Model Output Discussion 18th Nov.2013-12z onwards.

[nick sussex]

I was really hoping for a nov / dec 2010 type spell but realise that's gone up in smoke now, what i'm hoping for now is cold zonality to take over during december with a higher risk of significantly colder incursions as the jet digs further south, having said that, i'm looking forward to the frosty anticyclonic spell later this week, it should last around 7 days the further southeast one happens to be, turning more unsettled towards the northwest of the BI during the second half of next week.

Unfortunately Frosty there was never really a chance of that Nov/Dec 2010 set up, no clear signal for pressure rises over Greenland, the Strat then was  warmer than normal for the time of year and we have a different situation now.

 

At the moment we're really talking of variations on the same theme, ie where the high will be located and whether theres still a chance of some colder upper air being advected west on the southern flank of this. The current front runner is the high over the UK with any colder uppers being advected much further south into mainland Europe. Not to say it won't be cold at the surface for the UK but still uncertainties as to how much cloud will get pulled into the high and hence too early to say how much fog and frost will occur.

 

We've seen the ECM flatten the pattern out and that crucial upstream low shown here is much weaker:

 

 

Now compare this with the GFS 06hrs run for the same time:

 

 

 

If you look at the GFS in high resolution you can see its similar in trend to last nights ECM but spills too much energy east over Greenland so even with it dropping that shortwave se it still is a little underwhelming. In a nutshell I don't see the high having any chance of producing an easterly within 240hrs with cold uppers without the ejection of a shortwave se under the high and at the same time energy shearing away ne rather than east over Greenland.

 

Whilst theres some uncertainty upstream I wouldn't completely rule it out but the odds favour the high over the UK. We'll see a bit later on if theres any more twists in the first will it won't it saga of the season.

[Severe Siberian icy blast]

I was really hoping for a nov / dec 2010 type spell but realise that's gone up in smoke now, what i'm hoping for now is cold zonality to take over during december with a higher risk of significantly colder incursions as the jet digs further south, having said that, i'm looking forward to the frosty anticyclonic spell later this week, it should last around 7 days the further southeast one happens to be, turning more unsettled towards the northwest of the BI during the second half of next week.

hi frosty.the thing is there wasnt one model out there that looked like a servere cold spell was coming. Yes you found wintry looking ensembles but I could have posted as many mild ensemble members as you were with the cold ones. I recognise you love extremes. But it was and is misleading when you post such extreme charts. My brother who is also a netweather member cant read charts well so he believed what you posted and genuinely thought we were in for a very cold severe spell of wintry weather. Only for me to be his victim of his anger to wake up this morning and find things so different. The facts are we very rarely have severe weather in this country so the odds will always be against it happening. And if we do have cold zonality it will not deliver snow to many away from ground above 250mts asl . So lets be realistic please. Absolutely knowone knows what the weather will be like in 2wks time. Anything can happen. We have strong wave 2 activity forecast in the next 10 day's and a split vortex looking a distinct possibility so things will probably change again by the weekend. Even johns 500hpa charts he uses gave the forecast of high pressure to our northwest in the next 10 days but that also looks unlikely now . And as of yet we have had nothing go to plan since the start of the month. We dont even no if we will have the high over us next wk because untill its inside t72 anything can and does happen. So we can only go by what is in the reliable. Which is a cold week. With hill snow and lots of frost. But after Saturday is anybodys guess because even if we have all charts looking solid including the 500hpa anonamly Charts if its in fi its only a forecast and nothing more. It only takes one change such as a tropical depression , or stratospheric changes and the pattern changes. What will be will be. And even the professional charts the men at exeter uses get it wrong and have got it wrong as many times as any other model so I for one will have much less of rollercoaster winter this year than I did last winter because iv learnt lessons and thats what I hope others do. :-)

[Frosty.]

The GEFS 06z perturbations are overflowing with anticyclonic dominance in the run up to day 7 and 10, including the control run, it's variations on the same theme regarding high pressure position / orientation etc but almost total dominance of fine, benign weather with the usual seasonal hazards of fog and frost / ice....however, run things forward and there are a growing number of unsettled solutions but some which show high pressure lasting almost from start to finish, the mean reflects the gradual erosion of high pressure dominance, at least across the northern half of the uk.

[MPG]

Indeed, GFS has handled the siuation very well so far, so whilst things still have to happen the fact it's dragged ECM screaming and kicking back into line pretty much say it all.... and not for the first time I might add.  As Ian F has intimated the longer term trend is towards a milder, flatter pattern as we go into Winter proper, so perhaps best to enjoy the current cold spell and hopefully the upcoming frosty conditions- well until the next plunge shows up at T+384hrs of course....

Will be interesting to see peoples views if the GFS goes hell for leather for cold, and ECM is has none of it. You could post the exact same thing except change the ECM and GFS around in your paragraph. The METO said this month would be mild and flatter as you describe, got that wrong didnt they. Why trust in the trend outlined by Ian F? Is that because its going for what you prefer?

