Model Output Discussion - 12th December Onward

[Nick F]

Excellent post Chiono, I believe it will fail initially but Jan looks good bet. I also agree that the Siberian/Russian HP will back west and different to my forecast for mid Dec onwards where we look N / NNW for cold....we look east come January.

BFTP

With all due respect, can we discuss what the models are showing rather than what your forecast thinks will happen in January? An easterly in January is beyond the realms of any reasonable model outlook right now! I'm sure there are more relevant threads that you can broadcast your forecasts.

It does look like the NW troughing will hold back more in the run up to Xmas - which will at least allow the Azores high to ridge north across the Atlantic - which may at least lock us into a cool to cold NW'erly flow into and through next week.

[Kentish Kiwi]

http://www.wetterzen..._London_ens.png

distinct change in the IOW ensembles-

As said it hinges on the atlantic ridge gaining enough elevation North & the cold air coming along the southern flank-

S

Hardly any support whatsoever for 'the mildest Christmas period on record'. Looks distinctly below-average, with the mean not rising above average at all through the whole run...

[kold weather]

I don't see anything this morning other than a slight delay to what I have forecast.

Takle an actual look at the ensembles, they do develop the high you've been talking about but they shunt it far enough north in most cases to at least give us a fairly chilly set-up, some even go as far as to introduce a cold Easterly airflow...though personally I think thats abit too far out there for now.

Both the ECM and the GFS ensembles are not going into Bartlett territory, not even close!!

[Thundery wintry showers]

I don't see anything this morning other than a slight delay to what I have forecast.

In fairness if it verifies it will hardly constitute a slight delay. Many of us (myself included) were predicting a similar evolution around the 8th-10th December at one stage, as high pressure ridged across from the Azores, and in reality the high proved to be a short-lived ridge which got blasted out of the way by a southerly tracking jet.

This time around the main "fly in the ointment" for a prolonged mild period may prove to be the high pressure setting up too far north to allow mild moist south-westerlies to persist across most of the country, with a trough over Europe introducing the possibility of weak northerly and north-easterly outbreaks (as Kold said, an easterly is long odds against though). You might turn out to be right this time around but I see plenty of ensemble support for other possibilities- the ensemble mean is actually below average as Steve indicated.

In the meantime I have doubts about BFTP's predictions as well- it doesn't look likely that we'll be "looking east" during the second half of December (in particular the 18th-20th December is about as stark a case of "looking north" as it gets) and it is unclear if the easterly type is merely going to be delayed into January.

[Zakos]

I don't see anything this morning other than a slight delay to what I have forecast.

Not really. If models continue to delay a weather pattern in FI, its a pretty good indication that it wont happen. The NAEFS continually forecast a pressure rise to the south as you did, but it never made into even the 300 hour time zone. If models continually downgrade a cold spell, its quite likely it wont occur.

And now, even the NAEFS has backed away from this showing near average conditions.

Face it, there is currently virtually no support for your forecast. Just saying that Low heights to our north means a build up of pressure to our south is "inevitable" is not a valid statement IMO.

[Glacier Point]

The teleconnections were no better at the beginning of Dec, in fact they were probably worse, yet it hasn't really been mild at all.

hmm, CET running above average for the first 12 days of the month.

Anyhow, I'm sure you'll be sensing a subtle shift in those teleconnective analyses over the last few days: a change to the profile of stratsopheric winds; a trending upward of upper stratospheric temperatures towards normal values; a shifting in the forecast position of the main body of the polar vortex towards eastern Siberia; increased heat flux at 30hPa in the mid to high latitudes; and, a recent moderate to high strength Asian Mountain Torque, the last named which is of most interest here as it is likely to plump up the hemispheric mid latitude ridges putting pressure on the polar vortex from the 'outside'.

The modelling continues to evolve around the day 7-8 mark, finally getting to grips with the likely trough digging into Europe and the potential for enough energy to leak SE undercutting both the Russian High and disrupting the trough over Scandinavia reversing the mean pressure anomaly here for potentially the remainder of the winter.

I would best describe this as a dress rehersal for later in the month when we might get a better chance at amplification in the mean westerly flow to sustain a steady draw from the east. Interestingly the bias corrected GEFS MJO forecast projects a high amplitude phase 4 / 5 wave to develop towards month's end in the tropics which should help initiate another mountain torque event with potentially much more significance across the hemisphere.

