Model Output Discussion - Christmas and New Year

[ICE COLD]

Cant believe how many times I’ve said this over the last week but are say it again. Another brilliant run . Happy Christmas everyone

[kumquat]

Here come the streamers:

[beefy201]

Think people are getting a bit carried away hope I am Wrong .... cold air and a few wintry showers is the best we can hope for in the reliable time frame .... apart from the horrible storm Boxing Day /Sunday 

[Allseasons-Si]

That Siberian express is getting closer from run to run i tell ye,-16's getting into Scandi now.

a little shortwave in the Urals from 192 scuppered the true flow from the NE but still a good run.

Edited December 24, 2020 by Allseasons-si

[Mucka]

With a huge block in the Atlantic the only maritime air incursions and lows will have to come from the NW, moving down the E flank of that block which may make things marginal for a short time (or give a dump of snow) but should allow for the pattern to reamplify behind.

This could be a repeating pattern for a couple of weeks if we are lucky.

If we get a good trough alignment to the S of the UK then long fetch NE is possible which would bring much colder 850's later in the pattern.

There is always room for things to break down when you are surrounded by ocean but this is looking like a prolonged cold spell and becoming increasing cold as it progresses with plenty of snow chances.

The rare Winter patterns we pretty much live for as cold weather/snow fans in the UK.

Merry Xmas everybody and here is to a much better year for everybody next year.

Edited December 24, 2020 by Mucka

[Anthony Burden]

Just another great Synoptic set up from gfs pub run,it is totaly stunning to have these

recurring very wintery charts.Always looking for those gold Greenland and Scandinavian highes.

[chionomaniac]

5 minutes ago, chionomaniac said:

In situations like this I don’t look at surface conditions even up to 850HPa except just for fun. Main thing is always the 500hPa long wave pattern. So another good run. I can undoubtedly see the potential of a true cold arctic release of cold in every run..so close, but bizarrely never close enough. I’m convinced though, that it is only a matter of time. 

When we go back to the start of the month then there were certain indicators that created excitement for the longer range forecasters. The strat disruption was well advertised in the short term, but it was clear to long term strat watchers that a short term wave 2 split was just the beginning. The wave 1 East Asian stationary wave was likely to create a situation where a strong strat displacement was on the cards. For those who recognised that a traditional La Niña response was not forthcoming then the possibility of non tropical activity combined with tropical west based activity would lead to a strong meridional atlantic response was then on the cards and highlighted that fact. This could then reinforce the strat reaction with further wave 2 activity- this is yet guaranteed. But it may not be necessary either as the primary wave 2 source is Atlantic based.

 

so we are now looking at synoptic charts that were a possibility at the start of the month but are now a strong probability. Job done. Well, not quite. Typically in this part of the world the alignment of real cold to be released further south is teasingly close.  Lol well we can’t predict everything! But I still suspect that we will continue along the blocked Atlantic theme for a while especially now we will have strat bounce back feedback. It only takes one shot, with many rounds that we are being offered for the true release of really cold Arctic air to hit our shores. I really believe that we will not be disappointed for as long as the strat remains disturbed and disconnected from the trop. 

[Kasim Awan]

6 minutes ago, beefy201 said:

Think people are getting a bit carried away hope I am Wrong .... cold air and a few wintry showers is the best we can hope for in the reliable time frame .... apart from the horrible storm Boxing Day /Sunday 

I hope the heaviest of any snowfall Mon / Tue is at your location

[bluearmy]

Gfsp for the bin in fi ........ at the same place/time  that the eps have a black hole high anomoly, this run has a low anomoly 

[alexisj9]

50 minutes ago, Scott Ingham said:

The deeper system does mix out more cold for the south East. 

Get ready for imby posts tomorrow onwards hahaha 

It looks like my worst nightmare, better have some snow on the flip side. I've hated wind storms since 87.

