Model Output Discussion - Christmas and New Year

[Kasim Awan]

2 minutes ago, sheikhy said:

Euro4 goes west this time!!!mainly because it elongates the low a bit more as well!!this will not be resolved until literally just before the event!!!nowcast written all over it!!

The GFS is always too far out with the precipitation relative to the low centre at this range. Clearly evident for the 2019 event. Forecast is way too north. So whilst I agree about nowcasting, I also think probabilities can be appointed to the various solutions. Additionally I think we will see further tigthening around a solution by tomorrow's 6z.

[phil nw.]

No sign of any real change within the next 10 days from what i can see with +ve hts over the polar field and a weak buckling jet on a cold nw-se flow.

ECM/GFS mean charts  for day 10 

Just looking at some ens.outputs and there's no doubt we will go cold for the next 10 days with the 850's flatlining at around-4/-5c north and south.

These for Warks off the ecm

As for snow, it looks like thicknesses for the early part next week look ok(sub 528-as a rough guide)as the low settles over us.Still uncertainty where exactly will see any snowfall but minor troughs and shower activity can still crop up at quite short notice.

The impression i get then is the low slowly fills and the 500 hPa core starts to warm somewhat.We can see by the graphs below.See those thicknesses on the rise along with surface pressure.

A look at today's 00z London combined ens.for 2m temp.and expected rainfall trends.

I don't believe a true deep cold few days with widespread snow was ever on the cards for next week.Most of us have been talking about marginal conditions and this looks like the case..Still it will be cold with some seeing snow i am sure but more likely earlier in the coming week before things look drying out as pressure starts to rise.

I think a look at today's zonal winds forecast should allay any fears of a resurgent Atlantic jet flattening the pattern and returning us to the usual westerly zonality.

The speeds are going through the floor in early January with a possible reversal showing now.Based on this you would expect some really strong heights further north n future modeling as we enter January.

Not a bad place to be in as wait to see how much damage will be inflicted on the vortex from the continued warmings on the Stratosphere.

 

[alexisj9]

3 hours ago, Spah1 said:

Euro 4 usually very stingy with snow predictions, now seems too keen. 

Let's hope it's actually right lol, would be amazing to get some snow, out of this nasty wind, although thank goodness it's night time, as it would be an actual blizzard, which is something we don't generally get here in the UK.

[Tim Bland]

36 minutes ago, Kasim Awan said:

The hi res appear somewhat tighter in their resolvement of Monday's snow.

The ARPEGE & others produce a more easterly track further north across N Eng before swaying the precip more S of SE. The upshot is that a line from Liverpool to Bristol sees falling snow with the potential for >10cm as hinted at by the Arpege's pivotting before less of a push south east. This before more of a wintry mix on the south coast later as the precip looses it's cold by the time it heads south.

This solution is currently favoured with some sway both W/E possible e.g. refined to Welsh Borders or West Wales & as far N.E. as Leicester...

A middleground again speculated here by the HIRLAM however this could be a false sense of security - with a more W/E outcome possible.

The GFS is well north which seems unrealistic. So Welsh borders, Far west Mids & perhaps W Country atm favoured. 

Hi Kasim, can you post the charts showing 10cm + I’m just not seeing it anywhere  

[Guest]

2 hours ago, Beanz said:

Flight data points have increased hugely in the last year or so, they will still decrease over this period but accuracy is much better now than it was and the effect is less pronounced. 

Also shortly after the start of the pandemic ECM stated they’d managed to fill the majority of the gaps following the lack of flight data so reduced seasonal air travel now should really have almost no impact on model accuracy/output.  

[Kasim Awan]

1 minute ago, Tim Bland said:

Hi Kasim, can you post the charts showing 10cm + I’m just not seeing it anywhere  

The Arpege solution has 200mm of falling snow - unlikely to produce less than 10cm

[Methuselah]

Unusually tight temp-ensembles, out to the fourth. I guess that, for the foreseeable, cold air will be held in a vice-like grip, over the UK?

