General Model Output Discussion

[NorthNorfolkWeather]

The ukmo looks very interesting so far upto 120hrs with some major snowfall but impossible to get an accurate track of the low at this stage. The key here is that the flow looks east to se ahead of the lows, lower dewpoints and drier air being pulled up from mainland Europe.

South East, while still cold is milder than current and would mean the East probably having sleet. With the cold pool still mostly in place over the rest of the country, any further progression could see significant snow.

And that is a mighty complex Low, 4 centres, all rotating around each other

But, as you say, getting the track right this far out is impossible

Edited January 8, 2010 by NorthNorfolkWeather

[snowking]

Well the NAE is taking its sweet time to come out this evening

I'm still not convinced on any of the scenario's shown by the operationals this evening until ive seen the ensembles to be honest to see if there more agreement than previously

SK

[Duncan McAlister]

GFS and UKMO now trending towards cut-off undercutting lows rather the Atlantic winning out.

End maybe not in sight after all?

[NorthNorfolkWeather]

Come on. Model discussion. Models go out to T+384, so people are entitled to post such things.

Detailed discussion out at T300 or further probably is pointless, as it will be different, and could be totally different.

But I agree that as the models go out to T384, noone should be criticised for commenting on them if they bear what I said above in mind

[phil nw.]

The ukmo looks very interesting so far upto 120hrs with some major snowfall but impossible to get an accurate track of the low at this stage. The key here is that the flow looks east to se ahead of the lows, lower dewpoints and drier air being pulled up from mainland Europe.

Yes Nick even the more progressive GFS keeps the surface very cold around the midweek as the low approaches the SW.

Maybe freezing rain for the far south and snow for the Welsh,MIds and E.Anglia,either way could be treacherous on the roads.

Finely balanced as the cold surface temps. will be a big factor here and from where the flow is coming.

Edited January 8, 2010 by phil n.warks.

[Matt12]

Which mild breakdown is that matt, it doesn't exist on the three models runs tonight that have been released so far, GFS 12Z going for another cold two weeks just incredible. @O

The atlantic looks dead and blocking looks strong, can't see a change at all esp as we enter Feb traditionally one of the quietest months of the year.

Well, the models were still 'hinting' at 'milder' air arriving sometime around the 17th-23rdst. However, things have backtracked slightly this afternoon, so who knows? I think things are still up in the air as far as the long-term is concerned, and it seems like there is no reason that the models won't backtrack even more.

[casparjack]

Given the trend so far this evening i think we're seeing the models pull back from a complete breakdown and there are some possible major snow events for areas lucky or as the case maybe unlucky on the northern flank of those lows. I wonder if this continues well into January whether even cold and snow lovers might want something less cold.

As much as we all love the cold and snow just how much could the UK take!

As much as I can get!!

I agree, I think there is a definite hint already from the GFS that it may not be a straightforward collapse, eagerly awaited ECM 12z (as ever).

[Thundery wintry showers]

In the breakdown situations that are beginning to show in the models (Now that ECM has caught up with GFS)we always have lots of posts about how the "embedded" cold with resist (and perhaps even shrug off) these attacks.

Of course there is some obvious truth in this phenomenom, but I don't think it should be overated or become a straw to clutch at.

Have you ever thought that, if cold is so difficult to shift, we would never successfully get those WAA southerlies into Greenland that cause the height rises that create Greenie Highs.

You can't have it both ways, when we get an Arctic blast it's because the cold is being booted out somewhere else.

When the Jet (or the bigger synoptic picture) says shift, the cold shifts.

It may take 24 or 48 hours longer than computers say, but don't create false hopes.

Len

I don't think that's quite what the more knowledgeable people have been saying. Embedded cold does help keep surface temperatures lower despite higher 850s, but the point about "cold being difficult to shift" refers more to the persistence of northern blocking patterns. When we get transient blocks those shift quite easily, but once we become locked into a pattern with high pressure oscillating between Greenland and Scandinavia and lows tracking to the south, that can be very difficult to shift, and the forecast models regularly overdeepen lows and show the mild air making much further inroads than actually transpires when we get nearer the time.

With GFS and now UKMO supporting the "southerly slider" shown by ECMWF yesterday I think the odds are against any significant warm-up next week, regardless of what the ECM shows- of course if the ECM sticks to what it shows this morning it will be shorter odds than if it goes back to what it showed yesterday. The milder air will most likely not make it in until at least the second or third time of asking.

[chionomaniac]

The models past 168 should be treated with respect and suspicion but they are far from useless. Many a trend has been spotted at times far further out and I find them very useful as guides when looking at positions of upper air masses and heights and other macroscale features.

