Model Output Discussion - A cold start to Spring?

[Bricriu]

Just now, Johnp said:

I remember the days when people wouldn’t give the time of day to the UKMO day 6 chart - and now we’re having kittens over what it shows at day 7.

The old adage always applies - get the cold in first and then see what happens. 

But  it seems to be a trend across most of the models to break down the block. The chances are the ECM will show something smiliar. I hope not! 

[seabreeze86]

I most be looking at different charts or that pint I had with my streak was stronger than I thought 

[NewEra21]

Just now, Johnp said:

I remember the days when people wouldn’t give the time of day to the UKMO day 6 chart - and now we’re having kittens over what it shows at day 7.

The old adage always applies - get the cold in first and then see what happens. 

To be fair the UKMO was solid as a rock in the lead up to this upcoming spell, whatever it holds.

[snowblind]

Just now, Johnp said:

I remember the days when people wouldn’t give the time of day to the UKMO day 6 chart - and now we’re having kittens over what it shows at day 7.

The old adage always applies - get the cold in first and then see what happens. 

I still think the accuracy after 4 or 5 days on any of the models plunges off a cliff. Depending on the model the steeper the dive.

[winterof79]

No beef with this...and its yonks off.

There will be a waxing and waning of cold.

Cold pool still in play next Friday on GEM

[TSNWK]

Breakdown being suggested is aligned to Carol this morning who was unusually confident for bbc on chances for snow for  many early in week followed by milder air later.

[Matt Jones]

I have never understood the comments of the cold block will be hard to shift, it is simply not true as illustrated by the UKMO model this evening at 168hrs the azores high ridges in shoving the cold block east. Well lets see what ECM brings later as others have said no certainty that any chart is going to be correct at day 7.

[That ECM]

5 minutes ago, seabreeze86 said:

I most be looking at different charts or that pint I had with my streak was stronger than I thought 

It’s this that’s given me the hump. Yes could change and I do hope so.

[Rain All Night]

O weather gods, where are you taking us?

[StingJet]

11 minutes ago, Bricriu said:

According to the Met Office deep dive video they think this is the result of the first warming two weeks ago. So if that the case, then maybe we will get another round of blocking in another two weeks from the recent warming. If it is going to be a short lived cold spell it's somewhat disappointing given we have had the ssw and  mjo phases conducive to blocking. Unless one is somehow working against the other? Could that be possible? 

Yep that is my understanding too ( re SSW1 downstream effects starting to playout now)  .. this time next week we'll be chasing (in Fi) the mother of all scandi blocks and frigid easterly served up by SSW2 (don't quote me on that) 

Edited March 1, 2023 by StingJet

[winterof79]

Typical the word breakdown being thrown about like a rag doll.

I will enjoy my snow as we're due some up here having missed out so far.Then ill watch the BD get reduced to a blip before a second wave brings more of the white stuff.

Edited March 1, 2023 by winterof79

[alexisj9]

9 minutes ago, snowblind said:

I still think the accuracy after 4 or 5 days on any of the models plunges off a cliff. Depending on the model the steeper the dive.

Agreed,I can't believe people are looking at day 8-9 charts and moaning about what they show.

[Rob 79812010]

18 minutes ago, Matt Jones said:

I have never understood the comments of the cold block will be hard to shift, it is simply not true as illustrated by the UKMO model this evening at 168hrs the azores high ridges in shoving the cold block east. Well lets see what ECM brings later as others have said no certainty that any chart is going to be correct at day 7.

Yes I've often heard the TV forecasters say this! It strange because they don't often last longer than a week barring exceptional events 

[Mcconnor8]

2 minutes ago, Rob 79812010 said:

Yes I've often heard the TV forecasters say this! It strange because they don't often last longer than a week barring exceptional events 

I know off topic but what in the models made the 1963 big freeze for example last for months without warm air coming in? Did the Atlantic jet stream just collapse completely?

[Rob 79812010]

21 minutes ago, Matt Jones said:

I have never understood the comments of the cold block will be hard to shift, it is simply not true as illustrated by the UKMO model this evening at 168hrs the azores high ridges in shoving the cold block east. Well lets see what ECM brings later as others have said no certainty that any chart is going to be correct at day 

Even 79 and 2010 were interspersed with mild periods and they were 2 of the best winters

[Bricriu]

52 minutes ago, Matt Jones said:

I have never understood the comments of the cold block will be hard to shift, it is simply not true as illustrated by the UKMO model this evening at 168hrs the azores high ridges in shoving the cold block east. Well lets see what ECM brings later as others have said no certainty that any chart is going to be correct at day 7.

I was about to say maybe it's because we are dealing with a displacement instead of a split, but  then we had a textbook split in 2018 and still the cold spell was shortlived. 

So the excuse that we need a piece of Vortex on the Canadian side to give the block a boost might not be the full story.  Whether the tpv goes too far east or goes back west it amounts to an end of the cold spell. It's frustrating how delicate a balance it is for us to get cold in and then for it to last. 

Edited March 1, 2023 by Bricriu

[I remember Atlantic 252]

12 minutes ago, Matt Jones said:

I have never understood the comments of the cold block will be hard to shift, it is simply not true as illustrated by the UKMO model this evening at 168hrs the azores high ridges in shoving the cold block east. Well lets see what ECM brings later as others have said no certainty that any chart is going to be correct at day 7.

