Model Output Discussion - The Start Of Winter

[Nick L]

Aaaaand back to model discussion...

[Frosty.]

After my poor performance yesterday with negatives which are so unlike me when it comes to posting on here, I feel much better today and the models are firming up on an Arctic outbreak, what joy this is to see -8 T850 hPa flooding south with lots of snow showers peppering the UK and frosty nights BRING IT ON :-)

[bluearmy]

we have the first modelled wintry charts of the season upcoming (within a generally reliable timeframe) and as per winters prior to last, there are upgrades as well as the odd downgrade. We got used to so many years with downgrades that to see a solution where the intensity or duration of cold is increased within the next few runs is refreshing.

What we know is that there will be features running around the base of the upper trough. it would be a surprise if we got to the end of next weekend and nowhere across the uk found themselves with a decent snowfall. (Away from hills)

The extended ECM ens have consistently shown a push east of the Azores ridge as we get beyond mid month, bringing less cold uppers. That was reflected in the ens London T2 maxes. I wonder if a more pronounced trough next weekend may have an effect on this evolution?

[karyo]

Great to see the ECM offering wintry potential for next weekend in particular. The chart that Cloud 10 posted is snowfest even with -4 uppers as there is a slack flow from the land. Of course, that's only a possibility at this stage but nice to see.

 

On the other hand, both the GFS and the ECM seem confident in flattening the pattern after next weekend and tuning mild with no heights in the Arctic.

 

Karyo

[MR EXTREMES]

Great to see the ECM offering wintry potential for next weekend in particular. The chart that Cloud 10 posted is snowfest even with -4 uppers as there is a slack flow from the land. Of course, that's only a possibility at this stage but nice to see.

 

On the other hand, both the GFS and the ECM seem confident in flattening the pattern after next weekend and tuning mild with no heights in the Arctic.

 

Karyo

Indeed but when Ian f talks of nothing sustained through December does feel me with dread the models do reflect this to degree little worrying to say the least.

[karyo]

Indeed but when Ian f talks of nothing sustained through December does feel me with dread the models do reflect this to degree little worrying to say the least.

In a way we are making the best of a bad situation but I also get the feeling that our luck may be running out looking at the models past next weekend.

 

We need a stratospheric warming pronto!

[SMU]

Well its been a pretty decent couple of days - going from a mediocre chilly pattern to one that could deliver something a little more substantial.

 

The ECM is very interesting in the mid term, mainly for the central belt / North, however certainly nothing pinned yet. With sub -5c air & small shallow features that have developed in the flow the prospect of snow almost anywhere could crop up.

 

http://www.meteociel.fr/modeles/ecmwf/runs/2014120612/ECU1-192.GIF?06-0

 

What is perhaps equally interesting is the potential shown in the ECM for Atlantic ridging to align towards Scandi...

 

http://www.meteociel.fr/modeles/ecmwf/runs/2014120612/ECH1-216.GIF?06-0   We would need a bit more amplitude in the wave for this to come to fruition...

 

Lastly, after record breaking cold last year in the states- comes record breaking warmth this December with the +20 isotherm heading up into the central states!!http://www.meteociel.fr/modeles/ecmwf/runs/2014120612/ECH0-168.GIF?06-0

 

All in all an enjoyable period of model watching, even if it isn't quite the 'perfect' HLB synoptics

 

S
 

[kumquat]

Awesome to see some "South of the M4" charts - even if it is out in La-La land

 

[Frosty.]

On the other hand, both the GFS and the ECM seem confident in flattening the pattern after next weekend and tuning mild with no heights in the Arctic.

Karyo

I don't think the pattern will flatten out after next weekend, I can see further reloads of cold air from the nw in the run up to xmas..incidentally, the MO further outlook is for cold incursions mixed with less cold wet and windy spells into next year so no suggestion of mild mush taking over I'm pleased to say. Edited December 6, 2014 by Frosty.

[knocker]

Heres the saviour shortwave over Canada:

 

ECH1-144.gif

 

For newbies I've arrowed the direction of energy, the whole thing fluidly moves anti-clockwise, you can see this shortwave will engage the cut off low and it rides in on a more amplified wave upstream, as this phases it helps to pull those low heights nw and allows the high to ridge further ne.

