Model output discussion - The run up to Christmas

[Radiating Dendrite]

1 minute ago, StephenL said:

I'd imagine the uppers wouldn't be marginal

Think @terrier may disagree!

[feb1991blizzard]

Just now, Radiating Dendrite said:

Think @terrier may disagree!

joking aside though, for the initial part of this cold spell, -ie - the next 10 days, even Steve Murr agrees the uppers are marginal.

[Wynn D Woo]

3 minutes ago, StephenL said:

I'd imagine the uppers wouldn't be marginal

This is the UK though

[Day 10]

Morning all, just gone through about 30 pages stemming back through to the old thread, what a cracking read.

On what is essentially the first day of Winter proper we could not be better placed, to have these kind of charts now showing a day 5 is just great. The less said about whether the uppers are low enough or not the better I think.

We look to be entering a very good setup which as everybody knows is the hardest part, so let's get there first and then I'm sure the snow will follow.

Day 5, have a great Monday!

[DavidS]

26 minutes ago, Smartie said:

BANK!! think I'd sacrifice all of next winter for that chart to come off! 

Better hope Catacol  doesn't see that chart seeing as he's recently moved from down this way

Agreed, bank! If that comes off where I am in South Wales, they’ll be good sledging for days

[Methuselah]

6 minutes ago, feb1991blizzard said:

even Steve Murr agrees the uppers are marginal.

So now it's official?

[loafer]

6 minutes ago, General Cluster said:

So now it's official?

You sound like you are not a true believer....

 

[goes off to sharpen pitchfork and light flaming torch]

[ITSY]

Interestingly the control is also toying with a follow-on easterly. This is essentially interest part 3 of 4: 

- Xmas eve/day (rogue showers on initial northerly)
- Initial Greenland ridge/northerly (uppers good side of marginal but need watching nearer the time, not now)
- Follow-on something? Northerly/Easterly, sliders etc (eg. today's GFS op and control)
- SSW (1st-2nd week of Jan)

Bit of a rare list, that...anyway control  here: 


 

Edited December 21, 2020 by ITSY

[Matt H]

Not much to add other than the fact that the GFS has performed extremely well recently in predicting the upcoming pattern and has held steady in pretty much rolling out the same evolution with the heights retrogressing ever since the 18z on Thursday so my respect for the model has increased significantly.

The 06z ensembles are looking cold from Christmas onwards and even the uplift on Boxing Day has been watered down now to an average of about -2C. Brilliant to see the ensembles so tightly clustered at -5C virtually all the way through after Christmas and I can’t wait to see where the rest of this cold spell takes us further down the line if we pull off a SSW as well!

[kingdogleash]

10 minutes ago, General Cluster said:

So now it's official?

He is also said in the same sentance

Surprise snow for many

All just opinions though!

 

 

Edited December 21, 2020 by kingdogleash

[ITSY]

2 minutes ago, Frosty Winter said:

Not much to add other than the fact that the GFS has performed extremely well recently in predicting the upcoming pattern and has held steady in pretty much rolling out the same evolution with the heights retrogressing ever since the 18z on Thursday so my respect for the model has increased significantly.

The 06z ensembles are looking cold from Christmas onwards and even the uplift on Boxing Day has been watered down now to an average of about -2C. Brilliant to see the ensembles so tightly clustered at -5C virtually all the way through after Christmas and I can’t wait to see where the rest of this cold spell takes us further down the line if we pull off a SSW as well!

It's apples and oranges I know and I'm not comparing the substance here (there is no comparison), but I've not seen such persistent and tightly packed cold agreement since Dec 2010. It's startling really and quite refreshing! 

[Penrith Snow]

3 hours ago, Vikos said:

Good morning to my british friends

<--- white numbers are the height of the 0°C Isotherm in meters

a somewhat more realistic (not to be equated with pessimistic) view of certain things apart from the cold hype in this forum means something like an exclusion or an ingnoration, but ok, then let's be a grinch. but the external circumstances do not let me dream of winter wonder to the lowlands in the near future until new year's eve, to put it quite dryly. Too much mixing of the air mass with a high 0 ° C limit, high moisture% pushing dew points up, inflow over the warm north sea

Yet again, it's still to early to discuss excact outcomes after 144, but I would rather remain skeptical due to the experiences of the last few years. I just don't see the enough power in the system (really cold air masses).

