Model Output Discussion - cold spell to end Autumn

[MR EXTREMES]

4 minutes ago, Nicholas B said:

looking at the long term and backing up comments from GP & Tamara regarding heights building towards Scandi as the PV lobe over NE US pulls west , you have to say the postage stamps of the 06z GEFS are trending that way! as Bluearmy stated before.  

But then again every model flattening the heights to our northwest.

By mid week we have a cold Atlantic onslaught with the jet powering up towards the UK.

I really believe that a few days of cold maybe 5 days.

But clear trend is pretty much we lose the block to our west and with so much activity to our northeast then heights will struggle to build.

Although a fascinating start to winter.

 

[N/A]

1 hour ago, Draig Goch said:

Wind gusts for Sunday & Monday, some squally winds across the south & southwest England (as well as South Wales, more likely only on Sunday here) with perhaps the most severe winds becoming restricted to the south coast by Monday. Looks like quite a nasty spell of weather to come though after a relatively calm week. 

Well spotted! Lots of discussions about snow but very little mentioned about the severe gales that are forecast, even NW daily forecast has no mention of them for Sunday which I'm surprised at. It looks like Pembrokeshire will get a good buffeting (and not from snow) but Monday especially around Weymouth out to the Channel Islands looks very rough for a time. Yellow warning is already in place. I'll be mostly keeping a close eye on the models for wind rather than snow or even rain. 

[The Enforcer]

1 hour ago, bluearmy said:

I wouldn’t expect much more southward adjustment on Sunday - we have already gone up and down thirty miles over the past 24 hours so settling on a line top of the Severn estuary across to Luton and then up toward Peterborough and the wash - east of that line could be too warm for lying snow.

I disagree, I think the fax charts and other models are going to keep moving the fronts and the snow line around in small increments both northwards and southwards until around T+12.

Edited December 8, 2017 by The Enforcer

[Frosty.]

The word milder is creeping into the mid range outlook which indicates a change away from the generally meridional flow to a flattening out of the pattern with increasing strength from the northern arm of the jet bringing less cold / milder zonal atlantic conditions with spells of wet and windy weather, especially further n / nw but further ahead there are signs of change again with a colder / blockier pattern returning. .

Plenty of wintry weather in the meantime, a milder blip midweek followed by colder, brighter and showery conditions from the northwest with frost and ice risk returning for a time.

[Paul_1978]

23 minutes ago, Nicholas B said:

looking at the long term and backing up comments from GP & Tamara regarding heights building towards Scandi as the PV lobe over NE US pulls west , you have to say the postage stamps of the 06z GEFS are trending that way! as Bluearmy stated before.  

Agreed. And with that you only have to look at the Met Office view in their longer range output issues today, eg: 

Quote

UK Outlook for Saturday 23 Dec 2017 to Saturday 6 Jan 2018:

During the early part of this period we are likely to see a transition from spells of wet and windy weather moving across the UK towards more benign weather becoming established. This is likely to bring a mixture of colder, drier conditions and shorter lived milder, wetter and windier interludes. Snow is likely at times, especially in more northern and central parts of the UK. Temperatures will probably be below average overall.

So whilst appreciating this is not the Met Office outlook thread, you only have to look at all the evidence suggesting a return to colder conditions. The time period stated above is just starting to come into range on the GFS, so all eyes on the output for these suggested trends appearing, especially once we have got over the less cold spell that seems likely to follow during mid December.

[Derecho]

Wow what a week we have in store!

Looks like there will be a fair bit of heavy snow around with ~40 hours of consecutive snow for spots in the Midlands on the 06z . Of course still a lot of uncertainty at this point. Monday could threaten to steal the spotlight from sunday if the 06z GFS is to be believed... with blizzards too. But I'll emphasise things could change given the complicated nature of this pattern.





Things remain tricky.... it looks as though some milder air will come in this week for a short time, bit of a shame we'll be getting some heavy rain! Though later on in the week we could get more potential snow. The 06z GFS again seems bullish. 

So it looks like a soft exit from the cold this week with the European cold air still in just as much control as before. Either way some snow is better then no snow....

 Rain on Wednesday                             Snow later on? 
 

What next? Well its scenario time again and it remains somewhat similar to before. The threat of a return to zonality is there later on but I wouldn't bet on it. I hope we remain with the Scandinavian trough or the Azores high starts making its way across to Scandinavia. We will see what happens!

                20%                                                          35%                                                                 45%                                   
   

Anyhow feel free to critique, just my interpretation

 

 

Edited December 8, 2017 by Quicksilver1989

[radiohead]

5km WRF has very heavy snow right down on the south coast early Monday morning with winds gusting around 90 km/h.

By Monday evening :

[karlos1983]

6 minutes ago, radiohead said:

5km WRF has very heavy snow right down on the south coast early Monday morning with winds gusting around 90 km/h.

By Monday evening :

Pick a limb, you can have it. BANK!

RE Monday, I'm not convinced though, need to see what the 12z bring and if there is some consistency in the modelling from this morning. Seems a big ask following the considerable warm up down south on Sunday.

Edited December 8, 2017 by karlos1983

[Chesil View]

28 minutes ago, karlos1983 said:

Pick a limb, you can have it. BANK!

RE Monday, I'm not convinced though, need to see what the 12z bring and if there is some consistency in the modelling from this morning. Seems a big ask following the considerable warm up down south on Sunday.