 

The more dig of the jet over the eastern USA the further ne the high will get pushed, it does flatten out somewhat at T216hrs but I wouldn't worry about this just yet.

 

We have to hope for a bit more amplification in future runs, however the key trigger is that shortwave that gets the ball rolling.

 

I'm not too sure I'm following this Nick. Are you saying the low off the eastern seaboard engages the low Greenland and amplifies the upper trough leading to the situation  as shown? At the same time pushing Mid Atlantic HP east.

 

 

Charts courtesy weatherbell

Edited December 6, 2014 by knocker

[Methuselah]

 

 

All in all an enjoyable period of model watching, even if it isn't quite the 'perfect' HLB synoptics

 

S

 

Yes, Steve, I think you could well be right?? I do, however, think that when (if) it does happen, it'll initially take all the models by surprise...

[Polar Maritime]

A few posts have been moved/deleted/edited, Please only discuss the 'Model Outputs' as per thread title. There are other threads open for anything other than.

 

PM.

[bryan629]

Matt Hugo is going for a full on SSW  around Jan 7th .... good luck Matt with that . 

 

i got this from twitter and im really looking forward to that event, something else which is doing the rounds is the deep low progged for middle of next week has been marked as a sub < 930mb low. by Ryan Maue. 

 

Ryan Maue â€@RyanMaue  3 hrs3 hours ago

Warm seclusion / Icelandic Low forecast to generate 50-60 foot waves next week ... deep low pressure < 930 mb

 

 

Is it possible the models are underestimating the low values of next weeks storm?

 

edit... sos i meant over estimating the depth of next weeks storm 

Edited December 6, 2014 by bryan629

[Man With Beard]

Forecasters nightmare coming up next weekend. Experience tells me that snow is unlikely to be this extensive:

Also, we often see mild sectors creeping in as T0 approaches - if so, it's a case of how far east this goes?

I'd say if you live 150m above sea level, away from the coast, there's a good chance of seeing white stuff anywhere by next weekend. For lower areas, it's one of those instances where you may get a "surprise snowfall", but odds in favour of extremely cold rain with the odd flake on the windscreen.

[phil nw.]

Considering how little ridging there is overall in the jet flow across the Atlantic we are in a colder spell than a first glance at the 500hPa pattern would suggest.

The source of the west/north westerly flow is notably cold coming directly off Arctic Canada and the Greenland ice shelf with limited moderation over the Atlantic.

A look at T96hrs shows this quite well 

 

and as the coldest air continues south east later on this will bring the first real widespread cold snap of the Winter with near freezing daytime temperatures for some areas and snow on higher ground.

A look at the GFS 2m temperature graph for here in Warks shows the lower readings expected in the coming week. 

 

The trend in week 2 is to flatten the pattern and bring the winds more into the south west as the AH moves east but i think how  this pans out is very uncertain.Differences in the pace of change are showing between the ECM and GFS on this with the GFS much keener to sweep away the coldest air sooner.

The temperature graph above would indicate that the GFS Op is on the warm side of the clusters so there is some doubt on this potential "warm up".after next week.

 

[Nick L]

Forecasters nightmare coming up next weekend. Experience tells me that snow is unlikely to be this extensive:

Also, we often see mild sectors creeping in as T0 approaches - if so, it's a case of how far east this goes?

I'd say if you live 150m above sea level, away from the coast, there's a good chance of seeing white stuff anywhere by next weekend. For lower areas, it's one of those instances where you may get a "surprise snowfall", but odds in favour of extremely cold rain with the odd flake on the windscreen.

 

I sure am glad I'm not on forecasting duty next weekend if the ECM pans out!

 

Towards the end of the run, the ECM does flatten the pattern somewhat and we get drawn into a southwesterly flow. But do the ensembles support that? Well, not exactly. The clusters show plenty of solutions for a continuation of the unsettled and cool theme, with incursions of colder shots from the northwest at +240. In fact, I'd say the majority go for a colder-than-average theme. Just waiting for the rest of the EPS beyond day 10 and I'll report back.

[IDO]

The ECM mean suggests little support for the op at D9, which is usually  the case with ECM:

 

 

 

The ECM op Northerly at D7 has probably less than 50% support on it's ensembles:

 

 GFS mean: 

 

The ECM mean is not as strong for the Northerly as the GFS, and the latter had about 50% support. 

