Model Output Discussion:

[Weathizard]

UKMO Fax Charts for Tuesday look very promising for snow in the east in particular, UKMO has been very good in the past couple of weeks particularly with regard to timing and intensity of fronts and troughs, and unlike ECM and especially GFS has not been prone to major swings on a day to day basis. Ignore the GFS and stick to the ECM and UKMO, GFS seems to pick always go over board in its subtlety, it is never keen on showing a slow transfer from one pattern to the next, it just always goes for the extreme.

I agree, I trust the UKMO more than any of the other models, lets just hope they are right, quick question, could the snow for Tuesday reach the SE as well?

[johnholmes]

Some of you are talking absolute nonsense tonight. All models are showing potential for a cold to very cold spell – this is pretty much a certainty now. This run is just another variation on this theme. There is good reason to be optimistic. Why all the negative posts, I'm not sure. It is a developing situation as per normal. There is high confidence for the cold air backing up into the UK. This is all we need for now - what happens after this, is open to debate. The first hurdle is cleared however. This has often been the achilles heel in recent years. With good foundations, the final piece of the jigsaw will likely fall in place.

thank you-one of the few constructive and realistic posts in there this evening.

I have to say, shoot me down, call me names, but the model thread is getting to be very very poor in its posting quality. Just how any newcomers wanting to learn are expected too with the vast majority of posts in there is beyond me.

Any newcomer wanting to find out just what is likely to happen

pm any member of the team we will be happy to help

use the Met O Fax charts as the most realistic as to what will happen in that time frame.

[Matty M]

Very mixed set of 18z Ensembles.

Synoptic really not firmed up at all.

Likely to be cold though however the ridge is being portrayed to be quite weak,

[La Bise]

I'll applaud you instead John. Great fun to read but a very good reminder of the world of difference there is between the considered outputs of met pros and enthusiastic met nerds.

[Bobby]

Yawn, let's discuss the models:

GFS ensembles aren't as good if you want cold it has to be said, 12z ensembles only really had 1 milder member, much more now. A few more no man's land scenarios like the OP and ECM and quite a lot of channel lows, more than the 12z ensembles.

Some really cold runs too, all sorts really. A fair bit of uncertainty.

[Bobby]

Where can I view the METO charts beyond 120 hours?

Th Met Office FAX charts only go to 120, you can see them here:

http://www.meteociel.com/modeles/ukmo2.php?ech=0&carte=2000

[nick sussex]

Hi NIck,

Couple for yer, 1. Do you think the shortwave is no longer a threat? 2. Is the cold now a given?

Cheers

Well there were originally two shortwaves that we needed to worry about, the first one thankfully looks fine, this is the trigger shortwave that clears se'wards into France and allows the ridge to build south, the second shortwave is modelled to move south from Scandi, around 96 hrs, this is important as it allows the colder air to be advected sw'wards from that region, often in the past shortwaves have caused all manner of problems for the models and us!

The general model guidance is for this to slip towards the se of England, after this the ridge to the north extends south, its important that this shortwave clears the se and heads into the Continent. So overall then definitely yes to the first sw, and a very good chance for the second, however I'm being cautious about the second sw because I'd like to see this within T-72hrs to be certain about it.

In terms of cold theres a very good chance but with easterly set ups its always best to get within T-72hrs to be really sure, not all cold set ups require us to be this cautious but given the last week especially I think we just need to get to tomorrows runs and we'll be okay.

Edited February 4, 2010 by nick sussex

[Bobby]

London ensembles:

More milder runs appearing. Generally cold mean though.

Big scatter starting from the 7th - don't want to be a downer but FI starts after T+72, very dangerous looking beyond that with such a scatter (indicting high uncertainty) at such a short range. OK, the operationals are higher resolution but still... caution required.

Edited February 4, 2010 by Barb-

[cheeky_monkey]

as i mentioned earlier in the day the correspondence between warm weather across the prairies in Canada and cold in the uk...well the warm spell predicted here that coincided with the cold in the uk has been downgraded today maybe a hint as to why things have changed slightly with the models tonight?

[Duane S.]

Yawn, let's discuss the models:

GFS ensembles aren't as good if you want cold it has to be said, 12z ensembles only really had 1 milder member, much more now. A few more no man's land scenarios like the OP and ECM and quite a lot of channel lows, more than the 12z ensembles.

Some really cold runs too, all sorts really. A fair bit of uncertainty.

Yes please, can we???... Cringeworthy posts on here by some tonight.

