General Model Output Discussion

[NorthantsSnow]

I don't think confidence is increasing on any breakdown just yet.

It will have to happen at some point of course but even if it does I wouldn't rule out a rapid return to cold.

[Thundery wintry showers]

models suggesting that it might all be over later next week

Wishful thinking perhaps? There has been far more consensus on a breakdown of the cold spell at various intervals over the past three weeks and it has never come to fruition. The only model consistently showing a breakdown is the GFS which has performed poorly recently, while the UKMO and ECMWF are consistently keeping us in an easterly flow through to the end of their runs, with the ECM only hinting at a breakdown at T+240!

[Nick L]

Wishful thinking perhaps? There has been far more consensus on a breakdown of the cold spell at various intervals over the past three weeks and it has never come to fruition. The only model consistently showing a breakdown is the GFS which has performed poorly recently, while the UKMO and ECMWF are consistently keeping us in an easterly flow through to the end of their runs, with the ECM only hinting at a breakdown at T+240!

Indeed. If the GFS was to be believed the Atlantic would have kicked back into gear just after Christmas!

[Bobby]

The GFS has been hopeless lately - it's credibility has gone down quite a bit in my eyes. The ensembles are useful though but UKMO/ECM/GEM should be taken more notice of IMO.

[NorthNorfolkWeather]

I find it strange the way the GFS model has been so bad once it was upgraded from the Parallel run to the Operational. It seems to have returned to the old fault it had of always pushing the Atlantic at us, Sometimes in complete disagreement with every other model.

That said, there is only so much cold air in the Northern hemisphere and, at some point, we're going to have a breakdown. The possible vectors for this are South West, South, or South East. I think we can discount the south easterly at the moment, unless we get a flow from the Sahara, it will cool significantly because of teh cold continent. that leaves South West and Southerly. At the moment only a southerly would give us warm weather, and there's no sign of that on the charts, a South westerly would run into a cold pool and it would snow before it rained, perhaps with huge disruption.

Currently, I think BFTP's comments about the 14th-20th may be near the mark, but I'd actually push it out a little, perhaps the 17th-23rd. Assuming the Breakdown happens around then, we'll still have had a cold period longer than any winter since 1963.

Depending on what happens on that breakdown and the synoptics following it, we need a warmer, but not over mild period, or flooding will be an issue. Also from GP's comments, if we continue with The PV splitting, another block may form and we would have a reload

Interesting Times

[len]

models suggesting that it might all be over later next week

Indeed GFS was showing an Atlantic attack yesterday,....which brought the usual derision, because ECM showed no such thing.

But today, lo & behold, ECM has moved towards this idea of GFS's. I've a feeling I've been here before. My personal memory is that in these situations GFS is first to pick up the idea & ECM follows suit.

But GFS seems to be the model people love to hate?

But I've seen nothing from GP, Brickfielder, Chionomaniac,et al. in recent days?

Are they out sledging?

I would love to hear what their views are on GFS's idea???

Len

[pyrotech]

The GFS has been hopeless lately - it's credibility has gone down quite a bit in my eyes. The ensembles are useful though but UKMO/ECM/GEM should be taken more notice of IMO.

To be honest the GFS has pretty much played with a less cold - mild period at the end of some runs for a while and keeps moving it back. Pretty much what it does normally with cold for the UK much to disapointment of us on here in previous years. Obviously a breakdown will occur at some time but even that could be extremely interesting. The NAE did well with percipitation over lat 24 hours, but to its credit GFS did even better (Short range >24 hrs). I would normally go with NAE for short range percipitation.

ECM has the next week and into Fi mapped out better than GFS but do not think any have a handle on this past 48hrs. The European low may help keep our cold longer and not sure that much will change until jet comes back north which is not shown till over 10 days and that can easy be wrong if heights rise to our north which is fairly likely. Also a fair chance of a ssw event that would possibly help push cold air down over Europe, could effect us into february if it occurs, but we are being greedy now.

The main point is the cold continues for another week in the more reliable timeframe and longer with possible breakdown only well in Fi. What a fantastic wintry spell and i am pleased to say its been officially clased as coldest and snowiest since 80s which is what i forecast in autumn in the climate change forum.

Time to get my rubix cube out, drainpipe jeans and 80s music to go with it!

o

[swilliam]

Here's the 850hpa temps for the ECM. Looks interesting for the south with the possibility of further snow as the low bumps into the cold, still ages away however one to keep an eye on. To my eyes it seems as though the cold spell would break down after T240. Changes will always occur it at this time frame though. Overall still looking cold if not very cold for the short and medium term

ECM ensemble mean is colder than the op with the control run very cold. Most ensembles rise towards the end of the time frame

http://www.knmi.nl/e...agse/index.html

Looking at the ensembles in more detail.

1st thing to say is that the op is on of he milder solutions. Looking in detail it is clear that they split inot two groups at about t240. There is a clustered group that go for mild - presumably in these cases the block is overun or sinks. There are also a lot of cold solutions and some extremely cold. An example of this evolution is given by the control run on the GEFS ensembles

So the cold spell could end in a week to 10 days or there could be a reload.

