Model Output - General Discussion

[Lewis]

Well, at least nobody seems to be screaming "downgrades" today! In fact, as I suspected, the models have started to tone up this easterly a little as we get nearer the time, as quite often happens with easterlies that get within the reliable timeframe. Chances of snow events towards the southeast even before that, but in particular overnight Thursday/Friday looks a good bet for a fairly widespread snow cover for eastern districts.

The subsequent northerly is still too far out to firm up details but still looks very promising for cold/snow lovers.

Morning Ian,

Totally agree with you there, when i woke up and logged on this morning i was expecting to read about 9 new pages of dribble, but i was wrong for once, some very good post's and no downbeat talk.

I have to say that the models are looking very promising indeed, and i too noticed right away this morning that the Easterly is some what upgraded and prolonged, it has a little more bite too it with some cooler 850's pushing across the N and eastern coastal counties. The flow at one point get's a little tighter which is better as it will penetrate showers further inland (how far though is still a mystery i suppose it's lamp post watch/radar watch.

The Northerly tucking in behind hold's a lot of uncertainty to its movement & flow and also if there's any warmer sectors associated within the flow, I guarantee they will be one or two, but where they will be is beyond me, why I'm talking about it I don't know as it's still too far away, on a personal note a Northerly with a more NNW flow is not the best for my area, all the showers seem to push off coast and mainly hit your area, but that's all up in the air at the moment as i think this Northerly will deliver on a much wider note, it's going to be a very unstable airflow.

Any how 06z rolling out and it looks like another upgrade is on the way with the easterly.

Here's to more model watching! I'm enjoying this ride and i must say these charts are dream land.

Lewis

06Z is less progressive and delays the easterly out to friday.

Edited December 14, 2009 by Storm Force Lewis

[The PIT]

Well upgrade in FI land for the Northerly and a upgrade for easterly just in the reliable time frame. GFS must be in Xmas mood for once.

[Iceberg]

That's an increase in the easterly IMO, it makes more of the low, with the undercut it would give reasonable snow for the south. Quite an improvement,(it also makes the northerly probably more potent in the longer run).

[Altostratus]

It seems that everyone is in good spirits this morning and rightly so! It has been a tiring and anxious last few days but it seems we have turned a corner today, with cold and snow looking virtually guaranteed in places. It is time to relax, sit back and see how it all unfolds.

Regarding the question of snowfall distribution, it is, as many others have said, still far too early to say - this will likely come down to radar watching a few hours beforehand. A prime example of this was last February when Devon and Somerset were hammered even though the snow was not forecast there.

My assessment of the situation at present is that favoured areas in the east look good for the initial easterly and then as we move into the weekend, the emphasis shifts to the north as that bitter northerly kicks in. I would imagine most parts of the country would receive at least some snow from the northerly at some point. Polar lows are a distinct possibility too.

It’s exciting as there seem to be so many options for snow formation once the cold air has established. Too many times in the past we have lacked one of the two necessary ingredients: cold air and instability. Both are present in abundance here so anything could happen – don’t be surprised to see some surprise snowfalls if the northerly kicks in as currently shown.

Regarding a breakdown, my hunch is that the majority of models are being too progressive. Expect the cold air to last longer. I will be surprised if it has completely disappeared by Xmas. Anyway, let’s see what variation the 06Z will deliver…

[TEITS]

Certainly a slight upgrade for the E,ly and like TWS says at times this can be upgraded. I have often seen this once the E,ly falls into the +72 timeframe, so worth keeping an eye on this.

I will add that if the E,ly flow is slack then the snow showers won't penetrate very far inland. So the stronger the flow from the E the better.

[snowmadchrisuk]

dopvhost=charts.netweather.tv&doppl=0e5724d745712a2a45212a7a94e4213145212a87&dopsig=1fffcf2858f13c0f69ff9e220f43b6db

[Eugene]

510 dam line approaching us from two flanks both the east and north

http://www.wetterzentrale.de/pics/Rtavn1143.png

http://www.wetterzentrale.de/pics/Rtavn1202.png

http://www.wetterzentrale.de/pics/Rtavn1201.png

Incredible run so far really it is

[Duane S.]

Still plenty of details to firm up on but at last the event we have all been waiting so patiently (or not in some cases) for the past two weeks is nearly on our doorstep.

Loving the 06z so far, looks like an upgrade for the south so far...

[Lewis]

Sorry mods, but if this run verify's eastern coastal counties will get a pasting,

The precipitation is a-plenty on this run, with some heavy stuff!

Upgrades

[Optimus Prime]

06Z is less progressive and delays the easterly out to friday.

Err...am I looking at the wrong charts?

