Model Output Discussion - Snow for some, but what else is in store?

[Chesil View]

And now the ECM op joins the party. The incremental weakening of the Atlantic flow. Just a couple of days ago we had long fetch southwesterlies surging across the UK around day ten. Now the trend is one of increased amplification. Albeit still yet to push the whole of the UK into cold air but it feels as though that may be the direction of travel towards the end of January.

[Griff]

5 minutes ago, bluearmy said:

The strat has been rock solid on the ridge establishing around the n Atlantic sector from the north  in week 2 ....perhaps the 12z runs are beginning to sniff that imprinting onto the trop ..... let’s see how many eps members drift that way - mwb has indicated that this isn’t a completely left field option ...

 

2 minutes ago, Tim Bland said:

Early Feb often delivers a cold spell so wouldn’t be surprised if day 12-14 sees a ridge. It will probably be last chance saloon. Just gutted that after the promising start in Dec (PV never really got going ) followed by an early SSW, we still couldn’t get a decent cold spell in the heart of winter  

I'm not sure anyone wants to wait until the end of March for confirmation that we missed out on significant cold from the SSW, but from the little I've read on the subject it's far too soon to be drawing conclusions. Initially a lot of speculation here, mostly hoping for QTR, but any disappointment there in doesn't guarantee outcomes yet to play out. 

It would seem very prudent to keep a close eye for strat to trop effects. I thought that was the nature of the game, we wait and see

[Vikos]

8 minutes ago, Mike Poole said:

I think it could link with the previous high, as per:

Which would give a stronger ridge upstream of the UK, less sure re your location!

Ok... more runs needed

And south GB shares the same latitude with Germany (around 50°N)

But bluearmy pointed out something very good, indeed....

12 minutes ago, bluearmy said:

The strat has been rock solid on the ridge establishing around the n Atlantic sector from the north  in week 2 ....perhaps the 12z runs are beginning to sniff that imprinting onto the trop ..... let’s see how many eps members drift that way - mwb has indicated that this isn’t a completely left field option ...

Lets wait for the clusters....

[bluearmy]

4 minutes ago, Vikos said:

Lets wait for the clusters....

Little indication from the mean that it’s more than a handful 

[Frosty.]

I think this is the best ECM day 10 chart I’ve seen for a while, just when it looked like the wheels had come flying off..day 10 totally redeems itself..reminds me of a scene from dumb and dumber...now I want to see days 11, 12 & 13!!!!!!!!!

Edited January 17, 2021 by Jon Snow

[PolarWarsaw]

1 hour ago, Gadje said:

'gefs mean at d13 '  no comment.

Hi Gadje, 

Discussing a day 13 mean from the GFS that's actually going out of commission because of it's notorious woeful performance, especially after the Day 10 period, right during the middle of a period of time where the models haven't got a clue what's going to happen at Day 5. 

In terms of the models today, you really do have to feel sorry for the South, specifically those south of the M4. I am not hopeful of seeing snow towards the back end of the week as far South as Birmingham, so at this point I'd put the discussed areas above at no more than a 5% chance of seeing snowfall at the end of the week. Buxton north could see quite a wintry spell again from Thursday onwards. There has been a real divide across the country so far this year, more so than I can remember normally. 

In terms of realistically understanding where we go during this complex time, a point to remember whilst reading and one that is more apparent now and will be this week more so than usual, is reading the location of the poster commenting. There will be a large difference in tone of post depending on location.

It's not a perfect scenario, but we are still in a more promising, if frustrating situation than normal - there's plenty of marginal snow events on the horizon IMO, it just depends whether the exact IMBY nature of things is snow, or rain. 

 

Edited January 17, 2021 by Paul

[Don]

39 minutes ago, prolongedSnowLover said:

Weakly negative NAO with low pressure to the North East of the U.K. isn’t conducive to a severely cold spell.

I might be talking rubbish but didn't the cold spell of February 1991 coincide with a positive NAO?  I believe that winter had a positive NAO overall but was still cold.

[Daniel*]

2 minutes ago, Don said:

I might be talking rubbish but didn't the cold spell of February 1991 coincide with a positive NAO?  I believe that winter had a positive NAO overall but was still cold.

Yeah with +NAO you can still see cold spells. But we usually look to NE for blocking.

 

[stodge]

Evening all

A much more pleasant day in lowland East London - dry with some bright or sunny spells. Certainly after the recent chill and wet, a pleasant change but last night's models suggested rain and large amounts of it would be the dominant feature of our weather for the rest of the month. 4-5 inches of rain in the next 10 days for some western and south-western parts so let's see if the wet theme continues with controlling LP to the north and a series of secondary features coming off the Atlantic and moving through southern parts. Mild in the south but colder with opportunities for snow further north.

Onwards and sideaways.

