Model output discussion - The Hunt For Cold

[MattStoke]

Just now, AppleUK 123 said:

Indeed Matt, but I am worried somewhat. For eg, the video posted today by the Met Office,  "I've been talking to the medium range guys, longer range forecasters in regards to snow at end of November and they say there is no strong signal for that!" Absolutely devastated that the Met Office don't seem to agree with current output.

Met Office are always sensibly cautious at such range. ‘No strong signal’ doesn’t necessarily rule it out, and it’s too far away to talk about snow prospects anyway. 

Even if there’s no deep cold/snow in the next few weeks, the general picture for the winter ahead looks promising. Much rather be in this position now than be chasing cold and snow at the tail end of winter knowing it’s ‘now or never’ for this season.

Not going to get sustained raging westerlies in the near to medium term with the current model output. Look at how much high pressure there is in the Arctic region and how disrupted the PV is! Models also show a nice cooling down of continental Europe over the next couple of weeks, which can help bring a negative AO and mean more cold air to tap into further down the line should we get another easterly. Seasonal models also show a lot of northern blocking during the winter ahead. Not that I think seasonal models are worth much but it is good to have them on board.

[Met4Cast]

2 minutes ago, AppleUK 123 said:

Hello Daniel, always enjoy reading your tweets! Wouldn't it be more preferable for a Greenland high which will allow proper cold upper air temperatures towards us, rather than a Sceuro?

I think an Iceland/Greenland high would probably be preferable, it’d allow colder air to dig down into Europe on the Eastern flank as per the 12z GEM and almost 12z ECM. 

But.. a scuero high certainly wouldn’t be mild, but it wouldn’t allow proper cold to filter down towards the UK, unfortunately that does seem to have been a trend within the ops for todays runs, the ensemble means not quite showing that yet though, could be a case the higher definition of the ops is leading the way, or the ensembles have got a hold on it overall, time will tell!

[Met4Cast]

ECM day 10

Pretty decent ensemble mean there, strong signal for heights to be centered around Iceland extending from Greenland across to Scandinavia, good signal for low pressure to the South too, this is something we want to see continue going forward as it’s the ideal setup for getting true cold into the UK at this time of year.

ECM day 15

Naturally far more watered down with different ensembles offering different solutions but the general trend is still evident, high anomalies strongest to the North of the UK, Iceland > Scandi, though a signal for heights extending down into Europe with perhaps low pressure having more of an influence towards the South and West. 

I can’t make a habit of posting these charts since they’re behind a paywall unfortunately.

[jules216]

The EPS ensemble mean suggests that deterministic run was in a very mild cluster category 

[feb1991blizzard]

3 minutes ago, Daniel Smith said:

 

Is the trend from D13 D14 to D15 to push the low heights SE under the block or does it look like they are going to be pulled back into the Atlantic and the back end sag out the high and the whole thing collapse?  either way its still a mean SE flow at D15 from a 51 member suite so it aint too bad whatever.

[Midlander]

 

1 minute ago, Daniel Smith said:

I think an Iceland/Greenland high would probably be preferable, it’d allow colder air to dig down into Europe on the Eastern flank as per the 12z GEM and almost 12z ECM. 

But.. a scuero high certainly wouldn’t be mild, but it wouldn’t allow proper cold to filter down towards the UK, unfortunately that does seem to have been a trend within the ops for todays runs, the ensemble means not quite showing that yet though, could be a case the higher definition of the ops is leading the way, or the ensembles have got a hold on it overall, time will tell!

Yes definitely a case of more runs needed. I hope the Operational's this time are incorrect, but that is just my preference. The recent seasonal models do hold interest and do look really promising, especially compared to previous Winters. But I've always been one to get the best synoptics possible early on. I personally prefer to see the Wintry weather during the first half of Winter due to the shorter days. I do worry though when I hear people saying there be further chances down the road, because eventually one of these potential chances need to come to fruition otherwise we'll be in the same position as now in late Feb.

[northwestsnow]

Ec mean suggest to me its quite a way back to a +NAO set up post day 10..

[Met4Cast]

3 minutes ago, feb1991blizzard said:

Is the trend from D13 D14 to D15 to push the low heights SE under the block or does it look like they are going to be pulled back into the Atlantic and the back end sag out the high and the whole thing collapse?  either way its still a mean SE flow at D15 from a 51 member suite so it aint too bad whatever.

Difficult to say - There is a trend Eastwards of the low between day 10 & 15 but the center of the anomaly sits West of the bay of biscay so I would assume there’s a number of EPS members that go for a full undercut but also many that don’t 

Edited November 15, 2018 by Daniel Smith

[Summer Sun]

A quick look at the 12z ECM graphs and the mean and op are in good agreement up to the 18th and again from the 21st to 24th

Pressure wise they don't agree as well after the 19th so still plenty to resolve on this front yet

A quick look out in the Atlantic at that low and we can see how much support it has...

