Model Output Discussion - moving into Winter

[Chesil View]

13 minutes ago, Geordiesnow said:

As a general rule of thumb, any flow coming in from the open waters, you need uppers of at least -8 to gurantee snowfall though higher ground and perhaps well inland areas can perhaps get away with uppers higher than that. In terms of windflow, at least initially the easterly does not look too strong so there be less mixing so an increased chance of snowfall if the ingredients are right but I do suspect the cold air is not quite strong enough for most I'm afraid. If the - 8 hpa does hit the UK, aslong as there is PPN my confidence would 

 

This onshore wind across open waters with uppers of just minus 2c caused the worst blizzard since 1963 across south west England.

Edited November 28, 2022 by Chesil View

[Derecho]

8 minutes ago, RainAllNight said:

Why does warm air moving up around the high help the high to build?

Basically warm air advection towards the Greenland helps to build a ridge of high pressure as mild air rises up through the Greenland plateau. If this area of high pressure becomes large enough, it dislodges the polar vortex from its typical position over NE Canada. If we are lucky the cold air that is displaced heads towards us, which is exactly what happened in December 2010.

The bigger the area of high pressure, the more difficult it is to lodge. In this instance, a mild south-easterly extended from NE Africa to NE Canada!

Edited November 28, 2022 by Quicksilver1989

[Iceman2606]

Lovely 12z GFS mean. We await ECM...

[geordiekev]

8 minutes ago, RainAllNight said:

Why does warm air moving up around the high help the high 

No expert but the friction of the orientated adjacent lows drag warm air from tropics & the rest is balloon like

[Derecho]

4 minutes ago, Chesil View said:

 

This onshore wind across open waters with uppers of just minus 2c caused the worst blizzard since 1963 across south west England.

Crazy we both attached the exact same chart for our explanations!!

[Singularity]

1 hour ago, Catacol said:

That's great work - ensemble evidence of GSDM theory. Very clear signal of momentum surges across pacific and atlantic. Plenty of eddies. Lovely. It must be shockingly tedious work to run that data however you have managed to run it - but what does it look like when high AAM states are working alongside a Nino ocean base state compared to interfering with a Nina ocean base state? Can you produce a comparison? I'd be interested to know what impact, if any, the ocean base makes when run alongside a consistent AAM signal.

That’s a great idea, I don’t have the setup to go that far yet but could build it… time allowing.

Model shenanigans continuing apace, so many unknowns yet to be resolved.

[AdrianHull]

Quite a few are getting hung up on the uppers so far out again. Fair enough the South coast seems to get a little washed out by the Iberian low but the majority of the UK is fine for snow potential. Lets get the cold in first. Surface temperature will have an effect in some place with potential for some white stuff. Anyways it will be different again next run. Fingers crossed for everyone!

[johnny1972]



 

Good evening guys. Been a long time since I have been on here having joined in 2008. Missed the model watching and I see the usual suspects are still here.

Looking at the chart below the issue I see with the position of the trough is it continues to source its upper air from SE Europe rather than the east. Hopefully that will change with a slight switch east to support the scandi high and bring in the colder uppers from Russia from than greece

 

 

 

 

 

[Midlands Ice Age]

22 minutes ago, carinthian said:

Evening all . Exciting  for you lot ! Of all the models interpretations currently on offer its the UKMO run that interests me most from your prospective . During thIs weekend looks like a upper cold pool development to take place over Northern France , Low countries and into SE England with formation of a low circulation over the Southern North Sea which could enhance some instability. At this stage , a bit marginal for snow but could be increasingly possible. Forecasting cold pool development is never easy to identify especially of the homegrown type in NW Europe. However, it is now being shown in the medium term outputs and interestingly one to watch. 

C

Also note the development of the small elongated low pressure over north of Biscay.

Could be a clash here of the moisture from the south with the colder air incoming from the east, which will turn rain to snow fairly easily inland.

If the low is not sufficiently strong to overcome the heights it will swing away south eastwards, leaving us in an enhanced easterly flow.

A classic situation from 20 -30 years ago, when we ended up with  prolonged cold spells.

I share your interest. 

MIA

[Cheshire Freeze]

12 minutes ago, Iceman2606 said:

Lovely 12z GFS mean. We await ECM...

The mean is hiding a lot of variation. There are a number of perts where the deep cold never makes it, or comes to far west and merges with Atlantic troughing to promote a height rise to our S and advection of warmer uppers into the UK.

