Model Output Discussion - 28th November - 4th December

[SMU]

Evening all,

Tucked up cosy here on the highest hill in Lanarkshire waiting to go sledging tomorrow...

I think many have been pointing out that the pattern doesn't support any Greenland high pressure as the sum of the atmospheric feeds all equates to a strong jet and flat profile

You would think this would mean zero cold into the UK, however the glimor of hope is if the Ukmo is correct we can throw a ridge towards Greenland that is then sheared towards Scandinavia, the jet will then flow across the top of it...

The chances of easterly do increase then because the high will get flattened from the north meaning the shape will be nice and pebble and there will be a returning flow west underneath. The big picture as ever in winter is whether a ridge can gain enough lattitude before being forced east.....

FWIW at 168 The ECM started decent trough disruption towards Greenland but then dismissed it...

UKMO + GFS may be correct here....

And remember this years background signal MIGHT be fighting the bigger background signal of the last 3 years....

Work that out!

[Cheshire Freeze]

Evening all,

Tucked up cosy here on the highest hill in Lanarkshire waiting to go sledging tomorrow...

I think many have been pointing out that the pattern doesn't support any Greenland high pressure as the sum of the atmospheric feeds all equates to a strong jet and flat profile

You would think this would mean zero cold into the UK, however the glimor of hope is if the Ukmo is correct we can throw a ridge towards Greenland that is then sheared towards Scandinavia, the jet will then flow across the top of it...

The chances of easterly do increase then because the high will get flattened from the north meaning the shape will be nice and pebble and there will be a returning flow west underneath. The big picture as ever in winter is whether a ridge can gain enough lattitude before being forced east.....

FWIW at 168 The ECM started decent trough disruption towards Greenland but then dismissed it...

UKMO + GFS may be correct here....

And remember this years background signal MIGHT be fighting the bigger background signal of the last 3 years....

Work that out!

Yes Steve, that's exactly what I think is happening

[danm]

And remember this years background signal MIGHT be fighting the bigger background signal of the last 3 years....

Work that out!

I think i understand what you mean, but can you explain what you mean in slightly more detail?

[chionomaniac]

I kind of hinted at that to Blast the other day Steve. We have the signal of the last few years of the jet stream wanting to dive south, fighting against the stratospheric signal of this year pulling the jet stream north. Presently that leaves in a cold zonality. I don't think there will need to be much stratospheric change to tip the scales in the other direction.

Kumquat, there is no sign of a minor stratospheric warming never mind an SSW!

Edited December 4, 2011 by chionomaniac

[nick sussex]

The shambolic output continues this morning with no agreement and we're left in the dark as to what happens next week.

The UKMO still has its mid Atlantic ridge and the ECM tris to cut a low se'wards , the ECM then goes on off into the sunset by developing high pressure with a brief easterly into the UK.

Looking at the UKMO at 144hrs that ridge looks like its toppling towards Scandi, that would likely then bring a briefish easterly flow into southern areas before the high settles over the UK.

The GFS is similar but doesn't build the high far enough north, this topples into a more bog standard Euro high with perhaps some colder surface air into the se and south.

Now this is where it gets even more complicated, I hope everyone is suitably caffeined up at this time of the morning!

The ECM is by far the best output for potential because it cuts that low se'wards, you could have a chance of some snow as that clears from the UK because of the lower dew points pulled in from the east, after this it's a real tease and develops high pressure to the east, if you notice the PV tries to move in but begins to disrupt, if the pattern is held further west then this disruption will likely send a shortwave into France and subsequent bedlam would ensue in this thread! in fact in terms of pattern the ECM with a little tweek is by far the best output since last winter depending on your location, but if you want cold that hangs around it has to come from the east, its very unlikely you'll get a sustained northerly because of low heights near Greenland.

Now the UKMO is okay for some surface cold and even something a little more interesting if we can get the right jet cut back towards the Low countries, , the GFS is just a typical Euro high flattened by the jet, if you're a cold lover you want an outright victory for either the ECM or UKMO today and no half measures.

The GFS is totally underwhelming and you certainly don't want that to verify, the key is for the ECM if we get that low heading se'wards the further west the better, a very interesting day coming up!