I believe that any milder interlude that the models have suggested will get squeezed from both ends. It really depends upon the positioning of the Siberian trough and any pressure rises west to this.

[Thundery wintry showers]

I believe that any milder interlude that the models have suggested will get squeezed from both ends. It really depends upon the positioning of the Siberian trough and any pressure rises west to this.

So do I. It was notable that even the milder solution from the ECM this morning saw the block hold firm to the NE, and the fairly unlikely scenario of an Atlantic low stalling over Ireland before fizzling out and leaving us with high pressure.

[Wayneywoo]

Where would you say FI starts? T+72? T+96?

Either way, if those lows queuing up to run along south of the UK do, potentially a fair bit of PPN to come from those?

Can't wait to see the ECM tonight.

Just as people thought this morning the breakdown was agreed by all the models (apart from GEM and ECM to a point), suddenly we see something different AND the 12Z GFS was to be the run that seemed most reliable

We shall see :Baited Breath Smiley:

Edit: NAE still not viewable? Maybe they'll give an excuse for it not running correctly after it shows something '47esq this weekend :unsure:

Edited January 8, 2010 by Wayneywoo

[weather eater]

Come on. Model discussion. Models go out to T+384, so people are entitled to post such things.

Yes well, Gordon Brown is still Prime Minister but it doesn't mean he has anything worthwhile to say, same applies for weather models that go well beyond what they are capable of. The GFS is an American model and in typical American style it has to try to look further into the future than any other model. Look, discuss, but lets be honest most of us could do just as well with a pencil and paper and some guess work, or by examining the testicles of a dog.

However the models already appear to be backing off the mild breakdown of this mornings 00z runs, and although the weather looks like it will get less cold, a return to average temperatures or Atlantic domination looks unlikely at the moment.

[Nick F]

Have you ever thought that, if cold is so difficult to shift, we would never successfully get those WAA southerlies into Greenland that cause the height rises that create Greenie Highs.

You can't have it both ways, when we get an Arctic blast it's because the cold is being booted out somewhere else.

When the Jet (or the bigger synoptic picture) says shift, the cold shifts.

It may take 24 or 48 hours longer than computers say, but don't create false hopes.

Len

With regards to WAA bringing height rises, to create blocks, WAA is not confined to the surface and can occur above cold air while not displacing it - it can be very cold at the surface yet relatively warm air aloft for that level, e.g. 500mb can take place above to build these heights. What you have to bear in mind, is that cold dry air is alot denser than warm moist air, thus the frigid air in place over the UK will probably take several attempts by Atlantic lows to replace with milder air. And this evening's output so far shows the first attempt fails, with only the far south and southwest turning less cold/wrong side of marginal for snow for a time, before cold returns at the surface.

On another note, anyone seen the pool of -10C T850s that appears over eastern England from out of the blue by t+168? UK developing its own deep cold?

http://charts.netweather.tv/gfsimages/gfs.20100108/12/168/h850t850eu.png

Good to see also the UKMO sending that low east under the block across N France, a snow event for the south?

[Thundery wintry showers]

Yes, we'd probably go back to seeing sunshine and snow showers in eastern areas at around T+144-T+168 with uppers like those, I reckon.

In the meantime I still suspect that north-eastern coastal districts will see a slow thaw next week with onshore winds, slightly less cold air, and some sleet and graupel showers still firing in. In inland parts of the north, and generally across the south, it looks like merely warming up to around freezing, except near the south coast if the milder air temporarily pushes in on the southern flank of the frontal boundary.

[PubliusEnigma]

Morning all.

Well both GFS and UKMO are going for this breakdown middle of next week, with the Scandi high slipping south and introducing a mild southerly feed. I dismissed it yesterday but with both models holding firm overnight we need to consider it seriously, especially with the relatively short timeframe.

All eyes on ECM ... will it resist?!

Well looking at the ECM earlier it had at last fallen into line behind the GFS for a breakdown to Southerlies from Late on Wednesday.

TBH I hadnt spotted the UKMO, so with all 3 going for a breakdown, midweek, is there anyhope for anyother outcome other than the

said breakdown, or do we see the big thaw set in with the onset of rain coming in from the WSW ?

[Tom D]

On another note, anyone seen the pool of -10C T850s that appears over eastern England from out of the blue by t+168? UK developing its own deep cold?

http://charts.netweather.tv/gfsimages/gfs.20100108/12/168/h850t850eu.png

Good to see also the UKMO sending that low east under the block across N France, a snow event for the south?

With the cold uppers at that point the operational is an outlier but not unsupported for uppers becoming colder again.

http://charts.netweather.tv/ensimages/ens.20100108/12/t850London.png

But as for building that high pressure later on, it's a big outlier.

http://charts.netweather.tv/ensimages/ens.20100108/12/prmslLondon.png

Also interesting to note there is that the op has the low pressure coming further north than many of the other runs on the 14th and 15th.