 

[Mizzle]

1 hour ago, terrier said:

I agree the ecm does look a lot better this evening. But regarding 7-8c next week I think that will be pretty close. Don’t forget the North Sea is still around 12-14c which will moderate cold to our shores quite considerably. 

Forgive the newbie question, but what is the ideal sea temp for snow? I started weather watching about a year ago and understand warmer SSTs help create snow. Is it the temp itself that is important, or just in relation to upper air temp?

[Mapantz]

Just a friendly reminder folks; Can we keep on topic and refrain from Met Office discussions in here please?!

We have threads open for more general chit-chat:

[Duane S.]

People can bleat on about the Atlantic as much as they like, it is not, nor will it be, Atlantic dominated for a while. No doubt one or two will claim they were, yawn, correct when a system nudges in close by from the Atlantic, which it will, of course. There is a world of difference between Atlantic dominance and Atlantic influence. Even the best UK cold spells in history had plenty of periods where the weather started coming in from the west at times. It’s how readily the Northern Hemisphere atmospheric state is predisposed to Blocking that will determine whether we get the default prevailing uk weather or something, on occasion, much colder. That is of course is all determined by a myriad of drivers working with and against each other upstream. Enso, snow cover, QBO, MJO etc and then tweaked, for better or worse, by more localised factors.

If 0 = Flat global jet, raging PV, zonal as far as the eye can see, all backed up by the background signals.

and

10 = Eye popping eye candy charts day in day out, cross suite agreement (within realistic reason), solid ens,  highly amplified meridional jet, all backed up by the background signals.

We probably have ourselves a firm 8 going on 8 and a half to 9. 

To get a cold spell in ‘phase’ 0 is literally zero. There is no hope whatsoever. Unfortunately of course the opposite can never be said for being in a higher ‘phase’. It just increases our chances away from zero to something. Got to be in it to win it.

The Continental feed IS all but nailed on. It’s where we go thereafter that is massively up in the air. We can go whole winters without this much potential and we are only in mid November. Happy days.

The only word of caution ifrom me is beware the saggy Eastern side. I’ve  seen this before and it is often the ECM that picks it up first. Although it normally arises from an Azores High retrogression into Scandi. However, it does look like we may get 2 or 3 shots at cold, so  if the first doesn’t give -40 and 5 feet of snow, we should keep the toys in the prams for a bit longer at least. 

[I remember Atlantic 252]

3 minutes ago, s4lancia said:

People can bleat on about the Atlantic as much as they like, it is not, nor will it be, Atlantic dominated for a while. No doubt one or two will claim they were, yawn, correct when a system nudges in close by from the Atlantic, which it will, of course. There is a world of difference between Atlantic dominance and Atlantic influence. Even the best UK cold spells in history had plenty of periods where the weather started coming in from the west at times. It’s how readily the Northern Hemisphere atmospheric state is predisposed to Blocking that will determine whether we get the default prevailing uk weather or something, on occasion, much colder. That is of course is all determined by a myriad of drivers working with and against each other upstream. Enso, snow cover, QBO, MJO etc and then tweaked, for better or worse, by more localised factors.

If 0 = Flat global jet, raging PV, zonal as far as the eye can see, all backed up by the background signals.

and

10 = Eye popping eye candy charts day in day out, cross suite agreement (within realistic reason), solid ens,  highly amplified meridional jet, all backed up by the background signals.

We probably have ourselves a firm 8 going on 8 and a half to 9. 

To get a cold spell in ‘phase’ 0 is literally zero. There is no hope whatsoever. Unfortunately of course the opposite can never be said for being in a higher ‘phase’. It just increases our chances away from zero to something. Got to be in it to win it.

The Continental feed IS all but nailed on. It’s where we go thereafter that is massively up in the air. We can go whole winters without this much potential and we are only in mid November. Happy days.

The only word of caution ifrom me is beware the saggy Eastern side. I’ve  seen this before and it is often the ECM that picks it up first. Although it normally arises from an Azores High retrogression into Scandi. However, it does look like we may get 2 or 3 shots at cold, so  if the first doesn’t give -40 and 5 feet of snow, we should keep the toys in the prams for a bit longer at least. 

Nothing worse than that! chasing the dry windows, hoping they're timed for the day

[bluearmy]

36 minutes ago, jules216 said:

The EPS ensemble mean suggests that deterministic run was in a very mild cluster category 

 

Have removed the chart jules ..... we can self regulate posting paywall stuff but I believe when we do post them we should crop the charts to show the specific area we want to reference ...... we do run the risk that someone in Reading emails Paul to complain 

anyway, I’m not really understanding why you feel that T282 mean chart is out of kilter with the ec op which was building deep cold to our ne day 10. 

[Mike Poole]

Not much time to look at the models during the day, catching up with this thread now,  just before the 18z, a few things occur to me:

We've firmed up that the core high heights will be in the Greenland to Iceland area by day 10 and beyond.  Whether the area of high heights will extend to other areas is uncertain on the same time scale, so left on the table are the fairly extreme cold runs such as today's GFS 6z and yesterday's FV3 12z, but the ECM 12z of yesterday pulling the high back into Europe also possible.

