General Model Output Discussion

[East Herts Snow]

Sustained cold has been here for roughly 3 weeks already. The charts are amazing, with very little marginality anywhere in the British Isles, with the chance of some huge snowfalls, particularly in eastern and southeastern areas. This winter so far has been the coldest and snowiest overall since the 80s here, with more snow and intense cold to come.

Incredible stuff

LS

Your quite right LomondSnowstorm, Scotland keeps getting looked over. Probably down to the fact that us 'Southern Softies' presume that the folk in Scotland are used to cold weather!

Amazingly though the charts are saying one thing, members are saying "the most memorable synoptics in years" and yet the latest weather forecast right up to and incl. Tuesday on the Beeb is saying v.little snow - i'm confused! And that forecast is a downgrade on the one given a few hours ago!

Just shows how much uncertainty there is at the moment, due to the unusual synoptics associated with the very rare weather event we maybe facing in the next few weeks.

Edited January 3, 2010 by North Londoner

[damianslaw]

Short term i.e. out to Tuesday all the models are in agreement of a very cold flow of arctic maritime air brought in on a north easterly flow with associated troughs.

Many of the models including the FAX chart show a pronounced trough pushing through the whole country on Tuesday, this feature looks the most likely to give widespread snow, though amounts will be highest to the north and east as expected.

Beyond Tuesday signs that those heights over Greenland are becoming less strong, favouring a transferal to more of a mid atlantic block, however, it looks like some strong heights will build to the NE and advect our way, as shown by the 12z and ECM, to pull in a bitter easterly flow by the end of the week, which looks to be supported by low heights to the SW.

We will have some very cold uppers by then, look at how close the 510 dam thickness line is shown to be by Friday just off the Norway coast.

The models are showing proper old fashioned cold synoptics, its a real joy to see them.

[VillagePlank]

This time the set-up is not a certainty yet, but still more likely than not, and the synoptics not quite as picture perfect but given what has gone on over the last 23 years, pretty remarkable nonetheless. I suggest we worry about where the Scandi High goes when we get the Scandi High.

Yup - fully agre. However, the Scandi High is more or less written in stone, don't you think? I say that because the PFJ really is so far south, therefore high pressure is destined to build closer to the polar region. Whilst minor details (like the UK!) might still be left out in the open for question - surely, the Scandi High and the dissolution of the Greenie High is a dead cert - even if only for just a wee while.

[mountain shadow]

Yup - fully agre. However, the Scandi High is more or less written in stone, don't you think? I say that because the PFJ really is so far south, therefore high pressure is destined to build closer to the polar region. Whilst minor details (like the UK!) might still be left out in the open for question - surely, the Scandi High and the dissolution of the Greenie High is a dead cert - even if only for just a wee while.

Seems more of a Shetland High to me, which indicates a more prolonged cold period with retogression back to Greeland.

Bit of a washing machine at the moment. Greenie High towards Scandi back to Greenie...

[VillagePlank]

Seems more of a Shetland High to me, which indicates a more prolonged cold period with retogression back to Greeland.

Bit of a washing machine at the moment. Greenie High towards Scandi back to Greenie...

Yes, good point: high pressure is progged to hit Britain. It's shape looks a little suspect to me, and, not only that, it's depth south looks a little to shallow, too.

We shall see, I guess. My take on the matter is that high pressure must build some 100s miles north of the jet-stream. It always has happened, and it will continue to happen.

[John Cox]

Not being funny my friend- But whats the point of that post?- Like we dont know the detail will change- What value is that Adding-

This is about discussing the models & what they actually show- not discussing what they dont show-

Maybe an educated post of what could go wrong--

nah I guess not eh.....

Perhaps you would care to reference this-

http://www.meteogrou...e_forecast.html

Which is infact the ensemble data for the model that the UK MET use in conjunction with their own model-the fact that for London the mean doesnt get about 2/3c for 10 days

Or how about the panel map from the 18z- at T114

http://www.meteociel...&mode=1&ech=114

850's

http://www.meteociel...&mode=0&ech=114

& a little further at 150

http://www.meteociel...&mode=1&ech=150

Or how about from top down-

http://www.hpc.ncep....HEM_f120wbg.gif

http://www.meteogrou...thgt850_144.png

Ensemble Mean- is very consistent as well-

Infact Why do a fax chart for 120--- So much shortwave detail will change?........