[liltbrockie]

Up to 126 hrs and this really is looking like a great run... Much more ppn around and the UK being attacked from the north and east by cold...

Look at the cold spot NW France lol

[Lewis]

Err...am I looking at the wrong charts?

No your not mate,

It's less progressive as it does not bring the easterly and then Northerly in as quick, as it did in more of a reliable time frame.

Thats what i mean, but when it hits it's more potent.

Do you understand what i mean now?

[Upgrade]

oooh - these charts are looking very tasty indeed. The easterly is "tightening" which is a new development. i wonder if we will see progression into a fully developed north- easterly "screamer" - a very rare thing indeed these last few years. i certainly see some potential for it. keep watching the charts.

[Optimus Prime]

Do you understand what i mean now?

Not really no. The easterly is blowing by Wenesday/Thrusday with the coldest days Friday and Saturday (Friday and Saturday maxima well below freezing across much of England)

As for the Northerly that seems to be delayed slightly.

Very much how it's been for a while now. Colder - yes.

[Lewis]

Not really no. The easterly is blowing by Wenesday/Thrusday with the coldest days Friday and Saturday (Friday and Saturday maxima well below freezing across much of England)

As for the Northerly that seems to be delayed slightly.

Very much how it's been for a while now. Colder - yes.

I think you do miss understand me,

the easterly flow is all but there, but it's not until friday until we tap into the colder 850's, and it stays around longer.

So that my friend is less progressive.

[TEITS]

I think you do miss understand me,

the easterly flow is all but there, but it's not until friday until we tap into the colder 850's, and it stays around longer.

So that my friend is less progressive.

Your right the 06Z is less progressive in sinking our E,ly by around 6-12hrs.

At +102 the 0Z had the LP that is coming S centred just to the N of Scandinavia. On the 06Z the LP is centred further N around Svalbard. Due to the LP being further N the E,ly doesn't sink as quickly thus prolonging the E,ly flow.

[Optimus Prime]

So that my friend is less progressive.

Ahh I see what you mean.

The differences between the 06Z and 00Z;

MUCH more snow potenatial. Broadly speaking the air is slightly cold and less modified.

Edited December 14, 2009 by Optimus Prime

[Lewis]

Your right the 06Z is less progressive in sinking our E,ly by around 6-12hrs.

At +102 the 0Z had the LP that is coming S centred just to the N of Scandinavia. On the 06Z the LP is centred further N around Svalbard. Due to the LP being further N the E,ly doesn't sink as quickly thus prolonging the E,ly flow.

Cheers mate,

The ECM what was that like this morning, it is more or less the same as the 06z run.

Lewis

[Eugene]

http://www.wetterzentrale.de/pics/Rtavn2041.png - A Very snowy chart here, atlantic looking sluggish on 06Z it must be said.

[mwhalber]

It looks to me like the GFS keeps both the polar and russian cold pools away from england, however, the GEM seems to bring both over blighty on Sunday...and keeps them there for a significant period.

The GFS shows some precip/convection around the same period over the London area shortly before (-6h), but this is mixing models, so not very accurate.

My feeling is that the best chance for a major event, based upon current output is Sunday daytime. What do you guys think?

[Optimus Prime]

This little feature running across the south needs to be monitored;

Maximum temperatures around 2c-4c.

And those charts from 20th December are something really special. Slack winds, total snowcover I'm sure nearing -20c would be recorded under those conditions.

Edited December 14, 2009 by Optimus Prime

[Tom D]

Anyone else having problems with the GFS charts on net-weather? They seem to have stopped at +240.

[mwhalber]

This little feature running across the south needs to be monitored;

Maximum temperatures around 2c-4c.

And those charts from 20th December are something really special. Slack winds, total snowcover I'm sure nearing -20c would be recorded under those conditions.

agreed. This feature seems to be around on the NOGAPS for Friday Midday as well, with the eastern cold pool having arrived on the continent

Edited December 14, 2009 by mwhalber

[azores92]

in fi it starts to go pear shaped, with high pressure building on the continent, but the thing is, there is potentially so much to look forward to in the coming days, why worry about fi?

[TEITS]

I just wish to make a few points before I have to shoot off.

With regards to the E,ly im 100% certain much colder weather is coming from the E. However if I had to make a forecast with regards to snow amounts and where it would fall, my confidence would be around 10%. Even just 24hrs away my confidence would only be 50%. Always difficult to work out what will develop in the N sea and this is no different.

Remember a slack E,ly flow will only bring snow into E coastal counties. The stronger the E,ly flow the further inland the snow showers will penetrate.

As for the longer term take note its always within the lower resolution that the models are desperate to bring a return to milder weather. I wouldn't worry about this if I was you.