The first time we have some sort of agreement on a cold spell within the reliable timeframe. How anybody can knock the ECM for producing that run is quite beyond me. The only (slight) disappointment, as you pointed out Barb, is the 18z ens. A few more are suddenly not so keen and are having a little wobble. But as long as the 00z and 06z don't follow, which I really don't think they will, then nothing to worry about. I think this is nowhere near a done deal in terms of a memorable cold spell but in terms of at least something cold next week, it pretty much is now IMO.

The Atlantic can 'barrelling in' under these conditions is highly unlikely. There are potential spoilers out there but I struggle to see the 'Pest from the West' as one of them!

[nick sussex]

Cheers Nick,

Informative and easy to understand, indeed the first shortwave does seemed to have become less of a concern, and now I know where to look for the second. Is the first one's movement known as undercutting?

Sorry to bombard with Q's

Yes you could say its undercutting the ridge building down from the north. In terms of the second shortwave you'll know if the run is on the right track, if its moving sw towards the Southern North Sea and into the Low Countries. We definitely do not want it moving wsw or west but sw ssw even south at worse. You see now why I'm obsessed with these shortwaves!

[Guest North Sea Snow Convection]

Well, the model thread is famous so often for ridiculous OTT melodrama and tonight is one of those biggest (unfortunate) occasions . Just read this evenings offering and apart from a few sensible rational heads, the rest was ridiculous overreactive claptrap.

Having had a look at the 18z ensemble maps for both t120 and t144 I see nothing whatsoever to even start to fuss about. Most show an Icelandic ridge, most show an easterly or north easterly and there is the usual rogue one or two (literally) that show a south westerly or the like. Nothing new, nothing dramatic, nothing that suggests a subtefuge plan change of synoptics.

The only fly in the ointment is the latest fax chart - but I am sure that will improve

What IS the matter with people?? It's the weather for goodness sake!! Get a grip some of you.

Edited February 4, 2010 by North Sea Snow Convection

[Bobby]

NOGAPS 18z.

Similar to the GEM and GME.

The Atlantic can 'barrelling in' under these conditions is highly unlikely. There are potential spoilers out there but I struggle to see the 'Pest from the West' as one of them!

The Big 3 (GFS, ECM, UKMO) certainly show little sign of the Atlantic spoiling the party which is good news as these are the 3 best models and the operationals run at higher resolution than the ensembles. Definitely makes things safer though to have the ensembles solidly on board, but with a big scatter at just 2-3 days out, makes things a bit more shakey, I'm not convinced til that spread tightens. It's that trigger again, small changes at the crucial point can have big consequences much further down the line, that's where all the uncertainy is coming from. Chaos theory and all that.

[dallas]

Yes you could say its undercutting the ridge building down from the north. In terms of the second shortwave you'll know if the run is on the right track, if its moving sw towards the Southern North Sea and into the Low Countries. We definitely do not want it moving wsw or west but sw ssw even south at worse. You see now why I'm obsessed with these shortwaves!

Thanks Nick,now onto tomorrows runs with more info gleaned........and shortwaves to look out for

[Guest North Sea Snow Convection]

NOGAPS 18z.

The Big 3 (GFS, ECM, UKMO) certainly show little sign of the Atlantic spoiling the party which is good news as these are the 3 best models and the operationals run at higher resolution than the ensembles. Definitely makes things safer though to have the ensembles solidly on board, but with a big scatter at just 2-3 days out, makes things a bit more shakey, I'm not convinced til that spread tightens. It's that trigger again, small changes at the crucial point can have big consequences much further down the line, that's where all the uncertainy is coming from. Chaos theory and all that.

Well, thats it, it is all over, the NOGAPS must be right then

Regarding the ensembles I'm sorry but there simply isn't a big scatter.

Lets be cautious by all means, but scrutinising every nook and cranny like this one starts unearthing things that aren't even there!

If it has all imploded in the morning then by all means you can send me to the nunnery.

I'm away - night all .

Edited February 5, 2010 by North Sea Snow Convection

[TEITS]

As others have said some really silly posts tonight.

The problem in my opinion is some still have the attitude of "expect all cold spells to downgrade" which is being based on previous winters. Now clearly this attitude is wrong as the last 48hrs have illustrated. What I find ironic is the same members referring to downgrades are the same members who said a few days ago "thats the end of the E,ly". When will people learn to keep an open mind.

Im not at all surprised at the 18Z because you have to expect some different variations from each run. Now come tomorrow it might downgrade or even upgrade, frankly we won't know until tomorrow morning. I suspect the models are having difficulties in modelling the SW over Scandi and the direction that this takes. Also I imagine some of the ensembles are showing a similiar trend to the GEM/NOGAPS wrt a LP tracking S.

