Model Output Discussion

[shuggee]

A fresh MODEL OUTPUT DISCUSSION thread.

This thread is of course, to discuss the models.

It's not for posts about the lack of snow in your back garden, how you feel if a random chart at T+300 came off nor is it to post about the lovely people on the BBC forecasts and what they are saying. There are plenty of other threads for such chatter - the best being the new one pinned alongside this here:

Happy model watching

[len]

Craigers said on last page of locked thread.............

"GEM is my dream of a chart! which would be amazing for Yorkshire full stop! and with Europe being so cold already, it will deliver with more of a punch than of past years!!!"

Trouble is the deep cold has been shunted out of most of Europe.... http://www.uni-koeln.de/math-nat-fak/geomet/meteo/winfos/euisoTTPPWW.gif

6:00 am shows most of Europe marginal with barely a frost.

Any dry cold to help snow Tues/Wed has to come from the North or from Scandi

Len

Edited December 26, 2009 by len

[Sawel]

This post is in reply to a post by Worzel on the old MO thread.

Worzel you said this..."So in all the confusion we're back to looking at the GEM as a viable model.... "

The best verifiying models at +120 hrs in order are.... ECM --> UKMO --> GEM --> GFS

The best verifiying models at +144 hrs in order are.... ECM --> UKMO --> GEM --> GFS

People on here talk about the "big 3" as being the ECM, the UKMO and the GFS but the GEM is a better verifying model than the GFS.

Just because we can access much more information on 4 GFS runs a day compared to the limited information we can see on the GEM twice a day, people don't even bother their backsides looking at the GEM.

In reality, the big 3 consists of the ECM, UKMO and the GEM.

http://www.emc.ncep..../html/acz5.html (120 hrs)

http://www.emc.ncep..../html/acz6.html (144 hrs)

Edited December 26, 2009 by shuggee

[Nick F]

Hope everyone had a nice Christmas, quick look at the charts after being away from them these last few days.

The general broadscale evolution can be agreed on for this coming week of low pressure sliding to the south of the UK and cold air returning southwards across much of the UK by middle of the week. However, still alot of uncertainty with the detail, as always, with marginal set-ups, with regards to the position of the front drifting north on Tuesday to who will most likely see snow on its northern side as it meets the colder air sinking down from the north. At the moment, it would likely be Wales, The Midlands and perhaps northern half of East Anglia into Lincs seeing a spell of heavy snow by mid-week, with milder air across southern counties initially. But there is still scope this far off for the front to shift 100-200 miles north or south, which would make a big difference between getting rain/sleet/snow.

There does seem good consensus that the cold air will win by Thursday though. It's a shame that low sits over Scandavia, which holds back much colder air to the NE, though much of the UK should have sufficiently cold uppers/low thicknesses by end of the week for snow to fall to lower levels.

[Yeti]

Craigers said on last page of locked thread.............

"GEM is my dream of a chart! which would be amazing for Yorkshire full stop! and with Europe being so cold already, it will deliver with more of a punch than of past years!!!"

Trouble is the deep cold has been shunted out of most of Europe.... http://www.uni-koeln.de/math-nat-fak/geomet/meteo/winfos/euisoTTPPWW.gif

6:00 am shows most of Europe marginal with barely a frost.

Any dry cold to help snow Tues/Wed has to come from the North or from Scandi

Len

Good point. Temperatures have risen over 20c here from -16 to 4 in just a few days - the cold spell has gone entirely from virtually all of Europe except the northern half of the UK.

This would not necessarily be a problem if, like last time, the cold air were to come from the E, as Europe cools down BEFORE the UK in such setups. However cold air is arriving from a *shallow* cold pool over Scandinavia to the N/NE of the UK and Europe should actually cool down after the UK this time:

http://www.wetterzentrale.de/pics/Rtavn962.png

http://www.wetterzentrale.de/pics/Rtavn1682.png

The only potential problem with this is if we see this kind of setup:

http://www.wetterzentrale.de/pics/Recm2401.gif

Normally this would bring widespread blizzards along the "battle ground" with a strong SE wind blowing off the continent. However as upper temps tend to be higher in these setups, ground temps need to remain favourable to prevent rain, and if the continent is not cold enough this may not happen. Of course if such a setup occurred later on, like the ECM, there would be no problem, but the UK will probably have to wait until the cold air filters S for widespread low-level snow from a setup like the above.

Here's hoping the low tracks as far S as possible - this would favour everybody!

