Model Output Discussion - 12th December Onward

[Liam J]

GFS seems to be getting closer and closer to a Bartlett scenario with each run, air flow coming from the mildest directions possible for this time of year and if only we could have charts like this on offer during the Summer months!

You have to admire the optimism of some on here who somehow manage to pave a way for a cold pattern to evolve when quite frankly atm it looks like a wild goose chase of epic proportions.

Edited December 18, 2011 by Liam J

[OldMetMan]

Yes you can still get cold with a strong PV but further to the west especially near Baffin, indeed we've seen some easterlies with a strong PV on the western side of Greenland but in terms of being able to tap into at least some Arctic air we'd need that troughing to amplify over the eastern USA to allow for your ridge to get pulled further north.

We'll have to see what the models do with that weakish rise in pressure near the Arctic, often commented on by NOAA is the lack of observational data for that region, at least the stratosphere is moving in the right direction although its taking its time.

Yes that's right, it's a bit of a long shot based on the current synoptic situation, but it can happen. I think what bothers me still is the presence of that intense Asian HP so early in the winter and how it might build/redevelop W or NW. Yes, lack of arctic data must be a major problem when it comes to feeding the models so such development of HP must be very difficult for them to foresee.

If we are to get a major blocking pattern in the next few weeks, I think the clues will be in the model output fairly soon.

[shedhead]

Yes that's right, it's a bit of a long shot based on the current synoptic situation, but it can happen. I think what bothers me still is the presence of that intense Asian HP so early in the winter and how it might build/redevelop W or NW. Yes, lack of arctic data must be a major problem when it comes to feeding the models so such development of HP must be very difficult for them to foresee.

If we are to get a major blocking pattern in the next few weeks, I think the clues will be in the model output fairly soon.

Hi OMM - yes, they will need to be because given a 2, maybe even 3 week lag we are looking at early Jan as best case senario and in reality probably the 2nd week. You are right in so much as cold is possible with a deep PV over W Canada, IF it is far enough west, but it's recent and curently forecasted position makes it very difficult for what you allued too in 47 and 62 to happen again.

[OldMetMan]

Hi OMM - yes, they will need to be because given a 2, maybe even 3 week lag we are looking at early Jan as best case senario and in reality probably the 2nd week. You are right in so much as cold is possible with a deep PV over W Canada, IF it is far enough west, but it's recent and curently forecasted position makes it very difficult for what you allued too in 47 and 62 to happen again.

The above charts are for a few days prior to the onset of cold easterlies in both years. Looking at each, it is hard to imagine exactly what happened as being possible, yet it did, in quite a dramatic way.

As I said, it is a bit of a stretch. We'll see over the next few days if the models do start hinting at it.

[wolvesfan]

Morning all,

Shocking output for us cold lovers at the moment.

I'm no expert but IMHO and as the models are showing, we will not see any northern lattitude blocking anytime soon.The stratosphere is anomolously cold at the moment and although some of the models have been showing the polar vortex to set up around northern Russia,the transition will take time(if it happens at all).

I think until we see some change in the strat and the polar vortex the models won't change significantly from what we're seeing at the moment.

Do hope i'm wrong though.

[shedhead]

OMM - Point taken, but in the case of 62 decent heights were already evident over Scandi in the chart you posted and they quickly built in the 48hrs after that, introducing an Easterly by 22/23rd. This time around I think heights will build firstly across the UK, then slowly transfer to Scandi, so something of a longer process but ultimately worth the wait I hope.

Edited December 18, 2011 by shedhead

[OldMetMan]

OMM - Point taken, but in the case of 62 decent heights were already evident over Scandi in the chart you posted and they quickly built in the 48hrs after that, introducing an Easterly by 22/23rd. This time around I think heights will build firstly across the UK, then slowly transfer to Scandi, so something of a longer process but ultimately worth the wait I hope.

Yes, that's right. Interestingly, the GFS 06Z is suggesting at least the possibility of such a development, although it's again reverting to the usual SW flow at the end of the run. But it illustrates the kind of thing I was talking about - LP off the E coast of Canada.

[nick sussex]

I think those charts that OMM put up show why sometimes you never can tell whats round the corner.

The GFS 06hrs run continues with the same overall theme but with high pressure further north. We'll have to see whether this trend is replicated by tonights models.

[Thundery wintry showers]

karyo, a good April = a poor JJA (Summer) generally!

There might be a slight correlation there, but it's not a very strong one- consider the summers that followed the generally warm dry sunny Aprils of 1945, 1949, 1955, 1984, 1990, 1995 and 2003. 2007 and 2011 perhaps reinforced the belief that it's a strong generalisation.

