Model Output Discussion - The Start Of Winter

[Jason M]

low res on the parallel would be more than interesting if it didnt make such a complicated mess of the atlantic troughing.   shame - could have been some eye candy.

Indeed, interesting that both the old and new GFS FI charts look like someone just randomly drew a load of weather systems!! Don't pretend to know where we will end up, but something's clearly brewing.

[TonyH]

I'm very optimistic that parts of the UK will have a white Christmas due to the topsy turvy pattern of mild alternating with cold day to day, it should be mentioned that milder air looks like having more success next week, especially through the midweek period but overall it's rather chilly with wintry ppn in the north and occasionally across the south too. At least we are in with a shout for Xmas day to be white instead of the usual green but we require a bit of luck with timings.

Possible on high ground up north yes Frosty provided it coincides with cold Pm air. Green for at least 95% of us I should imagine though!

[Mucka]

As many know I am a cold ramper but lets be honest some of the comments with regards to the output are way off!!

 

Comments such as "mild weather pushed back into F.I" are wrong. For example the GFS is predicting max temps of 12C next Wednesday.

 

http://www.wetterzentrale.de/pics/Rtavn9617.gif

 

A more realistic assesment of the output is this. Turning milder next week especially midweek before turning colder again next weekend. Thereafter becoming mild again around Xmas before possibly turning colder again after Xmas especially in the N. At this stage no notable cold spell is likely and any snowfall more likely for the higher ground during the colder snaps with the driest weather in the S.

 

So your forecast for next week is mild and to back it up you have posted a snapshot of the mildest chart you could find? 

Average CET for next week should come in around average and here is UKMO for Tuesday, another misleading snapshot of next weeks weather.

 

[TonyH]

Last winter we would see cold charts pushed back continuously, this winter it seems the opposite with any mild weather pushed back well into FI. Apart from some slightly above average temperatures it remains below average throughout the reliable, looks like December will finish below average, while not massively so it is 1-0 to the OPI right now in my opinion, as most seasonal models predicted a mild December. If they were wrong about December, surely they can be wrong about the winter as a whole?

But there has been mild weather lately (13c reached in parts) and will be in the week ahead, albiet during the past week or so it has only been brief. As for December, very likely to end up above average with no especially cold weather suggested by the output.

Edited December 13, 2014 by TonyH

[TonyH]

All this mornings talk of mild and no sign of pattern change has me scratching my head a little even though the 00z runs weren't that appealing.

 

We currently have the output moving toward another chilly W/NW outbreak in 5 or 6 days time and it won't be mild out to then either with temps lifting from a little below average to around average generally before falling a little below again.

That takes us out to about day 8 where temps will recover to around average again and thereafter there is some uncertainty whether the Azores high will exert enough influence to bring in a drier milder regime for a while or we keep the same pattern that has been bringing us these brief warm sectors between colder PM flow. (But remember the AH has been repeatedly modeled to play spoiler yet as we come into the more reliable modeling time-frame the troughs have always been backed West and deeper and the AH displaced keeping a more amplified pattern)

 

The last week of December there is a signal for a pattern change with significant height rises in our sector. 

We cannot know if this will develop or how it will develop in line with Ian's thoughts but the signal is there and it favours an Atlantic ridge which would bring a higher probability of colder weather affecting the UK.

I beg to differ - with uppers of 5c or so mid week maxima should be 10 to 13c for many and very mild for the time of year.

[Mucka]

I beg to differ - with uppers of 5c or so mid week maxima should be 10 to 13c for many and very mild for the time of year.

 

That is fine, although I disagree it will get as mild as 13C and it will be the anomaly not the norm for the coming 8 days. I inferred from the tone of TEITS post that the general theme from here to Christmas was "mild", especially when he said "turning milder again". It is not representative of the output IMO.

I don't see the average temp for UK next week (or even England) being on the mild side. Somewhere around average seems likely overall though it may be a little above in the South and a little below in the North.

If TEITS had just stated a brief milder interlude for the South of the UK as a warm sector passes through then that would of been fair and informative.

Run up to Christmas looks like a continuation of the pattern and how amplified the pattern will be at that time will dictate how "mild" and long lasting any warm sectors are.

 

Here are 12z temps for central England which shows a brief warm up as the milder air passes through Wed/thu.

 

 

Edit.

Got you mixed up with Op so will edit to reference properly.

Edited December 13, 2014 by Mucka

[knocker]

I beg to differ - with uppers of 5c or so mid week maxima should be 10 to 13c for many and very mild for the time of year.

