Model Output Discussion - 19th - 25th December

[Frosty.]

Not exactly guranteed yet. What I'm hoping for is the timing of events to change. A predicted cold snap on the 23rd to either last longer; be more potent; start at a later date - the cold snap on Boxing Day to start earlier. I really am praying that we'll still be under relatively cool uppers come Xmas Eve and I would love it if we have some remaining lying snow on the ground come midnight 25th December.

I wouldn't call it a cold snap on the 23rd, temps of 5-7c is not a cold snap, unless you meant the scottish mountains where it will be cold but for most of the uk it's a cool blip following the mild days on wed/thurs and the mild days that follow the 23rd.

[phil nw.]

The 12z output so far shows the same outlook as earlier runs, and unfortunately,for those looking for it, nothing seasonal is promised for the Christmas weekend.

The first day of much milder weather is due to spread across the UK on Weds.

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

The Azores high then builds closer to the UK by the end of the week and with persistent low pressure to our North the flow becomes predominately South Westerly with any colder Pm air limited to brief incursions into the far North.

http://www.wetterzen...cs/Rukm1441.gif

The pattern beyond and into the following week on GFS continues with that blocking to our south extending into c.europe as the current european troughing warms out.

Here a Nhemisphere view at T180

http://hw.nwstatic.c...180/npsh500.png

Whilst the pattern overall looks pretty zonal it shows the High pressure very close to the UK that could well bring a colder feel as we pick up a drift off the continent-with some night frosts in some central and se areas.

Places further north and to the far west will likely have more cloud and dampness with a flow more off the Atlantic.

[IDO]

Not exactly guranteed yet. What I'm hoping for is the timing of events to change. A predicted cold snap on the 23rd to either last longer; be more potent; start at a later date - the cold snap on Boxing Day to start earlier.

I really am praying that we'll still be under relatively cool uppers come Xmas Eve and I would love it if we have some remaining lying snow on the ground come midnight 25th December.

There is little in the way of cold, maybe transitional cool in Scotland. The ensembles (GFS) have 100% confidence that by the 30th we will have a HP to our SW and be influenced by relatively mild weather. A week later the HP is slightly further East with above average temps. The end of GFS has no short term route to cold. In fact with the Jetstream way to our North, quite the opposite; aided by two HP's moving in to the picture from the SW and South. (I usually am skeptical of FI but in the current setup the confidence is quite high).

It looks like above average temps for the first half of Jan 2012. Something need to change in the next two weeks or the second half will also be a write off for cold. So effectively six weeks of Winter left...

[Optimus Prime]

It looks like above average temps for the first half of Jan 2012. Something need to change in the next two weeks or the second half will also be a write off for cold. So effectively six weeks of Winter left...

You're looking at models that deal with the weather, not high calculation climate models. Whatever it shows right now for weeks ahead will change. To say we will have the samt type of weather for the next 4 - 6 weeks is taking these comparible low resolution models way too seriously. The ensembles and GFS will not help you beyond 12 days so there is no point looking at them with any degree of confidence past that time frame.

[Swave Snow]

Well generally that is true but if we take the projected picture at T240, then broadly speaking such a pattern in terms of the broad synoptics will persist for considerably longer - the METO outlook going up to mid-Jan reflects this.

But to be fair they have chopped and changed a lot recently

Edited December 19, 2011 by Swave Snow

[IDO]

You're looking at models that deal with the weather, not high calculation climate models. Whatever it shows right now for weeks ahead will change. To say we will have the samt type of weather for the next 4 - 6 weeks is taking these comparible low resolution models way too seriously. The ensembles and GFS will not help you beyond 12 days so there is no point looking at them with any degree of confidence past that time frame.

Sorry, that's all I had to go on. At this time I was just commenting on the FI by GFS and as there was close to 100% confidence by the ensembles at Day 8 I therefore extrapolated that, confidence at +384 would be of relative significance.

[Robbie Garrett]

Just out of interest, what's the coldest March on record? can it be compared to something similar to November 2010? Saying because is there still a reverse chance of last year? i.e Later winter period rather than earlier?

Edited December 19, 2011 by Robbie Garrett

[Optimus Prime]

Just out of interest, what's the coldest March on record? can it be compared to something similar to November 2010? Saying because is there still a reverse chance of last year? i.e Later winter period rather than earlier?

No. 1962 was the coldest March on record (CET 2.8c) and was a month that was dominated by cold and frost throughout rather than an intense burst of cold that the end of November 2010 registered. Synoptically there are miles apart. And miles apart to what we have now (quite often the case historically)

[phil nw.]

