Model output discussion - cold spell approaching?

[Met4Cast]

2 minutes ago, Radiating Dendrite said:

Not to play devil's advocate but we heard the uppers will get colder mantra with the lead up to the last cold spell and they didn't. 

In regards to -8c uppers, has them last week and got 36 hours of rain. 

I'm quickly learning that only -10c guarantees snow.

Yes they did.

Initially we were looking at uppers around -4/-5c, they upgraded to around -8c as the time got closer. The reason for rain last week was due to a warmer surface layer, mostly down to the lack of proper cold across Europe + a warmer than average North Sea modifying the temperatures. 

850hPa's weren't the problem.

[Jason M]

28 minutes ago, danm said:

Can we stop the IMBY posts from all sides? For those down south like me, please stop going on about any perceived lack of cold. There’s so much still to be resolved. Likewise for those further north, saying it’s all good for you (especially when you’re at elevation) doesn’t do much good either. Even more so at the range we’re at now when we really don’t know exactly how cold it will be and where the coldest air will be. 
 

It’s getting really tiresome now - both those complaining and those saying that’s it’s good for them personally. 

If the people up north can't talk about the cold they are going to get and the people down south can't talk about the rain they will have, what's left to talk about? Sorry, but one of my pet hates is posts that tell others what they can and can't post.

The people up north are probably right to be a bit excited whereas the so called 'moaners' are also right to talk about the limitations of what we are seeing. Otherwise you just end up with mad unjustified ramping and a thumping great forum hangover when the cold spell that was literally never modelled fails to turn up (as per last couple of weeks).

FWIW I think snow is now highly probable Midlands northwards and whilst much less certain its very possible south of this. Its certainly a better position than the last so called cold spell because whilst 850s don't look much different its a different type of airmass. The disappointment is that yet again we can't sustain stable heights at a northerly latitude to our N or NE during the three key winter months and that limits the scope of what is achievable. 

[stodge]

Evening all

I'm beginning to enjoy this milder weather but that might put me in the minority here. Clear signs of a return to colder conditions next week irrespective of any brief colder incursion this week. The notion of the "battleground" getting plenty of interest with perhaps the trough aligning west-east through the middle of the British Isles leaving the south mild and the north cold - it's happened before, no reason why it couldn't happen again.

Still, let's see what tonight's contrafibularities provide.

12Z GEM: T+120 takes us to Sunday and a shallow LP lies to the north of the British Isles with a trough extending south-west. Heights persist over Iberia with a new HP building NW toward Southern Greenland. A WNW'ly air flow covers the British Isles. 850s are zero to minus four as some colder air moves into the north-west behind a cold front. The trough moves SSE down the North Sea and by T+180 is to the east of the British Isles. Upstream, the trough is clawing its way back north against the Greenland heights and the next Atlantic LP is looking to phase with the trough over the British Isles. Weak heights persist over Iberia. Colder air is pushing south over the British Isles in a NW'ly flow with uppers of -4 to -8. From there, the evolution gets a little "odd" - essentially, the cold air of the trough over the British Isles engages with the warm sub-tropical air to the south-west and explosive cyclogenesis occurs with a deep LP over southern Britain By T+240. Another deep LP spins away to the west of the Azores while strong heights persist over Greenland. Milder air pushes into the far south but it remains cold to the north with a keen ESE'ly wind and I can't imagine someone somewhere wouldn't cop a lot of snow from that evolution.

 

12Z GFS OP - GEM ends dramatically implausible to this observer but there you go. On then to the GFS OP. At T+120 there are already some differences with the GEM. The Atlantic LP is more vigorous and to the south-west of Iceland. Heights exist to the south and west of this potent little LP but it's calm over the British Isles with a ridge of HP from Iberia keeping it quiet. 850s of zero to minus four so nothing too dramatic at this time.  From here, the LP moves slowly east before starting to sink south across the British Isles. The ridge is extending south from Greenland to the Azores while residual heights remain over Iberia. A cyclonic or W'ly flow over the British Isles by T+180 with uppers still zero to minus four with the coldest air still out to the west. The trough meanders east and south east across the British Isles and by T+240 is over northern Germany with an extension back west. A new Atlantic LP is developing and slowing moving toward north-west Europe while heights persist over Greenland. 850s of -4 to -8 across the British Isles at this time.