[azores92]

So the cold spell could end in a week to 10 days or there could be a reload.

yes this is definitely a possibility, and that really would make an exceptional winter. the lack of vorticity over greenland this winter has been astounding. another retrogression is not out of the question at the moment, but a SSW would definitely give us some ammunition. in the meantime though, the met office are talking about the easterlies in the next few days picking up more instability and therefore leading to more snowfall for the united kingdom.

[pyrotech]

Not going to use models for percipitation until within 24 hrs as there will be developments not picked up until that timeframe. Obviously east coastal areas do best but would not rule anywhere out.

[Thundery wintry showers]

Indeed GFS was showing an Atlantic attack yesterday,....which brought the usual derision, because ECM showed no such thing.

But today, lo & behold, ECM has moved towards this idea of GFS's. I've a feeling I've been here before. My personal memory is that in these situations GFS is first to pick up the idea & ECM follows suit.

But GFS seems to be the model people love to hate?

Has it? Here is the ECMWF at T+168:

http://charts.netweather.tv/ecmimages/20100106/00/ecm500.168.png

So, the lows start to try to attack from the south-west, but we keep a cold ESE flow over the UK. Uppers should have moderated to some extent by then, but coming off a frozen continent it should still be cold, especially towards the southeast.

Out to T+240 and we have this:

http://charts.netweather.tv/ecmimages/20100106/00/ecm500.240.png

The low slides across the south and then heads out east allowing the generally easterly flow to continue. Chances of a subsequent breakdown from that monster low in the Atlantic but still a strong Scandinavian High and relatively high pressure over Greenland which could encourage it to undercut.

I don't see how this constitutes falling into line with the GFS? The only major change on the ECM is it has got rid of the NE'ly reload at around T+192 and instead kept relatively modest cold coming in from the east- but no breakdown like on the GFS.

[Shiny_Bottom_1]

I think in fairness to Mushy, it is a point I would concur with.

The NOAA picked up on using the mean of the GFS, rather than the operational run.

However, if you at Derbyshire, the mean still looks ok until about the 17th, perhaps the 19th in terms of 850's. If the op run dropped, so would the mean, being one of the milder solutions.

The operational is a fantastic run, and with some support from other GFS members, looks like there is also some support from the ECM in terms of T2M temps.

However, the ECM ensembles also back up some increase in the 850's, with generally a split in how this is going to develop from mid-week next week.

Two questions:

1. On the ECM ensembles posted, for which location is this?

2. Does anybody have access to the ECM 00z 850 ensembles?

Is a warming of the 850's nailed? No. But in the same breath, neither is continuation of cold.

But what we do have, is model disagreement, which in terms of the time frame, is still open to much changes and possibilities.

Interesting that the 06z GFS mean is perhaps better than the 00z, the increase in 850's (again for Derbyshire) is brought in nearly a day early.

Nobody is looking for a breakdown, but I am not 100% convinced in terms of mid to long term patterns, the GFS is useless and should be discounted.

Really, details of mid-week next week will be clearer (but still not set up in good confidence) by the weekend.

Either way, it does not look like becoming mild in any time frame (GFS Op always goes higher than is realistic when it hits its lower res).

[johnholmes]

models suggesting that it might all be over later next week

you never know mushy you might get your hoped for mild Feb-mind you if its not got any milder by the time I come back from skiing very early Feb I shall be joining you!

[nick sussex]

Has it? Here is the ECMWF at T+168:

http://charts.netweather.tv/ecmimages/20100106/00/ecm500.168.png

So, the lows start to try to attack from the south-west, but we keep a cold ESE flow over the UK. Uppers should have moderated to some extent by then, but coming off a frozen continent it should still be cold, especially towards the southeast.

Out to T+240 and we have this:

http://charts.netweather.tv/ecmimages/20100106/00/ecm500.240.png

The low slides across the south and then heads out east allowing the generally easterly flow to continue. Chances of a subsequent breakdown from that monster low in the Atlantic but still a strong Scandinavian High and relatively high pressure over Greenland which could encourage it to undercut.

I don't see how this constitutes falling into line with the GFS? The only major change on the ECM is it has got rid of the NE'ly reload at around T+192 and instead kept relatively modest cold coming in from the east- but no breakdown like on the GFS.

Good post TWS

I do laugh when people try and make a case for the gfs currently when even NOAA in the USA are slating it's operational runs and going mainly with the ecm and its ensembles. If it's not good enough for it's home country to use why on earth would we want to follow it over in Europe. I knew as soon as it saw that Scandi high that it would start going AWOL in its later output.

At some point there will be a breakdown but given the set up and previous experience it's not going to be quick and will probably take several attempts.

Edited January 6, 2010 by nick sussex

[Shiny_Bottom_1]

when even NOAA in the USA are slating it's operational runs and going mainly with the ecm and its ensembles.

Hi Nick.

Didnt they favour the GFS Ensemble mean though?

This perhaps is the key point to look at, rather than the operational.

[Iceberg]

WRT a breakdown, the GFS ensembles have been persistantly for a good 3 or 4 days had the 13th as the point where the -5 850 line is nolonger reached on the ensemble mean, by and large is has a 50/50 split as to whether a slight warming occurs in the south at this point.

