General Model Output Discussion

[Alex95]

Just to clarify (and if I'm wrong I'm sure others will clarify that ) the models seem to be predicting this in terms of snow:

Thursday: Snow showers NE England/E Scotland

Friday: Snow showers N/E Scotland, E England, E Ireland

Saturday/Sunday: Some uncertainty, possibly prolonged snow in Scotland, snow showers in most other eastern districts of England and Ireland

Early next week: Snow showers still piling in across E Scotland + England with the possibility of prolonged snow edging into the south should the depression get far enough north.

If I'm wrong please let me know as this is simply my amateur take on things, and btw I know there is a chance of snow in the SE tomorrow night but I didn't mention it as it should be insignificant and marginal. I expect the most snow to be in Eastern Scotland and NE England (particularly the North York Moors), with other Eastern districts of England doing well. Anywhere else could get some heavy snow but it will appear at shorter notice.

[johnholmes]

The models, out to T+48=UK Met and GFS then T+72 onwards includes ECMWF, so for the more immediate short term type forecasting are in pretty fair agreement.

To sum up, and trying to get a more sensible idea into here than some folk are giving, not all by any means. I'm sure that all but the newest of arrivals here are becoming aware of those posters who should be read and those best skipped over.

End of yet another jh non direct model comment.

Back to the models.

The start of the New Year is going to be cold for everywhere in the UK; frost, severe in places for pretty well all parts except the far SW coastal regions, even here don't be too surprised if you find white on your windscreen on at least one morning-probably frost!

-10 to -15C mins WILL occur, obviously not widely but the usual places especially as some will get a fresh clean snow cover.

Of snow then obviously its northern and eastern/central Scotland in the main firing line, both from N Sea showers and that low expected to track into the country over the weekend.

Eastern and NE'ern areas of England are also in much the same situation and for the same reasons, the risk extending into the SE before the combination of the high to the NW and the low to the SW back the winds SE.

How far north any effect of precipitation from this low extends-this far out is pure conjecture, so best left at that-conjecture.

The overall pattern is locked into cold, from basic synoptic charts out to items like AO/NAO/PDO and perhaps even further out. So for cold lovers enjoy whatever the weather brings you of the cold variety over the next 10 days possibly out to 20 days-beyond that then go see a crystal ball lady!

re the above about snow

I should add that as the low/trough moves south then as winds change to onshore in other places, N Ireland along with parts of NW England, Cheshire gap etc and Wales, then sharp snow showers are likely so keep an eye on the radar folks wherever you are.

Edited December 30, 2009 by johnholmes

[phil nw.]

I find these charts a good view of the upper flow of cold air coming south over the UK at T96hrs. on 12z ECM

http://www.ecmwf.int...3012!!chart.gif

The small low showing on the fax bringing the air straight off the Greenland Icecap, if you follow the isobars.

http://www.meteociel.../fax/fax72s.gif

By T120hrs.

http://www.ecmwf.int...3012!!chart.gif

Look how far south the arctic air digs down,the advantage(if you are looking for cold)of a well placed omega block.

No chance of a Northerly toppler here,the jet is well South as can be seen.

Great setup.

Edited December 30, 2009 by phil n.warks.

[Ian Fergusson]

The models, out to T+48=UK Met and GFS then T+72 onwards includes ECMWF, so for the more immediate short term type forecasting are in pretty fair agreement.

To sum up, and trying to get a more sensible idea into here than some folk are giving, not all by any means. I'm sure that all but the newest of arrivals here are becoming aware of those posters who should be read and those best skipped over.

End of yet another jh non direct model comment.

Back to the models.

The start of the New Year is going to be cold for everywhere in the UK; frost, severe in places for pretty well all parts except the far SW coastal regions, even here don't be too surprised if you find white on your windscreen on at least one morning-probably frost!

-10 to -15C mins WILL occur, obviously not widely but the usual places especially as some will get a fresh clean snow cover.

Of snow then obviously its northern and eastern/central Scotland in the main firing line, both from N Sea showers and that low expected to track into the country over the weekend.

Eastern and NE'ern areas of England are also in much the same situation and for the same reasons, the risk extending into the SE before the combination of the high to the NW and the low to the SW back the winds SE.

How far north any effect of precipitation from this low extends-this far out is pure conjecture, so best left at that-conjecture.