[kold weather]

So I still see nothing to yet sway me from the 28-29th snow event possiblity, the only concern again is exactly where any secondary depression forms. It IS possible it forms too far south, indeed history tells us these things do tend to adjust south so we need to be aware of that when looking at the output.

If there is a band over England, especially on the northern flank if the secondary depression forms, then there will be snowfall, perhaps quite alot...BUT its a very large if still this far out.

[kold weather]

2 minutes ago, chionomaniac said:

so we are now looking at synoptic charts that were a possibility at the start of the month but are now a strong probability. Job done. Well, not quite. Typically in this part of the world the alignment of real cold to be released further south is teasingly close.  Lol well we can’t predict everything! But I still suspect that we will continue along the blocked Atlantic theme for a while especially now we will have strat bounce back feedback. It only takes one shot, with many rounds that we are being offered for the true release of really cold Arctic air to hit our shores. I really believe that we will not be disappointed for as long as the strat remains disturbed and disconnected from the trop. 

Yeah I think the biggest risk is going to be if we set-up a longer term west based -ve NAO, something not too dissimilar to the ECM. These can be a nightmare to dislodge because you are in a decent -ve AO pattern at that point and those LP trains can be tricky to shove sufficiently far away (they tend to be quite chunky Lp's from experience size wise) to bring the cold back down into our shores. Of course when that does happen that typically tends to be when very major snow event can happen of course. 

Hopefully we get the usal eastward adjustments as we move closer to the timeframe to allow us to reduce that threat. A half way house would be ok eventually and probably give us a shot at a snow event beforehand, but a real legitimate west based -ve is going to be wasting quite considerable amount of ideal time.

[sheikhy]

Lets hope we dont see that run again from the paralell!!lucky from what ive seen of it its not done that well anyway!!

[Allseasons-Si]

WOW!!!

the 18z gefs mean at 192 v's the 12z at 204.

Edited December 24, 2020 by Allseasons-si

[snowangel32]

Reading from the shadows normally 24 hours behind due to the rapid comments in the past 7 days. Just gone through 40 pages and woww what a read better than any book or film. Keep expecting that downgrade but thankfully that hasn't happened yet. Best model viewing since 2010 and the ermm the fabled beast from the East that we won't mention lol.

 

Thankyou to all the people for your excellent posts and keeping us all up to date.

 

May we all get a snowy nirvana, Merry Christmas ❄

[matty40s]

3 minutes ago, Allseasons-si said:

WOW!!!

the gefs mean at 192

Looks like ...

 

 

I think 28th is almost nailed on for a snow fest, west , central and south,  not sure the East will get much.

Are the Scottish ski resorts opening this year, could be a bumper snow season if these charts keep piling the cold in.

Edited December 24, 2020 by matty40s

[Mapantz]

I'd just like to wish everyone on here a very Merry Christmas!

Try to relax and enjoy yourselves and hopefully, you'll get the weather you're looking for soon. There's certainly going to be a lot of it in the coming days, so whatever your preference, you should be in luck!

 

[kold weather]

47 minutes ago, Geordiesnow said:

I think any snowfall at lower levels will be transient regardless, as soon as the PPN stops and clears during the day, the temperatures will rise(around 3 or 4C) and that is why I been going on about the poor uppers in this aspect aswell as the fact it will be marginal for some. 

I think in this set-up your never going to get upper temperatures much below -6/7c due to the source of the LP, unless you have a really exceptional set-up (Dec 10 comes to mind) but those are a once in 25 years type jobs.

I agree that any snow that does settle may melt fairly quickly. Alot will also depend on timings of when the front arrives in your location. Those that get it overnight or IF it hangs around long enough into the following evening may well get quite abit of settling snow. For those that get it during peak daytime hours it maybe more of a struggle.

However I *still* stand by that somewhere is going to get a decent snowfall out of this (10cms+) IF it forms far enough north. That would be by far my bigger concern, not whether its cold enough.

[Allseasons-Si]

1 minute ago, Mapantz said:

I'd just like to wish everyone on here a very Merry Christmas!