Mind you Karlos the supposed warm up down south on Sunday is based on the forecast track of the slider being exactly correct . Which going on past experience is something I still have doubts about.

[Snowmadsam]

The NetWeather SR model also goes further south, a small 20 miles south would really benefit much of South Wales and the South West.

 

Edited December 8, 2017 by Snowmadsam

[inghams85]

13 minutes ago, Snowmadsam said:

The NetWeather SR model also goes further south, a small 20 miles south would really benefit much of South Wales and the South West.

 

This isn't further south it's just it doesn't go out to the period that the slider low swing NE

[Chesil View]

20 minutes ago, Broadmayne blizzard said:

Mind you Karlos the supposed warm up down south on Sunday is based on the forecast track of the slider being exactly correct . Which going on past experience is something I still have doubts about.

Just to reiterate the point the latest Meto fax for 12z Sunday has the centre of the first slider over Birmingham. That is still nigh on 48 hours away. It is perfectly excusable for that model to have the low centre 50 miles out at that range. A 50 mile southward correction would present a somewhat different picture going forward.

[Snowmadsam]

12 minutes ago, inghams85 said:

This isn't further south it's just it doesn't go out to the period that the slider low swing NE

Marginality is going to be a big factor for this weekend. The now-casting will really begin Saturday evening and early Sunday morning for those on the edge of snow/rain.

A fascinating time ahead for sure.

[swfc]

4 minutes ago, Broadmayne blizzard said:

Just to reiterate the point the latest Meto fax for 12z Sunday has the centre of the first slider over Birmingham. That is still nigh on 48 hours away. It is perfectly excusable for that model to have the low centre 50 miles out at that range. A 50 mile southward correction would present a somewhat different picture going forward.

Indeed and northward. I guess they have a better take on this ete being a professional outfit. Monday looks pretty dire and dank but hopefully next week we pick up a stronger signal on regard to pressure rising to the nne!!!

[DR(S)NO]

 Tomorrow night is looking  like the coldest night for a long while in Scotland with some widespread severe frost ( following an ice day in many places ) ...could somewhere get down to -15c?

Not too shabby for December and certainly it’s been a much more seasonal end to Autumn and beginning of Winter..

[Chesil View]

37 minutes ago, swfc said:

Indeed and northward. I guess they have a better take on this ete being a professional outfit. Monday looks pretty dire and dank but hopefully next week we pick up a stronger signal on regard to pressure rising to the nne!!!

yes swfc could easily be 50 miles out to the north as well. 

[tynevalleysnow]

Wonder if the UKMO 12z has trended north as my local METO forecast has gone from 0% to 80% heavy snow Sunday. Just a thought.

Edited December 8, 2017 by tynevalleysnow

[Dean E]

While we await the 12z GFS, its worth mentioning that while this slow southward modelling has occured over the last 24 hours, many models are now showing quite large snowfall totals further south. London grinds to a halt after 2cm of snow, imagine 10-20cm?

WRF highlighting this now

Of course, these high res or 'rapid refresh' models are always all over the place with their predictions, worth a watch as we go over the 24 hours.

Oh and how about strong winds to boot come Monday evening rush hour? 

I think we are now slowly starting to get a better grip on movements of the Low now, but what an interesting time to be model watching! (Head still hurts from last week)

Edited December 8, 2017 by Dean E
Missing photo

[Ali1977]

Milder spell then colder possible blocked patterns end of Dec early Jan going off earlier Fergie tweet - backing up GP and Tamaras thoughts, so even with all this weeks snow still more positive stuff potentially in the pipeline!! Long way off of course. 

Edited December 8, 2017 by Ali1977

[warrenb]

I have a feeling it is going to be even further south. Just at 15hr it seems the high wedge is just a little stronger

[Catacol]

5 hours ago, TEITS said:

The Low on Monday is becoming concerning!

Beyond all this excitement and the milder, flatter more mobile pattern is gaining momentum in the output as I mentioned a few days ago. I know this contradicts the posts by GP, Tamara but its consistently being shown.

Not my interpretation of what GP said at all. He made specific reference to a period of Canadian trough impact on the pattern. Tamara has also been rock solid on stating that a period of more westerly influence was likely prior to any further pattern amplification in later December on the back of not too big a fall in global atmospheric momentum (hopefully). For my own part I have noted transition of the MJO quickly through phases 5 and 6 (both of which promote a westerly pattern) before heading towards 7/8.

In short - the modelling is following an entirely predictable period of transition with the expected variations on a theme. If it continues to follow the expected pattern we will see heights to the north appear in the extended output once again before too long. Everything this year seems to be happening more quickly than expected - so maybe between Xmas and New Year. Until then a lot of NW airstreams with occasional northerly.... so cold/cold but not a big freeze.

[warrenb]

4 minutes ago, warrenb said:

I have a feeling it is going to be even further south. Just at 15hr it seems the high wedge is just a little stronger

Nope further north

[NO LONGER POSTING]

We were told numerous times that a southern correction on the up and coming lows was going to be the case and that is kind of what we have seen, we still have a fair few runs to get through yet before the event(s) Even then it will be a case of watching the radar and live pressure chart.

 

EDIT: Looks slightly north thus far, contradicts my above post well lmfao

Edited December 8, 2017 by Surrey

[bluearmy]

Slightest adjustment north although it looks to restrict the snowfall less to the east as per met office updates 

[shaky]

Its weird cos the first 30 hours into the frame everything was slightly south!!but then it jumped north slightly!!