12Z Parallel - well, the GFS OP gets to the same point as the GEM but 60 hours later so we can call GEM progressive by comparison. Let's see where Parallel sits. Again, a slight variation at T+120 with a ridge extending west from the HP which is positioned further north on Parallel than on some other models. A SW'ly air flow for northern and western parts but a light flow further east. The LP is more complex with centres to the north-east and south-west of Iceland at this time. 850s are broadly negative, mainly zero to -4 but with some colder air in the mix at this time. From here, the divergences become considerable. It looks as though heights to the south and south east over Europe are much stronger and that keeps the trough and the jet further north. The Greenland ridge doesn't extend as far south and east and the Atlantic trough is aligned positively across northern and western Britain and into Scandinavia leaving southern and eastern areas in a mild or very mild SW'ly air flow by T+180. +4 850s for the south, -4 uppers for the north so quite a sharp gradient. Moving on and strong heights to the south over the Mediterranean continue to keep the trough to the north and west and feed very mild air up over the British isles and north western Europe by T+240. An awful 850 chart for coldies with very mild air (uppers to +8) spreading across western and central Europe and any colder air kept well to the north and east.

12Z ECM - Parallel is a right kick in the gonads for cold fans but it shows what can happen if heights get too powerful to the south. On then to ECM and by T+120 most of the puzzle pieces are where they should be. The LP is to the north of the British Isles with the trough back into the Atlantic and heights building toward Greenland. The last of any milder air is clearing out of the south-west with colder air moving down across the British Isles by this time. The LP extends east and south east across or to the east of the British isles and by T+192 has a centre over the Baltic leaving a slack flow over the British Isles. Heights extend south and east from Greenland at this time. Uppers are -4 to -8 with even colder air coming down into northern Scotland. In the following 48 hours, the trough remains over or just to the east of the British Isles with a new LP over southern England by T+240. The Greenland heights are perhaps starting to weaken. Cold air persists over the British isles with uppers below -8 in many areas.

I make it 3-1 to cold at T+240 this evening and the synoptic evolution of GFS OP, ECM and GEM isn't too dissimilar. Parallel fails because it blows up heights over the Mediterranean which stops the trough sinking over the British Isles and north-west Europe. Moving further ahead, let's see how the vastly divergent GFS OP and Parallel continue further into FI (T+312 and T+384 respectively).

It's all very battleground - oddly enough, Parallel is mostly mild but ends colder while OP is mostly cold but ends milder (at least for southern areas). Neither has a raging PV strangely enough but both wash the warmer uppers out of Greenland by about T+288 after which there's plenty of weather if southerly-tracking LP systems are of interest. As for Control, a thing of beauty for fans of snow with the LP systems a smidgen further south so the colder air remains over most of the British Isles with plenty of Channel-type LP systems.

On to the 10 HPA charts, the warmings from the Siberian side continue but the vortex seems more resilient and holds the line.

Conclusion: the temptation will be to look to the north or the east but the key place to look is the south. For the cold air to hold over the British Isles, we need to keep heights as low as possible to the far south especially over the Mediterranean. Parallel is a nightmare for coldies because strong heights over the Med and south-east Europe stop the trough dropping far enough south to put the British Isles on the cold side and instead we get a flow of mild or very mild SW'lies with the cold air held to the north and east. The other models all profile this differently but the future evolution of the "battleground" is also dependent on the profile to the south. IF the trough digs deep enough in the Atlantic, heights rise across southern Europe, the trough aligns positively and the milder air prevails. If it doesn't, shallow areas of LP can run east into north-west Europe and the British Isles stays on the colder side. It is, as someone has said, a "high risk high reward" scenario. Parallel shows what can go wrong, Control shows what can go right. It's on a knife edge.

[Matt H]

4 minutes ago, Radiating Dendrite said:

Not to play devil's advocate but we heard the uppers will get colder mantra with the lead up to the last cold spell and they didn't. 

In regards to -8c uppers, has them last week and got 36 hours of rain. 

I'm quickly learning that only -10c guarantees snow.

It depends on dew points as well though. So many factors have to come together for decent snowfall.

[Cheshire Freeze]

2 minutes ago, Radiating Dendrite said:

Not to play devil's advocate but we heard the uppers will get colder mantra with the lead up to the last cold spell and they didn't. 

In regards to -8c uppers, has them last week and got 36 hours of rain. 

I'm quickly learning that only -10c guarantees snow.

This is exactly the pertinent point. 

