Model Output Discussion - 8th December Onwards

[OldMetMan]

Some preliminary thoughts ahead of the later model runs.

The see-sawing that is taking place within the models currently does, I think, represent one of the most difficult weather trends to forecast in winters when it happens - the battle between mild zonal conditions and cold blocked ones - and the tussle that takes place in the atmosphere, and how the models depict this, can be frustrating and also fascinating to watch. Plus I do believe that in general the models have a pretty hard time with them.

As far as what we might be facing in this current situation, although the outcome for later this week is, I think, still highly uncertain, as far as I can see we are likely to see this mild v cold battle for some time yet, maybe well into January. It has the "look" of previous such battles, some more severe than others and many more where the cold never quite made it. But this time around, I sense we might be seeing the real deal at some point.

The advance indicators of such a spell can sometimes be seen some time in advance, such as a low-latitude jet and a build up of very cold air to the E and/or NE. At present, while we do have a cold pool to our E plus a substantial HP over N Russia, I think it is not that cold and on that basis it seems to me that Atlantic systems will be more able to make more NE progress than otherwise.

However, we are in the depths of winter and there have already been indicators of unusual cold over Europe (the massive snowfall that paralysed areas of Russia not that many days ago) so, from the model perspective, I think the GFS in particular is going to continue with the mild/cold alternating for a while BUT....ultimately I feel there will be a significant cold breakthrough - quite possibly very cold - and out of the models that seem most likely to see this happening first I would say the GFS, the GEM or the UKMet will be the candidates.

Meanwhile, to see a perfect historical example of this process at its best, take a look at the last week of December 1978 in the archives, which culminated in the most ferocious blizzard I can remember across the south with day time maxs of -3C. The chart below says it all - a cold lover's dream!

[MKN]

Not good for breakdown snow apart from Scotland.

Karyo

Keep your eye on the surface conditions. 3pm Thurs temps range between -1 up to 4/5c down the spine of the country into the midlands. Most areas have dew points below zero aswell.

[Gavin Hannah]

Yes Yes Yes as said by Meg Ryan! Lets have this low further south and have some of that above!

That almost exactly looks like the current output for the exception of this LP system!

Edited December 9, 2012 by IBringTheHammer

[karyo]

The Atlantic low may have moved further south compared to the 6z but it is deeper and rounder which brings a much milder flow from the south.

Karyo

[beng]

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=114&mode=0&carte=1

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=120&mode=0&carte=1

Far West Atlantic - small system that produced the southerly runner on the 06z is forming.

[Jonan92]

00z run was much much better

00z

12z

[clark3r]

Wonder if this a trend and the low ill go further south in coming runs?

[MKN]

Well by 120 the 12z is very progressive there needs to be more pressure from the northeast to give a snowy breakdown. still fun and games for 24 hours in Scotland at least.

[karyo]

Keep your eye on the surface conditions. 3pm Thurs temps range between -1 up to 4/5c down the spine of the country into the midlands. Most areas have dew points below zero aswell.

Yes, but there is no precipitation. By the time the precipitation arrives the upper air temperatures are above 0c.

00z run was much much better

00z

12z

Agreed!

[Matty M]

unfortunately the UKM has the SW moew developed at t60 and is unlikely to be good.

[swfc]

Full on atlantic low developing so in that respect not as good as the ooz..Still better in the early stages but swings and roundabouts as to say

[ITSY]

Look at the chart below - sure the weather would be wet and dull here, but with that huge block over Siberia, the potential for massive medium-term changes in the model output are huge. The power of the Atlantic against that block is an immense battle. Somewhere in Europe (in this run, Russia) will see some epic snowfalls. For the moment, it looks like cold short-term, Atlantic mid-term but after that is anyone's guess. The Block has a lot of power...

Edited December 9, 2012 by ITSY

[SMU]

http://www.meteociel...96-21.GIF?09-17

ouch-

After this mornings 00z uptick, no consistency from that pattern building- the UKMO is poor.

S

Edited December 9, 2012 by Steve Murr

[Matty M]

UKM final nail on coffin. We had a slight bit of hope this morning. It is now gone.

[cooling climate]

Before the 12z GFS run came out I thought to myself I would not be surprised if the over

progressive 12's shows a dartboard low and sure enough.

Where this run stands with the UKMO and ECM we will have to wait and see.

[Snowmad79]

Some preliminary thoughts ahead of the later model runs.

The see-sawing that is taking place within the models currently does, I think, represent one of the most difficult weather trends to forecast in winters when it happens - the battle between mild zonal conditions and cold blocked ones - and the tussle that takes place in the atmosphere, and how the models depict this, can be frustrating and also fascinating to watch. Plus I do believe that in general the models have a pretty hard time with them.