Instead of telling me what to post or when or whenever to get excited- how about adding some value...

BTW the SW thread is here -

http://forum.netweat...ell-discussion/

S

Hi Steve.

I have to agree with you. I was quite surprised by this post.

Our Irish Met office for the 1st time that i can remember said that their medium term forecast range of 10 days showed no sign of a let up in this cold spell. From them that is indeed pushing the boat out and showing their confidence in this amazing winter.

Edited January 3, 2010 by John Cox

[Thundery wintry showers]

Glacier Point's post in the teleconnections thread suggests the high meandering towards Scandinavia for a time before retreating back to southern Greenland towards midmonth. That would imply a continuation of the sunshine and snow showers regime in eastern England until around 10 January, and then perhaps for a time we may see the cold air get mixed out by warmer air from the depressions to the S (indeed, similar to how January 1987 ended, but probably not as extreme- we'd most likely see those 850s rise to nearer -5 rather than -10 to -15, which would still be low enough for sub zero temps towards the SE, but would turn it warmer towards the NE). Then perhaps a reload from the north towards the third week?

If so, the attack from the SW, eventually bringing milder weather, that I went for in my monthly outlook could be delayed by another week, giving us a shot at a sub 2C CET month let alone a sub 3C CET one.

As I've mentioned in earlier posts, the setup is quite similar to January 1985 which was a very snowy month in most southern and eastern regions, but much less so in parts of the west, and this is true of most prolonged cold setups, except for those which involve west based -ve NAOs giving northerly/north-westerly outbreaks. South-eastern areas usually end up coldest relative to average. So yes, it will be mainly dry and cold- for some. But not for others.

With regards cold weather payments and the like, it's worth noting that those of us who know of those who cannot cope well in these sort of severe spells- particularly the fragile and elderly- should keep an eye on them as these conditions can send energy bills through the roof and make mobility difficult for them. On the other side of the coin, those of us who enjoy the prolonged cold spell and/or wish for it to continue into the foreseeable future should not feel guilty for doing so- for starters, we can't control the weather so there's no point in suppressing desire for any type of weather just for the sake of being "considerate". Best of both worlds- make the most of it if possible, and help out those who aren't in a good position to do so if possible.

[Frosty.]

Just seen these from the updated 12z ( had the 00z up until 10 mins ago)

If people cannot view these with a modicum of excitement then were there in the wrong game- as they depict something like a 1/25 event....

So have I got cause to ramp it- yes certainly- because just for once things are actually in place for a brilliant cold spell-

S

We should all savour these charts because they are right on our doorstep so to speak. This winter has already been so much better than the typical tedium we endure for at least 9 weeks out of 12 and it's about to turn really Arctic in the next few days with a blast from the past to remember...I, for one am really excited by this and can't wait for the 00z to churn out.

[TEITS]

Some interesting comments this evening so I will add my view to the models.

There is no doubt that excitement is fully justified. Now what we have to remember is the excitement isn't because of the detail i.e snow but the general pattern. Now our normal winters consist of looking at E,lys at +300 in mid Feb after a very mild Dec, Jan. However this is very different as we're looking at a different evolution to the cold spell that we are already experiencing. I shall explain below.

Here are the charts at +72 which many will agree is a fairly reasonable timeframe.

http://www.wetterzentrale.de/pics/Recm721.gif

http://www.wetterzentrale.de/pics/Rtavn721.png

Now I think its safe to assume a cold front is going to move S with NE,lys following behind this front.

When we look at +144 this timeframe is always subject to change. Now for this reason you're better off looking at the ensemble mean than individual runs. Below is the ensemble mean from the GEFS at +144.

http://91.121.94.83/modeles/gens/run/gens-21-1-144.png?18

Now once you look at +192 and beyond it becomes even more susceptiable to change. Again you're better off looking at the ensembles.

http://91.121.94.83/modeles/gens/run/gens-21-1-192.png?18

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

So a simple summary of the outlook is remaining cold with snow becoming more widespread next week especially in E regions and the SE. Now there is still some uncertainity whether this will be a NE/ENE/E,ly. Based on what I have seen so far from the models I would say ENE,ly. Beyond and the general trend from the models is for pressure to remain high around Iceland/Greenland with little sign of a return to mild weather.

So yes we're perfectly entitled to be excited at the overall trend. However we cannot be excited about snowfall prospects yet because the finer details need sorting out.

