Model output discussion - The run up to Christmas

[Matt H]

1 minute ago, That ECM said:

Thanks for taking the time to reply and add to my learning. That’s why I enjoy this site. Was a time I didn’t know what I was looking at all but through learning areas and from others you learn more and more. 
 

Thank booferking also.

Same, from a standing start I’ve learnt so much from the experts like Steve and several others over the years and I’ve enjoyed getting involved in the conversation this year even though my knowledge is far less than most.

[warrenb]

Remember the ecm was dragged kicking and scream to the pattern change, so it would logically be the first to deviate. Interestingly on the bbc look ahead last week they showed the ecm output but then said the gfs outcome was the preferred.

Edited December 21, 2020 by warrenb

[northwestsnow]

Day 10 EC..

The block to the NE is huge.

[supernova]

7 minutes ago, Steve Murr said:

To get some cold longevity out of an atlantic high we need a cut off wedge over Iceland to keep the atlantic alligned on a very sharp NW > SE Axis, when you weaken the wedge the jet axis softens up to a more positive angle ( more towards west to East ) 

The ECM is the worst of the bunch however overall its modelling has been pretty poor.

Compare the ECM 216 1st the GEM 216 you see the key difference which leads to a milder ECM. 

Thats why even post 168 you never see anu proper cold air over the UK

 

6 minutes ago, Allseasons-si said:

Hi Heath i will try and explain...

1,we need the trough to be cut off and to drop a lot further S/SE as much as possible

2,this will then open up the heights over the  top

3,once 1 and 2 do that then the advection would take place from east to west

of course this is just based on that chart and it is day ten,the modelling will come up with different types of scenarios up until then.

V helpful posts both. At least this year we get the chance to examine and discuss charts across all models with genuine potential, although no real BOOM-worthy cold in the foreseeable as has been covered to death by Uppers-gate. Meaningful roads to  certainly better than we're used to and Strat activity bodes well. Lots to cheer in an otherwise mostly cheerless year!

[Valleyboy]

41 minutes ago, DiagonalRedLine said:

Some great agreement occurring their between the 3 models, albeit with the UKMO the most amplified in the Atlantic. Signs of the upper trough over the UK and Scandinavia being cut off from the area of very low heights and Vortex areas on the opposite side of the Northern Hemisphere. Looking good

(Edit: I agree for the UK area, some additional shifts East or South-East of the Low Pressure would be very welcome)

We really need the low pressure to move south east much quicker, if it does , then it’s game on, if it stays anchored over the UK, then it’s rain, apart from high ground.

[Scott Ingham]

3 minutes ago, PolarWarsaw said:

There has been a lull of posts in here today because for all money we look to be heading into another situation as we did early month - close but no cigar. Yes, there is certainly more back bone to the cold this time and yes, over the years there has been numerous little events unfold that have delivered surprise snowfalls (and are likely to again) - but the reality for the most of us, is that after weeks of waiting and being patient we are not even remotely staring down the barrel of a cold and snowy spell. 

Lots of cold rain, sleet and some isolated snow looks likely. 

If I lived in Scotland, Northern England or somewhere like Oldham for example then I'd be quietly content that I will see some potentially accumulating snowfall in the next 10 days or so. Given the vast majority of posters live at 100m's< in this country and the wider population of this forum will be posting from inner city locations or more specifically south of the M4, this is not a pattern that should be rejoiced in for current prospects at the surface - for the immediate term that is. 

Again this evening, we are seeing 'amazing' looking synoptical charts that for whatever are NOT fulfilling the same potential for the weather at the surface. I refer back to early month for a rinse and repeat, albeit with more potential to deliver this time. 

If there was signs of a Bartlett or an aggressive Atlantic spell in the models for the 1st week of January...the model output thread would be a very different place tonight. 

Let's hope the ECM comes back towards the GFS. 

A lot of peopoe that do post live up North though and you have to factor that in. It doesnt have to be a snowy spell all the way to the south coast for it to be considered a good period of winter weather.

Compared to a December average this is an historicaloy significant piece of winter weather which has only just started.

Its not going to warm up in the next 2 or 3 weeks. Its only going to get colder as further bouts of amplification kick into gear and then we have events in the strat.