12Z GEM: T+120 takes us to Friday by which time the main LP is to the north-east of Shetland with a NW'ly air flow over the British Isles. The next Atlantic LP is well off to the west with heights over the Canaries and Greenland at this time. 850s of -4 to -8 across the British isles by this time.  From there, not much changes as secondary LP cross southern Britain with the main LP to the north and north east by T+180. The air flow remains WNW but with heights rising to the far south and the next Atlantic LP going nowhere in mid-ocean I suspect milder air is approaching but at this time it is only flirting with the far south while it remains cold in the north. From there the jet tries to push north but it doesn't quite happen and instead the Atlantic LP moves east across the British isles and basically the complex trough remains very much in charge with the Azores HP suppressed to the south. The initial push of mild air has been reversed by T+240 with cooler 850s of zero to -4 over most parts. I've added the cumulative rainfall chart for T+240 - again note the large totals for southern and western Britain.

GEM keeps the wet theme and while the south is never too cold, the north keeps the coldest air for longest so you'd think some snow would be possible and especially to higher ground.

12Z GFS OP - the storm GFS models is quite fierce and is around 955MB at T+96 - 24 hours later it's filled a little and moved NE towards Norway leaving a NNW'ly flow over the British Isles. By that time, 850s of zero to -4 in the south but -4 to -8 elsewhere as colder air digs in from the north. Moving on, the LP fills and heads back west and by T+180 is just to the north of Scotland with a slack NW'ly flow over northern parts. Further south, secondary LP off the Atlantic have moved across southern areas with heights over southern Iberia and North Africa. By T+180 uppers of -4 to -8 remain over most areas but milder air is approaching from the south west. From there, the evolution becomes messy and more interesting. The Atlantic LP tries to move north but is shunted back west as heights build from the Pole  while a small LP approaches from the south west and looks to run along the Channel. Milder air with positive uppers to +4 has reached southern and western areas but the cold hangs on especially in the north east. The rainfall totals look horrendous for north wales and north west England with 4-5 inches in the next 10 days so I wonder if we'll be seeing more flooding along the Severn later this month.

OP ends as a battleground with heights building down from the north. Intriguing.

12Z Control - with Parallel having ended its 30 day trial, I'll switch over to Control for a second bite at the GFS output. The T+120 isn't too far removed from the OP. Moving on, the secondary LP systems have been running across southern Britain but by T+180 a brief ridge is in charge but again I don't see huge differences from OP at this stage. Uppers of -4 to -8 remain across the British Isles at this time with milder air approaching. More differences with the OP at T+240 with the main Atlantic LP far to the west and a broad but slack trough across the north of the British Isles and Scandinavia. A new LP is approaching southern Britain with heights to the far north. Milder air has moved into the south but colder air remains over Scotland.

Control slightly different from OP but the broad theme of an Atlantic trough and a jet further to the south than you might suppose and residual heights to the far north.

12Z ECM - no huge surprises from the European model at T+120. Colder air is feeding down from the north by this time. Moving on and the Scandinavian LP continues to fill as a new Atlantic LP moves towards Ireland with the main system far to the west. Heights to the south and a SW'ly flow over most of the British Isles. Positive uppers are over Ireland and the south west but the north east in particular keeps colder air for now. As we know the road to hell is paved with tantalising T+240 charts from ECM and tonight is no exception. The LP moves east across the British isles and is over Denmark but with upstream amplification we end on a N'ly for the British Isles but the uppers aren't that cold yet.

Signs perhaps of renewed uncertainty in the model output as we approach month end - again, with no raging PV or Atlantic the opportunities for amplification are there. 

A quick glance further ahead at both GFS OP and Control in further FI:

Unfortunately, Control hasn't finished the 12Z but OP has and it's more than a little interesting. As I expected a few days ago, the Scandinavian HP finally comes into view and while the 500 chart might look like a near miss, the 850s tell a different story with some cold air for the end of the month and it remains very close by into February as a real east-west battleground develops and the Atlantic looks a lot quieter. Is this symptomatic of the MJO moving through 6-7-1 and offering some opportunity for amplification.

Conclusion: the immediate theme is wet but coming into the far edges of FI are more than a few hints of a new cold evolution with GFS OP leading the way and ECM hinting at something different. Let's see if this develops over the next few days as a new trend. For now, I'm much more worried about flooding.

[BlueHedgehog074]

Just a little heads up. For those discussing/complaining about other members in here with others, be better to carry on the discussion over Private Message. Thanks

[ScottSnow]

1 hour ago, prolongedSnowLover said:

The NH pattern is unfavourable to allow deep cold conditions over the U.K. especially in the South. Too much cyclonic between Scotland and Norway and an established positive NAO to allow anything other than normal winters weather.

The SSW has already failed to deliver with the vortex all set to recover during the remainder of the winter.

I disagree. The effects of a SSW usually take at least a month to be fully felt at the surface. This coupled with Feb usually being the winter month that the Atlantic is quietest I believe means we have the best chance of prolonged cold weather still in front of us. Also we now have cold air in Scandy Eurasia so if we do get favourable Synoptics they will hopefully produce widespread snow.