[Snowaddict]

I think you have read my post out of context sawel.

Several days ago I posted as below, but I was told by several members that these models were everything from rubbish to cannon fodder and to stop posting them as I was just trying to wind people up. Needless to say at the time they were showing some of the mildest senarios at 132hrs...

Posted 22 December 2009 - 22:48

GME is generally an excellent model out to T+132hrs (it is German after all) and GEM has proven time and time again not only to spot trends but also provide some of the most reliable modelling in the T+120 to T+192hr timeframe. Therefore with respect I am not as you suggest using the least reliable charts to prove a rather baseless point - far from it in fact.

This post has been edited by Worzel: 22 December 2009 - 22:49

I would be interested to know, Worzel, what's your opinion on the developing evolution at the moment? What do you see as the medium term outcome?

TETIS was spot on earlier in his reply to you. Whenver you see any deviation from a colder pattern on the outputs you are first to highlight this. You know very well that many people on here would truly like to see deep, bitter cold advected across the UK & Ireland.

Your post was not taken out of context at all, GEM is performing very well in the Northern Hemisphere when weighted against all of the other models.

Your approach is remarkably similar to a previous poster, Jemtom!

Regardless of the outcome, at least there are many on here who genuinely want to see traditional synoptics & conditions but are still able to give an objective overview.

The main points up for review on the coming 12Z's...

• We need to see a continuation of a more southerly track for these lows in the coming week, or at least a more rapid southward progression of the colder air..
• We need to see a shift away from that nuisance trough over Scandi, which is proving very troublesome in blocking extremely cold air to the northeast.
• Longer term we need to see neater trends in terms of the longevity of the pattern..

[Yeti]

I think you have read my post out of context sawel.

Several days ago I posted as below, but I was told by several members that these models were everything from rubbish to cannon fodder and to stop posting them as I was just trying to wind people up. Needless to say at the time they were showing some of the mildest senarios at 132hrs...

Posted 22 December 2009 - 22:48

GME is generally an excellent model out to T+132hrs (it is German after all) and GEM has proven time and time again not only to spot trends but also provide some of the most reliable modelling in the T+120 to T+192hr timeframe. Therefore with respect I am not as you suggest using the least reliable charts to prove a rather baseless point - far from it in fact.

This post has been edited by Worzel: 22 December 2009 - 22:49

Interestingly on weather forums in Germany (wetterzentrale forum) and Spain people tend to look at the GEM and GME a lot more than we do - I've always found the GEM a good, reliable and consistent model and it's a shame we don't look at it more often (and no that has nothing to do with today's output! )

Trust the Brits to favour the American and British models

[nick sussex]

I think you have read my post out of context sawel.

Several days ago I posted as below, but I was told by several members that these models were everything from rubbish to cannon fodder and to stop posting them as I was just trying to wind people up. Needless to say at the time they were showing some of the mildest senarios at 132hrs...

Posted 22 December 2009 - 22:48

GME is generally an excellent model out to T+132hrs (it is German after all) and GEM has proven time and time again not only to spot trends but also provide some of the most reliable modelling in the T+120 to T+192hr timeframe. Therefore with respect I am not as you suggest using the least reliable charts to prove a rather baseless point - far from it in fact.

This post has been edited by Worzel: 22 December 2009 - 22:49

I agree the GEM is a good model and has improved alot this last year, the GME however is not reliable, soon people will be sticking up the Russian model which makes the GME look good! As we now have a big 4 IMO all the other models are fun to look at but that's it. If someone want's to prove a point about a trend they need to support this with one of the big 4.

[Geordiesnow]

I must say, i had to smile at some of the comments when reading that last thread, if all the models trended towards last nights GFS 18Za and UKMO runs, you can forget about a widespread snowy spell.

Short term, it upgraded again, even the UKMO now wants to send the low further South, how the height rises in the north and lower heights in the south is uncertain. I'm not sure why people are worrying about charts that are so far out, they are likely to change all the time. I did wish the FI charts of yesterday carried on today's runs but they havant but that is not a disaster by any means.

Who knows what the 12Z's might show, hopefully they keep the low as far south as possible and let the ne'lies dig in for a while.

[Cecil Hogmanay Melchett]

Well we have the beeb going for cold next week and that will do for starters.Longer term i am beginning to have

real doubts,the models *seem* to be picking up on height rises to our south which is preventing the trough

over Scandy from dropping south and allow the siberian high to ridge west.