[Frosty.]

Some interesting comments this evening so I will add my view to the models.

There is no doubt that excitement is fully justified. Now what we have to remember is the excitement isn't because of the detail i.e snow but the general pattern. Now our normal winters consist of looking at E,lys at +300 in mid Feb after a very mild Dec, Jan. However this is very different as we're looking at a different evolution to the cold spell that we are already experiencing. I shall explain below.

Here are the charts at +72 which many will agree is a fairly reasonable timeframe.

http://www.wetterzentrale.de/pics/Recm721.gif

http://www.wetterzentrale.de/pics/Rtavn721.png

Now I think its safe to assume a cold front is going to move S with NE,lys following behind this front.

When we look at +144 this timeframe is always subject to change. Now for this reason you're better off looking at the ensemble mean than individual runs. Below is the ensemble mean from the GEFS at +144.

http://91.121.94.83/modeles/gens/run/gens-21-1-144.png?18

Now once you look at +192 and beyond it becomes even more susceptiable to change. Again you're better off looking at the ensembles.

http://91.121.94.83/modeles/gens/run/gens-21-1-192.png?18

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

So a simple summary of the outlook is remaining cold with snow becoming more widespread next week especially in E regions and the SE. Now there is still some uncertainity whether this will be a NE/ENE/E,ly. Based on what I have seen so far from the models I would say ENE,ly. Beyond and the general trend from the models is for pressure to remain high around Iceland/Greenland with little sign of a return to mild weather.

So yes we're perfectly entitled to be excited at the overall trend. However we cannot be excited about snowfall prospects yet because the finer details need sorting out.

Spot on TEITS, perfectly sums up where we are. This is without doubt the most intense and exciting phase of model watching I have seen since I joined 4 years ago. Next week is going to deliver big time.

[J10]

With regards cold weather payments and the like, it's worth noting that those of us who know of those who cannot cope well in these sort of severe spells- particularly the fragile and elderly- should keep an eye on them as these conditions can send energy bills through the roof and make mobility difficult for them. On the other side of the coin, those of us who enjoy the prolonged cold spell and/or wish for it to continue into the foreseeable future should not feel guilty for doing so- for starters, we can't control the weather so there's no point in suppressing desire for any type of weather just for the sake of being "considerate". Best of both worlds- make the most of it if possible, and help out those who aren't in a good position to do so if possible.

Good point and I agree.

[Guest North Sea Snow Convection]

Some interesting comments this evening so I will add my view to the models.

There is no doubt that excitement is fully justified. Now what we have to remember is the excitement isn't because of the detail i.e snow but the general pattern. Now our normal winters consist of looking at E,lys at +300 in mid Feb after a very mild Dec, Jan. However this is very different as we're looking at a different evolution to the cold spell that we are already experiencing. I shall explain below.

Here are the charts at +72 which many will agree is a fairly reasonable timeframe.

http://www.wetterzen...ics/Recm721.gif

http://www.wetterzen...cs/Rtavn721.png

Now I think its safe to assume a cold front is going to move S with NE,lys following behind this front.

When we look at +144 this timeframe is always subject to change. Now for this reason you're better off looking at the ensemble mean than individual runs. Below is the ensemble mean from the GEFS at +144.

http://91.121.94.83/...21-1-144.png?18

Now once you look at +192 and beyond it becomes even more susceptiable to change. Again you're better off looking at the ensembles.

http://91.121.94.83/...21-1-192.png?18

http://www.knmi.nl/e...agse/index.html

So a simple summary of the outlook is remaining cold with snow becoming more widespread next week especially in E regions and the SE. Now there is still some uncertainity whether this will be a NE/ENE/E,ly. Based on what I have seen so far from the models I would say ENE,ly. Beyond and the general trend from the models is for pressure to remain high around Iceland/Greenland with little sign of a return to mild weather.

So yes we're perfectly entitled to be excited at the overall trend. However we cannot be excited about snowfall prospects yet because the finer details need sorting out.

It's zzz time now - but Dave, that is a very very good post and a very good summary. Putting aside my own comments about the outlook earlier

And I think TWS post is very valid too

Edited January 3, 2010 by North Sea Snow Convection

[john w]

Just home and some interesting discussions tonight.

The potential for widespread snow on Tues/Wed seems to have come from nowhere today, it didnt exist last night from what I remember (it existed for the NE and NW yes) but the South pending towards the SW certainly looked like having a dry run and this was reflected on the models.