Of course you can get snow with -5 or -6 uppers but it's a lottery. You could just as easily see rain and the usual grey and drab scenery. The upcoming pattern looks good, but it flatters to deceive. 

The last cold spell I saw one fall of snow that gave a cm or two which then swiftly melted. A series of milder sectors in the N flow meant rain and not snow. 

If you want a proper, non marginal, cold spell then today's output is utter tosh.

[Chertseystreamer79]

37 minutes ago, Zak M said:

Good ECM this evening! The cold starts to flow towards us as early as day 7!

I think the UKMO is on its own here. It seems to be the only model that actually phases the lows in the Atlantic.  It will be interesting to see whether it will continue phasing them tomorrow - hopefully the ECM doesn't latch on to this!

My mocks was scheduled for this month and if schools didn't close then I would have been extremely busy revising. I am a little annoyed at this, but there are loads of positives - one of them being the fact that I can sit at home for most of the day watching the models, and, if this ECM run comes off, I could spend most of the day enjoying the snow if any falls.

Away from all of that, it is looking very promising towards the end of the month. Exciting times ahead!

12 ukmo phased them  at 144 it didn't...did I miss something else?

Please enlighten?

[danm]

2 minutes ago, Jason M said:

If the people up north can't talk about the cold they are going to get and the people down south can't talk about the rain they will have, what's left to talk about? Sorry, but one of my pet hates is posts that tell others what they can and can't post.

The people up north are probably right to be a bit excited whereas the so called 'moaners' are also right to talk about the limitations of what we are seeing. Otherwise you just end up with mad unjustified ramping and a thumping great forum hangover when the cold spell that was literally never modelled fails to turn up (as per last couple of weeks).

FWIW I think snow is now highly probable Midlands northwards and whilst much less certain its very possible south of this. Its certainly a better position than the last so called cold spell because whilst 850s don't look much different its a different type of airmass. The disappointment is that yet again we can't sustain stable heights at a northerly latitude to our N or NE during the three key winter months and that limits the scope of what is achievable. 

By all means people can talk about where is or isn’t more likely to see snow, but the constant complaining (or gloating) when the action is still so far from the reliable is what I don’t think adds to the thread. It makes it very frustrating and less of a pleasant place. 

[Zak M]

Just now, Chertseystreamer79 said:

12 ukmo phased them  at 144 it didn't...did I miss something else?

Please enlighten?

Whoops, sorry. That's my fault. Not sure how I didn't notice!

[Timmytour]

I'm getting the Stellas in ready for the pub run.....

[Methuselah]

There are a few people on here (mostly, but not exclusively, born/residing north of Hadrian's Wall) who seem to think that we, here in the SE, have hogged all the snow, these past few years. We'ell blow me down with a snowflake, were the lying snow, courtesy of 2018's BFTE, not the only lying snow I've seen, since 2013!

Come on peeps... It's all swings and roundabouts!

[Singularity]

3 minutes ago, Met4Cast said:

Yes they did.

Initially we were looking at uppers around -4/-5c, they upgraded to around -8c as the time got closer. The reason for rain last week was due to a warmer surface layer, mostly down to the lack of proper cold across Europe + a warmer than average North Sea modifying the temperatures. 

850hPa's weren't the problem.

This.

I think too many on here are using that spell of weather as a benchmark for next week. Due to different airmass origin, that’s not a valid approach. 

It’s very difficult for the UK to see much below -5*C 850s within a broad trough due to all the vertical mixing that goes on - but this also lowers the freezing level compared to non-trough conditions.

On top of all this, sea temps have inevitably cooled a bit since the last spell - especially nearshore where the cold air temps made their mark.

[Chertseystreamer79]

2 minutes ago, Zak M said:

Whoops, sorry. That's my fault. Not sure how I didn't notice!

It was weird at the time too...and short lived but hey...now all the models didnt phase them!!!

[Bartlett High]

5 minutes ago, Timmytour said:

I'm getting the Stellas in ready for the pub run.....

Ha ha...my pram is amply stocked and the sertraline locked away in the cupboard.....for now!

[Allseasons-Si]

As i mentioned earlier that i would post the day ten means side by side and here they are

EPS and GEFS mean anomalies...

i hope you like them cos i do,...going to watch footy now and i will be back later for the pub  lockin...

later's.

 

[feb1991blizzard]

3 minutes ago, CreweCold said:

This is exactly the pertinent point. 