[snowmadchrisuk]

What I see overall is High pressure over us gradually sinking South and no real undercut to save it , so what we probably need a reset of the pattern where it all flattens out and then starts again at square 1. It will mean a couple of weeks of boring weather , but still probably foggy and frosty , followed by a few days of Westerly's , but by the time we have been through all that it will be Mid Dec and we will likely have a much better chance with the next Cold shot....... i have been following the NH Charts and the one thing you notice is the P/V really wants to split and if that happens the chances of our next Cold shot delivering is greatly increased . 

[shedhead]

But why trust the 'longer term' trend to a milder, flatter pattern any more than a longer term trend to a colder, wintry pattern which we are told by many to ignore unless it reaches the T72 timeframe?

 

Genuine question...

 

I do seem to recall somebody posting the METO 16-30 day outlook from 1st November recently, which suggested we would be bathed in mild Westerly winds around now and throughout the upcoming 'below average' period.

 

I'm not saying the return to milder conditions won't happen - I'm just asking the question why we should trust the mild signal any more than any other weather type at 10-15 days out?

 

I personally feel that the status quo will remain for some time yet, and the HP that is sitting slap bang over the UK by the end of the week will not be going anywhere fast, but after that, who knows? 

 

Interesting times ahead for sure...

Hi KS...in essence the models find it much easier to handle weather from the S and W than they do the N and E. So although very little is ever written in stone, a predicted switch to milder weather from the S or W post T+144hrs is much more likely to verify than swing to colder weather from the N or E. This is often the reason we see so much angst in here to be honest, because most of us want to see the least likely option verify, but unfortunately it rarely does in the longer term.

Edited November 19, 2013 by shedhead

[Methuselah]

Please cut out the personal remarks...

[radiohead]

After seeing the significant chopping and changing over the past week on all of the models it should be clear that the only thing which should be written off is the notion of taking any output beyond about T168 at face value.

[johnholmes]

I wish I could say with any degree of certainty what December will bring? How some folk, as some folk seem to genuinely believ, December will not have cold in it is quite beyond my understanding of meteorology. Bit like those that said something similar about no cold for November. Even my ex colleagues got that wrong with all the data they have. Best shot is low level cold for most of the rest of the month thanks to surface high pressure in the area of the UK, exact position still not clear. Mild seems pretty unlikely for the bulk of the UK. From early December then too far ahead for me to try and predict.

[Catacol]

But why trust the 'longer term' trend to a milder, flatter pattern any more than a longer term trend to a colder, wintry pattern which we are told by many to ignore unless it reaches the T72 timeframe?

 

Genuine question...

 

I do seem to recall somebody posting the METO 16-30 day outlook from 1st November recently, which suggested we would be bathed in mild Westerly winds around now and throughout the upcoming 'below average' period.

 

I'm not saying the return to milder conditions won't happen - I'm just asking the question why we should trust the mild signal any more than any other weather type at 10-15 days out?

 

 

Indeed - that was my post and I'll add at this stage not only do the models often struggle at long range but observations over the last few years suggest to me that impacts in the stratosphere seem to be poorly modelled at tropospheric level. I know experts will jump on that statement and tell me that all the data is fed in, and that the product out the other end doesnt "ignore" anything, but i have felt for a while that at long range the models are rather 2 dimensional in their appreciation of patterns and sometimes specific strat modelling will pick up on a change that is then not well appreciated by op runs until much nearer the time.

 

We have one such situation now with wave 2 warming and a splitting vortex forecast from 216 through to 240 and who knows how far beyond. It seems likely that our mid atlantic ridge will gently collapse - and personally I have been surprised just how strong it has turned out to be as I had expected a NW flow for the latter half of November and not the near block we have now... So I would not be surprised to see mid atlantic heights re emerge at the start of the month with the possibility of the vortex setting up shop over siberia and the chances of a northerly once again. This was modelled in the extended GFS yesterday - and the GFS does sometimes pick up on a trend (it picked up on our current ridge at the start of november when the Met were calling mobile). Today the GFS is less bullish about that setup at long range, but this chart for Nov 29 shows what may be possible.

 

Edited November 19, 2013 by Catacol_Highlander

[johnholmes]

hello all

Can we stop posting stuff about the Met Office PLEASE. Discussion of what you feel the models are showing not forecasts from others is what this thread is for. By all means post comments about them in the correct thread-many thanks

[MPG]

Hi KS...in essence the models find it much easier to handle weather from the S and W than they do the N and E. So although very little is ever written in stone, a predicted switch to milder weather from the S or W post T+144hrs is much more likely to verify than swing to colder weather from the N or E. This is often the reason we see so much angst in here to be honest, because most of us want to see the least likely option verify, but unfortunately it rarely does in the longer term.

Is there any evidence to back this up? Do the models just go into S SW outcome post 144 therefore thats what happens? If the models are not fed any data relating to S or SW theme then surely they wont show it?

Edited November 19, 2013 by MPG

[johnholmes]

So is there any point in any weather organisation putting their necks on the line in producing long range forecasts when the data becomes so unreliable?