I have had to remove a couple of posts which were not discussing the model outputs.

If you have want to talk C.E.T. comparisons with other months/winters please take them to the appropiate threads.

[Frosty.]

It looks like above average temps for the first half of Jan 2012. Something need to change in the next two weeks or the second half will also be a write off for cold. So effectively six weeks of Winter left...

Oh my god what a depressing post, writing off over 40 days of winter. :smiliz46:

There is no doubt we are entering a phase with a sw/ne angled jet with high pressure to the south or southwest and maybe eventually the southeast and lows pushing east to the north of the BI so it will be a mild christmas but you can't write off the first half of jan as confidence in the model output drops away significantly by the start of the new year.

[stewfox]

What is concerning about this model discussion is that like the summer where everyone was waiting for a ridge to develop to our east. The same is happening this winter with the SSW. I'm not saying it will or won't happen! But even if it does as some have pointed out, it doesn't directly mean a big Greenland high and extreme cold! My advice would be to take a look at trends developing and particularly whether a ridge is likely to develop to our west/northwest, other factors also need to be considered.

Does seem to be more of a herd mentaility

Wait for the stratosphere to warm up and then we get a pro longed cold snap due to start by 15th Jan,all things being equal. Dismiss the next 3/4 weeks..

Might as well just close up shop for 4 weeks.

Since when did back ground signals 'dictate' the model outcome at T384 as a majority seem to suggest now ?

Edited December 19, 2011 by stewfox

[Summer Sun]

ECM tonight for the festive weekend

Christmas Eve

http://www.wetterzen...cs/Recm1201.gif

Christmas Day

http://www.wetterzen...cs/Recm1441.gif

:smiliz19:

Dry, settled and temperatures around 7 to 10c I would think.

[phil nw.]

Oh my god what a depressing post, writing off over 40 days of winter. :smiliz46:

There is no doubt we are entering a phase with a sw/ne angled jet with high pressure to the south or southwest and maybe eventually the southeast and lows pushing east to the north of the BI so it will be a mild christmas but you can't write off the first half of jan as confidence in the model output drops away significantly by the start of the new year.

Hi Karl,

Indeed the placement of the surface features,especially the High can make a considerable difference to the surface conditions.

We will have to see what the other output says but on the GFS the trend seems to build that High close to the SE.

Warks Ens

.

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

The mean after a rise falls back towards 0c --so not especially mild considering the pattern at first glance.

Edited December 19, 2011 by phil n.warks.

[January Snowstorm]

A pretty dire set of runs.

The shops will be happy and of course the racing contingent.

Indeed the Christmas racing looks like having a frost free event.

Not even a good storm to look fwd to.

Ah well, it's only the weather

[Frosty.]

Hi Karl, Indeed the placement of the surface features,especially the High can make a considerable difference to the surface conditions. We will have to see what the other output says but on the GFS the trend seems to build that High close to the SE. Warks Ens .http://hw.nwstatic.co.uk/ensimages/ens.20111219/12/t850Warwickshire.png http://hw.nwstatic.co.uk/ensimages/ens.20111219/12/prmslWarwickshire.png The mean after a rise falls back towards 0c --so not especially mild considering the pattern at first glance.

Hi phil,

Yes the placement of the high is far from being resolved yet and I noticed on the canadian ensemble model this morning that the high builds across the whole of the uk in FI bringing frosty and foggy weather, so there are still lots of options but the xmas weekend will at least be mildish with Tm air flowing around the top of the high, let's hope we get a cold anticyclonic spell after christmas instead of mild and rather cloudy with sw'ly winds.

[snow drift]

As I've said before, we can extend our outlook beyond the so called reliable timeframe where zonality is concerned, I think we can accept that this time with the High pressure surge from the South, that we are going to end up where the 06z and now the 12z puts us at around T240.

Ian, you have given extended outlooks for awhile now and looking back, there was no mention of the snow that some areas have seen just recently. If you look at the models and what they are currently showing, one can make assumptions but as you well know things can and do change quickly. I think it fool hardy to believe that due to the surge of pressure from the south, that we will end up with what the models are suggesting for 10 days time. So much depends on where this pressure goes to what will be the outcome in the longer term.

[mountain shadow]

Certainly no sign of a prolonged Bartlett on tonights ECM, full of promise at T+168 with an Arctic high possibly linking with an Atlantic ridge. ECM ensembles may show some prpoer cold solutions.

[phil nw.]