 

I would be inclined to agree although I wouldn't use the dreaded term 'mild'. In fact all of the GFS op 5 day anomalies are above average until the end of the run apart from the odd frost hollow in Scotland.

charts courtesy weatherbell

Edited December 13, 2014 by knocker

[fergieweather]

Last winter we would see cold charts pushed back continuously, this winter it seems the opposite with any mild weather pushed back well into FI. Apart from some slightly above average temperatures it remains below average throughout the reliable, looks like December will finish below average, while not massively so it is 1-0 to the OPI right now in my opinion, as most seasonal models predicted a mild December. If they were wrong about December, surely they can be wrong about the winter as a whole?

Disagree. Broad December outlook of average/slightly milder/often windy looks fine thus far. OPI not factored into seasonal assessment by main operational centres (such as UKMO) nor will be until peer-reviewed/independently tested etc., so not relevant until it's accepted as a key metric of winter prospects (which it may or may not become). Issue from here is whether we start to see any resolution to some conflicting signals and key uncertainties by turn of year, drivers of which remain enigmatic.

[TonyH]

I would be inclined to agree although I wouldn't use the dreaded term 'mild'. In fact all of the GFS 5 op day anomalies are above average until the end of the run apart from the odd frost hollow in Scotland.

charts courtesy weatherbell

Not sure what to use other than mild though Knocker, I have always and always will to express above average temperatures during the cold half of the year

Disagree. Broad December outlook of average/slightly milder/often windy looks fine thus far. OPI not factored into seasonal assessment by main operational centres (such as UKMO) nor will be until peer-reviewed/independently tested etc., so not relevant until it's accepted as a key metric of winter prospects (which it may or may not become). Issue from here is whether we start to see any resolution to some conflicting signals and key uncertainties by turn of year, drivers of which remain enigmatic.

At last

[Evening thunder]

No mild weather hmm I am forecast a max of 13C on Wednesday, and a min of 12C Wednesday night... (Exeter). 

 

 

It may not last long, and may not affect the north so much, but it has as much place in discussion as brief NW'erly shots too. Alternating milder sectors and cooler PM flows describes things quite well I thought.

 

Personally I'm glad to see mild interludes being shortened and any greater predominance of PM air with potential clear frosty weather as winds fall slack. 

 

Good to see a post from Ian too explaining that the OPI is not yet factored into their longer range/seasonal forecasts (why should it be, would be very hard to justify a failed forecast based on using an at present un-peer reviewed index). Funnily enough despite for some reason being described as 'pretty poor' by a certain well known member and others before winter started, The Met Office's thoughts for December at least look like being pretty close to the mark. One can hope their latest thoughts for the New Year will be too

Edited December 13, 2014 by Evening thunder

[LomondSnowstorm]

I think average is about right for most, although for pretty much all of Scotland (rather than just the highest ground as it was for all of last winter) it looks more like cold with occasional mild incursions rather than mild. Maxima for Monday and Tuesday in particular are significantly below average, and even for the CET zone only around 4-6C, with the potential for some low level snowfall at times on Monday too (moreso for the likes of Inverness but also for central and southern Scotland too):

    

 

After Tuesday night into Wednesday's mild incursion it looks like a north/south split develops through to Friday, with cooler Pm air further north and Tm air persisting further south, and eventually another toppler north/northwesterly looks in the offing by Saturday, bringing colder air further south:

It's not exactly deep or prolonged cold by any means but, combined with last week's cold and hints of a more prolonged northerly by the end of the month, it looks like December may end up below average for Scotland, Ireland and much of northern England, which is a far cry from last December where almost everywhere in the British Isles had temperatures well above average. And RE the seasonal forecasts it's far too early to judge - the OPI (highly expermental) and SAI (more widely accepted) which are both indicating similar things for this winter both appear to correlate better with cold in January/February than December (and of course neither claims to guarantee cold here, merely predict the general AO state for the winter) and most of the LRF's I saw, no matter their overall winter outlook, went for a cyclonic,westerly dominated period with a lack of blocking in our vicinity for the first half of December, which has evidently materialised.

Edited December 13, 2014 by LomondSnowstorm

[fergieweather]

Erm, to be very clear: OPI hasn't been peer-reviewed. To say it's 'poor' is pre-empting rigorous independent assessment and unfairly dismissing work by it's authors. It may or may not be onto something, but for now we can't assess this in any informed fashion, so it's not factored into key seasonal prognostics.

[johnholmes]

why oh why cannot folk post charts, comment on them, use whichever suits you, others STOP making comments about folk and how they assess the charts. Post your own with your version of what is happening with them.

Most new folk soon pick up which of you is in the mild camp and which is in the cold camp along with the very few who try to post objectively.

We get this every year-why?

Post the charts and TRY to stop being selective and make objective comments on the WHOLE run not bits that suit.

It ain't rocket science nor does it need huge experience.

Edited December 13, 2014 by johnholmes

[nick sussex]

Interesting to see the GFS, GFS P and GEM start to develop more amplification towards the T240hrs mark with troughing digging into the central USA.