As far as what we might be facing in this current situation, although the outcome for later this week is, I think, still highly uncertain, as far as I can see we are likely to see this mild v cold battle for some time yet, maybe well into January. It has the "look" of previous such battles, some more severe than others and many more where the cold never quite made it. But this time around, I sense we might be seeing the real deal at some point.

The advance indicators of such a spell can sometimes be seen some time in advance, such as a low-latitude jet and a build up of very cold air to the E and/or NE. At present, while we do have a cold pool to our E plus a substantial HP over N Russia, I think it is not that cold and on that basis it seems to me that Atlantic systems will be more able to make more NE progress than otherwise.

However, we are in the depths of winter and there have already been indicators of unusual cold over Europe (the massive snowfall that paralysed areas of Russia not that many days ago) so, from the model perspective, I think the GFS in particular is going to continue with the mild/cold alternating for a while BUT....ultimately I feel there will be a significant cold breakthrough - quite possibly very cold - and out of the models that seem most likely to see this happening first I would say the GFS, the GEM or the UKMet will be the candidates.

Meanwhile, to see a perfect historical example of this process at its best, take a look at the last week of December 1978 in the archives, which culminated in the most ferocious blizzard I can remember across the south with day time maxs of -3C. The chart below says it all - a cold lover's dream!

Very informative post as per usual. Thanks. Here's how the senario above was looking some 6 days or so prior:

Edited December 9, 2012 by Snowmad79

[MKN]

Yes, but there is no precipitation. By the time the precipitation arrives the upper air temperatures are above 0c.

Agreed!

Yup unfortunately the shape of the low pressure is not good. Still we all know what the gfs is like at showing huge lows that they then shy away from. Hopefully itl be better shaped and not as strong over coming runs.

[Snowman.]

Lost are southerly tracker but that lows looks interesting. A smaller amount of energy on the east coast as well but its too far out to even consider.

Edited December 9, 2012 by SN0WM4N

[snowking]

http://www.meteociel...96-21.GIF?09-17

ouch-

After this mornings 00z uptick, no consistency from that pattern building- the UKMO is poor.

S

True, but 20mb deepening as it makes the jump from high to low res?

Not impossible but a little improbable

SK

[Gavin Hannah]

Look at the chart below - sure the weather would be wet and dull here, but with that huge block over Siberia, the potential for massive medium-term changes in the model output are huge. The power of the Atlantic against that block is an immense battle. Somewhere in Europe (in this run, Russia) will see some epic snowfalls. For the moment, it looks like cold short-term, Atlantic mid-term but after that is anyone's guess. The Block has a lot of power...

Agreed if the low develops as progged here, it would not take long for it draw in colder air from the east, north and north west.

Keeping an eye on it at t.144. The low is getting squeezed flat. It could easily undercut. Just need it to be further south.

Compared the the 06Z..

The Low is tilted at a different angle and the Channel low is gone, so not on the same trend as 06 and 18Z post t.72, but, a bigger chance of the low sliding under if we can get it moving further south as the current run has demonstrated it doing.

All I'm going to say is that the time frame post 72 hours is looking very interesting...... watch this space.

Edited December 9, 2012 by IBringTheHammer

[OldMetMan]

Yes Yes Yes as said by Meg Ryan! Lets have this low further south and have some of that above!

That almost exactly looks like the current output for the exception of this LP system!

It was exceptionally cold air involved on that occasion with a remarkable temperature gradient across the frontal boundary. An occluding LP went right up the Channel and temps to the S of the front over the Channel Isles were +10C! I shall never forget that one!

[ITSY]

Indeed, to see this at T+144 is pretty unusual

Only minor tweaks here or there would send our temperatures plummeting. This run, as per at the moment, could go either way. Either mild or v cold. take your pick, mine is with the cold scenario, as heights look to gather momentum to the East of Greenland, the easterlies spread back in across northern europe and the low is a bit further south.

EDIT: Very close to where we want to be at 156.

Edited December 9, 2012 by ITSY

[Snowly does it]

12z clearly much more progressive and in line with the MetO updates - turning milder and SWerly from Friday. Whilst there are small corrections early on that go the way they need to if cold were to prolong, the overall pattern is much less cold on this compared to previous runs - especially the 6z where cold air was not far away. Here the above 0 uppers are chunky and dominant. It will be hard for a cold spell to develop if that fat Atlantic low doesnt do something different.

[Dampdorset82]

Am i the only that cant see a cold potential from the 12z run? I see a deep area of low pressure that will be bringing in wet and windy weather and a serious issue for flooded areas? Im talking about a reliable and semi reliable time frame here.

[Ian Brown]

UKM final nail on coffin. We had a slight bit of hope this morning. It is now gone.

Well I think after the last couple of days it was stretching it for the Lows to take that South Easterly track that would have kept us on the cold side. Our focus should be now on the fact that by T144, pressure is still OK over Greenland the block out East means that the Atlantic is going no further than the tip of Norway.