Try to relax and enjoy yourselves and hopefully, you'll get the weather you're looking for soon. There's certainly going to be a lot of it in the coming days, so whatever your preference, you should be in luck!

 

Anything lurking under the UKV buddy?

[Geordiesnow]

6 minutes ago, kold weather said:

I think in this set-up your never going to get upper temperatures much below -6/7c due to the source of the LP, unless you have a really exceptional set-up (Dec 10 comes to mind) but those are a once in 25 years type jobs.

I agree that any snow that does settle may melt fairly quickly. Alot will also depend on timings of when the front arrives in your location. Those that get it overnight or IF it hangs around long enough into the following evening may well get quite abit of settling snow. For those that get it during peak daytime hours it maybe more of a struggle.

However I *still* stand by that somewhere is going to get a decent snowfall out of this (10cms+) IF it forms far enough north. That would be by far my bigger concern, not whether its cold enough.

I think whilst this low did originated from warmer climes in America, you still expect a low that is coming near Greenland to have a colder flow to it than it does, maybe like you say - 6 or - 7 uppers which would make this event really on the right side of marginal. As it is, the uppers around - 3 to around - 4 which put things more on a knife edge except when the winds are slack because of evaporative cooling low thicknesses. 

Im growing into the camp somewhere will get lucky and get a decent snow event but I do feel it will be somewhat localised, the Midlands and especially higher ground looks the most favoured at this stage. 

 

[Allseasons-Si]

So we have the day ten means from both the 18z gefs side by side with the ECM mean,the ECM more robust with the Atlantic high but in general they look about the same

i am happy with that

[kold weather]

7 minutes ago, Geordiesnow said:

I think whilst this low did originated from warmer climes in America, you still expect a low that is coming near Greenland to have a colder flow to it than it does, maybe like you say - 6 or - 7 uppers which would make this event really on the right side of marginal. As it is, the uppers around - 3 to around - 4 which put things more on a knife edge except when the winds are slack because of evaporative cooling low thicknesses. 

 

I suspect its the angle of approach od this low that means it takes a long time over water which moderates the temperatures upwards further, its coming down from the NW-SE direction which for plunging lows tends to be not be a great direction, you typically want a move due north-south type plunge.

The fact that this set-up is cold enough snow in this type of plunging low set-up is actually not all that common in these types of set-ups and is probably due to just how vigorous the upper low remains (they normally weaken off once they head SE.) You normally in WNw/NW airflows have a strong low remaining somewhat further north.

I don't expect the snow zone to be too large in width. The best case is we get a cyclonic loop, in which case somewhere close to the center of that loop will get probably a good 12-18hrs of snow (take a look at Jan 10 for an example of that in CS England) but the models have somewhat moved away from that idea. However these features are tricky to forecast and I'd rule nothing out just yet, from getting a big event like that one, to getting absolutely nothing as the low struggles to form or forms too far south in the channel.

Edited December 24, 2020 by kold weather

[Daniel*]

It does seem to me like we’re on the cusp of a proper cold spell next week largely unimpressive cold wise but thereafter no possibilities can be ruled out. 

[Tim Goffer]

12 hours ago, kold weather said:

I'm increasingly confident of a snow band somewhere in the southern half of trhe country over the 28-29th period. Some uncertainties still with the exact evolution and subtle changes in the development of any secondary low will make the difference between a quick dusting in a fairly small area to a 15-20cms type dumping (though again limited in geographical extent).

Literally every model I've seen thus far this morning has an area of snow somewhere in the southern half of the country, so its 100% cold enough.

The biggest uncertainty in my mind is whether or not the secondary low forms as has been advertised this morning, still probably 1-2 days too soon to be real confident on that, and indeed on the 

[Allseasons-Si]

Dear Santa

i see you are on your travels,have you got pert 25 in your sack

i don't want a play station 5 or a bike or a colored tv,...just this,thankyou. 

 

Edited December 24, 2020 by Allseasons-si
typo