The low coming up is obviously the uppermost on peoples minds but im watching events in the middle timeframe which

will determine of its a short cold snap(3-5 days) or something more memorable.

[SMU]

Well we have the beeb going for cold next week and that will do for starters.Longer term i am beginning to have

real doubts,the models *seem* to be picking up on height rises to our south which is preventing the trough

over Scandy from dropping south and allow the siberian high to ridge west.

The low coming up is obviously the uppermost on peoples minds but im watching events in the middle timeframe which

will determine of its a short cold snap(3-5 days) or something more memorable.

Here we go then guys- the most eagerly anticipated set of 12'zeds in a long long time---

Good luck & lets hope for a clasic run from them All-

even the WMA!

S

[Barb]

Here we go then guys- the most eagerly anticipated set of 12'zeds in a long long time---

Good luck & lets hope for a clasic run from them All-

even the WMA!

S

Strap yourselves in because the rollercoaster is about to set off once again I think...

[SMU]

Strap yourselves in because the rollercoaster is about to set off once again I think...

yep-

THe 12z is slowing the evolution down just slightly- if your running frame for frame comparisons with the 06z then run the gap to 12 Hours & not 6hours-

Steve

[Barb]

All looks a bit further North on this one.

[Matt12]

More like "anywhere in southern England". There were 13 successive days of snow cover in parts of the Midlands in February 2009, and parts of northern England are currently experiencing their 9th successive day of snow cover.

To be pedantic there was a 10 day cold spell in parts of southern (especially south-western) England as well in late December and early January 2008/09, but it did not feature much in the way of snow.

I think the longer-term outlook will continue to chop and change with time. What matters now for cold/snow lovers is that the models have all positioned the low for 28/29 December further south, allowing the cold air to head south a lot sooner and with far less uncertainty.

True. I did exaggerate quite a lot.

I would still be surprised if we have a 15 day cold spell though. Having said that, I would absolutely love to be proved wrong. Whatever happens, we will probably see some snow shortly after the new year, which will be nice, especially having just had a cold spell before Christmas as well.

Edited December 26, 2009 by Matt12

[MKN]

Further north but still looks like wales and the midlands are in the firing line for some snow possibly. Shame its not +12 because id be getting excited then, seen many chances like this go to far south or north, very small margin for error in these setups imo.

[Barb]

A bit further North on this run but there's more precip about so I'll take that thank you very much. Most should be snow from an IMBY perspective.

Of course it'll probably come down to the day itself before we know where it's all gonna happen.

[Barb]

Wow... 42 hour blizzard showing on this run for valleys and mid Wales.

[SMU]

The 12z is a spectacular one with significant snow for some parts of the West & wales, possibly even the west country & ireland- not to mention Eastern scotland through convection-

not quite so good for the South & SE- the key though is some consistency on the 'cone' of error- yesterday was all over the shop- lets see what the UKMO & ECM bring to the Party- as well as how far the models sustain the cold-

S

[Cymro]

Wow... 42 hour blizzard showing on this run for valleys and mid Wales.

Sorry you say valleys so does that mean that Carmarthenshire, Pembs and say Swansea won't come trumps with this? If so I fail to see what angle your looking at. Much more precipitation on this run which is looking very good but theres a ew days to go and it could all change .

[Matt12]

The only certainty is that the charts WILL change in the coming days! Look how much they have changed, even since yesterday!!!

[Barb]

Sorry you say valleys so does that mean that Carmarthenshire, Pembs and say Swansea won't come trumps with this? If so I fail to see what angle your looking at. Much more precipitation on this run which is looking very good but theres a ew days to go and it could all change .

I say valleys because the elevation here will help and Mid Wales because it's further North into the cold. Looks like the sweet spot on this run but you should get snow also. Anyway, pointless discussing in detail one run. In general though in this set up Valleys/Mid Wales/West Midlands are always going to be in the prime firing line.

[Supercell]

Woah... this is a snow machine for some areas. Band after band of ppn smashing in to the cold air.

[swfc]

The 12z is a spectacular one with significant snow for some parts of the West & wales, possibly even the west country & ireland- not to mention Eastern scotland through convection-

not quite so good for the South & SE- the key though is some consistency on the 'cone' of error- yesterday was all over the shop- lets see what the UKMO & ECM bring to the Party- as well as how far the models sustain the cold-

S

just a quick one steve.Whats stopping the low slipping sse and the high pushing down bringing an easterley.thanks

[Barb]

Be different next run of course.