    

     

I'll put that down to light winds, freezing fog and possible snow cover...

And the NH Profiles look okay: 

    

    

Patiently awaiting the PV getting nuked!

[Ashme]

No posts in the last 55mins!! All ok I trust??? Or am I having issues my end???

[chris55]

1 hour ago, Kasim Awan said:

The Arpege solution has 200mm of falling snow - unlikely to produce less than 10cm

I don’t think I’ve ever seen such divergence  in ppn location/snowfall location between the models run to run. Each one is markedly different to the other! 

[Norrance]

3 minutes ago, Ashme said:

No posts in the last 55mins!! All ok I trust??? Or am I having issues my end???

Boxing day lunch maybe. To get back on topic here is current fax chart showing the squeezing of the isobars and the source of the incoming colder air.

[That ECM]

2 minutes ago, chris55 said:

I don’t think I’ve ever seen such divergence  in ppn location/snowfall location between the models run to run. Each one is markedly different to the other! 

I would suggest it’s because of the way it pivots.

[SLEETY]

didnt the chinese seasonal model go for a blocked and easterly January,could well be corre

http://forecast.bcccsm.ncc-cma.net/web/index.php?pred_start_date=2020-12-01&pred_elem=GH500&pred_region=GL&submit=M01&ChannelID=65#pred_seasonal

Beijing Climate Center Climate System Model (ncc-cma.net)

 

Edited December 26, 2020 by SLEETY

[Kentspur]

3 minutes ago, SLEETY said:

didnt the chinese seasonal model go for a blocked and easterly January,could well be correct.

Cant seem to find it online though?

Yep as did the JMA

[Djdazzle]

Overanalysing every run looking for whether precipitation has moved 10 miles is a quick route to insanity!

It will chop and change right up to the final few hours. Go and have a drink and forget it for a while!

 

[danm]

5 minutes ago, Djdazzle said:

Overanalysing every run looking for whether precipitation has moved 10 miles is a quick route to insanity!

It will chop and change right up to the final few hours. Go and have a drink and forget it for a while!

 

Absolutely right. I know why we all do it, but we only pay attention to minute changes in the short term modelling of precipitation when snow is involved. Think about how rain at any other time is often different to what is forecast when we don’t pay attention to it. 

[NewEra21]

Got a feeling somewhere will get a suprise big dump of snow this week, due to a trough or some other feature popping up at short notice that the models haven't picked up on.

Wouldn't be surprised if many of us wake up to at least a few dustings of snow when we open the curtains during the week ahead.

Maybe I'm being too optimistic, but with such a complex system over us, surprises are bound to occur imo.

Edited December 26, 2020 by NewEra21

[I remember Atlantic 252]

2 minutes ago, NewEra21 said:

Got a feeling somewhere will get a suprise big dump of snow this week, due to a trough or some other feature popping up at short notice that the models haven't picked up on.

Wouldn't be surprised if many of us wake up to at least a few dustings of snow when we open the curtains during the week ahead.

Maybe I'm being too optimistic, but with such a complex system over us, surprises are bound to occur imo.

@Kasim Awan will definitely, would love to live there

[Djdazzle]

2 minutes ago, NewEra21 said:

Got a feeling somewhere will get a suprise big dump of snow this week, due to a trough or some other feature popping up at short notice that the models haven't picked up on.

Wouldn't be surprised if many of us wake up to at least a few dustings of snow when we open the curtains during the week ahead.

Maybe I'm being too optimistic, but with such a complex system over us, surprises are the bound to occur imo.

This is my mindset too - consider any snow as a surprise next week. Far less likely to be disappointed then. I’m hopeful that no matter what happens next week, it will be a precursor of a more sustained cold spell afterwards.

[Methuselah]

MetO red warning out... expect low-flying teddies, dollies, Stickle bricks, toy soldiers, and random bits of Duplo, anytime from tomorrow evening. Moderate to heavy accumulations are expected, in most-favoured areas!

