Model Output Discussion - 28th November - 4th December

[Snowmad79]

GFS Sticking with a reasonably potent PM blast next week giving snow to low levels as far south as the midlands and some significant accumulations over scotland.

http://hw.nwstatic.c.../h850t850eu.png

ECM in agreement but UKMO sticking to its guns and has a much more watered down version with any snow confined to scotland.

http://www.meteociel...=120&carte=1021

ECM op sticking with another cold snap in FI but as it has no support very unlikely to materialise. I cant see that HP ridging as far North let alone any further North which is what would be needed for anything significantly wintry.

http://www.meteociel...map=0&archive=0

So all in all nothing out of the ordinary but still a heck of a lot better than we could of expected a week ago.

Least the ECM has kind of stuck with its 12z version last night with regards to the atlantic ridge and HP trying to move northwards towards greenland. Never say never. And I might be wrong but the GFS and ECM seem like they want to pull the PV into Scandi which could spice things up a little ?, The GFS most certainly does while weakening and disecting it.

[cyclonic happiness]

Be glad you don't live in the Netherlands!!

Looks really severe for them, I bet they are leaping into action as we speak?!!! :o

[Aaron]

That looks epic, I need to go to the Netherlands..!

[feb1991blizzard]

Least the ECM has kind of stuck with its 12z version last night with regards to the atlantic ridge and HP trying to move northwards towards greenland. Never say never. And I might be wrong but the GFS and ECM seem like they want to pull the PV into Scandi which could spice things up a little ?, The GFS most certainly does while weakening and disecting it.

True and the GEM 0z is conducive to snowfall in their outputs as well so i suppose im wrong to say it has no support, just waiting for the ECM mean and spread to be updated but the key thing here in my opinion (and i know im going to sound boring) is the Met office text forecasts, we need to see them upgrade to at least mention potential for low level snow,

Edited November 30, 2011 by feb1991blizzard

[Liam J]

GFS 00z still shows a well developed depression running through the UK during Sunday although small shifts north with each run, ECM and UKMO have a much weaker shortwave passing further south than the GFS, still uncertainty over how this is going to play out. We will have to wait a few more days before we have agreement on the outcome post Saturday.

Saturday is looking very windy across the north with widespread gales developing.

Edited November 30, 2011 by Liam J

[nick sussex]

The ECM ensemble maps upto 168hrs:

http://www.ecmwf.int...t!2009112700!!/

As you can see unsettled looking but differences with ridging to the west and the placement of low pressure.

The ECM ensemble mean does give some support for some amplification upstream at 168hrs, although not as good as the operational run.

http://www.meteociel...=1&map=1&type=1

Again though my interest is drawn to the ensemble spreads at 240hrs:

http://www.meteociel...=1&map=1&type=2

The areas with most spread are the eastern USA at 168hrs and running se through the UK at 240hrs.

The outlook should however see the pattern flatten out but how much and what happens to any high?

Edited November 30, 2011 by nick sussex

[Robbie Garrett]

I received the following response from the UKMO

The latest charts are showing an increased probability of snow, both on hills and possible low ground to the north, but it is all very transitory, perhaps 1 to 3 days in length before it turns milder again before we get another cold blast. There is certainly no sign of anything of an easterly. However, the winter has only started, so we will see.

[nick sussex]

Given the GFS 06hrs run so far you can see why we're seeing that ECM ensemble spread in the eastern USA and later in Europe.

The interraction between that deep low crossing Canada and the developing shortwave further south in the eastern USA will determine whether we see the ridge retrogressing, possibly setting up a cold shot from the nw.

This is an interesting turn of events, the cold stratosphere is saying one thing but the models don't seem to be listening!

If we get an amplified trough developing then things could get interesting, although any height rises over Greenland are likely to be temporary, at this point given the very cold stratosphere it would be really making the best out of the overall pattern.

Edited November 30, 2011 by nick sussex

[Gavin Hannah]

This is an interesting turn of events, the cold stratosphere is saying one thing but the models don't seem to be listening!

It is certainly an exciting period of model watching at the moment.!

I am liking the current setup from the models in the short time too. It's looking good for nice cold shot from this weekend for the majority of the UK. How far south low level snow gets is still up for grabs tho. West highlands have had a good amount of overnight snow while the east has had a smaller amount. We just need to get today out of the way and it looks good for the ski resorts to start building up a base over the next week to two weeks.

[A Winter's Tale]

Given the GFS 06hrs run so far you can see why we're seeing that ECM ensemble spread in the eastern USA and later in Europe.

The interraction between that deep low crossing Canada and the developing shortwave further south in the eastern USA will determine whether we see the ridge retrogressing, possibly setting up a cold shot from the nw.