The overall pattern is locked into cold, from basic synoptic charts out to items like AO/NAO/PDO and perhaps even further out. So for cold lovers enjoy whatever the weather brings you of the cold variety over the next 10 days possibly out to 20 days-beyond that then go see a crystal ball lady!

re the above about snow

I should add that as the low/trough moves south then as winds change to onshore in other places, N Ireland along with parts of NW England, Cheshire gap etc and Wales, then sharp snow showers are likely so keep an eye on the radar folks wherever you are.

John - succinct, learned and measured summary - as ever. Thanks.

[MAF]

Thank you John, as ever, to the point and balanced. a question, if i may. in my very amatuer way i am seeing the cold period to be mainly dry. do you feel that any PPN will be light, or sustained? i also (correctly or not) notice a possible setup in the models for a band of PPN to come in from the East and possibly create a Thames streamer. any ideas?

as for crystal balls. perhaps we should nickname you mystic John

regards, Mick

[TEITS]

I know we're all very keen to see what happens into next week. However again the GFS indicates snow showers for E areas tomorrow.

http://www.wetterzentrale.de/pics/Rtavn304.png

During Friday it looks as though a trough is going to push S from the NE.

http://www.wetterzentrale.de/pics/Rtavn424.png

[Bolton67]

I know we're all very keen to see what happens into next week. However again the GFS indicates snow showers for E areas tomorrow.

http://www.wetterzen...cs/Rtavn304.png

During Friday it looks as though a trough is going to push S from the NE.

http://www.wetterzen...cs/Rtavn424.png

http://www.wzkarten.de/pics/Rtavn424.png

TETIS.. wash streamer?

[SMU]

http://91.121.94.83/modeles/gfs/run/gfsnh-0-54.png?18

Anyone been noticing how the Norway trough is getting furtherr & further south & west with time- maybe a threat of heavy snow along the east coast & up to scotland-

Steve

[Thundery wintry showers]

I expect much of East Anglia, away from the northern and eastern coastal fringes, to see a snow cover on Friday as well, because the cold air will be firmly established by then. Maybe even parts of the SE for a time, though with winds backing northerly showers will tend to become more confined to the far east as the cold air digs in.

[winter watcher]

The models, out to T+48=UK Met and GFS then T+72 onwards includes ECMWF, so for the more immediate short term type forecasting are in pretty fair agreement.

To sum up, and trying to get a more sensible idea into here than some folk are giving, not all by any means. I'm sure that all but the newest of arrivals here are becoming aware of those posters who should be read and those best skipped over.

End of yet another jh non direct model comment.

Back to the models.

The start of the New Year is going to be cold for everywhere in the UK; frost, severe in places for pretty well all parts except the far SW coastal regions, even here don't be too surprised if you find white on your windscreen on at least one morning-probably frost!

-10 to -15C mins WILL occur, obviously not widely but the usual places especially as some will get a fresh clean snow cover.

Of snow then obviously its northern and eastern/central Scotland in the main firing line, both from N Sea showers and that low expected to track into the country over the weekend.

Eastern and NE'ern areas of England are also in much the same situation and for the same reasons, the risk extending into the SE before the combination of the high to the NW and the low to the SW back the winds SE.

How far north any effect of precipitation from this low extends-this far out is pure conjecture, so best left at that-conjecture.

The overall pattern is locked into cold, from basic synoptic charts out to items like AO/NAO/PDO and perhaps even further out. So for cold lovers enjoy whatever the weather brings you of the cold variety over the next 10 days possibly out to 20 days-beyond that then go see a crystal ball lady!

re the above about snow

I should add that as the low/trough moves south then as winds change to onshore in other places, N Ireland along with parts of NW England, Cheshire gap etc and Wales, then sharp snow showers are likely so keep an eye on the radar folks wherever you are.

I thought Southern And Eastern areas John would be perfectly set up for connective snow with the wind direction obviously not very surprised and confused :lol:

[Frosty.]

Would I be right in thinking there is a polar low heading into scotland this weekend? that could prove a potent feature and would pep up the snow showers into something prolonged and heavy? Anyway, the charts are far better than we should be expecting as I understand we are going through a stratospheric cooling episode at the moment but we seem set to remain in a negative NAO pattern for the time being. AWESOME potential for the next 6-15 days, I think a maximum of 15 days before the pattern breaks down although it could go either way? With an Arctic and or Polar Continental airflow dominating i'm sure there will be troughs embedded in the flow to give everyone at least some snow and in scotland i'm sure some record minima will be recorded during next week.