The key themes here are likely to be the continued lowering of pressure over mainland Europe and coming and going of the ridge developing to our NE.

[casparjack]

hmm, CET running above average for the first 12 days of the month.

I was looking at the CET earlier to compare with my own records - Philip Eden has the latest figures on his site as 5.2c (-0.3c) - so just below. http://www.climate-uk.com/

Not wanting to be contrary, just trying to help...

[SMU]

I don't see anything this morning other than a slight delay to what I have forecast.

These are your posts for reference

So then on the 8th december you say curtains to xmas 7 new year-

Ian Brown, on 08 December 2011 - 09:36 , said:

A very progressive outlook this morning with some potentially damaging winds in Scotland particularly. Longer term the forcing looks like leading to increasing heights to the South, with the possibility of a SW-NE tilted jet perhaps giving a very mild Xmas to New Year period.

your 22 day forecast.....

So then the low for this week

think nearer the time these systems will be taken much further North. The pattern is so progressive at the moment it is difficult for the models to get a handle on systems in the mid-range, I certainly don't see the situation leading to the jet going South - quite the reverse come the final third of the month

So its ended up going North then-@??

What is a usual following on from persistent low heights to the N and NW is development of the downstream ridge, be it the Azores High edging NE towards France or a proper Bartlett. Obviously this is coupled with the Stratospheric profile at the moment.

Next weekend looks a classic trigger for this to happen, with a toppling High following a brief North Westerley, this typical leads to a minimum 10-14 days mild zonality thereafter. And looking at the extended GFS and I expect the ECM at what will be around T216, its going to be a long haul to get out of that sort of synoptic.

so we are expecting a belt of high pressure to the south of us in the near future?

Edited December 13, 2011 by Paul
Removed the personal stuff - have also removed Ian's personal comments

[Backtrack]

hmm, CET running above average for the first 12 days of the month.

Anyhow, I'm sure you'll be sensing a subtle shift in those teleconnective analyses over the last few days: a change to the profile of stratsopheric winds; a trending upward of upper stratospheric temperatures towards normal values; a shifting in the forecast position of the main body of the polar vortex towards eastern Siberia; increased heat flux at 30hPa in the mid to high latitudes; and, a recent moderate to high strength Asian Mountain Torque, the last named which is of most interest here as it is likely to plump up the hemispheric mid latitude ridges putting pressure on the polar vortex from the 'outside'.

The modelling continues to evolve around the day 7-8 mark, finally getting to grips with the likely trough digging into Europe and the potential for enough energy to leak SE undercutting both the Russian High and disrupting the trough over Scandinavia reversing the mean pressure anomaly here for potentially the remainder of the winter.

I would best describe this as a dress rehersal for later in the month when we might get a better chance at amplification in the mean westerly flow to sustain a steady draw from the east. Interestingly the bias corrected GEFS MJO forecast projects a high amplitude phase 4 / 5 wave to develop towards month's end in the tropics which should help initiate another mountain torque event with potentially much more significance across the hemisphere.

The key themes here are likely to be the continued lowering of pressure over mainland Europe and coming and going of the ridge developing to our NE.

Thank you for your excellent informative post as usual GP.

I see you're still sticking to your Easterly theme later on in the season. Great for cold if we can eventually get some cold pooling going over Europe.

Other than that, if that's true, it's going to be a poor Winter in the West if you're correct, in terms of snowfall that is. Although this is not always the case.

Back to the models, and I'm interested in the temperature profiles for the weekend thanks to a Northerly. We could be seeing painfully low night time minima in Northern England & Scotland, models indicate lows of -15C in the highlands on Saturday night, and as low as -10C in England. Could be a taste of Winter finally for those like me in the West, who haven't seen a glimpse of cold yet. Fun times ahead.

[dragan]

i caanot believes my post get evaluated, and ian brown be annoying like this!!

[dragan]

NW trough keeping back up to christmas, I think that Azores high to ridge north across the Atlantic to keep most people cold/cool. This is my positive thoughts.

Very changable, nothing is set into the stones.....i think following the Met is good idea (as always )

[bluearmy]

ecm ens for london trending milder on the 00z having trended cooler for a few runs. thus the swing to and forth of fi continues. nothing really mild for the festive period although its possible that the ridge could set up in a position to bring us some mild temps. ian confuses me a tad - last december, he was 'well into the freeze', yet he continues to spout the warm option for fi, irrespective of what the ens show.