This is an interesting turn of events, the cold stratosphere is saying one thing but the models don't seem to be listening!

If we get an amplified trough developing then things could get interesting, although any height rises over Greenland are likely to be temporary, at this point given the very cold stratosphere it would be really making the best out of the overall pattern.

Sounds very interesting! At the moment the cold spell for the weekend will really be at it's best on Monday with the -5C line in the southern parts of England and a real prospect for not only falling snow but lying snow for some parts of lowland scotland.

[Zakos]

GFS has downgraded the chance of snow to low levels in the south, although sleet at least is still quite likely.

It has also downgraded the severity of cold in the initial cold snap.

However, in doing so, has significantly upgraded the possibility of following cold blasts, which at this stage seem quite potent.

The GFS Ensembles (00z) are also indicating at continual reloading cold blasts.

Interesting times ahead, things are slowly improving from a cold perspective now that dreaded euro high is gone!

[Gavin Hannah]

Sounds very interesting! At the moment the cold spell for the weekend will really be at it's best on Monday with the -5C line in the southern parts of England and a real prospect for not only falling snow but lying snow for some parts of lowland scotland.

Deep FI has the -5 line diving south into southern france at t.228. This is around the same time the ECM hinted at the riding of the HP into greenland. While the latest run on the ECM backs away from this idea, and the GFS goes for a flatter outcome, it's going to be interesting indeed to watch what happens to the ridge.

GFS has downgraded the chance of snow to low levels in the south, although sleet at least is still quite likely.

It has also downgraded the severity of cold in the initial cold snap.

However, in doing so, has significantly upgraded the possibility of following cold blasts, which at this stage seem quite potent.

The GFS Ensembles (00z) are also indicating at continual reloading cold blasts.

Interesting times ahead, things are slowly improving from a cold perspective now that dreaded euro high is gone!

It would seem the PV has a six barrel shooter aimed at us and Europe! Bring it on!

[nick sussex]

It is certainly an exciting period of model watching at the moment.!

I am liking the current setup from the models in the short time too. It's looking good for nice cold shot from this weekend for the majority of the UK. How far south low level snow gets is still up for grabs tho. West highlands have had a good amount of overnight snow while the east has had a smaller amount. We just need to get today out of the way and it looks good for the ski resorts to start building up a base over the next week to two weeks.

To be honest if you saw how below average the stratosphere temperature was running you'd wonder how on earth the models have managed to come up with synoptics even close to wintry at the moment!

For this reason I'd be loathe to talk this up too much but the actual trigger to develop some more interest isn't well into FI. It's really that deep low which crosses Canada, you want this to deepen as much as possible and then it to pick up that shortwave and amplify, at that point the WAA into Greenland will do its trick.

It's unlikely to last too long as any pressure rises over Greenland are temporary because of that cold stratosphere but if the UK can get a shortish northerly or nw polar flow out of this then I'd take that as its really making something decent out of very mediocre ingredients.

[A Winter's Tale]

Deep FI has the -5 line diving south into southern france at t.228. This is around the same time the ECM hinted at the riding of the HP into greenland. While the latest run on the ECM backs away from this idea, and the GFS goes for a flatter outcome, it's going to be interesting indeed to watch what happens to the ridge.

It would seem the PV has a six barrel shooter aimed at us and Europe! Bring it on!

-5C line in FI is quite usual but I think FI is quite useful at time for indicating patterns so HP in Greenland is quite interesting but quite unlikely to happen.

I remember that a lot of folk on here said that a strong polar vortex would mean a poor winter (or start to) so If we get a few decent NWly or Nly blasts then I'm sure that the intensity of cold up there could make for some interesting weather if it's aimed at us.

[kold weather]

Rathert interesting 06z GFS this morning with the flow more or less staying from the WNW/NW throughout a good chunk of the run. Not too bothered about whether we keep the -5hpa air for too long, its just key that we keep a constany supply from the northern part of the Atlantic rather than south as obviously average/slightly below is miles better than way above.

ECM not as good this morning but the ensembles suggest it maybe a touch under-doing any topple northerly attempt in 7-8 days time.

[Gavin Hannah]

Perhaps the PV is so cold and spinning so fast it's bringing it's lunch back up and we are getting covered so to speak haha!

[bluearmy]

To be honest if you saw how below average the stratosphere temperature was running you'd wonder how on earth the models have managed to come up with synoptics even close to wintry at the moment!

For this reason I'd be loathe to talk this up too much but the actual trigger to develop some more interest isn't well into FI. It's really that deep low which crosses Canada, you want this to deepen as much as possible and then it to pick up that shortwave and amplify, at that point the WAA into Greenland will do its trick.