Meanwhile, unusually the GFS is progging high pressure to be much further north than the UKMO/ECM, with the latter two staying with a zonal pattern, mild in the south and near average in the north. It is increasingly looking as if the main polar maritime incursion around Christmas will occur on Christmas Eve with a warm cloudy moist W to SW flow on Christmas Day.

It is possible that some, mostly on high ground, may see some snow early tomorrow as fronts push in from the west, though this will soon turn back to rain.

[shedhead]

The irony is I think we have to go through a spell of mild/very mild SW'erlies, if we are to see heights firstly build here and then later transfer NEwards. It's obviously a shame this transition has to co-incide with

Xmas, but I'm sure for every coldy in here bemoaning this fact, there are probably 10,000 businesses who are absolutely delighted. Let's not lose sight of the fact we're not yet 3 weeks in to Winter proper and

IF things pan out as many of us hope/expect we really can look forward to something decent in January. If not.... well it's only weather and not the end of the world.

Edited December 18, 2011 by shedhead

[Thundery wintry showers]

I don't agree with the first part- one possible evolution towards something cold and snowy, which wouldn't require a spell of SW'lys, would be the jet continuing to track NW-SE and high pressure extending west into Scandinavia over the top of low pressure over central/southern Europe. However we have no choice in the matter and a spell of SW'lys looks pretty likely at present.

[shedhead]

I don't agree with the first part- one possible evolution towards something cold and snowy, which wouldn't require a spell of SW'lys, would be the jet continuing to track NW-SE and high pressure extending west into Scandinavia over the top of low pressure over central/southern Europe. However we have no choice in the matter and a spell of SW'lys looks pretty likely at present.

I think you are being a little pedantic TWS. Perhaps i should have said..... given the current situation I think we have to go through a spell of SW'erlies bla, bla, bla. However, I think you knew what I meant.

Edited December 18, 2011 by shedhead

[Thundery wintry showers]

I don't necessarily agree even there- a return to the earlier model runs showing more of a W to NW'ly type with a NW-SE jet might do the trick for example. The only thing I can say for a spell of SW'lys is that it currently looks very likely regardless of whether it eventually produces a cold snowy outcome or not.

[Timmytour]

GFS seems to be getting closer and closer to a Bartlett scenario with each run, air flow coming from the mildest directions possible for this time of year and if only we could have charts like this on offer during the Summer months!

You have to admire the optimism of some on here who somehow manage to pave a way for a cold pattern to evolve when quite frankly atm it looks like a wild goose chase of epic proportions.

Probably the same optimism shown 10 days ago when the models were showing today as being similar to what they now say will be the case in 10 days time! Then it seemed like today would be giving us temps in double figures....we've just had a shower of sleet here! :-)

[bluearmy]

as it seems some of you are not aware what the ens mean was showing for today on the 8th dec, i'll post it again

to say that we are not seeing what the nwp forecast 10 days ago is plain wrong (as posts often are on here - including mine !!)

[Liam J]

Probably the same optimism shown 10 days ago when the models were showing today as being similar to what they now say will be the case in 10 days time! Then it seemed like today would be giving us temps in double figures....we've just had a shower of sleet here! :-)

I disagree, many places will be pushing double figures within a few days time not 10, we knew a week or so ago that we'd be entering a rather cool zonal period with shots of cold air from the north at times and that has been the case? Whilst we haven't had very cold air filtering down many places have still been on the right side of marginal for snow.

Edited December 18, 2011 by Liam J

[karyo]

Well, so far, December has been kind to us (especially us living in the northern half of the country. As I type this, there is snow outside and it was only a few weeks ago that some members were making bold statements about a mild December and no snow till January at the earliest!

I am hearing with interest the discussions about a mid latitude high taking over for the end of December/early January. As things stand, this is our best chance for cold weather, now that the jet is expected to track a little further north.

With the stratosphere starting to warm considerably, the jet should start showing signs of slowing down which may encourage high pressure and surface cold to take over. Whether we see proper northern blocking in the 2nd half of winter, is not a question I will attempt to answer.

As for the warm April-cool summer idea, I couldn't care less! Winter is my favourite season! lol

Karyo

Edited December 18, 2011 by karyo

[BLAST FROM THE PAST]

Firstly, its very cold currently, secondly lying lowland snow is NOT the norm in Dec or indeed Christmas so lets not stress or jump on 'really bad for coldies' bandwagon, thirdly the models aren't disastrous for coldies as some seasonal weather still in offing, forthly who says that GFS deep FI is correct or indeed any other model in FI?