You cant downplay the start to this winter its been fascinating and is only going to get more and more newsworthy. Playing it down is your perogative and your entitled to but i wont be taking any notice of that because myself including most on here know what is lurking by the passing week

[stodge]

Evening all

Let me start this evening's ramblings with an apology and a rant. I did a full analysis of the 12Z models for the medium to longer term and started having problems attaching charts. I pressed on and finished and then found the thread was closed and my entire contribution lost so all I will say to the Mods, who, to be fair, did apologise for what happened is this:

Aaaaaaaaaaaaaaaaaaaaarrrrrrrrrrrrrrrrrrrrrrrrrrrrggggggggggggggggggggggggggggghhhhhhhhhhhhhhhhhhhhh!!!!!!!!!!!!!!!!

That's better . On then to this evening's model mutterings. Last evening's output, while not as stellar as Friday, was a marked improvement on Sunday and promised a colder spell of some sort albeit with a very uncertain evolution as we go into 2021, all against the background of a split PV. It seems, on any number of fronts, we are cursed to live in interesting times.

12Z GEM: - a better evolution for cold fans last evening than on Saturday but worth stressing none of this a done deal yet. T+120 is St Stephen's Day or Boxing Day if you prefer. N great surprise at this time - the LP is starting to head south or south-=east and the HP is slowly easing back to the west or north-west while maintaining a ridge to the south of the British Isles so a reasonable day for many. That all changes rapidly and by T+180 the trough is over or just to the east of the British Isles with a cold NNE'ly over Scotland and Ireland. 850s -4 to -8 so you'd think snow from any precipitation at night. The evolution to T+240 is similar to that postulated by the ECM 12Z OP yesterday evening. A new LP forms over eastern Greenland and the trough aligns NW-SE across the British Isles with the HP similarly aligned in mid-Atlantic and hints of heights rising to the far north-east. Minus 4 850s to end the year but the really cold air is digging further west and that worries me is it would create cyclogenesis to the west and pull milder air back up over the British Isles in the early New Year (suggested by GFS in far FI over the past couple of days). Also worth noting is a more noticeable PV formation in the usual place.

12Z GFS OP - another run of ebbs and flows last night switching from very cold to very mild very quickly in far FI (see above) so where are we this evening? As I commented yesterday evening, GFS is more progressive than GEM even at this time with the LP already showing its head to the NW on Saturday (T+120). By T+180, the LP has moved south - the profile isn't too different from GEM with the main centre over England and a second centre just to the north of Scandinavia. A cold N'ly wind down the western flank but -4 850s over much of the British Isles. By T+240, much of the British Isles remains cold with a N or NE'ly wind with a complex LP to the east but unlike GEM a small ridge of HP has split the trough . The Azores HP is in position and a new LP coming off the eastern seaboard.  On into 2012 and by T+312 signs of a return to a more usual pattern but it's slow and pressure is high to the nE but with the Azores HP edging into North Africa the Atlantic trough is slowly aligning more positive. T+384 looks much milder with a SW'ly flow despite heights over Greenland and to the east. It looks like a west-based negative NAO pattern but I could be wrong. 

12Z ECM - an interesting if messy conclusion yesterday evening but tonight will doubtless be completely different. T+120 is a recognisable blend of GFS OP and GEM. By T+192, the LP has moved south and now sits over to just to the east of the British Isles but the Greenland heights have rapidly collapsed and a new Atlantic trough is moving off Eastern Canada. By T+240, however, that LP has swing SE to be just off the north coast of Ireland with heights appearing to the east and the Azores HP ridging in to mid-Atlantic. It's a logical progression from the previous evening's scenario and hints at a return to the negative alignment pattern we saw recently. 850s of -4 for many during the day on New Year's Eve so chilly and you'd think any precipitation might well be snow especially to higher ground.

Looking elsewhere, the 12Z GFS OP 10 HPA forecast doesn't quite split the PV tonight but does leave it severely diminished and weakened. the 12Z Control is largely cold or very cold until far FI and ends with a stand off between milder Atlantic systems to the south and west and colder anticyclonic conditions to the north and east.