ECM ensembles means for London have today on the 00Z gone to 5C max daytime temp (albeit right at the end of the run).

I think the first glimmers of a breakdown might be occuring in the models, but its far too soon to know how realistic this is, maybe somewhere between the 15-20th might be in with a shout but that's still a while away yet.

[Cheshire Freeze]

Interestingly, the GFS control run tries to retrogress the high, but never really strengthens it

http://91.121.94.83/modeles/gens/run/gens-0-1-192.png?6

[❄️❄️❄️❄️❄️❄️❄️❄️❄️]

It really is amazing to think that we are looking into the depths of FI for mild weather, when most of the country has been below average for the past 3 weeks. Usually in recent years we would be looking for cold weather in distant FI after weeks of mild!

[Optimus Prime]

I think the first glimmers of a breakdown might be occuring in the models, but its far too soon to know how realistic this is, maybe somewhere between the 15-20th might be in with a shout but that's still a while away yet.

Can't see things warming up even at your picked range.

[Thundery wintry showers]

I think it's pretty certain that those 850s will warm up at some stage- there isn't an infinite supply of cold air and this easterly is bound to be modified from the north and/or SE towards the 12th-15th.

But I think "breakdown" in many cases is putting it a bit strongly- we will only get something mild out of this, particularly towards the southeast, if lows start streaming in from the Atlantic. A continental flow with 850hPa values of -3C will still be very cold in the southeast, and fairly cold even in the north. Even in the winter of 1963, 850hPa values were sometimes near freezing during easterly outbreaks, yet the surface temperatures were around freezing for many. One difference that would make is that it would bring dry cloudy weather instead of sunshine and snow showers.

[johnholmes]

very sensible post Ian

[mushymanrob]

Which models? the latest ecm shows winds from russia all next week and the ukmo also looks very cold with a continental flow. I think the 12z will tell us whether the ecm follows the gfs or the other way round.

the 06z gfs is clear that by the end of next week it would become less cold then by the end of the run mild. ok, its 1 run, but isnt that what are discussing? besides this scenario has cropped up a few times now.

hasnt the gfs been performing very well?..i beg to differ! its been constant in the build up to this cold spell when the ecm provaricated.

Only a few years ago, we would have been more than happy with a 3/4 day cold snap. Now we're looking at a possible breakdown still over a week away! Many people (myself included) would have thought a cold spell like this would have been almost impossible not so long ago.

we?.... we are looking for a breakdown?... nah mate... I am! lol.. lets face it, in most mild winters everybody looks to fi for signes of a cold spell.... well im looking to fi for a return to my beloved mild weather! . if i cant have a great dumping of snow, id personally sooner it be mild.

Wishful thinking perhaps? There has been far more consensus on a breakdown of the cold spell at various intervals over the past three weeks and it has never come to fruition. The only model consistently showing a breakdown is the GFS which has performed poorly recently, while the UKMO and ECMWF are consistently keeping us in an easterly flow through to the end of their runs, with the ECM only hinting at a breakdown at T+240!

wishful thinking indeed...but why not? my general dislike of cold weather is no secret.

most models though into fi suggest the greenland high to move... now where it moves and indeed IF it moves may well determine the pattern for the rest of winter. ok my monies on a lengthy scandi high with the beast blowing in from the east, but it might not happen, it might drift into southern europe, it might sit just to our northwest in which case mild air will eventually ride over the top of it and warm us up! all these scenarios have been suggested in my occassional view of the charts.

[Neilsouth]

http://www.wetterzentrale.de/pics/Rngp961.gif

http://www.wetterzentrale.de/pics/Rukm961.gif

http://www.wetterzentrale.de/pics/Recm961.gif

http://www.wetterzentrale.de/pics/Rgem961.gif

http://www.wetterzentrale.de/pics/Rgem961.gif

http://www.wetterzentrale.de/pics/Rgme1081.gif

Increasing risk of snow into the east and south east as the week progresses !

Edited January 6, 2010 by neilsouth

[mushymanrob]

I think it's pretty certain that those 850s will warm up at some stage- there isn't an infinite supply of cold air and this easterly is bound to be modified from the north and/or SE towards the 12th-15th.

But I think "breakdown" in many cases is putting it a bit strongly- we will only get something mild out of this, particularly towards the southeast, if lows start streaming in from the Atlantic. A continental flow with 850hPa values of -3C will still be very cold in the southeast, and fairly cold even in the north. Even in the winter of 1963, 850hPa values were sometimes near freezing during easterly outbreaks, yet the surface temperatures were around freezing for many. One difference that would make is that it would bring dry cloudy weather instead of sunshine and snow showers.

tbh another feb 86 would be a nightmare... we had no snow here and a month of biting cold, dry easterlies.

[Bobby]

Increasing risk of snow into the east and south east as the week progresses !

That would blast snow right across Britain, not just the East and South, hence the Met Office warnings.

http://www.metoffice.gov.uk/weather/uk/uk_forecast_warnings.html?day=5