[andy_leics22]

Would I be right in thinking there is a polar low heading into scotland this weekend? that could prove a potent feature and would pep up the snow showers into something prolonged and heavy? Anyway, the charts are far better than we should be expecting as I understand we are going through a stratospheric cooling episode at the moment but we seem set to remain in a negative NAO pattern for the time being. AWESOME potential for the next 6-15 days, I think a maximum of 15 days before the pattern breaks down although it could go either way? With an Arctic and or Polar Continental airflow dominating i'm sure there will be troughs embedded in the flow to give everyone at least some snow and in scotland i'm sure some record minima will be recorded during next week.

As far as I know... Polaw Lows don't get picked up by models.

[Thundery wintry showers]

No, it's a trough heading south-south-west from Scandinavia, and it's not associated with much precipitation in itself, but should help generate some significant shower activity in areas exposed to onshore winds around its periphery. Recent runs are progging this feature further west and south with time, introducing a significant chance of snow showers for north-west England on Saturday, which may extend to parts of Wales in future runs if the current trend continues.

[Paul]

As far as I know... Polaw Lows don't get picked up by models.

That's not strictly true, polar lows are usually fairly small mesoscale features so would be unlikely to be picked up by the medium range models such as gfs, ecm etc, but higher res models are more than capable of picking them up.

[Guest]

As far as I know... Polaw Lows don't get picked up by models.

You are quite correct, Polar Lows don't get picked up by the models, however, the conditions which allow Polar Lows to form are picked up by the models, and by serial straw clutchers like myself.

[Alex95]

http://91.121.94.83/modeles/gfs/run/gfsnh-0-54.png?18

Anyone been noticing how the Norway trough is getting furtherr & further south & west with time- maybe a threat of heavy snow along the east coast & up to scotland-

Steve

Yes I have noticed this, I can't think of any similar examples, but I suspect the risk is there for some prolonged snowfall for the NE as well as Scotland, I saw a fax chart earlier with an occlusion across N England.

[kold weather]

http://www.wzkarten....cs/Rtavn424.png

TETIS.. wash streamer?

I'd have thought thats quite possible, as well as the Kent streamer, that should set-up further east this time round as the flow looks a bit more northerly then last time.

Anyway IMO the most plauseable solution right now is a E/NE/N airflow till about the 9-11th, then high pressure to slowly build over the UK...after that much depends on the exact location of the PV, we want it to get shunted towards Eastern Canada, with a block in place already the southerly jet could try to undercut the high and even if that doesn't happen any shortwaves on the eastern part of the high should keep heights quite close to the UK...

[Optimus Prime]

As far as I know Polar Lows generally don't originate from the NE. They usually track long distances from direct north? They do sometimes crop up without being expected by the run of the mill models.

[Alex95]

As far as I know Polar Lows generally don't originate from the NE. They usually track long distances from direct north? They do sometimes crop up without being expected by the run of the mill models.

I might be wrong, but didn't the polar low in Dec 2000 which affected Western areas come on the back of a NE'ly flow?

[andy_leics22]

That's not strictly true, polar lows are usually fairly small mesoscale features so would be unlikely to be picked up by the medium range models such as gfs, ecm etc, but higher res models are more than capable of picking them up.

Ok thanks boss I appreciate that See... I am a mere amateur

[Optimus Prime]

That's what one looks like. 2004 or March 2006 was the last one I believe.

Would definitely as Paul sais be one for the higher resolution models to pick up nearer to the time. Can't see anything of the like on the GFS.

[Southender]

Can someone explain what a polar low is please and why it appears to be such an exciting phenomenon?

[Snooz]

You are quite correct, Polar Lows don't get picked up by the models, however, the conditions which allow Polar Lows to form are picked up by the models, and by serial straw clutchers like myself.

but a PL straw clutcher maybe, but we love him - CMD recently posted some charts with interesting reasoning in the Scottish thread about this feature/low (we've been watching it for a couple days) - if you'd like to take a look in there frosty - maybe help?

certainly even the first two bands preceding the main event were much more "curly/curved" in their early formation too, but I presume that these mystical creatures need sustained cold to keep going, which of course wasn't quite present while the cloud bank from the south's low was still there.

[kold weather]

18z doesn't even develop the low this time round and instead focuses in on the southern low to take over...

18z is also yet AGAIN amazingly progressive run!!

[Geordiesnow]

Heights decrease from Greenland from this run quicker however we do keep the cold ne'ly flow but things do start to get a little messy it has to be said, could be the GFS trying to over complicate things again with shortwaves?

Apart from that, this run looks like the UKMO too me albeit alot more messy.