As for temps, it is a cold run for the south but not unsupported, whilst it is by far the warmest run after +180 for the north.

http://charts.netweather.tv/ensimages/ens.20100108/12/t2mLondon.png

http://charts.netweather.tv/ensimages/ens.20100108/12/t2mAberdeenshire.png

[snow1975]

Regarding February I'm pretty sure it will be milder and will have some spells of south-westerlies. However I'm not convinced that it will be mild all the way through. My eye turns to the Februarys of 1966 and 1985, both of which followed cold snowy Januarys and were mild early and late but had an easterly spell in the middle, which in the case of 1985 was enough to make it a fairly cold month overall.

El Nino winters can bring more frequent cold spells to northern Europe and the UK in late winter according to this http://www.metoffice.gov.uk/corporate/pressoffice/2008/pr20081209.html?zoneid=79048

[Thundery wintry showers]

They can indeed, and that's one of many lines of evidence running counter to the prospect of a homogeneously warm February. The closest match is perhaps 1966, which was also an El Nino winter characterised by frequent north-easterly episodes, and as mentioned above February 1966, although mild overall, wasn't devoid of snow events.

[phil nw.]

GEM not allowing the Mild in with the full undercut.

http://www.meteociel.fr/modeles/geme_cartes.php?&ech=120&mode=0

http://www.meteociel.fr/modeles/geme_cartes.php?&ech=120&mode=1

http://www.meteociel.fr/modeles/geme_cartes.php?&ech=144&mode=1

http://www.meteociel.fr/modeles/geme_cartes.php?ech=144&code=&mode=0

Colder uppers than GFS at this point for the South.

Snow for many i would think.

Well looking at the ECM earlier it had at last fallen into line behind the GFS for a breakdown to Southerlies from Late on Wednesday.

TBH I hadnt spotted the UKMO, so with all 3 going for a breakdown, midweek, is there anyhope for anyother outcome other than the

said breakdown, or do we see the big thaw set in with the onset of rain coming in from the WSW ?

Take a look at the surface temps. at T144 P.E.

I wouldn`tcall a breakdown yet.

http://www.wetterzentrale.de/pics/Rtavn14417.png

The far SW for a brief spell maybe on the more progressive GFS but if you look closely at the undercutting on the GEM and UKMO then it can be seen we are still in the Cold.

http://www.wetterzentrale.de/pics/Rukm1441.gif

http://www.meteociel.fr/modeles/geme_cartes.php?&ech=144&mode=0

The jet still well south here too.

Still the ECM to come but i can`t see where the Atlantic is sweeping in here.

[Ben_Cambs]

Im not sure about tomorrow nights event, and how far North the snow will get. Although I think there may be an upgrade in PPN from the major models for Sunday

[Snowyowl9]

As much as we all love the cold and snow just how much could the UK take!

I could take this as theres a strong east/SE wind it would level it off, already have just over 1 foot of snow.

http://www.wzkarten.de/pics/Rukm1441.gif

I wouldn`t want GFS to come off though as I`ve just the uppers that would be very serious indeed a major freezing rain event or Ice storm.

http://91.121.93.17/pics/Rtavn1201.png

http://91.121.93.17/pics/Rtavn1202.png

http://91.121.93.17/pics/Rtavn12017.png

Edit:just freezing light drizzle on that actually.

Edited January 8, 2010 by Snowyowl9

[Matty M]

ECM following its Outlier Operational run this morning.

Might well have spotted a trend with it.

Could be breakdown next week on the ECM, perhaps alot of snow on Tuesday/Wednesday before it.

But different to GFS

[bluearmy]

not liking this ecm run. the low makes too much headway east for my liking. i expect the uppers will be slightly above 0c under that shortwave over the se which doesnt spell snow. freezing rain would be just great with no grit left!! anyway, should nt analyse too closely but givent eh other nwp, was expecting the slider.

[igloo]

ECM following its Outlier Operational run this morning.

Might well have spotted a trend with it.

Could be breakdown next week on the ECM, perhaps alot of snow on Tuesday/Wednesday before it.

But different to GFS

totally agree with you on that the ECM is by far the best model out to +168 where as the GFS is a pile of crap after +96

[snowmadchrisuk]

The GFS 12z Ensembles have also now switched and most go for the milder option , Indeed later next week the 12z Op was a mild outlier. Snow before hand without doubt , but the milder option is still there and we all must take note of that. My personal take at the moment is the Mild air won't win out at the first attempt but it may well do at the 2nd .

It won't let me Edit , but I meant on my post that later next week the Op was a Cold outlier.