I've enjoyed Dec so far and some potentially good 'weather' still to come. I'm very happy with the way this month has gone, is going as all seems 'on track'

But 'discussing' potential scenarios or potential developments either way is good

BFTP

Edited December 18, 2011 by BLAST FROM THE PAST

[gareth73]

Well what ever happens this year the last two Decembers and early Jans were very wintery and I am flying to Alberta on the 11th Jan so I will get my snow in the Rockies and I have never been disapointed. Frozen lakes to walk on etc. (All safe as Canada Parks tests and allows) December has been eventful and not dull as expected so let us see what the end holds and then into Jan and maybe more snow for some!

[Cloud 10]

as it seems some of you are not aware what the ens mean was showing for today on the 8th dec, i'll post it again

to say that we are not seeing what the nwp forecast 10 days ago is plain wrong (as posts often are on here - including mine !!)

Seems a better match than the the op run.

Its no wonder NOAA use ensemble forecasts a lot!

[Frosty.]

The Ensembles show a large anticyclone to the south of the uk becoming the dominant feature during the next 7-10 days across the southern half of the uk at least, so it should become mainly dry eventually although it will turn much milder as Tm air blows around the top of the high and across the uk. Low pressure will be to the north of the uk keeping scotland and maybe n.ireland in a more unsettled westerly flow but milder than currently. I think the chance of a white christmas is gone for just about the whole of the uk and very probably for the new year too, the ensembles keep the uk in a moderately mild westerly flow with tropical maritime origins but if the main anticyclone does spread further north into the uk, it will bring a lot of frost and fog to southern britain between xmas and the new year, probably milder and more unsettled for northern britain throughout.

[Duane S.]

A lot of doom n gloom around. I actually think the 06z shows some subtle promise

Going forward to around the last week of December to my eyes there appears to be an opportunity of a ridge build up through the UK or maybe even further west. I get the feeling this will be played out in different ways by the models in the coming days. I suspect any initial attempted height build oop north will likely be repelled but I can certainly see it paving the way for a 2nd and 3rd shot which may bear more fruition into early Jan. I'm getting more convinced we're going to see an Arctic high (quite possibly appear with little warning) before any Greenland and/or Scandi/Siberian heights affect us later on this winter. A rare beast but quite possible IMO with the current setup/teleconnections

[SP1986]

I personally do wish people would refrain from this 'them and us' flavour to posting it's becoming tiring, and the model output thread is becoming increasingly difficult to read!

Anyhow as for the models, they are quite consistent at the moment, as I see it, a milder spell on the way, but it's not necessarily the end of frost, if high pressure sets up as the GFS shows (oops Karl beat me to it!) - however looking at the ECM, it's having none of it, I wonder which one will end up being correct (or indeed if any end up being correct?)

[A Winter's Tale]

I think the chance of a white christmas is gone for just about the whole of the uk

Not exactly. The latest models show The Northern third of Scotland under -5C uppers which could be good enough for snow. There's still plenty of time for change and what I'm looking out for is:

1) The Polar Martitime incursion on the 23rd to last longer

2) For the -5C uppers on Xmas Day to be a bit further south

Timing and positioning is key here and things will change a lot. Hopefully a bit closer to the time we'll see some -5C uppers in at least the north third of the UK near or at Christmas Time.

[TonyH]

My take on the coming week up to the Big Day!

Weather guide for west Wales and the central Midlands December 19th to Christmas Day 2011

Headline: Often mild; quite unsettled with some rain at times. A Green Christmas

This weeks guide is less of a headache than the last- with a much more straight forward set up!

Clear and frosty tonight, especially in the Midlands, the frost will have gone before dawn though in west Wales.

Monday will be somewhat milder than of late with a succession of troughs crossing the UK bringing spells of rain to all parts.Quite windy.

Clearing on Monday evening, but probably too much breeze for much in the way of frost, and a few showers keep going for west Wales.

The brief ridge gives a dry and possibly frosty start to Tuesday, but cloud increases during the afternoon, although rain should hold off until the evening, so, a dry bright day for the Midlands.

From Tuesday night we are in very mild Tropical maritime air, flowing between a large high to our south and a mid Atlantic low pressure system. Some rain or drizzle at times Tuesday night through to early Friday really, although very little for the Midlands, where it may also brighten from time to time, but a mostly cloudy and rather damp spell for west Wales. Very mild, temperatures above 11c both Wednesday and Thursday.

The. by now, weak cold front finally gets through later on Friday, bringing a spell of rain, but probably not much again for the Midlands, and also a cool down, with the chance of a slight frost first thing on Christmas Eve.

The big day looks like seeing a mild west or SW flow over us, so no snow or even frost, most definitely a Green Christmas!

For supportive model charts see the Welsh thread:

http://forum.netweat...46#entry2193646

Edited December 18, 2011 by TonyH