[chionomaniac]

I haven’t had time to analyse the models up to day 6 and work Out what happens next.  What I would have said that a period of unsettled weather would continue with both mild and cold outbreaks thrown into the mix with all three.  With the ensembles messier than a plateful of spaghetti I think it may be a few days before a new coherent signal is shown.

[Paul]

The GFS 18z may be delayed again tonight - NCEP having data dissemination issues again. 

[IDO]

9 minutes ago, PolarWarsaw said:

Hi Gadje, 

Discussing a day 13 mean from the GFS that's actually going out of commission because of it's notorious woeful performance, especially after the Day 10 period, right during the middle of a period of time where the models haven't got a clue what's going to happen at Day 5. 

 

You are my harshest critic, but I make no bones about it and never have, I focus on the medium term. There are plenty of comments on pre-d5 but that takes little in the way of interpretation from my POV as the verification is very good at that point. 

For me, looking at that d13 chart, here:

I am intrigued by the continuation of that reverse zonal flow to our north, in a mean at that range. That may in fact be an imprint from the strat? If not what is going on? These questions and possible answers pique my interest!

Posters still get excited by the much discredited d10 ecm height-biased charts but you do not disparage those. The ecm d10 mean:

We can all enjoy different aspects of model watching and if you disagree maybe some reasons other than it is d13, and your alternative take so we can have a pleasant discussion? Cheers.

[BLAST FROM THE PAST]

 

this epitomises what Roger is saying, the storm could very likely start sending further troughing further south...and that’s where this starts and leads to.

half of winter still ahead, I think we sit in a reasonable place going forward.

 

BFTP

Edited January 17, 2021 by BLAST FROM THE PAST

[Frostbite1980]

1 hour ago, prolongedSnowLover said:

Weakly negative NAO with low pressure to the North East of the U.K. isn’t conducive to a severely cold spell.

Neither is it a positive NAO like you are saying!

[damianslaw]

As said this morning it is a chaotic picture, and difficult to pinpoint eventual trends longer term. Models showing signal for secondary lows or runners zipping into the base of the deep trough and this would I imagine suppress any attempt for those Iberian heights to ridge north.

A very plausible evolution would therefore be increased amplification in the azores high, as these developments anchor down on the Iberian heights, kicking them west, trough then allowed to advect away east and most importantly SE into Europe, this would then allow height rises to our NE with the azores high riding over with a link up. Indeed this is exactly what the GFS is showing today.

All eyes mid week on these secondary low/frontal/runner features running into the base of the trough.

 

[Don]

4 minutes ago, damianslaw said:

All eyes mid week on these secondary low/frontal/runner features running into the base of the trough.

Yes. I would have thought there is potential for surprise snow falls cropping up just about anywhere towards the end of the week and into the weekend.  Perhaps some nowcasting scenarios?

Edited January 17, 2021 by Don

[Had Worse]

That straggling front over the Northwest is further south.

Edited January 17, 2021 by Had Worse

[Mike Poole]

Well the ECM clusters are a thing, 5 in the pre T96 timeframe, then 1 only in the next two timeframes, then 3 in the long range T264+:

So in the mid range there is too much uncertainty to split clusters, and then there is in the longer term.  This happens sometimes, particularly when a SSW is the hidden driver of patterns down here.  

So what of the 3 clusters?  Well some HLB is clear for all, but it is way too far north most of the time, Cluster 3 looks like a route to a Scandi high which would probably suit us best.  But don’t forget the uncertainty earlier.  

[damianslaw]

3 minutes ago, Don said:

Yes. I would have thought there is potential for surprise snow falls cropping up just about anywhere towards the end of the week and into the weekend.  Perhaps some nowcasting scenarios?

Yes definitely a nowcast situation. The models will struggle to pinpoint the development and trajectory of such features I imagine. I'm expecting the models to also position the major frontal feature due to arrive later tomorrow to a possible slightly more southerly position, with the colder air to the north have a greater forcing, this in itself could change the situation for later in the week to one more conducive for more widespread cold and wintry conditions.. 

Fax charts are the ones to look at first this week before the models I feel.

[sebastiaan1973]

Hardly any real cold members in the plume. EC240H average shows a cold Scandinavia.

On the long term it seems two variants: polar maritime and subtropical air

Edited January 17, 2021 by sebastiaan1973

[sebastiaan1973]

Interested in seeing the EC members ?

Model charts for Europe (Mean Sea Level Pressure) | ECMWF IFS HRES (10 days)

METEOLOGIX.COM

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ECMWF IFS HRES (10 days) - Current forecast valid for 01/29/2021, 01:00am of parameter "Mean Sea Level Pressure", model chart for map "Europe"

 

[BLAST FROM THE PAST]

2 minutes ago, sebastiaan1973 said:

Hardly any real cold members in the plume. EC240H average shows a cold Scandinavia.

That cold pool in Scandi is important imo.  That storm won’t pass through, then we see the future follow up troughs getting shunted on more southerly track as they won’t be able to follow it’s track.  This then opens doors to future developments.

 BFTP

[Malcolm Edwards]

I think the models are suffering from bye polar disorder.... Sorry mods couldn't resist.