Model Output Discussion 4th Dec.2013-12z onwards.

[nick sussex]

You're right mate.

 

The problem is at this range shortwave activity near Iceland won't be picked up, so on the face of it although that chart looks interesting I'd certainly be wary of getting too excited over that GFS.

 

Its less of a problem with a proper Greenland block but in this type of set up those shortwaves often pop up and stop the colder air from making it as far south as the GFS suggests.

 

The interest earlier is how far south the jet can come, the horseshoe low heights set up is condusive to some sinking as theres a relaxation over the northern chunk of Greenland and the Siberian ridge is helping things. The lower resolution GFS is a bit messy really with the PV moving east and then back west again, as it moves the pattern will flatten out somewhat.

 

Not bad in the higher resolution in terms of the trend, still nothing majorly wintry standing out though.

[Gael_Force]

Yes, definitely the best of a bad situation. Thundersnow events would be likely in places if the 12z is anywhere near eventual reality.

 

With such low thicknesses, upper air would be dragged down to the surface quite easily I think. If you look on the Netweather charts (once updated), I suspect thickness values will easily be sub 528 dam across a lot of the UK. Certainly not warm into FI.

 

Sub 520 in fact.

 

[R.P. McMurphy]

Yes peturbation 11 would lead to widespread damage over here in Ireland.

 

http://modeles.meteociel.fr/modeles/gens/run/gens-11-1-60.png?12

 

No doubt about that Matty. 100mph widespread and 80-90mph across NW England.

 

It wouldn't be pretty.

[UV-RAY]

The problem is at this range shortwave activity near Iceland won't be picked up, so on the face of it although that chart looks interesting I'd certainly be wary of getting too excited over that GFS.

 

Its less of a problem with a proper Greenland block but in this type of set up those shortwaves often pop up and stop the colder air from making it as far south as the GFS suggests.

 

The interest earlier is how far south the jet can come, the horseshoe low heights set up is condusive to some sinking as theres a relaxation over the northern chunk of Greenland and the Siberian ridge is helping things. The lower resolution GFS is a bit messy really with the PV moving east and then back west again, as it moves the pattern will flatten out somewhat.

 

Not bad in the higher resolution in terms of the trend, still nothing majorly wintry standing out though.

For IMBY those charts look better than anything since December 2010, granted they may not bring a cold spell but at least I may see some snow out of such a set up and maybe even some lying snow for a couple of days.

[Summer Sun]

GEM has the low at 950mb on Thursday

 

 

Into Friday and the weekend the low continues to affect the north though it does turn slightly calmer by Sunday

 

Edited December 16, 2013 by Summer Sun

[terrier]

Really hope the models downgrade over next few days regarding the storm potential. That would be awful output for people over the Xmas holidays. Yes we might all like extremes. But please not over Xmas with a lot of family's travelling about.

[nick sussex]

The horseshoe low heights configuration or seeing as its nearing Xmas the reindeer formation! This is quite important to the jet axis and whether it will edge further south:

 

 

You can see those purples have lifted out of the northern chunk of Greenland, helped to some extent by the Siberian ridge extending over the top of the right antler!

 

This acts to edge the jet south, after this the GFS moves the main chunk of the PV east, preferably if that's going to happen you want it east and staying there not heading back west again.

 

 

 

 

[Summer Sun]

GEM still looking stormy for Christmas eve

 

 

GFS at the same time

 

[nick sussex]

For IMBY those charts look better than anything since December 2010, granted they may not bring a cold spell but at least I may see some snow out of such a set up and maybe even some lying snow for a couple of days.

I think you'll need some altitude, maybe you're high up but the GFS at that range in this type of set up has a known bias for overdoing the southwards extent of cold. I'm surprised you think its the best set up since December 2010, I can understand easterlies being a let down in your area and suspect you need a nw component to deliver but maybe I'm hard to please but I'm still underwhelmed.

[Cheshire Freeze]

I think you'll need some altitude, maybe you're high up but the GFS at that range in this type of set up has a known bias for overdoing the southwards extent of cold. I'm surprised you think its the best set up since December 2010, I can understand easterlies being a let down in your area and suspect you need a nw component to deliver but maybe I'm hard to please but I'm still underwhelmed.

 

Properly cold zonality is as rare as a tooth on a hen. At least the output at the minute is opening up the possibility.

[TSNWK]

The horseshoe low heights configuration or seeing as its nearing Xmas the reindeer formation! This is quite important to the jet axis and whether it will edge further south:

 

gfsnh-0-168.png

 

You can see those purples have lifted out of the northern chunk of Greenland, helped to some extent by the Siberian ridge extending over the top of the right antler!

 

This acts to edge the jet south, after this the GFS moves the main chunk of the PV east, preferably if that's going to happen you want it east and staying there not heading back west again.

What a brilliant descriptive post –Thank you. Let’s hope Rudolf is around in a week’s time on the forthcoming instalment of the ECM

[IDO]

The GEFS have still not made their mind up about Christmas Day. The spread remains high over the UK:

 

 

This is again expressive of the ensembles around that date, but the UK trough sinking SE still has a good showing along with a more westerly zonal flow and there remain a few more settled charts. The Control is for me the best scenario we will get out of the current pattern:

 

T240:   T324: 

 

I know, not what the Daily Express promised, but on the cold side of the jet: 

 

 

The op pushed the PV east but it recoupled with the Greenland lobe, mitigating the troughing; the control keeps some of that energy over Siberia.