It's unlikely to last too long as any pressure rises over Greenland are temporary because of that cold stratosphere but if the UK can get a shortish northerly or nw polar flow out of this then I'd take that as its really making something decent out of very mediocre ingredients.

i am very surprised to see the ecm ens spreads indicating that a mid atlantic ridge is likely next week. given the spread on uppers over greenland, i think we may see some ramping re the period approaching mid month quite soon. as you say, any ridging should get flattened quite quickly. however, not sure anyone would expect the kind of ridge shown on the ecm ens suite, given the telecons and strat temps. are we about to witness something strange ???

[Gavin Hannah]

Nick, is this Low you were referring to over Canada??

[kold weather]

Its a quickfire ridge BA, when it comes to those sorts of ridges the strat doesn't really come into it, I've seen many times us have super cold uppers in the bad old days and still get some fairly potent, if short lived topplers. Plus if you look at the flow which is broadly W-E in the central Atlantic anyway at the moment its not all that difficult to amplify that a little more in that broadly zonal set-up to get some colder air down.

I'd be a little more surprised if we don't have a high trying to ridge into Europe by the 15th, but we'll see!!

I'd also be a little surprised if the models were not overdoing any mid-atlantic ridging...

[Frosty.]

The models show a flat ridge moving across the uk on friday and then a deepening depression crashing into nw scotland on friday night with wet and windy weather spreading to all areas by saturday, it also looks a bit milder on saturday in southern areas but beginning to turn colder further north with showers gradually becoming more wintry through sat/sun, further south is less cold with heavy rain and strong winds. Into next week it's fairly chilly with showers or longer spells of rain but more of a wintry mix for northern britain with mountain snow, the models are not really showing a cold snap but it does look much cooler than we have been used to and there will be hill snow in the north.

[nick sussex]

Nick, is this Low you were referring to over Canada??

Yes that deep low in Canada is key, having just read the latest NOAA update they do expect an amplifying trough over central Canada at day 7.

ON DAY 7...THE HIGH HEIGHTS OVER ALASKA AND THE NORTHEAST PACIFIC

LEADS TO AMPLIFICATION OF A CENTRAL CANADA TROUGH. AS THIS

OCCURS...A COLD FRONT IS FORECAST TO MOVE SOUTH ACROSS THE

NORTHERN PLAINS AND POSSIBLY THE UPPER MS VALLEY. TIMING AND

PHASING DIFFERENCES WITHIN THE CANADIAN 500 MB TROUGH LEAD TO

TIMING DIFFERENCES OF THE COLD FRONT ARRIVAL AND PROGRESSION.

So at the moment that is likely to verify but its what happens as it encounters that shortwave that will make all the difference in Europe.

[Snowmadsam]

Yes that deep low in Canada is key, having just read the latest NOAA update they do expect an amplifying trough over central Canada at day 7.

ON DAY 7...THE HIGH HEIGHTS OVER ALASKA AND THE NORTHEAST PACIFIC

LEADS TO AMPLIFICATION OF A CENTRAL CANADA TROUGH. AS THIS

OCCURS...A COLD FRONT IS FORECAST TO MOVE SOUTH ACROSS THE

NORTHERN PLAINS AND POSSIBLY THE UPPER MS VALLEY. TIMING AND

PHASING DIFFERENCES WITHIN THE CANADIAN 500 MB TROUGH LEAD TO

TIMING DIFFERENCES OF THE COLD FRONT ARRIVAL AND PROGRESSION.

So at the moment that is likely to verify but its what happens as it encounters that shortwave that will make all the difference in Europe.

what could happen?

[Gavin Hannah]

Ok Nick, a bit of a newbie questions, IF the low deepens, picks up the shortwave and amplifies to a significant level, What's the best and worst outcomes for us in the UK?

[nick sussex]

i am very surprised to see the ecm ens spreads indicating that a mid atlantic ridge is likely next week. given the spread on uppers over greenland, i think we may see some ramping re the period approaching mid month quite soon. as you say, any ridging should get flattened quite quickly. however, not sure anyone would expect the kind of ridge shown on the ecm ens suite, given the telecons and strat temps. are we about to witness something strange ???

Yes it gets stranger by the day!

I wouldn't be too confident in things yet but certainly I'm very encouraged by todays developments from a cold perspective, this will certainly be a feather in the cap of the ECM if it verifies.

For fear of causing this thread to implode with excitement I'm going back to my miserable cynical self for the rest of the day!

No on second thoughts I think I'll remain festive and positive that even with rather poor teleconnections we may see a northerly, it maybe brief but certainly welcome!

[tinybill]

all i say it looks interesting for next week

Edited November 30, 2011 by tinybill