Conclusion - it looks as though we will get a colder interlude for 3-5 days minimum between Christmas and New Year with opportunities for snow for plenty. Hopes for a Greenland HP appear to be fading and as might be expected a weaker PV and diminished zonal winds are helping the Russian HP to become a player in the New Year with the options of negative trough alignment or a stand-off between competing air-masses. Plenty to resolve after New Year as you'd expect and with the PV still under pressure we just need the cards to drop right for a January cold spell. All in all, an encouraging start to the week.

 

[Allseasons-Si]

15 minutes ago, warrenb said:

Remember the ecm was dragged kicking and scream to the pattern change, so it would logically be the first to deviate. Interestingly on the bbc look ahead last week they showed the ecm output but then said the gfs outcome was the preferred.

I also remember that no model picked up this amplification in the Atlantic and then boom it just suddenly appeared one evening on the gfs,it just shows you how unpredictable the weather can be sometimes.

Edited December 21, 2020 by Allseasons-si

[Mike Poole]

Just musing about the lack of cold air.  Where is it?  Here’s the situation now.

1. it isn’t very cold over the pole - a -AO.  So the cold is displaced south.

2. Cold over Russia/Siberia - there’s a lot here to tap into but it is closed off for now, a favourable SSW like 2018 could unleash it towards us.

3. Cold over northern USA and west of that.  No chance of getting that here!

4. Lack of cold near UK and north and east of us.  

Solutions, either a long draw system from the north, hold a cold synoptic pattern long enough for the air to cool pretty much in situ (most likely, given likely repeated re-amplifications in the current set up), or SSW bringing in long draw easterly. 

But it could snow somewhere as early as Wednesday night.  

Edited December 21, 2020 by Mike Poole

[Weathizard]

ECM mean at day 8 looks pretty nice, although.... the shape of those cold uppers over the pole is certainly something

[Scott Ingham]

1 minute ago, Weathizard said:

ECM mean at day 8 looks pretty nice, although.... the shape of those cold uppers over the pole is certainly something

Its ECMs tribute to my naked run through Rotherham

[Smokeone]

13 minutes ago, Scott Ingham said:

A lot of peopoe that do post live up North though and you have to factor that in. It doesnt have to be a snowy spell all the way to the south coast for it to be considered a good period of winter weather.

Compared to a December average this is an historicaloy significant piece of winter weather which has only just started.

Its not going to warm up in the next 2 or 3 weeks. Its only going to get colder as further bouts of amplification kick into gear and then we have events in the strat.

You cant downplay the start to this winter its been fascinating and is only going to get more and more newsworthy. Playing it down is your perogative and your entitled to but i wont be taking any notice of that because myself including most on here know what is lurking by the passing week

A lot of people also are from the south that post on here. But I am very enjoying all the posts on here at the moment including yours. Keep it up. 

[Vikos]

9 minutes ago, Mike Poole said:

 

 

Solutions, either a long draw system from the north, hold a cold synoptic pattern long enough for the air to cool pretty much in situ, or SSW bringing in long draw easterly. 

 

No need for a SSW (which, when occurs, will bring the cold at the earliest in February). Have look in the Vortex-Thread. I am still seeing a rather big minor warming then a tech SSW.

But we don't need a SSW for a "Beast from the east".

Predicting that this EC Chart is somehow right

cold air masses will build up quite fast under that russian high, and using floor currents, it can sneak all the way through, since there isn't alot atmosphric dynamics. Then, with the right placement of highs and lows, real cold air is available for us, without any warm seas to heat it up.

Just stay relaxed, cold will come, maybe not this week, but winter is at least ongoing for 2-3 months...

Edited December 21, 2020 by Vikos

[tight isobar]

Mustn’t grumble..  and why not gain.. as we further

[LRD]

7 minutes ago, Weathizard said:

ECM mean at day 8 looks pretty nice, although.... the shape of those cold uppers over the pole is certainly something

I see it's pointing at where it usually shoots its cold load in winter. Rejecting us again

GFS spaghetti for London:

Forecasters nightmare predicting where it will rain and where it will snow. West and NW favoured at the moment - elevation will obviously help (a bit like the shape of those uppers)

Edited December 21, 2020 by LRD

[SLEETY]

Maybe the Siberian High will be the big player eventually.Its been effecting our weather by stalling the lows and Ecm looks to be building it strongly at the end of the run,lets hope this is the new trend.