Can we stop posting stuff about the Met Office PLEASE. Discussion of what you feel the models are showing not forecasts from others is what this thread is for. By all means post comments about them in the correct thread-many thanks

[legritter]

Things could all change by tomorrow ,we could even see a brilliant coldie run from GFS in an hours time and tonights runs could pull something out of the bag ,Two weeks ahead forecasting is one hell of a gamble ,we dont know what mother nature is cooking up, way up in our upper atmosphere .we have the science but its only in its infancy ,looking at current models and data suggests to me nothing is set in stone , some very constructive Posts as you would expect on our TOP forum ,but also some frustration showing on others ,lets look forward to this winter and all learn together 

[Ian Brown]

Is there any evidence to back this up? Do the models just go into S SW outcome post 144 therefore thats what happens? If the models are not fed any data relating to S or SW theme then surely they wont show it?

Well the first thing to say is that the models are not showing mild at T144 or even T240.

 

However the point by Shedhead is correct, if the models do start showing mild at T144 or T168 from the position of mid-latitude HP, then it is highly likely to verify. Why ? Well it will be because the High is sinking into Europe.

 

If the sinking is going to happen, as suggested by the METO, then the models have a margin for error of several hundred miles as the jet returns over the declining block and though specific temps and rainfall are not easy to define at T144, the general pattern is. Now take an easterly and the setting up of that, effectively suspension of HP rather than sitting, and one wrong move and it’s over or heavily diluted and this can go wrong within T72-96.

[shedhead]

Well the first thing to say is that the models are not showing mild at T144 or even T240.

 

However the point by Shedhead is correct, if the models do start showing mild at T144 or T168 from the position of mid-latitude HP, then it is highly likely to verify. Why ? Well it will be because the High is sinking into Europe.

 

If the sinking is going to happen, as suggested by the METO, then the models have a margin for error of several hundred miles as the jet returns over the declining block and though specific temps and rainfall are not easy to define at T144, the general pattern is. Now take an easterly and the setting up of that, effectively suspension of HP rather than sitting, and one wrong move and it’s over or heavily diluted and this can go wrong within T72-96.

Correct Ian...all Ian F alluded to was a potential 'milder' drift in the 10-15 day range, no one has mentioned the weather becoming mild.  The prob with getting proper cold into the UK is everything needs to fall into place perfectly and that is a very big ask, whereas the route back to mild from a cold position is simple by comparison.

Edited November 19, 2013 by shedhead

[fergieweather]

 

Correct Ian...all Ian F alluded to was a potential 'milder' drift in the 10-15 day range, no one has mentioned the weather becoming mild.  The prob with getting proper cold into the UK is everything needs to fall into place perfectly and that is a very big ask, whereas the route back to mild from a cold position is simple by comparison.

The 'winter's finished' whines are plainly daft: simply because the DECIDER products *currently* lean towards a SW flow (at least into the west of UK) early December is hardly the same as them exhibiting a compellingly strong signal for this at the complete exclusion of any other outcome. Note a minority of EPS stamps keep the colder blocking by then (something UKMO are at pains to stress) and at this very early juncture neither they, nor anyone with any sense, will put their cards down on the eventual outcome with any degree of confidence.Note, too, that the consistent recent EC32 signal to retain the blocking remains steadfast in yesterday's update too. So to stress, I see little point in hyperventilating about currently varied model outcomes into early December; nor taking these tentative bits of output as somehow being a fait accompli regarding the winter period as a whole.

[Methuselah]

I don't know how, given that no-one can accurately forecast weather for more than a few days, anyone can write off December: it hasn't even started yet!

 

And, on the subject bias - biases are like bottoms; we all have one.  So please, can we not all be a tad more self-aware when castigating others, for theirs?

Edited November 19, 2013 by A Boy Named Sue

[mountain shadow]

Dare I mention the dreaded "faux cold" aka Murr block?.

Seems this could be the way the models are trending with colder air in the south East and milder cloudier weather type into Northern Ireland and Scotland?

No doubt the 12z will give us something different

[Tamara]

I think there ought to be a bit more reading between the lines that there are some who post on this thread who like to try and suggest how the pattern may evolve some time ahead based on attempts at reading background factors and potential atmospheric signals -  but that these are used as a measure of progress to test against and are not intended necessarily to be taken at face value as any definitive long term forecast. This isn't crystal ball gazing - and should not be confused as such, and not discouraged in any way as such posts from members like these can prove useful for discussion and as a learning tool.

[shaky]

Nothing on the 12z so far peeps?!!this thread is pretty dead out right now

[radiohead]

Melissa/Ex-Melissa has been tracking a little further east on the past two GFS runs now. At T72 it looks like it may not rotate around the other low now and instead head east or southeast.

 

Edit : Well, not this time, but it looked close.

Edited November 19, 2013 by radiohead

[Joe Levy]

72 hours in and some small differences on the positioning of shortwaves and the extent of high pressure. I have no idea what implications this would have, this is merely a neutral commentary post haha!

[Summer Sun]

Nothing on the 12z so far peeps?!!this thread is pretty dead out right now

 

Give it 15 to 30 mins once more of the run is out

 

So far we have little change

 

Edited November 19, 2013 by Summer Sun

[karlos1983]

looks like that low is getting ejected south east? or is it just me?

 

Or not in the next couple of frames.

Edited November 19, 2013 by karlos1983