Future will show.

So, with no anger, it's "just the weather", and ATM there are things in the world which are much more important than if it will snow here or there or not. As europeans, we need to stick together, somehow

Great Post and I agree 100%, I can Ramp as much as the next guy but some of the comments on here this morning are way too optimistic. IMO the downfall of next weeks low is its pure size and intensity as it will suck in milder air off the Atlantic and then the North Sea as it heads south, this really isn't a mid December 2010 scenario when the southward movement of the vortex over the UK was preceeded by a bitter northerly flow.

With uppers of -4c and loads of moisture i just can't see widespread snowfall away from high ground.

Happy to be proved wrong but I will be driving to Kirkstone Pass next week as I think I will need its 1500feet altitude to see any real snow.

BTW my German friend many Brits really miss being part of the European Community and as Arnie once said "I'll Be Back"

Andy

[Vikos]

6 minutes ago, ITSY said:

This is essentially interest part 3 of 4: 

- SSW (1st-2nd week of Jan)
 

That is not clear, evaluation if it has been a SSW per definition comes AFTER the event, since there are many different parts to be fulfilled it to be a SSW!

Not to mention, that 06z is more to show a strong minor warming

[Penrith Snow]

1 hour ago, TSNWK said:

And dearest netweather geeks.. I propose we all swear a solemn pact between each of us.... NOT A GOD DARN WORD TO FAMILY AND FRIENDS FOR NOW PLEASE!

I’m sure we have all been there

 

Absolutely!  I remember explaining to my wife how the SSW of early January 2019 would result in a bitterly cold late January and February similar but longer than the BFTE spell the previous March

How she mocked me when 6 weeks later the warmest winter spell on record resulted in a late February BBQ  

Andy

[Man With Beard]

1 hour ago, TSNWK said:

And dearest netweather geeks.. I propose we all swear a solemn pact between each of us.... NOT A GOD DARN WORD TO FAMILY AND FRIENDS FOR NOW PLEASE!

I’m sure we have all been there

 

I know this post was in jest but goodness me it's true - I can't remember a snow forecast south of Birmingham that can be predicted confidently before T72.

With the current pattern, to get a major snowfall any location will be relying on disturbances coming in from the north west, but not so far inland that air with a long Atlantic sea-track is introduced. It's a fine balancing act. I think we're in a good position for this to occur between 28th and 30th but the geographic window in which it might happen is not that big. A larger cold pool would make it easier. Even with these charts, areas south of Birmingham in particular still need a little luck. North of Birmingham in areas away from the far west, though, I think you may need a sledge soon  still don't tell anyone though!

Edited December 21, 2020 by Man With Beard

[swfc]

26 minutes ago, General Cluster said:

So now it's official?

He's not the messiah!! He's a very naughty boy!!!

[BlueHedgehog074]

Let’s make sure we keep it to the models please. Thanks guys

[A.J]

1 hour ago, TSNWK said:

And dearest netweather geeks.. I propose we all swear a solemn pact between each of us.... NOT A GOD DARN WORD TO FAMILY AND FRIENDS FOR NOW PLEASE!

I’m sure we have all been there

 

I've already told my kids it will snow but haven't yet divulged which decade..... so we're all good. .....hello to all by the way,....haven't been in here for years it seems 

[MATTWOLVES 3]

Just for fun,but nice to see ECM precipitation graphics showing some decent snow around,and not just reserved to the North..but focused more towards w/sw areas also.. Also a nice looking extended mean out towards the 5th of Jan...remaining cold basically.

[Downburst]

Saturday 26th (Boxing Day) and we still have a westerly flow, with relative mild conditions, despite what so many posts say. Of course this is 6 days away, so not 100% accurate. (If it was a northerly it would be of course)

 

Then one week from now we are into true northerly from the Arctic, very cold,  but for how long? 

 

 Wednesday of next week, we are in a returning air flow by then, not warm, but not arctic either. So as ever there is a short window for this to work out.

 

This low crossing Iceland is forecast to really zip down rapidly early next week. West of UK, but may if it comes off provide a lot of snow in the west, we shall see. One to watch

[Jason M]

9 minutes ago, Frosty Winter said:

Not much to add other than the fact that the GFS has performed extremely well recently in predicting the upcoming pattern and has held steady in pretty much rolling out the same evolution with the heights retrogressing ever since the 18z on Thursday so my respect for the model has increased significantly.