I also note that prospects for the South were a little more promising T-72 hours ago for tonight and now there appears to be little in the way of precipitation for the C-South. Radar showed a few showers expected over London and SE by 3am though I would not be surprised to see these fizzle out to leave all but a dusting. Finally I refer that all were excited by a potential 27/28/29th event for sig snow which came to fruition in part, but not to the levels expected. Again our interpretative forecasts by the METO were correct.

Now considering the slack flow I think the models are overplaying precipitation amounts. The speed of which the supposed event on Tues/Weds takes to clear the country is so slow I think the progression for showers is minimal...I just do not think the energy and uplift in the front will be present to produce widespread snow. I agree and wouldnt dare dispute that some areas/pockets will see sig accumulations from it. I could end up (amd would gladly for the wishes of many) be wrong on this. However the fact that the consistancy in the South at least was for relatively dry to next weekend until about t-12 in the latest model outputs, I am sticking with dry.

To improve potential we need bands and/or faster flow of the fronts. I just think weds event will dry out before it gets too far inland and for that reason Im inclined towards Village Pranks reasoning. BUT much as I hate the snow I hope for the majority on here that I am wrong.

My comments centimental to central south area...but as criticising models a tad thought best for this forum.

Edited January 3, 2010 by john w

[Freezing-Point]

I know not quite on topic, but it shows how accurate the models can be....Classic scences now in Newcastle very heavy snow and -1c with lots of potential for the rest of the night

[Lewis]

There's some marginal CAPE around off the coast of Norfolk mid-week for a smidgen of a time (Tuesday night into Wednesday morning) and 700hPa vertical velocity does rear it's head from time to time, but it's not organised even though negative LI is present. One for the skew-t charts the day before, I think.

However, GFS, as has already been said, can do badly at this. I expect some small areas of 'surprise' very small areas of low pressure to form such that it will give favored locations a dumping. I think I've already alluded to this, but, I think, the trick is to look 'beneath' the GFS grid.

Someone said that local experience is the key. I agree with that, wholeheartedly, but the underlying fundamentals must be good too. And, generally, they are - that is to say, that precipitation is the only variable left to play with.

I have been reading VillagePlank's posts tonight, i have behaved very well today on these forums, so i'll try not to spoil it...

So im replying to same of the point's he has made.

Right, regarding precipitation.

1. Pressure is rising to the N and showers continue, on a rather slack NNE flow.

2. The North sea SST'S are still very warm (warmer than average at a temp of 7-8c)

3. OF course the Easterly is dry, everyone knows that and we don't need a science lesson.

4. The greater the distance of the North sea surface temps and the upper 850's = More convection, and more showers.

5. Showers will form widely, and will penetrate inland with a strong flow, current charts suggest a sustained wind speed of 25mph gusting 35-40mph in places (especially the East Yorkshire coast line, and the SE (KENT) area.

I would like to add that Steve Murr, and Nick in particular has been going on about this for some time, they are very experienced with the models, along with Kold Weather, it's a forum and everyone is open to expressing their thoughts and own opinions, and people choose and trust posts from certain member's, like i trust Steve Murr, Kold Weather's, Nick's, TEITS, TWS, etc.

I would like to express this as much and as nicely as i can.

This is happening, this event is going to be a cracker for large parts of the U.K especially for those exposed to the Easterly wind. The North Sea is perfect, absolutely perfect. I just had a pressure rise of around 5-6mb, and guess what showers are still forming and pushing inland.

From an "In my back yard" point of view, i understand how that North Sea works, and boy is it going to deliver this week.

Lewis

Edited January 3, 2010 by grab my graupel
As in pm

[MR EXTREMES]

absolutely storm ive seen the radar thease are not fading showers either,

this event the models are predicting are very much a big event when where and how much is down to the right setup but snow will come.

i expect vp your get some aswell but hey theres good agreement on all models so you cant argue with that.

also if you look at my pic your see joe b that was taken in scotland recently, the poor thing is already neck deep in snow,

hopefully he will get out in time for next winters lrf lol.

Edited January 3, 2010 by badboy657

[scottishandy]

Another great 00z run. Greenie high to Norwegian High to Greenie high to Uk high. Absolutely no hint of atlantic on this run.

Remarkably similarity to ECM 12z out to T192.