 

This might develop further and we could see some more interesting outputs showing up for the Christmas period, there could be some wildish swings in terms of the pattern over Europe as you're effectively going from flat as a pancake upstream at T192hrs to more amplified at T240hrs.

 

I really hope the ECM follows this trend and the outputs get behind this even more tomorrow, it would be great to see some colder conditions for  Christmas and the New Year.

[joggs]

Thanks Fergieweather for the updates.Sorry mods

[Evening thunder]

Erm, to be very clear: OPI hasn't been peer-reviewed. To say it's 'poor' is pre-empting rigorous independent assessment and unfairly dismissing work by it's authors. It may or may not be onto something, but for now we can't assess this in any informed fashion, so it's not factored into key seasonal prognostics.

 

Quite agree Ian, assuming this refers to my post I have edited it as I don't think I made it very clear.. I wasn't calling anything poor myself or referring to the OPI at that point, just mentioning that some members of the forum had previously described the Met Office's longer term outlook/contingency planners forecast effort as 'pretty poor' for not taking account of the OPI and some other indexes, which I didn't think was fair.

 

Apologies for any off topic/unsuitable material, just trying to clarify things here so I am not misunderstood, and before was trying to show mild as well as cold weather was showing in the models, averaging out to around average.. 

 

Edit: admittedly this is from my southern England viewpoint and for the north things trend more to the cold site due to a predominance of polar/Arctic maritime air.

Edited December 13, 2014 by Evening thunder

[bluearmy]

Mean uppers for New York around -10c approaching new year. the east coast amplification will create an Atlantic ridge of some description. still decent fi gefs anomolys for cold although I can't see a sustained greeny ridge at moment. However, we could manage a broad nw European trough which could draw the jet se and leave us on the cold side of the trough.

[Snowman.]

why oh why cannot folk post charts, comment on them, use whichever suits you, others STOP making comments about folk and how they assess the charts. Post your own with your version of what is happening with them.

Most new folk soon pick up which of you is in the mild camp and which is in the cold camp along with the very few who try to post objectively.

We get this every year-why?

Post the charts and TRY to stop being selective and make objective comments on the WHOLE run not bits that suit.

It ain't rocket science nor does it need huge experience.

The best post here today.  

 

 

 

So far today the Parallel has been increasingly amplified and keeping the PV disrupted.

 

 

The OP however doesn't want any of this and continues to blow the jet.

 

[Nouska]

One cannot get away from the fact that some very mild nights are forecast thus skewing the accumulated five day anomalies - what is surprising is that the month to date plus all these (next seven day) milder interludes should still amount to below average in my native turf and just on average in the south.

 

 

Source is a useful page for looking at reanalysis and forecast of temperature data.

 

http://www.karstenhaustein.com/climate.php#forecast

[Tim Bland]

ECM has a PM flow from NW nxt weekend. Uppers of -6 even in the south could allow for wintry showers for all of uk

http://www.meteociel.fr/modeles/ecmwf.php?ech=72&mode=0&map=3&type=0&archive=0

[Hotspur62]

Apologies for not showing charts but my pc skills are not upto much but one thing that seems consistent in all models is the Azores High not moving much in next 240hrs.I know it is only one aspect of things falling into place to eventually get cold but in the FI it does pull further West in last few frames of GFS and if this continues to become a trend maybe this could trigger a pattern change as the likes of S Murr,Tamara are indicating in the last few days of the year. Sorry if I have got this all wrong but until this happens and/or Heights rise to our North we are in the same pattern for next 10 days which although a bit monotonous is still fascinating to watch how it all evolves and maybe, just maybe, may result in a pattern change which would result in a lot of happy people on this forum. I hope Ian F"s comments on the future firm up and turn into reality lol

[johnholmes]

re my little rant above-I will post a reasonably in depth look at the rest of December as I see it using a variety of charts, yes you might even see a link to something other than the dreaded 500mb anomaly things!

Too busy today to devote enough time.

[Polar Maritime]

Yes Tim, Pretty much in line with GFSP for around the 20th.

 

Edited December 13, 2014 by Polar Maritime

[Mucka]

Interesting...

 

 

Sign of trough disruption out to the West, almost enough to stir some coldies out of hibernation but a long way off (Can I keep this straw BTW?)

Edited December 13, 2014 by Mucka

[Frosty.]

After the warm autumn, I'm happy to see proper winter being ushered in with temperatures generally balancing out fractionally below the seasonal average which frankly is a minor victory in an otherwise warm last quarter. The cold incursions certainly have more punch compared to the limp wristed efforts last winter although so far it's mostly been the north which has benefited but looking at the models I can see the balance tipped in favour of colder outbreaks than anything especially mild..mild blips yes but mostly on the chilly side. :-)