Edited December 4, 2011 by nick sussex

[nick sussex]

There is no support for the ECM in the GEFS ensembles so that at the moment is looking like a longshot, the low to the nw could verify but its trying to get enough amplification upstream to force it se'wards and not too far east, the whole ECM relies on that low cutting se through the UK.

The UKMO has little support in the GEFS, you'd think one of the Euros would have at least some backing, more especially the UKMO which isn't really that much different from many of the previous GFS operational runs.

The ECM ensembles will be out shortly, so let's see what they have.

The ensemble maps upto 168hrs have a few solutions similar but not the same angle of low, theres a wide variety of outcomes in them.

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2009112700!!/

Edited December 4, 2011 by nick sussex

[Frosty.]

The Gfs and Ecm 00z are chalk and cheese this morning, the gfs is a huge disappointment for southern britain in the week ahead with only very brief cold, mostly the temps look around average but the charts look very messy and there will at least be some heavy rain to help ease the chronic drought situation in southeast britain, northern britain looks colder at times with wintry showers and hill snow but less cold midweek with rain rather than snow. The ecm would be my choice for further ahead with the high to the east and undercutting lows setting up strong cold SE'ly winds and a risk of battleground rain/snow events but the gfs is only leading us back to mild zoneality with the jet further north and mild, dry rather cloudy sw'ly dross in the run up to christmas.

Edited December 4, 2011 by Polar_ Low

[phil nw.]

Thanks for your very usefull analysis Nick S.

Yes we can see the at T144 the models diversifying.

http://www.wetterzentrale.de/pics/Rtavn1441.png

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

http://www.wetterzentrale.de/pics/Recm1441.gif

Looking just beyond that point GFS would still give some frosty conditions with surface cold for a while under the UK high ,but inevitably with all the energy going over the top it sinks it into a milder Euro High by the end.

Not sure about the UKMO after 144--it could ridge more towards Scandi for a while but the core of the Hts look to be south of the jet and it will likely go the same way as GFS afterwards.

ECM is better for coldies ,pushing some energy south of the uk with that cut off low keeping us in a colder pattern.

[Weather Boy]

Absolutely, PL. Significant downgrade from the GFS. What happens after the cold snap Friday/Saturday (if you can still call it that after the downgrade!) between ECM and GFS could hardly be more different, with the ECM having a deep low over southern England, sinking south to bring in an Easterly, whilst GFS throws a huge and very intense high over much of the UK that meanders around the UK and the continent, but is generally centred over southern England.

What with the teleconnections, not to say many of the forecasts on this site (especially GP's) and at the Meto, you'd surely have to favour the GFS scenario? It will be interesting to see which backs down.

Btw - in terms of model performance, can I ask what an Earth happened to that storm that was going to play havoc for Scotland, then Eastern England and especially the Netherlands? Wasn't that supposed to be today? Whatever happened?

[cyclonic happiness]

The Gfs and Ecm 00z are chalk and cheese this morning, the gfs is a huge disappointment for southern britain in the week ahead with only very brief cold, mostly the temps look around average but the charts look very messy and there will at least be some heavy rain to help ease the chronic drought situation in southeast britain, northern britain looks colder at times with wintry showers and hill snow but less cold midweek with rain rather than snow. The ecm would be my choice for further ahead with the high to the east and undercutting lows setting up strong cold SE'ly winds and a risk of battleground rain/snow events but the gfs is only leading us back to mild zoneality with the jet further north and mild, dry rather cloudy sw'ly dross in the run up to christmas.

I couldn't find any meaningful rain for the Midlands on the GFS or the METO charts over the entire run.

Do, you think we'll be able to get something?

[nick sussex]

The Gfs and Ecm 00z are chalk and cheese this morning, the gfs is a huge disappointment for southern britain in the week ahead with only very brief cold, mostly the temps look around average but the charts look very messy and there will at least be some heavy rain to help ease the chronic drought situation in southeast britain, northern britain looks colder at times with wintry showers and hill snow but less cold midweek with rain rather than snow. The ecm would be my choice for further ahead with the high to the east and undercutting lows setting up strong cold SE'ly winds and a risk of battleground rain/snow events but the gfs is only leading us back to mild zoneality with the jet further north and mild, dry rather cloudy sw'ly dross in the run up to christmas.