I haven't looked at each ensemble member but its clear some must be suggesting a LP tracking along the S. Look at the Kent ensembles and then compare to Cambs and you will se far less scatter in Cambs than kent. This suggests a LP system tracking along the S.

http://cirrus.netweather.tv/ensimages/ens.20100204/18/t850Cambridgeshire.png

http://cirrus.netweather.tv/ensimages/ens.20100204/18/t850Kent.png

Always maintained that we won't know until at least Saturday how exactly this will pan out. However keep an open mind for tomorrow morning runs because they might upgrade or downgrade. Just don't assume they will downgrade because of previous winters because that isn't how weather works!

[SP1986]

I think the silly posts are countered by some unrealistic expectations of cold tonight. Prolonged cold well to be honest we don't know that yet.

What do you define as prolonged cold anyway?

If the realistic timeframe is 72 hours surely it's premature for some people to be predicting prolonged cold spells.

Whilst one side may be silly with their downgrades suggestion, the other side is perhaps too much expectation around something that is still developing.

Realism must be worked from both sides!

(ps its worth noting that there are some realistic posts floating around)

Realistic (and neutral) in my opinion is that we have a good agreement for a period of cold weather, with frost and possible snow showers. The length at the moment is trending into the middle of the week but this is not certain.

There is a mix between some model outputs, some in the realistic timeframe suggest high pressure settling over inviting some potent cold upper air to allow frost and snow showers. Some suggest an easterly.

It is difficult to weigh up the potential after this.

[LomondSnowstorm]

Well, thats it, it is all over, the NOGAPS must be right then

Regarding the ensembles I'm sorry but there simply isn't a big scatter.

Lets be cautious by all means, but scrutinising every nook and cranny like this one starts unearthing things that aren't even there!

If it has all imploded in the morning then by all means you can send me to the nunnery.

I'm away - night all .

Night Tamara. Let's hope that the post on my PM does not come to fruition. John has been integral to the entire forum and I'm sure we would all regret it very much if he left.

Anyway, I can sort of understand the ridiculous apprehension some people are having tonight, given the wild swings seen just a few days before with even the ensembles changing drastically by the day. However, tonight is probably the least nervous I've been about the models in a long time. Cold has moved into 3 day territory http://www.wetterzen...cs/Rtavn721.png

Ensembles, as posted above, have good agreement for cold and I'm just awaiting the 00Zs with anticipation.

Savour these charts - it's not often we see this after such a cold winter so far. A total flip tomorrow looks unlikely, more likely I feel is a clearer picture developing, most likely a cold one, more especially the further northeast you are (in terms of likelihood of cold, not neccessarily intensity of cold, as that is most likely in the east/southeast). Dry and cold? Possibly. But unless the high is directly over the UK or uppers are above -5 there will always be the potential for unexpected snow events.

Bickering just puts a damper on a very nice set of runs tonight.

LS

Edited February 5, 2010 by LomondSnowstorm

[DaBrigg]

For where?

Matty do you mean for your location? You are often critical of others posting IMBY so would be quite interesting for you to clarify.

Im not Matty, but the Dublin 12z ensembles were a little better than the 18z.

There was only one member not going for cold on the 12z, and the mean hit -10C, where as the 18z has a few more mild ones in there, and the mean only gets down to -7C. The 12z had unrealistically good agreement for this far out IMO. It would have been foolish to expect little or no change in subsequent runs. Considering some of the wild swings we have seen of late, I fail to see what all the fuss is about. The 18z ensembles are probably closer to the 06z, so still very good overall.

Personally, I dont have a strong opinion one way or the other whether we get a cold easterly, or a cold frosty high pressure, like what the ECM is going for. I live on a north-east facing coast, and easterlies just result in temps hovering at +2C day and night, no frost, and either heavy showers of graupel, or uselessly light snow flurries.

I may actually prefer a slacker wind scenario, with clearer skies. At least that way the temps may manage to get sub-zero at some point.

Edited February 5, 2010 by DaBrigg

[Thundery wintry showers]

My opinion remains the same as before. Tonight is too early to be able to call this north-easterly outbreak "nailed on"- there's even a slight chance that it might not come off at all. If, however, we see cross-operational agreement for a north-easterly blast come tomorrow evening, and good ensemble support, I will suggest that it's pretty much nailed on.

Anything less and we may have to wait until Saturday before anything is nailed on one way or another.

[Duane S.]

I haven't looked at each ensemble member but its clear some must be suggesting a LP tracking along the S. Look at the Kent ensembles and then compare to Cambs and you will se far less scatter in Cambs than kent. This suggests a LP system tracking along the S.