Aye, 'cold block hard to shift' tends to be more of a hopecast, so many times the Atlantic moves in with ease, normally with a whimper

[Mike Poole]

6 minutes ago, Rob 79812010 said:

Yes I've often heard the TV forecasters say this! It strange because they don't often last longer than a week barring exceptional events 

It is not so much whether the cold will be harder or easier to shift, that will depend on the scenario.  It is whether the cold will be harder to shift than the models think that is the issue.  This sometimes can be the case.  I am happy with the 12z runs so far, I don’t think the models yet have a good handle on what happens after the cold is in place, either to the blocking or to any lows moving in from the Atlantic i.e. undercutting or just barging the cold away - barging the cold away is more unlikely than the models are suggesting in my view.

Edited March 1, 2023 by Mike Poole

[Rob 79812010]

10 minutes ago, Mcconnor8 said:

I know off topic but what in the models made the 1963 big freeze for example last for months without warm air coming in? Did the Atlantic jet stream just collapse completely?

I read that in 63 the depth of cold and extent over the Arctic was unusual that year. Also I think that there were fronts that caused temporary warm ups in the South but the cold would win. Dec 10 was the only one in my lifetime. 

12 minutes ago, Mike Poole said:

It is not so much whether the cold will be harder or easier to shift, that will depend on the scenario.  It is whether the cold will be harder to shift than the models think that is the issue.  This sometimes can be the case.  I am happy with the 12z runs so far, I don’t think the models yet have a good handle on what happens after the cold is in place, either to the blocking or to any lows moving in from the Atlantic i.e. undercutting or just barging the cold away - barging the cold away is more unlikely than the models are suggesting in my view.

I really hope so. Its great when it does stick around!

[Stuie]

Was a bit worried reading all the breakdown comments. Posted the UKMO 0z this morning and here is the 12z.

If anything, a slight upgrade.

[Man With Beard]

18 minutes ago, RainAllNight said:

O weather gods, where are you taking us?

They all seem keen to through out a trough running into cold air.

It does seem primed for snow opportunities next week.

[I remember Atlantic 252]

24 minutes ago, TSNWK said:

Breakdown being suggested is aligned to Carol this morning who was unusually confident for bbc on chances for snow for  many early in week followed by milder air later.

Last few GFS runs have shown this, Atlantic from 12th

[Captain Shortwave]

10 minutes ago, Matt Jones said:

I have never understood the comments of the cold block will be hard to shift, it is simply not true as illustrated by the UKMO model this evening at 168hrs the azores high ridges in shoving the cold block east. Well lets see what ECM brings later as others have said no certainty that any chart is going to be correct at day 7.

Depends on the mechanics of said breakdown. If it is a direct attack with a trough to the west moving east we often see the trough disrupt and sheer away as it hits cold dense air over Europe. However in set ups with blocking to the north west then we often see the jet returning northwards over Europe as heights continue to back westwards.

Anyway, the UKMO day 7 chart does possess an area of interest over future runs.

 

That area of higher heights over Eastern Greenland is the sort of scenario where we could retain heights that could steer Atlantic lows further south later on. Something to keep an eye on.

Something like this….

[Mike Poole]

1 hour ago, Met4Cast said:

Interestingly - If this current period of blocking is mostly trop led on the back of the MJO triggering a rise in +FT, now +MT and overall surge in +AAM then the SSW impacts may yet to be felt. 

Fairly good agreement that the SSW will be enhancing the early March blocking rather than "causing" it directly so I think we can probably expect another round of blocking towards the middle of March or sometime in the second half of the month. Where that sets up/how it impacts the UK is a different matter entirely, but does lend to the suggestion of March coming in below average. 

My view is that the SSW impacts are very much being felt right now.  I think we are at the switch point where the tendency to blocked patterns is now more due to the SSW rather than the MJO, and it seems a reasonable timescale since the Feb 16th event for that to be the case.  I’m less swayed by the second reversal specifically as I regard it all as one evolution, although I think attributing additional model volatility over the last week to it is fair.  

It is the sheer speed at which the transfer of the trop PV to the Eurasian side is taking place - I don’t think that would happen without the imprinting of the strat vortex.  I agree that another round of blocking is possible, we know a SSW can have an effect for weeks afterwards, and I think in 2018 that did come in waves.  By the time we get to April, I imagine we’d rather it went away, but for now, once again, the most exciting period of winter is in spring!

Edited March 1, 2023 by Mike Poole

[Battleground Snow]

3 minutes ago, Captain Shortwave said:

Depends on the mechanics of said breakdown. If it is a direct attack with a trough to the west moving east we often see the trough disrupt and sheer away as it hits cold dense air over Europe. However in set ups with blocking to the north west then we often see the jet returning northwards over Europe as heights continue to back westwards.

Anyway, the UKMO day 7 chart does possess an area of interest over future runs.

 

That area of higher heights over Eastern Greenland is the sort of scenario where we could retain heights that could steer Atlantic lows further south later on. Something to keep an eye on.

Something like this….

Glad someone else noticed that, the Azores won't ridge into the UK if that ran on further, although I would still rather the gem solution