Good post Frosty and sums things up perfectly.

The GFS is underwhelming with a capital U! the ECM has little or no support, the UKMO is not bad and we might see some surface cold from that, how long that lasts will depend on the PV.

The models seem to be taking turns to go their own way, I suppose you could say the UKMO has been most stable over the last few days.

Anyway it makes for good model watching to see which model has called this correctly.

[Grimsby Snow Lover]

I have just looked through the majority of runs this morning and find the GFS on its own when looking at a northerly forecast for Friday. ECM is supported by the UKMO, NOGAPS, GEM.

Although they are subtle differences they all have the Atlantic high further west allowing the low to the north to sweep down the eastern side of the British Isles. Lets hope the following runs continue to show this northerly and the GFS comes on board again.

I am not looking passed Friday at the minute as this is where I believe FI begins

http://www.wetterzen...cs/Recm1201.gif ecm

http://www.wetterzen...cs/Rukm1201.gif UKMO

http://www.wetterzen...cs/Rngp1321.gif NOGAPS

http://www.wetterzen...cs/Rgem1321.gif GEM

Edited December 4, 2011 by Grimsby Snow Lover

[shedhead]

Absolutely, PL. Significant downgrade from the GFS. What happens after the cold snap Friday/Saturday (if you can still call it that after the downgrade!) between ECM and GFS could hardly be more different, with the ECM having a deep low over southern England, sinking south to bring in an Easterly, whilst GFS throws a huge and very intense high over much of the UK that meanders around the UK and the continent, but is generally centred over southern England. What with the teleconnections, not to say many of the forecasts on this site (especially GP's) and at the Meto, you'd surely have to favour the GFS scenario? It will be interesting to see which backs down. Btw - in terms of model performance, can I ask what an Earth happened to that storm that was going to play havoc for Scotland, then Eastern England and especially the Netherlands? Wasn't that supposed to be today? Whatever happened?

Again this only serves to highlight the utter futility of following every run though, there really is no point, especially at the moment when there is little or no inter model agreement beyond 96hrs.

Edited December 4, 2011 by shedhead

[Cloud 10]

The ECM ensemble mean not interested in a scandi high,unlike the operational.

ECM mean>

ECM op.>

I certainly wouldn't bet against it though given the rather volatile model output at the moment. :wacko:

[Harsh Climate]

Absolutely, PL. Significant downgrade from the GFS. What happens after the cold snap Friday/Saturday (if you can still call it that after the downgrade!) between ECM and GFS could hardly be more different, with the ECM having a deep low over southern England, sinking south to bring in an Easterly, whilst GFS throws a huge and very intense high over much of the UK that meanders around the UK and the continent, but is generally centred over southern England.

What with the teleconnections, not to say many of the forecasts on this site (especially GP's) and at the Meto, you'd surely have to favour the GFS scenario? It will be interesting to see which backs down.

Btw - in terms of model performance, can I ask what an Earth happened to that storm that was going to play havoc for Scotland, then Eastern England and especially the Netherlands? Wasn't that supposed to be today? Whatever happened?

I don't know how you can say the gfs has downgraded. Regarding FI or any upcoming good cold spell it hadn't shown anything remotly interesting! Only in the last day or so has it hinted at possible heights building towards greenland or any decent building blocks to upcoming cold. So in the last couple of days were making progress, especially from the ECM and UKMO too.

We must avoid comparing run to run as its just futile and will just create unecessary ups and downs every single day lol. Look at the output on a whole for a few days, then compare it to a few days before that, thats the best way to unscramble the mess that is the model outputs in this very difficult period lol.

[Weather Boy]

I don't know how you can say the gfs has downgraded. Regarding FI or any upcoming good cold spell it hadn't shown anything remotly interesting! Only in the last day or so has it hinted at possible heights building towards greenland or any decent building blocks to upcoming cold. So in the last couple of days were making progress, especially from the ECM and UKMO too.

We must avoid comparing run to run as its just futile and will just create unecessary ups and downs every single day lol. Look at the output on a whole for a few days, then compare it to a few days before that, thats the best way to unscramble the mess that is the model outputs in this very difficult period lol.