[coriolis]

years ago the only way I'd get to see a long range chart was via the Farmers weather bulletin and had I seen this at the time I'd be mightily excited

http://www.meteociel...=144&carte=1021

[johnholmes]

welcome to Net Wx Coriolis-love the name

very true for most people-even I watched it when not on duty!

[Iceberg]

Wow it's quiet in here. The models all seem as good as they did before tbh, ECM on a slightly different solution but it's allow to play occasionally.

I put the below the SW thread, but seeing it's so quiet in here it only looking a few days ahead, and tbh probably applies in part to the south central, SE and maybe even the a little further north as well.

It shows IMO, how it won't be as dry as perhapes some in the model thread thought last night away from the east coasts, it also backs up my comment in the model thread last night.

Sorry in advance for the length of the post and to give a bit more optimism for the SW.

As the models have been looking fantastic for ages now, and looking beyond 144Z is pretty pointless I've just concentrated on the Tues/Wed period, for the snow event that might happen.

Firstly GFS and the way it handles it (this isn't my preference but we just have more detail to hand for it) we can then look at the other models and whether they are likely to increase the event or decrease it.

GFS

Attached are three precip ensembles for Dorset, Somerset and Devon (Sorry I am selfish).

As you can easily see there is total support for precip in all three areas on the 5/6th of Jan. The ops run was one of the least precipitas.

Most areas in the south west could reasonable expect to see around 2cms. (The first widespread snow for SW this winter).

However there is also a good chance of seeing maybe 3cms. Taking into account this is an average I would probably say 2-5cm (5cm over higher evalation).

Now it gets a bit more controversial we have a few members expanding the snow event for somerset and dorset out past to the 7th, if this occurs I would up the totals to 15-20cm, but is only maybe a 20% chance on the GFS.

So that's GFS but how does this compare to the other models METO and ECM.

To start with the precip firstly comes from an organised front(temperature differential created) that moves south Tuesday, however its enhanced due to the lower pressure to the SE of the front, increasing instability.

A closed circulation low then comes in/forms and moves SE.

Essentially the lower the pressure, the more the instability, the more the precipitation.

Attached are the pressure ensembles for Dorset you can see that the lowest pressure for Dorset from the ops run is 1005, in line with the GFS ensemble average.

The runs that produced the heavy snow event go down to 1000 or just below.

So to start with METO,

We have a minimum of 1001mb and 1003mb for the 6th and 7th.

For the ECM

We have a minimum of 1000mb and again 1001 to 1003 for the 6/7th.

This puts them in the higher precip category of the GFS Ensembles, maybe not the full on 20cm's !.

Both ECM and METO keep the High pressure further NW, ECM in particular stalls the closed circulation off the south coast, prolonging the snow on the 7th for Hampshire, Dorset and Somerset ( maybe Devon and Wiltshire a bit as well).

So where does this leave us.

Well I fully admit there is a lack of data for ECM and METO but essentially for the Tues/Wed/Thur period.

A minimum of 2-5cms for most of the SW.

A 60% chance of maybe 5-10cm for the SW.

A 40% chance of maybe 10-15cm for the SW.

This has the big caveat that the METO and ECM might be ensemble outliers with little support down here (I have no way of knowing).

But my assumption is that they are representative of their model suites.

[FENDER.]

looking at it from a national point of view, The main chance of snow seems to be from the troughs coming down Tuesday/Wednesday. Away from the S/E and East coastal regions, most places are likely to be fairly dry untill then.

[West is Best]

Morning all. Well, pretty sensational overnight runs. The GFS is such a cold run for the coming week. We haven't seen the like of this for a long time. Brilliant ensembles too.

If you accept that there were a few days less cold around Christmas (hardly mild for most) then this has been going since around, what, 14th December? I believe snow has fallen somewhere in the UK everyday since then and looking at the models there is a distinct possibility we might see 30 consecutive days. When did that last happen?

Most of the snow action looks like gearing up next week.

[Neilsouth]

The models did look good last night , but im not liking ecm's slack north east , easterlies....

[tinybill]

morning all looked at all the latest updates all i can for the end of the week is the absolutely storm for most parts of the uk,

[West is Best]

im not liking ecm's slack north east , easterlies....

That comment is a sign of our expectations now!

I agree it does go slack after T120 before HP builds over us, but still juicy in the next 5 days. ECM is being quite erratic too, so I'm not too concerned.