. NW and W parts will see the driest and sunniest conditions with frost. 

Into next week, the signal for something colder from the NE, still very much there as heights pull away to our NW towards Greenland. 

[ALL ABOARD]

2 minutes ago, kold weather said:

We are basically in a summer pattern which in itself is interesting. However even in the depths of summer you can still end up with large 980-990mbs low in the mid atlantic. 

It'd be somewhat bad luck, but it definately could happen, indeed the phase 3-4 progression of the MJO would suggest thats a real possiblity as well. 

Lets hope though that we maintain enough of a structual block and keep that LP to our SE that we need not worry about it.

Of course. 

But that's usually down to the strength of the sun which causes additional energy. 

Null and void this time of year. 

[Allseasons-Si]

Mean at 174 matches the op.

[kold weather]

1 minute ago, Stu_London said:

Still no nailed on widespread snow event 

Suspect some will fall next week and there will be accumulations in places but uppers and dewpoints remain the main issue. 

I'm hoping that we don't end up with a quick flush out then very west based -ve NAO which resets us back to the SW airflow.

IF we can avoid that, perhaps this next week is better viewed a primer event.

It'll cool things down so if we do end up with a marginal set-up down the line (which in this type of evolution is possible) then it may well be the right side next time.

Note the ECM 12z has quite a decent cold pool to our NE to draw upon by 240hrs.

The key is we MUST not have that LP just fill out to our west. If that happens the odds of this thing collapsing rises exponentially. Over the UK or even better just to our SE will probably ensure another 10-14 days of cold from that point.

[nick sussex]

The least stressful route is the shortwave tracks south a touch further east than on the GFS18 hrs run .

That would guarantee that Arctic blast given the block in the Atlantic is strongly supported . 

That also mitigates any issues in case low pressure to the south deepens too much and starts heading ne.

The shortwave tracking south to the west of the UK is asking for trouble and needs too many other things to go right. 

 

[Jason M]

3 minutes ago, The Enforcer said:

Isn't this another easterly sourced from south-eastern Europe? Where are those dew point charts?

That would likely be okay for snow. Sourcing from a long way East is okay. The problem at the moment is that we are sourcing from the eastern med rather than eastern europe. Small differences but very different outcomes.

[Singularity]

In many ways the 18z GFS isn’t far from where the 12z ECM would have headed had it not let another low slip through by southern Greenland on 7th.