Of course you can get snow with -5 or -6 uppers but it's a lottery. You could just as easily see rain and the usual grey and drab scenery. The upcoming pattern looks good, but it flatters to deceive. 

The last cold spell I saw one fall of snow that gave a cm or two which then swiftly melted. A series of milder sectors in the N flow meant rain and not snow. 

If you want a proper, non marginal, cold spell then today's output is utter tosh.

Whilst i agree slushfests are not my thing either really, a screaming E'ly or NE'ly is the only thing that floats my boat, decent uppers are still poised across Norway at 240, disappointing update on the eps extended from bluearmy though, a bit gutted about that, but cold uppers not guaranteed to get blasted out the way, and while as long as they remain there, we are still in the game.

[Frostbite1980]

5 minutes ago, Bartlett High said:

Ha ha...my pram is amply stocked and the sertraline locked away in the cupboard.....for now!

Citalopram is my tipple and it has the word pram in it now where are those toys

[IDO]

14 minutes ago, Met4Cast said:

Imagine throwing your toys out of the pram when you've got an EPS mean like this.

Better than anything we've seen since 2018. Seriously, some of you need to temper your expectations. Not every single cold spell is going to be the next BFTE or 2010. The pattern looks great going forward. The Det runs will continue to chop and change, and whining about 850hPa temperatures 10 days away is a complete & utter waste of time.

Of course, d10 uppers can change but I would not say it is a waste of time to look for the cause and effect of the current modelling of their temps and discuss the likelihood of upgrades?

This is the mean anomalies for 850s for the next 10-days and as a mean it should give us an idea as to what to expect with this pattern:

 London>

The ecm mean currently shows no sign of being able to sink colder uppers to the base of the trough (cut-off low) where the UK is? Even the coldest runs showing no wild runs, that is indeed relevant to the setup.

Anyway we are over the first hurdle and synoptic wise no complaints and now down to what develops post-d10 to get a blocked pattern with cold and snow? Too early to say whether this pattern is likely to hold, though neither ecm or gfs look to keep the GH for more than 4-5 days atm.

The usual caveats: (1) that uppers are not the be all or end all, but they certainly take the marginality away if they were colder for us in the south in lowlands? (2) the pattern may change, but surprisingly there is solid inter-model support for up to the d10 phase (ecm, gfs and gem means). (3 And the further north the better for cold.

 

[PolarWarsaw]

14 minutes ago, Radiating Dendrite said:

Not to play devil's advocate but we heard the uppers will get colder mantra with the lead up to the last cold spell and they didn't. 

In regards to -8c uppers, has them last week and got 36 hours of rain. 

I'm quickly learning that only -10c guarantees snow.

The flip side of the above is that 850's aren't the only significant factor in snowfall for the UK? 

(Has this been mentioned before on this forum? )

The previous cold spell had air sourced from milder locations in Europe and thus, all supporting factors for lowland snowfall weren't in the right place. What is shown on tonight's ECM is sourced from much colder air. 

DP's and 850's hand in hand would be much more likely to provide, even for those in the South. 

Battleground and 'North of the M4' will be used a lot in the next week or 2 IMO. 

[Methuselah]

6 minutes ago, Bartlett High said:

Ha ha...my pram is amply stocked and the sertraline locked away in the cupboard.....for now!

Have a problem? Call netweather's baby counsellor: 

[Radiating Dendrite]

16 minutes ago, Met4Cast said:

Yes they did.

Initially we were looking at uppers around -4/-5c, they upgraded to around -8c as the time got closer. The reason for rain last week was due to a warmer surface layer, mostly down to the lack of proper cold across Europe + a warmer than average North Sea modifying the temperatures. 

850hPa's weren't the problem.

There was a patch of -8c for about a day - hardly a fantastic upgrade. 

This feels like another great looking synoptics but poor 850s saga. I am being a little IMBY, bet as a SE member who has seen sod all bar the odd frost for three years, I think I have every right to be.

[Battleground Snow]

Remember back to just 48 hours ago when the ECM and EPS were not interested in a Greenland high... Are we really going to say that the uppers in days 8, 9 and 10 are going to verify as shown? 

Most important development today is no phasing and WAA up to Greenland. Even this wasn't a sure thing at 7am this morning.