 

By the end of FI no NH chart has the PV in a similar state, with many alternatives, however the one common factor is the lack of very cold uppers over the UK and the nature of these, all are slack flows. So given the variance of the (PV) output this is not a good sign for an incoming wintry spell.

 

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=384

Edited December 16, 2013 by i'm dreaming of...

[nick sussex]

Properly cold zonality is as rare as a tooth on a hen. At least the output at the minute is opening up the possibility.

Cold zonality yes is rare but you can't sustain it without some blocking to the n/ne, maybe if the PV chunk goes east and stays there that might open up an opportunity.

[phil nw.]

That secondary low modeled for overnight Weds.into Thursday looks like bringing gales and rain to many areas as it sweeps across the nw of the UK.

A brief blast of polar maritime air following behind likely to bring snow showers to many northern higher levels especially those facing w or nw-some snow maybe to the mountains further south.

 

This looks like the theme through the holiday period.Rain and wind then blustery sometimes wintery showers with hill snow behind the cold fronts before the next low approaches.

Certainly monitoring the potential development of deep lows along the polar front will be needed as to the main risk areas.

Many areas of the UK are likely to be affected as the jet continues on it's relentless track towards the UK.The difficulty in this volatile pattern is to identify when and where these wave depressions develop and then their likely track.

A lot going on in the next couple of weeks to keep forecasters busy.

[bluearmy]

 

The horseshoe low heights configuration or seeing as its nearing Xmas the reindeer formation! This is quite important to the jet axis and whether it will edge further south:

 

gfsnh-0-168.png

 

You can see those purples have lifted out of the northern chunk of Greenland, helped to some extent by the Siberian ridge extending over the top of the right antler!

 

This acts to edge the jet south, after this the GFS moves the main chunk of the PV east, preferably if that's going to happen you want it east and staying there not heading back west again.

 

those of you who were concentrating some days back may recall i mentioned these little pockets of higher heights likely to be shoved into the arctic by the ridging to our ne. although the ridging is transient, i did say that these small areas of higher thicknesses/uppers could create some interesting nuances once they found themselves detached from the ridge whence they came. nick, i would say that this little area over greenland you have illustrated at day 6 it the product of the ridging into n scandi we see on day 3. infact, this mornings ecm op had it still affecting the greenland area by day 10. it doesnt look too much (though it does raise uppers to around -4 at day 5 just n of greenland), but coupled with the pressure from the siberian ridge, it is deflecting the jet on a more southerly track.

[Weathizard]

Cold zonality yes is rare but you can't sustain it without some blocking to the n/ne, maybe if the PV chunk goes east and stays there that might open up an opportunity.

Also, from the times I've seen 'cold zonality' modelled the cold air tends to get massively filtered down as you get closer to the time.

[UV-RAY]

Cold zonality yes is rare but you can't sustain it without some blocking to the n/ne, maybe if the PV chunk goes east and stays there that might open up an opportunity.

That looks like a possibility Nick, but we all know just how those SW can wreck such dreams. Still at least we're viewing charts that show such possibilities instead of what was on offer this time last week.

[UV-RAY]

I think you'll need some altitude, maybe you're high up but the GFS at that range in this type of set up has a known bias for overdoing the southwards extent of cold. I'm surprised you think its the best set up since December 2010, I can understand easterlies being a let down in your area and suspect you need a nw component to deliver but maybe I'm hard to please but I'm still underwhelmed.

My views on easterlies are well known in the regional threads Nick, bar 96,91 and 78/79 none of them have delivered diddly squat here. Sorry for being off topic Mods, I'll slap my wrist and promise I won't do it again. :-) Edited December 16, 2013 by Sceptical Inquirer

[Matty M]

Could even be a white Christmas for some with this chart on the northern flank of that low.

Edited December 16, 2013 by Matty M

[Summer Sun]

Another very unsettled update from ECM from the Christmas period

 

[cooling climate]

No change in the offering. Poor charts if your looking for sustained cold snowy

winter weather. Apart from some transient snow higher up here and there 

until we start to see changes ie warming in the lower to mid strat which will

encourage blocking to the north then things are not going to change very much.

 

Is there a Christmas skin out this year.

[nick sussex]

Could even be a white Christmas for some with this chart on the northern flank of that low.

I think with some evaporative cooling a chance, it does look very nasty though on the southern flank in terms of winds. Not liking the look of that at all, especially if it gets corrected south.

 

Hopefully something shallower even if it verifies.

[SW Saltire]

No change in the offering. Poor charts if your looking for sustained cold snowywinter weather. Apart from some transient snow higher up here and there until we start to see changes ie warming in the lower to mid strat which willencourage blocking to the north then things are not going to change very much.Is there a Christmas skin out this year.

That is mainly correct it would seem for most of England and Wales, however, if one lived in Inverness I'm not sure if it is so accurate. I'll bow down to superior knowledge but wouldn't the ECM's predictions for the Christmas period not give a chance of snow in Scotland, especially the North of the country. Although, as you say, it won't last any more than a couple days at best. Edited December 16, 2013 by SW Saltire

[Stuie]

At least there are signs of colder air getting into the high pressure dominated Europe.

Edited December 16, 2013 by StuieW

[phil nw.]

At least there are signs of colder air getting into the high pressure dominated Europe.

 

Indeed plenty of cold about the Northern Hemisphere at 2mtr level.

A look at these 2 images 12hrs apart show night and day forecasts around Weds/Thurs

 

those underline our relative mild climate for our latitude-particularly in this current Atlantic driven setup.

Continental landmasses have the ability to achieve and maintain deeper cold away from influences of the oceans.