 

However both the GFS Op and Control and the ECM op and UKMO all go for the Northerly so at the moment they could have spotted the trend and be leading the way. Either way there are good clusters on both models so remains a possibility.

[Nick L]

So beyond day 10, we're looking at a continuation of the cool-to-cold theme going by the EPS, and remaining unsettled. Interestingly, there also remain tentative hints of heights dropping over Europe and a Scandi high setting up shop in the far realms of FI.

Edited December 6, 2014 by Nick L

[SMU]

Hi Nick-  is that in the 216-240 arena or further deep into FI- 288 -300?

cheers

S

[Frosty.]

Let's not forget it's looking cold for most of the time before that arctic surge even arrives, it's only Tuesday when temperatures go up a bit as the wet and windy weather blows through quickly followed by colder uppers and increasingly wintry showers. There is already very good agreement on our first proper cold blast later next week and including the weekend..just the opening salvo of wintry weather ahead...BANK :-)

[Weather Boy]

The ECM mean suggests little support for the op at D9, which is usually  the case with ECM:

 

ECM1-216-5.GIF  EDM1-216-2.GIF

 

The ECM op Northerly at D7 has probably less than 50% support on it's ensembles:

 

EDH1-168.GIF.png  GFS mean: gensnh-21-1-168.png

 

The ECM mean is not as strong for the Northerly as the GFS, and the latter had about 50% support. 

 

However both the GFS Op and Control and the ECM op and UKMO all go for the Northerly so at the moment they could have spotted the trend and be leading the way. Either way there are good clusters on both models so remains a possibility.

Where you have both GFS and ECM (and indeed other models) ops all going for a potent northerly for several consecutive runs at this range, then it is very likely to happen. The ensembles, especially the GFS do tend to have to be dragged along kicking and screaming after the op has spotted the likely solution in near FI.

It's pretty clear to me that at the end of next week there is going to be a northerly. A backtrack at this point would be surprising and embarrassing, although of course we have seen them before at closer range than this. Ignoring that fairly remote possibility, the main questions for me are

1. How potent will it be?

2. To what extent will it be associated with snowfall (and how far south) and

3. How long will it last?

As to 3 I have saw no runs this morning suggesting it will be more than a snap, but that is definitely FI at this point and Nick L's post above is tantalising in that respect!

[knocker]

So beyond day 10, we're looking at a continuation of the cool-to-cold theme going by the EPS, and remaining unsettled. Interestingly, there also remain tentative hints of heights dropping over Europe and a Scandi high setting up shop in the far realms of FI.

 

As far as I can see on the extended anomaly has the HP is quite away to the east and the main players remain the LP to the NW and HP to the SW giving this unsettled W/NW flow with about average temps. Which agrees with your assessment? T240-336

Edited December 6, 2014 by knocker

[Nick L]

Hi Nick-  is that in the 216-240 arena or further deep into FI- 288 -300?

cheers

S

 

Around the 288 mark, but the signal persists in some form all the way through to the end at +360.

As far as I can see on the extended anomaly has the HP is quite away to the east and the main players remain the LP to the NW and HP to the SW giving this unsettled W/NW flow with about average temps. Which agrees with your assessment?

 

Yes this is the predominant theme, but it's good to see some hints of the HP further west.

 

Either way, mild is not a word I'd use to describe the further outlook.

Edited December 6, 2014 by Nick L

[nick sussex]

Normally at this point I search around the NCEP state forecasts in the USA to see which model they prefer for that important shortwave, unfortunately this isn't really much help tonight because this is really mainly effecting Canada.

 

In terms of which model they prefer for the coastal low near New England they are still leaning towards the ECM for that.The ECM ensembles for De Bilt show the operational run departs from the main cluster and becomes a cold outlier on days 9 and 10.

 

The actual change starts relatively early and this has such a big impact on the how the pattern evolves that I think we'll just have to wait to tomorrow to see if those ensembles move towards the operational or if this is a one hit wonder.

[fergieweather]

Around the 288 mark, but the signal persists in some form all the way through to the end at +360.

 

Yes this is the predominant theme, but it's good to see some hints of the HP further west.

 

Either way, mild is not a word I'd use to describe the further outlook.

For me, the striking aspect is frequency of 'dartboard' lows to N (or even over) UK dominating the 12z clusters out to T+360. A very unsettled look indeed.