Edited January 12, 2021 by Battleground Snow

[jacke]

I must get out of my outlets seat for a moment. If you have not closely read Catacols latest post, please do, so much common sense. As a lurker it is perhaps easier to track comments as well as the charts and trends. Firstly the comments overall. I suspect I am not alone among us quiet ones in saying this forum is on the verge of sinking into a mindless table of counter comments and petty back biting of some members. Please think a little before you write. Please do not let this fabulous forum sink into the mire.

No professional background in any of this but years and years of chart and weather watching. So dare I say that this has been a season of too much 850s fear and loathing. Yes of course they are important but not in the single isolation that some members place them. The fact that there are reasonable charts showing them this winter instead of the normal westerly dross has led to them being taken out of context.

Like most on here I am pretty baffled by the swings and roundabouts of the current output. What I am convinced off is substantial change around the period 19th Jan onwards which has been the projected period for many members. I also feel that changes will not be dramatic as some may think but will beon the cooler side at least. The background theme of most charts will be sadly wrong if that is not the case. And remember Cooler surface temps can be an important factor to coldooling not just 850s. This is not likely to be a repeat of the Dec attempts. Much more in our favour, historically the actual period of winter. My father was always adamant that the 1947 winter came out of the blue so never give up on some extreme weather if that is your thing. As a passing comment, having lived in the same location for nearly 70 years I have noticed how many coastal gulls move inland to my location if severe cold or particularly cold easterlies are afoot. You won't find them on a chart but I will post if I see an increase over the coming days! 

[Malcolm Edwards]

1 minute ago, jacke said:

I must get out of my outlets seat for a moment. If you have not closely read Catacols latest post, please do, so much common sense. As a lurker it is perhaps easier to track comments as well as the charts and trends. Firstly the comments overall. I suspect I am not alone among us quiet ones in saying this forum is on the verge of sinking into a mindless table of counter comments and petty back biting of some members. Please think a little before you write. Please do not let this fabulous forum sink into the mire.

No professional background in any of this but years and years of chart and weather watching. So dare I say that this has been a season of too much 850s fear and loathing. Yes of course they are important but not in the single isolation that some members place them. The fact that there are reasonable charts showing them this winter instead of the normal westerly dross has led to them being taken out of context.

Like most on here I am pretty baffled by the swings and roundabouts of the current output. What I am convinced off is substantial change around the period 19th Jan onwards which has been the projected period for many members. I also feel that changes will not be dramatic as some may think but will beon the cooler side at least. The background theme of most charts will be sadly wrong if that is not the case. And remember Cooler surface temps can be an important factor to coldooling not just 850s. This is not likely to be a repeat of the Dec attempts. Much more in our favour, historically the actual period of winter. My father was always adamant that the 1947 winter came out of the blue so never give up on some extreme weather if that is your thing. As a passing comment, having lived in the same location for nearly 70 years I have noticed how many coastal gulls move inland to my location if severe cold or particularly cold easterlies are afoot. You won't find them on a chart but I will post if I see an increase over the coming days! 

That interesting regarding gulls moving inland. I too have noticed some rare birds appearing here in marazion. Sign of things to come? 

[Penrith Snow]

1 hour ago, East_England_Stormchaser91 said:

It’s funny this obsession with a West based NAO. I’d rather see a West based NAO than a big +NAO

Also, if the West Based NAO is a very large one, it could still extend its influence and land us with some very cold weather and will drive the jet stream way south. 

The advantage of a NAO that is slightly west based is that the Arctic air spends longer over the North Atlantic and approa hes the UK from the West. Ok this lifts the uppers but massively increases the chances of snow a across the bulk of the UK. Surely that's better than a screaming frigid direct northerly where you have to be on the beach at Scarborough to see any snow.

I understand its maybe not the  best situation for the southeast but you are at risk from runners along the troughs bottom.

Prizes for all!

Andy

[East_England_Stormchaser91]

4 minutes ago, Penrith Snow said:

The advantage of a NAO that is slightly west based is that the Arctic air spends longer over the North Atlantic and approa hes the UK from the West. Ok this lifts the uppers but massively increases the chances of snow a across the bulk of the UK. Surely that's better than a screaming frigid direct northerly where you have to be on the beach at Scarborough to see any snow.

I understand its maybe not the  best situation for the southeast but you are at risk from runners along the troughs bottom.

Prizes for all!

Andy

Absolutely right. Plus we are a small island, where 200 miles of a pattern shift can win or lose you the game! It’s very fine margins.