Well, HC, I don't view every run (in fact quite often I just read the thread without viewing the models themselves!) - so I certainly don't compare run to run! I can't recall which run I last viewed probably yesterday that showed (I thought) quite a potent northerly blast, hence my comments about snow in the south (albeit not the south coast) being a possibility.

The buckling and less generous reach of the snow now being progged is, in my view, a serious downgrade from the last run that I viewed yesterday. But maybe I just saw the peak of the GFS's view of the cold blast.

Edited December 4, 2011 by Weather Boy

[nick sussex]

Just a few things pulled out of the NOAA discussions which will effect the pattern in Europe.

DURING WED-THU GUIDANCE IS STILL HAVING DIFFICULTIES IN RESOLVING

THE EVOLUTION OF A SHRTWV FCST TO CROSS THE ERN HALF OF THE CONUS.

ERN PAC/WRN

NOAM DETAILS BECOME LESS CERTAIN BY DAYS 5-7 FRI-SUN... WHICH IN

TURN LEADS TO QUESTION MARKS WITH DOWNSTREAM FLOW.

Full discussions here:

http://www.hpc.ncep....epd/preepd.html

The ECM relies on more amplification upstream to cut that low se'wards, earlier the phasing of that shortwave into the main Canadian troughing will effect how much of a ridge develops in the Atlantic, until theres agreement on them then all the output is liable to chop and change.

Edited December 4, 2011 by nick sussex

[kold weather]

I may go against the grain here but the GFS is more sustainable and far easier evolution to a cold set-up than the ECM.

ECM would be VERY difficult to sustain with the PV the way it currently is and requires alot of factors to fall into place...if anything goes wrong your going to end up with a deep atlantic SSW airflow and very mild temps. The ECM op run is close to this solution by 240hrs but we would JUST get away with it in the east. That is why so few models/ensembles go along with the ECM, because its damn hard to get it to come off!

00z ECM requires at least 2, maybe 3 cutters to get a much colder set-up in, the slider would re-introduce somewhat milder air judging from experience.

00z GFS is FINE...nothing wrong with it at all considering background parameters, ECM looks better but in truth its probably milder than the GFS and with little chance of snow as its just not cold enough flow...and very tough evolution as well, though 240hrs isn't far off being a cracker...

[nick sussex]

Following on from KW's post its true the ECM is very high risk and could end up with the mildest solution if that low doesn't cut se'wards, the UKMO is okay in that the ridge is likely to topple towards Scandi and you'd probably end up with some colder inversion for a while.

The GFS is a very normal type outcome with the PV where it is, you just have to hope the high can get far enough north. If you're feeling lucky go for the ECM, if you're hedging your bets go for the UKMO!

The ECM with its high risk has of course a much greater reward if things go well but of course IF it goes well and thats the big question.

Looking at the ECM De Bilt ensembles, the operational run is backed by the control but thats it, the main clustering looks like a more mobile type of set up.

http://www.weerplaza.nl/15daagseverwachting/default.asp?type=eps_pluim

Edited December 4, 2011 by nick sussex

[bluearmy]

sorry KW - dont see that GFS is more likely to lead to cold than any of the other models. as far as ecm op is concerned, any model wanting to push upper as high as -4c in the area of svaalbard has my attention. i read that the ecm ens mean at day 10 doesnt support a scandi height rise. quite the opposite, looking at the chart attached on the post. remember that ens mean charts are always suppressed in amplification wrt operational output. any bump in mean heights represents a mean ridge and vica versa with troughs. things going on in fi to keep me interested - nothing more than that at the moment.

[BLAST FROM THE PAST]

Evening all,

Tucked up cosy here on the highest hill in Lanarkshire waiting to go sledging tomorrow...

I think many have been pointing out that the pattern doesn't support any Greenland high pressure as the sum of the atmospheric feeds all equates to a strong jet and flat profile

You would think this would mean zero cold into the UK, however the glimor of hope is if the Ukmo is correct we can throw a ridge towards Greenland that is then sheared towards Scandinavia, the jet will then flow across the top of it...

The chances of easterly do increase then because the high will get flattened from the north meaning the shape will be nice and pebble and there will be a returning flow west underneath. The big picture as ever in winter is whether a ridge can gain enough lattitude before being forced east.....

FWIW at 168 The ECM started decent trough disruption towards Greenland but then dismissed it...