[BlueHedgehog074]

26 minutes ago, Valleyboy said:

We really need the low pressure to move south east much quicker, if it does , then it’s game on, if it stays anchored over the UK, then it’s rain, apart from high ground.

That would be good, so we can pull down colder air from the North or North-East. Despite the models generally consistent with the how deep the Low Pressure is over the UK towards 144 hours, wouldn’t be too surprised if the Low becomes a little less deeper on the day itself. Maybe much less deeper, although that currently seems like a long shot. That of which should also help to make things a bit more favourable for wintry weather. Especially since models seem prone to over-blowing Lows at times

Edited December 21, 2020 by DiagonalRedLine

[Scott Ingham]

4 minutes ago, Smokeone said:

A lot of people also are from the south that post on here. But I am very enjoying all the posts on here at the moment including yours. Keep it up. 

Oh I know yeah. I just think you have to be careful not to make sweeping statements and be careful to not to say theres no snow for everyone which ever way it looks. I love winter weather i hope we wll all get in on the action 

[Kent Clipper]

Evening.

We virtually have cross model agreement now on a general pattern that introduces the initial cold incursion on Christmas Eve. Indeed Christmas Eve evening and early Christmas morning continue to offer some snow flurries to many eastern coastal counties of England and Scotland all the way down to ....yes, Kent ! 

Its a potent little blast this one, relative to recent standards with 521 dam, -8c (850s) and -3c (925s) at 00.00hrs on 25/12 here in Folkestone. ( I noticed a very slight kink on the 12z GFS over the low countries for this period, suggestive of a weak frontal or trough feature.

A dusting first thing on the big day would make up somewhat for a torrid year for many.

Thereafter we have the diving trough feature circa 27th onwards. Incredible agreement on the longevity of this one as well with 850's levelling out at -5 to -6 for several days. There is the continued signal for more of a NNE'ly flow towards New Year but that is way in FI and useful only for observational purposes at present.

The iffy looking 850 Hpa's have been the subject of many discussions in recent days. It is my opinion that the precipitation around is going to swing the right of white rather than wet for various reasons.

1. Time of year, very little solar insulation.

2. Slack set up, we create our cold pool all the time we keep this synoptic set up.

3. Thicknesses are circa 520-525 for many for much of the week. (Easily supportive of snow).

4. Pressure is circa 980mb meaning that the '850Hpa' temperature is closer to the boundary layer

5. The airmass is unstable. Mesoscale trough features will only show up within 48 hours in most cases.

6. Our old friend evaporative cooling will play its hand due to a lack of mixing out breezes.

Whatever happens its a fascinating set up and one that will keep forecasters and amateurs on their toes for the next couple of weeks. The ingredients are all there on the sideboard ready. They need to all be added to the bowl though to make this potentially quite a memorable one, not that this will be difficult for many of us snow starved SE Kent folk that somehow escaped the beast from the east back in late Feb / early March 2018.

Cheers, Steve.

 

Edited December 21, 2020 by Kent Clipper

[IanT]

23 minutes ago, Scott Ingham said:

...It doesnt have to be a snowy spell all the way to the south coast for it to be considered a good period of winter weather...

You’re new here aren’t you?

[Kentish Snowman in Yorks]

2 minutes ago, SLEETY said:

Maybe the Siberian High will be the big player eventually.Its been effecting our weather by stalling the lows and Ecm looks to be building it strongly at the end of the run,lets hope this is the new trend.

I have noticed that in the far reaches of the last couple of GFS runs that high pressure to the North East has been flexing its muscles and pushing in our direction so it is within range of affecting the UK.

Maybe look East in early January?

[PolarWarsaw]

45 minutes ago, Scott Ingham said:

A lot of peopoe that do post live up North though and you have to factor that in. It doesnt have to be a snowy spell all the way to the south coast for it to be considered a good period of winter weather.

Compared to a December average this is an historicaloy significant piece of winter weather which has only just started.

Its not going to warm up in the next 2 or 3 weeks. Its only going to get colder as further bouts of amplification kick into gear and then we have events in the strat.