PS: I is bored, waiting for the 12Z!!!

Edited December 26, 2020 by General Cluster

[BARRY]

2 minutes ago, Djdazzle said:

This is my mindset too - consider any snow as a surprise next week. Far less likely to be disappointed then. I’m hopeful that no matter what happens next week, it will be a precursor of a more sustained cold spell afterwards.

time to erect the snow dome me thinks. So much talk about snow from the GFS Euro4 and ECM

[Eagle Eye]

Runs have been showing Scattered Snow for most of the next few Weeks how would we read that off Models and what seperates

this

From this

In the first one you see the Jet Stream is showing the air coming down from the Arctic called an Upper and will bring Polar Air Along With it. 

In the 2nd one you can see the Jet Stream bringing Air from the Atlantic this Air is bringing mild unstable air(Low's don't have to be Cold more bring Rain and are unstable) this is called a Returning Polar Maritime Air parcel. The 2nd Low will bring Unstable Air and more Connectiveness in this you can have Thunders now when this Mild Air Goes Below 0oc. 

How do you Interpret These charts. 

Such as the 2st one an Arctic Northernly will bring Cold Air and Polar Air Parcels which will most likely bring below 0oc Air In Winter and Snow which will be Wider And Longer lasting. It is important to note that we can get Air from Scandanavia called a Beast From The East which isn't garuanteed but will most likely bring Showery Snow 2018 was an Example Of this. A high in Winter coming up from Europe US Called An Azores High and brings Tropical Maritime Air Which Is Humid And Mild And This Will Bring 10oc And Above Most likely. 

 

[I remember Atlantic 252]

Just now, General Cluster said:

MetO red warning out... expect low-flying teddies, dollies, Stickle bricks, toy soldiers, and random bits of Duplo, anytime from tomorrow evening. Moderate to heavy accumulations are expected, in most-favoured areas!

Aye, mine when high ground gets it all, always been a believer of elevation makes snow more likely

[Gael_Force]

6 minutes ago, Sheldon Cooper said:

Runs have been showing Scattered Snow for most of the next few Weeks how would we read that off Models and what seperates

this

From this

In the first one you see the Jet Stream is showing the air coming down from the Arctic called an Upper and will bring Polar Air Along With it. 

In the 2nd one you can see the Jet Stream bringing Air from the Atlantic this Air is bringing mild unstable air(Low's don't have to be Cold more bring Rain and are unstable) this is called a Returning Polar Maritime Air parcel. The 2nd Low will bring Unstable Air and more Connectiveness in this you can have Thunders now when this Mild Air Goes Below 0oc. 

How do you Interpret These charts. 

Such as the 2st one an Arctic Northernly will bring Cold Air and Polar Air Parcels which will most likely bring below 0oc Air In Winter and Snow which will be Wider And Longer lasting. It is important to note that we can get Air from Scandanavia called a Beast From The East which isn't garuanteed but will most likely bring Showery Snow 2018 was an Example Of this. A high in Winter coming up from Europe US Called An Azores High and brings Tropical Maritime Air Which Is Humid And Mild And This Will Bring 10oc And Above Most likely. 

 

Todays snow satellite illustrates your point well. Big beefy snow showers (red tinge) as the arctic parcel comes south.

 

[Battleground Snow]

Minor improvements on the icon in relation to the ridge into Greenland, the low around Newfoundland ideally needs to stay further south west to help suck better heights up. 06z v 12z

 

[DogToffee]

37 minutes ago, General Cluster said:

MetO red warning out... expect low-flying teddies, dollies, Stickle bricks, toy soldiers, and random bits of Duplo, anytime from tomorrow evening. Moderate to heavy accumulations are expected, in most-favoured areas!

PS: I is bored, waiting for the 12Z!!!

Where's the red warning? I can see an orange one for wind in the south, but only yellows otherwise.