The 06z ensembles are looking cold from Christmas onwards and even the uplift on Boxing Day has been watered down now to an average of about -2C. Brilliant to see the ensembles so tightly clustered at -5C virtually all the way through after Christmas and I can’t wait to see where the rest of this cold spell takes us further down the line if we pull off a SSW as well!

These graphs can often be quite useful and at face value these show strong agreement for the next period. However this is one of those occasions where a clustered 850 graph hides a multitude of sins.

It is quite clear from looking through the individual GEFS that there is a lot of variance of outcomes in terms of synoptics and this gets obscured by this graph. One thing that is clear from the individual GEFS however is that the 'airmass' is almost always the same under each of the different scenarios. Personally I'm disappointed with this because its telling me that regardless of the variations on the theme we are very unlikely to access any significantly cold air. Its true that its colder than 'normal' but its super marginal under an airmass that has maritime rather than continental properties. I genuinely  thought last nights pub run was a step forward but for me its not been followed through this morning.

At the risk of being being the Grinch its much like recent days output and a bit meh IMHO but completely respect others are excited and see things differently and some will certainly see snow falling.

Still plenty of interest going forward though with an SSW for Jan and of course we all know anything can happen with long range charts (say beyond day 8). Certainly a better position for this stage in December than for many winters past and we can't rule out something significantly cold appearing in the first couple of weeks of Jan.

 

[Kasim Awan]

GFS 06Z evolution is sensible. Has a polar low diving SSE at D7 creating room for further amplification, I expect the SE Greenland / Iceland area to have higher heights forecast by upconing output for D8-9. This could well yield a surface easterly into the first week of January.

[SLEETY]

The uppers are lower now for Xmas eve then  was forecasted a few days ago, which shows you that the uppers being forecast for next week could get much lower too, and it's still  way too far to make any forecast regarding snow. 

Snow is very fickle at low-levels sometimes not arriving as forecast and vice-versa, even at 24 hours. 

I bet the Met office are dreading the next ten or more days ahead regarding where it will or won't snow, away from the high ground. 

I can imagine John Holmes can vouch for the difficulty the Met office have always had at forecasting snow at low_levels in UK

 

[West is Best]

I've been keeping off here because I haven't wanted unintentionally to annoy people.

However, in the interests of balance I have to post this as it has been showing up for days and days. If anyone tells you that the really cold scenarios after Boxing Day are 'nailed on' then there are three significant reasons why I don't yet believe it.

1. We always get this and they always downgrade. Without exception.

2. The upstream blocking still doesn't look sufficiently robust to me. Whether it's the mid-Atlantic High holding in place or retrogressing into Greenland, neither remains for very long and that's, frankly, a recipe for trouble.

3. Most significantly the ensembles continue to show a significant number of members bucking the trend. This from the 6z where, once again, the operational is running below the mean:

 

I'm sorry to appear like a party pooper and I hope I'm wrong.

[Matt H]

5 minutes ago, Jason M said:

These graphs can often be quite useful and at face value these show strong agreement for the next period. However this is one of those occasions where a clustered 850 graph hides a multitude of sins.

It is quite clear from looking through the individual GEFS that there is a lot of variance of outcomes in terms of synoptics and this gets obscured by this graph. One thing that is clear from the individual GEFS however is that the 'airmass' is almost always the same under each of the different scenarios. Personally I'm disappointed with this because its telling me that regardless of the variations on the theme we are very unlikely to access any significantly cold air. Its true that its colder than 'normal' but its super marginal under an airmass that has maritime rather than continental properties. I genuinely  thought last nights pub run was a step forward but for me its not been followed through this morning.

At the risk of being being the Grinch its much like recent days output and a bit meh IMHO but completely respect others are excited and see things differently and some will certainly see snow falling.

Still plenty of interest going forward though with an SSW for Jan and of course we all know anything can happen with long range charts (say beyond day 8). Certainly a better position for this stage in December than for many winters past and we can't rule out something significantly cold appearing in the first couple of weeks of Jan.

 

Yes I agree, it’s a shame we can’t access any uppers much lower than -5C at this stage but hopefully further down the line we will be able to do so. Just have to work with what we’re being offered until then.