UKMO + GFS may be correct here....

And remember this years background signal MIGHT be fighting the bigger background signal of the last 3 years....

Work that out!

Intersting point of the day that one. Also ECM hasn't ditched it this morning...very interesting development?

BFTP

I kind of hinted at that to Blast the other day Steve. We have the signal of the last few years of the jet stream wanting to dive south, fighting against the stratospheric signal of this year pulling the jet stream north. Presently that leaves in a cold zonality. I don't think there will need to be much stratospheric change to tip the scales in the other direction.

Kumquat, there is no sign of a minor stratospheric warming never mind an SSW!

Hi Ed

That is my point [eg perturbation cycle, -ve PDO etc] and nice to see some interest stirred. Perturbation kicked in Feb 2007....coincidence? It is a player IMO

BFTP

[kold weather]

sorry KW - dont see that GFS is more likely to lead to cold than any of the other models. as far as ecm op is concerned, any model wanting to push upper as high as -4c in the area of svaalbard has my attention. i read that the ecm ens mean at day 10 doesnt support a scandi height rise. quite the opposite, looking at the chart attached on the post. remember that ens mean charts are always suppressed in amplification wrt operational output. any bump in mean heights represents a mean ridge and vica versa with troughs. things going on in fi to keep me interested - nothing more than that at the moment.

The ECM op is milder than the GFS, I'm willing to bet any money on that out to 240hrs, the ECM is a classic looking chart but isn't quite there. The GFs looks 'boring' but I'm willing to bet you'd get a signifcant inversion in such a set-up and probably fog/freezing fog with it.

As others have said there really isn;t any support for the ECM op run, I'd feel confident that 7-8 times out of 10 the ECM solutuion will lead to a cold shot for Europe but we'd be just too far west probably with fronts straddling the country. We'd need probably a strong low to cut-off at 240hrs and its next to impossible to tell what would happen next. Most of the time a new LP will form its just whether it can cut-off or whether the PV swings it round to the north. Tough call!

Remember when I say cold with the GFS...its inversion cold...which would be highly likely given the time of year and the set-up before it.

Overall though there is nothing really to moan about in the models today, I think things are setting up rather nicely considering the near record AO values we have had in the last few days...and I think the ECM is a BIG hint for what will happen deeper into winter, just think right now is too soon...

[shedhead]

Out to 96hrs the 06 GFS sticks with it's 00 set up, so I'd expect it to have high pressure over us again at 144hrs and as a result still be against the ECM evolution for that time.

[johnholmes]

If we look closely at the latest 500mb anomaly chart outputs it is possible to make a case out for either the T+240 GFS or ECMWF charts.

But the main form horse must be on pressure rises, at that time scale, say out to T+3 days or so later, occurring to the SW of the country, so more settled anticylconic type weather edging in from the SW. How much fog and frost there would be is of course entirely dependent on cloud cover and that is impossible to say this far out. Again the betting would be INITIALLY, given where the ridge would originate from, a fair amount.

What happens beyond that can be no more than speculation NOT forecasting in my view.

[bluearmy]

The ECM op is milder than the GFS, I'm willing to bet any money on that out to 240hrs, the ECM is a classic looking chart but isn't quite there. The GFs looks 'boring' but I'm willing to bet you'd get a signifcant inversion in such a set-up and probably fog/freezing fog with it.

As others have said there really isn;t any support for the ECM op run, I'd feel confident that 7-8 times out of 10 the ECM solutuion will lead to a cold shot for Europe but we'd be just too far west probably with fronts straddling the country. We'd need probably a strong low to cut-off at 240hrs and its next to impossible to tell what would happen next. Most of the time a new LP will form its just whether it can cut-off or whether the PV swings it round to the north. Tough call!

Remember when I say cold with the GFS...its inversion cold...which would be highly likely given the time of year and the set-up before it.

Overall though there is nothing really to moan about in the models today, I think things are setting up rather nicely considering the near record AO values we have had in the last few days...and I think the ECM is a BIG hint for what will happen deeper into winter, just think right now is too soon...

point taken re inversion cold on gfs. my thinking is leaning more towards the longer term and i see the pattern on ecm as being one which will take us in a better direction for proper cold as we head towards late december.