I've been through every ensemble and by 300 hrs there is a theme of the trop PV starting to close up the blocking...what I take from that is we'll likely need to see another cycle of amplification to get something more sustained later in December. Greenland heights just aren't very stable. It wouldn't hurt to see the strat help us out there. With that in mind, our best case scenario is that the heights around Greenland don't fizzle out to the NW...we want to see them pushed back E so that we stay in the game (that's where 62/63 was so successful).

[feb1991blizzard]

47 minutes ago, Met4Cast said:

This is the best day 10 ensemble mean you could possible hope for, heck, dream for.

Unbelievable.

does go quickly west based after though.

 

[Cheshire Freeze]

This is what we don't want to see

[Met4Cast]

3 minutes ago, feb1991blizzard said:

does go quickly west based after though.

 

That isn't what I would call west based..

[Cheshire Freeze]

This is what we do want to see

[LetItSnow!]

Just now, CreweCold said:

This is what we don't want to see

Forgive my relatively untrained eye but that looks a little too fast moving, dare I say unrealistic, at least in most cases. Plus it’s also one run out 16 days in advance. Food for thought but not worrying me at the moment. 

[AdrianHull]

4 minutes ago, feb1991blizzard said:

does go quickly west based after though.

 

Just as well this chart is 14 days out then. But back to the reliable time frame things are looking positive!

Edited November 28, 2022 by AdrianHull

[Cheshire Freeze]

This the jackpot scenario and what we should aspire to see

[Continental Climate]

I don't hold much hope for this upcoming cold spell. Probably going to be chilly this weekend with cold rain in the east. Possible snow over high ground. The solid synoptics of a couple of days ago seemed to have collapsed. My guess would be a west based NAO. Hints now of blocking giving way to more natural December fare. There has never been the slightest hint of an operational showing solid wintry potential within 168 always out past 10 - 12 days. Never gets closer does it. 

[Radiating Dendrite]

A few already looking for the breakdown lol. 

Out in lala land the models are always too progressive. We either get a high on steroids or a resumption of dart board lows. The answer is likely in the middle, a possible waning of heights and then either another cycle of amplification or a messy breakdown. 

[Mandy Orme]

I have been observing the forum as I am in no way shape or form able to make sense of any runs or charts ect but absolutely love reading what you have all written and have always been interested in the weather .

I adore cold weather in winter  and get very excited if it shows any chance of it . living in the far south it's been so mild bordering on warm for quite a while now, am I right in thinking from what you all have written that we are going to get something colder ? I don't mind if it's not record breaking but cold enough to wear a jumper and coat without boiling to death lol.

Many thanks for any replies and just want to say  you are all so clever and I really enjoy this forum even if I couldnt tell one end of the chart from another,although I do try.

[blizzard81]

Big improvement from ecm for next Monday. Yesterday's 192 compared to today's 168.

[Cymro]

5 minutes ago, Continental Climate said:

I don't hold much hope for this upcoming cold spell. Probably going to be chilly this weekend with cold rain in the east. Possible snow over high ground. The solid synoptics of a couple of days ago seemed to have collapsed. My guess would be a west based NAO. Hints now of blocking giving way to more natural December fare. There has never been the slightest hint of an operational showing solid wintry potential within 168 always out past 10 - 12 days. Never gets closer does it. 

'The solid synoptics of a couple of days ago seemed to have collapsed.' 

In what way can synoptics collapse?

Sorry if this is a silly question but I fail to understand your statement here

 

Regardless of the final outcome on the ground. 

[AdrianHull]

2 minutes ago, Radiating Dendrite said:

A few already looking for the breakdown lol. 

Out in lala land the models are always too progressive. We either get a high on steroids or a resumption of dart board lows. The answer is likely in the middle, a possible waning of heights and then either another cycle of amplification or a messy breakdown. 

They should ban 14 day charts on here . I could draw better ones myself

[That ECM]

1 minute ago, Mandy Orme said:

I have been observing the forum as I am in no way shape or form able to make sense of any runs or charts ect but absolutely love reading what you have all written and have always been interested in the weather .

I adore cold weather in winter  and get very excited if it shows any chance of it . living in the far south it's been so mild bordering on warm for quite a while now, am I right in thinking from what you all have written that we are going to get something colder ? I don't mind if it's not record breaking but cold enough to wear a jumper and coat without boiling to death lol.

Many thanks for any replies and just want to say  you are all so clever and I really enjoy this forum even if I couldnt tell one end of the chart from another,although I do try.

You will need a jumper come the weekend. Max of 6-7 stiff nne wind which will make it feel 1-2. 

[Ali1977]

ECM about the put us in the freezer, this is starting to get v v interesting - what a crazy NH profile 

Edited November 28, 2022 by Ali1977