[SMU]

Just the usual winter 'butting'.....

Heres the 06Z panel maps at 192-

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=192

The key area is the jet streak at around 150-170 over the central atlantic- if its West - east then Ians forecast will appear to some traction-

If its tilted SE NE then maybe a halfway house for the UK- the more towards the North it swings the more chance we have of a more seasonal Xmas-

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=3&ech=192

S

Edited December 13, 2011 by Steve Murr

[Paul]

Can we keep to the models and only the models in this thread please - there's really no need for all the personal sniping and point scoring..

[Alex]

The storm is further south on latest GFS, Meto continue with the warnings, wonder if they are being cautious or they know something ?

[SMU]

Anyway back to the models..... as posted above...

Just going on from what people keep saying-

the jetstreak over the atlantic at 144 has big repercussions down the line-

west east & we could well look like this towards xmas

http://176.31.229.22...s-3-1-192.png?6 which is what ian hopes/forecasts/expects

or more North & it can go like this...

http://176.31.229.22...s-0-1-240.png?6

A breather I think before the 12's

[johnholmes]

I'll post some thoughts in here post the possible Atlantic storm Thur-Fri when I get a chance-very interesting possibilities, including the 'storm' situation.

Edited December 13, 2011 by Paul
Can we just keep to the models please John.

[OldMetMan]

I've been trying to figure out the change of direction the models are taking today.

I talked yesterday about the possibility of a warm frontal wave developing ahead of the potential storm, and today the UKMet has picked up on this idea more noticeably. I still think the wave is being overdeveloped by them, such waves usually are quite shallow and fast moving - as the GFS has depicted.

It seems the cold upper trough associated with the deep low to our NW has dug down further than originally thought and the jet is displaced further S also. Looking at the GFS it seems to be simply running the warm frontal wave ahead of the developing system and then leaving the main LP behind, whereas before it was moving the whole thing bodily NE. I would suggest that the reason for this is that the LP is not expected to engage the jet fully, with only the wave being caught, although someone with more technical knowledge than me, do put me right if you think that's wrong.

Meanwhile, cold air will continue to sink south across the country so the risk of snow is now increasing steadily, well, at least for places away from the coastal strips.

It's been a remarkable series of runs from all the models soit will be extremely interesting to see how it actually pans out.

[johnholmes]

I've been trying to figure out the change of direction the models are taking today.

I talked yesterday about the possibility of a warm frontal wave developing ahead of the potential storm, and today the UKMet has picked up on this idea more noticeably. I still think the wave is being overdeveloped by them, such waves usually are quite shallow and fast moving - as the GFS has depicted.

It seems the cold upper trough associated with the deep low to our NW has dug down further than originally thought and the jet is displaced further S also. Looking at the GFS it seems to be simply running the warm frontal wave ahead of the developing system and then leaving the main LP behind, whereas before it was moving the whole thing bodily NE. I would suggest that the reason for this is that the LP is not expected to engage the jet fully, with only the wave being caught, although someone with more technical knowledge than me, do put me right if you think that's wrong.

Meanwhile, cold air will continue to sink south across the country so the risk of snow is now increasing steadily, well, at least for places away from the coastal strips.

It's been a remarkable series of runs from all the models soit will be extremely interesting to see how it actually pans out.

I tend to support most of what you have posted, especially about the warm front wave not being initially forecast nor that its necessarily correct yet in how its being dealt with.

The comment from Nick F in anwser to a post that it may be tomorrow before any firm 'handle' is made on the actual evolution is perhaps about right.

It is certainly a wake up call to all forecasters as to what/why and how events are being handled by the models for Thur-Fri. I would be amazed if UK Met do not set up their own operational review of this. Perhaps an article, probably pretty technical, in a few months time, in R Met Soc journals?

Edited December 13, 2011 by johnholmes

[OldMetMan]

I tend to support most of what you have posted, especially about the warm front wave not being initially forecast nor that its necessarily correct yet in how its being dealt with.

The comment from Nick F in anwser to a post that it may be tomorrow before any firm 'handle' is made on the actual evolution is perhaps about right.