You cant downplay the start to this winter its been fascinating and is only going to get more and more newsworthy. Playing it down is your perogative and your entitled to but i wont be taking any notice of that because myself including most on here know what is lurking by the passing week

 

Oh absolutely, but in order for it to be a notable spell of cold and snow in my opinion - we need to see the vast majority of the country involved, not favoured locations. These said locations see snow in marginal set ups each winter because they are exactly that, favoured. If the upcoming spell of weather rinsed and repeated for the entire of the next 3 months - it would be one of the worst winters ever for central and southern England, but a winter of records in Scotland.

Much like in summer, if the South and East has a 20 day heatwave but in Bristol and Manchester it's not been the warmer side of 21c, then using a national based forum thread to proclaim it was the great heatwave of X year, would be ludicrous. 

Take your point on board with what's been forecasted in the next few weeks with regards to the strat and I have enjoyed your posts/contributions, one of the plus points so far this season. But I think it's fair to say calling this a significant piece of weather historically needs to be watched for the time being. 

Charts and model watching has been fascinating, I agree. It hasn't been interesting at the surface though, it's just rained a lot. Sooner or later these nice patterns have to produce, or else it will turn into a giant waste and honestly, the atmosphere of this thread will be much worse if all this time waiting leads to nothing.

There's plenty of time for that to happen, but my point was referencing the here and now. There's very little low land, widespread snow forecast in the next 10 days and if the charts verify as shown tonight,  there won't be. That doesn't disregard the strat and how interesting of a position we are in, but vice versa - a good set of strat charts don't deliver snow either. 

There has to be some balance in this thread.

Winter Strat/Models - Fascinating, impressive, exciting. 

Winter at the surface - Predominantly above average, miserable and wet, in short - NOT exciting.

The bottom 1 negates the top 1 and will continue to do the longer we go into winter without that notable, widespread snowy spell. That's my point, we need to address a balance in this thread so all kinds of posters involved are understanding and that the Strat looks great at the moment, we are in a good position. Ultimately, at the surface - in the immediate future, it's nothing outstanding and has been quite dismal up to now. 

I noted you called this winter so far 'outstanding' last night and as much as I admire your posts, think they are brillantly informative and could only wish to reach the standards of knowledge you have - it's been outstanding on the internet, but not outside the nations windows.

We need to be really careful not to confuse people in here and keep separate what is happening in the strat, to what actually happens at the surface. The strat can be as good or bad as it wants, but there can't be ignorance to what's happening in the here and now. There also cannot be questions or bickering about the other opinions, given it seems there are posters on different time lengths and wave lengths. 

To keep that simple, for example; you named winter outstanding last night and it has/could be in the strat (that's your focus and wave length). What I'm saying tonight, is that it's been miserable at the surface and the strat/reality disconnect will probably be the route of confusion, bickering and arguments. Whereas, it shouldn't be and people can help others by making their preference known. 

 

Edited December 21, 2020 by PolarWarsaw

[Mike Poole]

JMA of interest again, I like to use this as a rough idea of where the UKMO would go if it went beyond T144, here’s both:

On to T192:

Brings the low further south than other output which is good, alignment not perfect, but there is a small margin of error in drawing cold from the north at the moment!  

[Uncertainty]

ECM mean at day 10 looks a sight upgrade to me, higher heights into Greenland and a tad sharper with the mean ridge, 12z:

0z

The Euro trough also slightly further SE. 

GEPS have been the flattest of the big 3 in recent weeks, not today. A simply incredible anomaly here.

Not gonna get flustered by ECM ops at day 9 / 10 in a pattern it struggles with.

PS first glance at EC46 looks really, really good till mid Jan!

Edited December 21, 2020 by Uncertainy

[Skullzrulerz]

I'm going to be honest regarding the models and where we are at the moment 

I'm concerned regarding the ECM tonight as it seems to be less favourable to say the least regarding a ridge or any high pressure around Greenland we will need most importantly and I really hope it's not the start of new trend...

The GFS seems okay for any snow potential with the most favourite places being Scotland and high ground in northern England though there is a chance they can be some low level snowfall somewhere 

Haven't looked at the ICON but the UKMO looks good in terms of heights 

In my personal opinion I would think having a mixture of the GFS/ECM would be the best outcome for any snowfall 

But in general the lack of cold air is truly something