Great spot there TEITS, I hadn't looked at that. I think that is exactly why we have the scatter. I posted yesterday that it may well be far more nail biting for us in the far south than those further North but wit that there stands the chance of a spectacular channel low in just the right place.

Another day closer, no downgrades today, all VERY good so far.

[TEITS]

Hi Teits,

When (if ever) do you think it can be called as 'nailed on' I see you mention Saturday so 48hours I guess?

Thanks

Well for me the uncertainity is especially from +84 to +120. Hopefully by Saturday the general trend for the early part of next week will be within the relatively reliable timeframe of +72.

What I have learn't in all my years of model watching is +0 to +72 and the general trend remains very similiar by all models. However +72 to +144 is a completely different kettle of fish and this timeframe can see differences between each models with variations between each runs. During this timeframe I have seen cold spelld downgraded and upgraded which is why im keeping an open mind for tomorrow. I will add I kept an open mind a few days ago when some were saying "no chance of a cold spell".

I will finally that back in the 1990s computer models only used to forecast to +144. Now in my opinion the accuracy of +72 to +144 hasn't really improved much. However for +72 to +144 my faith has always been with the UKMO with my preference for the ECM being for the longer range.

[TEITS]

Just looked through all the ensembles and to be honest a majority are excellent but I can see the reason why some locations have more scatter.

The general trend is we pull in a colder NE,ly flow although the backing SW of the cold pool varies. Some members are like the UKMO whereas a couple are like the GEM/NOGAPS. Some members suggest a cold NE,ly flow before a LP in the Atlantic attempts to move in. However as this occurs we see the LP split with a SW tracking SE across S regions.

I suppose at the end of the day alot depends on your location and what you prefer. Personally my preference is with the safter UKMO bringing convective snowfall. The Atlantic with the potential of frontal snowfall is always a gamble.

I will finally add that the trend I am noticing with the models, especially the ensembles, is to introduce the colder E,lys much earlier with each subsequent run. Worth keeping an eye out for this. Also whilst some of the GEFS members at +120 aren't as favourable as the 12Z, the +144/+168 actually show more potential than the 12Z so its a case of swings and roundabouts.

[Guest North Sea Snow Convection]

Night Tamara. Let's hope that the post on my PM does not come to fruition. John has been integral to the entire forum and I'm sure we would all regret it very much if he left.

Anyway, I can sort of understand the ridiculous apprehension some people are having tonight, given the wild swings seen just a few days before with even the ensembles changing drastically by the day. However, tonight is probably the least nervous I've been about the models in a long time. Cold has moved into 3 day territory http://www.wetterzen...cs/Rtavn721.png

Ensembles, as posted above, have good agreement for cold and I'm just awaiting the 00Zs with anticipation.

Savour these charts - it's not often we see this after such a cold winter so far. A total flip tomorrow looks unlikely, more likely I feel is a clearer picture developing, most likely a cold one, more especially the further northeast you are (in terms of likelihood of cold, not neccessarily intensity of cold, as that is most likely in the east/southeast). Dry and cold? Possibly. But unless the high is directly over the UK or uppers are above -5 there will always be the potential for unexpected snow events.

Bickering just puts a damper on a very nice set of runs tonight.

LS

Night - I was intending to be asleep already by this time!! I also wasn't actually intending to even visit here at all tonight after watching television with the household and QT this evening!

I agree entirely about John. His comments and experience are always valued by everyone -even if some people appear not to listen to the advice!

I do understand that people get anxious, because there are many members who want to see more snow and cold weather . Totally understandable (to a point anyway) but there is just no point whatsoever in becoming a gibbering wreck over a computer model projection

There shouldn't be anything to bicker about (well that should always be true actually) How so so much better do things look now than they did just a couple of days ago??. Irrespective of whether the coldest air arrives or not (which I think has a good chance of happening anyway)

Anyway, really is time to sign off for tonight now

[David-kig]

f1 is very messing don't look at that but otherwise still trending with the ECM 12z high pressure close by taking longer to reogress towards greenland. generally gfs 00z is cold and dry. slight downgrade on uppers and most get pushed in france. see no easterly on his run just a slack flow. bring sunshine and frost. overall nothing great on the snow behalf

i see outlook being cold and dry next week with a chance of an easterly later next weekend. at the moment

UKMO is now on this trend with only far eastern parts having best chance of snow. high pressure close by slower at bring easterly overall. set back on bring the beast

btw is that high sinking????????? :s

Edited February 5, 2010 by David-kig