It is certainly a wake up call to all forecasters as to what/why and how events are being handled by the models for Thur-Fri. I would be amazed if UK Met do not set up their own operational review of this. Perhaps an article, probably pretty technical, in a few months time, in R Met Soc journals?

Thank you John, I must say I do find it baffling that all the models seem to have gone awry here, although we are still 2-3 days away of course so that could still change again.

I have always trusted the UKMet output above all others and it came as a revelation yesterday when I watched the video by their chief forecaster on their web site explaining just how they interpret the model output. I believe you posted about this matter recently? Anyway, I guess I rather naively thought that it was much more straightforward. I should have realised, as I often see this process that the chief forecaster uses in judging the likely outcome when looking through the National Hurricane Centre's discussions on tropical disturbances - often the judgement of the forecaster is crucial in getting it right when different model output gives different outcomes.

Yes, I think you're right, this particular forecast has changed so radically, it certainly calls into question, either the models themselves, or their interpretation so perhaps they will learn vauable lessons as a result.

[feb1991blizzard]

I have to say that ECM 240 looks interesting, i admit i dismissed the idea of any link up between any Atlantic high and a retrogressing Russian high out of hand and maybe i owe that bloke in the video whos name escapes me an appology as the ECM shows how it could happen, still odds against in my opinion and i favour the GFS evolution but even that seems to be backing away from any of Ian Browns SUSTAINED euro heights now as high if anything looks like it may set up to our west for XMAS which wouldnt send us into the freezer but it certainly wouldnt be the Barbeque weather he has been predicting since November.

[Thundery wintry showers]

I think it's a warning to not to get too carried away with possible severe weather events involving explosive depressions, even if the cross-model support is overwhelming, unless the event is less than 4 days away. I'm not going to bash the MetO operational forecasters, as back on Sunday I really thought that Friday looked a dead cert for severe gales in central and northern areas and, had I been in their position, I would almost certainly have made the same mistake.

In the meantime, well done to John and also Nick F for refusing to commit to many specifics regarding the low.

I also agree that this sort of issue would be well worth an article in some of the journals- the question "how did it go wrong and why?" is surely material that could be used in scientific papers.

[No Balls Like Snow Balls]

I think it's a warning to not to get too carried away with possible severe weather events involving explosive depressions, even if the cross-model support is overwhelming, unless the event is less than 4 days away. I'm not going to bash the MetO operational forecasters, as back on Sunday I really thought that Friday looked a dead cert for severe gales in central and northern areas and, had I been in their position, I would almost certainly have made the same mistake.

In the meantime, well done to John and also Nick F for refusing to commit to many specifics regarding the low.

I also agree that this sort of issue would be well worth an article in some of the journals- the question "how did it go wrong and why?" is surely material that could be used in scientific papers.

But has it really gone wrong. All the meto have done is put out a yellow warning meaning "be aware", I don't recall anything released by the met saying wooooooooaaaaa we are all gonna get severe winds on Friday FACT!!, all i have heard is words like potential, uncertain etc.

Edited December 13, 2011 by No balls like Snow Balls

[johnholmes]

But has it really gone wrong. All the meto have done is put out a yellow warning meaning "be aware", I don't recall anything released by the met saying wooooooooaaaaa we are all gonna get severe winds on Friday FACT!!, all i have heard is words like potential, uncertain etc.

partly true but not all as you suggest which is the key and I suspect the reason the senior man yeaterday tried to illustrate his dilemma with the differing solutions. Fact is though the UK Met model, yesterday was wrong it WOULD SEEM at the moment, and hence their changed track/depth of the low in susbequent Fax charts.

Its far from a done deal and it may well end up as some kind of middle road between the earlier charts suggesting exiting near newcastle with central pressure <950mb and the later versions somewhere over southern England and about 975-980mb.

[casparjack]

But has it really gone wrong. All the meto have done is put out a yellow warning meaning "be aware", I don't recall anything released by the met saying wooooooooaaaaa we are all gonna get severe winds on Friday FACT!!, all i have heard is words like potential, uncertain etc.

You might have missed it, but they even referred to a major event in their 6-15 day outlook over the weekend I think (I don't have a copy), saying the 'peak of the current stormy period being the 16th of December would be followed by a more settled spell for most areas', or at least something to that effect.

However, despite our frustrations they largely do a very creditable job in an area where real wins are rare...

Edited December 13, 2011 by casparjack