Looking forward, from a cold/snow point of view, I think we want to see the centre of the high to remain as modelled, but to keep low heights into the SE, and anything from the Atlantic to slide under the block.  For snow, particularly in the south, we do need to see some longevity of the pattern, just because it's so early in the season.  

Let's see what the pub run brings...

Edited November 15, 2018 by Mike Poole

[Methuselah]

The most important consideration, for me, is that continental Europe has sufficient time in which to really cool down - temps of -20C or less will do fine - so that any subsequent easterlies will be brutal enough to give us what we all (most of us, anyway!) want: snow, snow, snow and yet more snow, all punctuated by a few short-lived periods of snow...

Anything that keeps European winds coming from the Arctic will do nicely!

Edited November 15, 2018 by Ed Stone

[damianslaw]

As occurred, deep cold air can quickly pool over the continent as we move into December, its density can become preety profound and this difficult to shift, if and this is the big factor, we maintain a rather sluggish jet. There are no signs of a rampant jet setting up shop anytime soon, as there hasn't been since February.

The end of November will see more energy transferred unusually so into the southern arm of the jetstream, and thus likely to say there as we enter December. I suspect any atlantic attack will be fractured, stutturing into nature, disrupting trough springs to mind as the block holds firm to the north and east. Its just how I see things.

 

[ALL ABOARD]

18z icon slightly better tonight as the high punches further into Greenland compared to its 12z .. Small steps 

[SMU]

ICON 18z is awsome all the way to 120-

much better cut of deep cold into scandi - indicating the cleanest possible route to deep cold a couple of days later-

best run yet in a good timeframe ~

[Mike Poole]

Upgrade at T120 on the ICON 18z, with the high modelled a tad further north, 18z first, 12z second at same time:

Block also strong at high latitude on the JMA at T192:

[weatherguy]

Yup, the ICON giving us the lovely "surprised bear" NH pattern at 120h...

Good to see the high being cut off slowly in the east.

[Derecho]

2 hours ago, mb018538 said:

I don’t understand what some people were expecting? Maxes of 2-3c? Reality check - it’s still November, the seas were very warm this year after the hot summer, and the uppers aren’t bone chilling. 6-8c is perfectly reasonable. If it had been 2 months later it’s a different ball game.

Get sufficiently cold uppers and the maxes will tumble and the warm seas will be a snow machine. It had been a possibility if the high retrogressed to Greenland and it would have brought in a sufficiently cold spell that would have delivered something snowy for many areas.

As it is though we just have a dull week with maximum temperatures a little below normal. We can do much better then that during November. Fingers crossed future runs bring back the idea of retrogression.

Edited November 15, 2018 by Quicksilver1989

[Optimus Prime]

16 minutes ago, damianslaw said:

As occurred, deep cold air can quickly pool over the continent as we move into December, its density can become preety profound and this difficult to shift, if and this is the big factor, we maintain a rather sluggish jet.

 

Always wondered whether this statement is scientifically proven? It's common knowledge that colder air is denser than warmer air, but is it actually that hard to shift for this part of the world (surrounded by the ocean and the winds)

There are certainly examples where the cold appears to form a wall against warmer moister air, but there are equally as many examples where cold air has been quickly pushed well away despite all the odds.

I think it's more to do with pressure. Wherever the pressure moves, the air will be displaced with it regardless of density. Even huge cumbersome cells of high pressure tend to get easily overwhelmed in this part of the world. 

[SMU]

2 minutes ago, Quicksilver1989 said:

Get sufficiently cold uppers and the maxes will tumble and the warm seas will be a snow machine. It had been a possibility if the high retrogressed to Greenland and it would have brought in a sufficiently cold spell that would have delivered something snowy for many areas.

As it is though we just have a dull week with maximum temperatures a little below normal. We can do much better then that during November. Fingers crossed future runs bring back the idea of retrogression.

Also have a slight SE flow & the airs going over about 26 milea of water !!!

Im still certain on a few snow flakes her next week @150M

[Derecho]

6 minutes ago, Steve Murr said:

Also have a slight SE flow & the airs going over about 26 milea of water !!!

Im still certain on a few snow flakes her next week @150M

Yeah I do think with elevation show showers are a possibility in the SE, its a shame that the continent was so warm during the first half of this November as it could have made a difference but the continent can cool down quickly.

Nevertheless I'm hopeful that blocking conditions will occur in winter given the lower sea ice will reduce the temperature gradient between high and mid latitudes (weaker jet) and we have a solar min on the way. If we build the cold up nearby over Europe I don't mind missing out on something snowy for the timebeing. We have had more meridional jet stream patterns in recent years its just often been the case that NE Canada has been in the right place to our cost, one can hope this year Europe is in the right place!

Anyhow all eyes on the 18z