Yes as expected the ECM paints the same zonal picture up to Xmas weekend and beyond

http://www.wetterzen...cs/Recm1441.gif

The High again modelled close to the South of the UK so maybe some surface cold with night frosts for some places.

In the later part of the run the jet is modelled further south so some less mild air returning.

http://www.wetterzen...cs/Recm2401.gif

Overall then the models agree on a mobile westerly pattern but with High pressure close to the south at times.

More unsettled in the north with some brief colder incursions.

Edited December 19, 2011 by phil n.warks.

[IDO]

Does seem to be more of a herd mentaility

Wait for the stratosphere to warm up and then we get a pro longed cold snap due to start by 15th Jan,all things being equal. Dismiss the next 3/4 weeks..

Might as well just close up shop for 4 weeks.

Since when did back ground signals 'dictate' the model outcome at T384 as a majority seem to suggest now ?

Since September the AO has been positive for over 90% of the time. This is a strong pattern and this will dictate an average winter the majority of times. I have seen little evidence in the medium term that the AO will turn negative, other than fleetingly. ECM predicted the blocking in the last two years but they have not forecast it this year. Although there is warming in the higher stratosphere this has not percolated down to the lower end so the PV looks like remaining strong.Therefore Northern Blocking looks an outside bet for the next four weeks. Currently to our East temps are mild compared to the last few years. Any Easterly feed from a Northern based HP is likely to reflect this and we are unlikely to experience any real cold. The current setup precludes any prolonged cold and that is what I have commented on. When we have an improvement in the synoptics it is then we can post as to the likelihood they will lead to cold.

[Thundery wintry showers]

Judging by the latest outputs, Christmas Day will have a NW-SE split with a dry sunny zone towards the SE, a dull wet zone towards the NW, and a dry cloudy windy zone in between. The highest temperatures will occur in the east of the dry cloudy zone due to the fohn effect. The dry sunny zone will have the lowest overnight minima with chances of a slight frost.

The latest GFS run suggests that the dry sunny area will cover East Anglia, much of southern England and perhaps parts of the S and E Midlands and Lincolnshire, and the ECMWF looks pretty similar, but the UKMO has the high slightly further south, suggesting cloudy skies for the majority.

Beyond that and it is depressing fare for snow lovers with high pressure rooted to the SE, albeit good news for those who prefer milder weather, particularly towards the SE where it probably won't be persistently grey and drizzly, although it's worth noting that this pattern doesn't start until T+144 so there remains some uncertainty over how long it will be before the high either advances northwards or gets shunted away south-eastwards.

[karyo]

Certainly no sign of a prolonged Bartlett on tonights ECM, full of promise at T+168 with an Arctic high possibly linking with an Atlantic ridge. ECM ensembles may show some prpoer cold solutions.

The 0z ECM had the jet on a more southerly track on its later stages compared to the 12z. The artic high you mention is notable for the first part of the run but unfortunately loses steam and fizzles as the run progresses.

I hope the ensemble mean is better than the operational.

Karyo

[damianslaw]

Models painting a very traditional 'winter' pattern with strong heights to our south and low heights to our NW pulling in a southwesterly.. In these set ups the default position is to always keep the same pattern going, so I'm not surprised there are no indications of a pattern change in the models for the foreseeable future. However, what I will say, is even in what may appear to be a 'very hard to shift' pattern, reliable timeframe is still 6 days at top.. and sudden development can and often do occur. Look at the last 3 weeks the models have had to react to very short term developments scuppering there original thoughts.

One strong possibility as we head towards new year is for anotherdeep low to our NW to develop and we have seen many of these this month this moving on a more southerly position and once again we are in a run of cold polar maritime air, forcing the azores high back westwards - indeed this set up is very plausible given the strong temp gradient in north atlantic- this isn't suddenly going to dissapear, what the models don't predict very well are 'such low pressure systems'.. so all eyes to our NW in the coming days and what happens off the eastern seaboard of USA.

I am predicting lots of doom and gloom in the this thread and on the forum in general during the run up to christmas from snow and cold lovers.. patience is the word this winter...

[TEITS]

All im going to say about the model output is from now into the xmas period it looks dire for those wanting cold, snow. However don't let those fool you by saying this will last into Mid Jan. The truth is you cannot tell how Jan will pan out based on the current model output. I still remember Feb 05 when the model output was dire and then the chart below appeared out of nowhere.

http://www.wetterzentrale.de/archive/ra/2005/Rrea00120050226.gif

I shall be following the Stratosphere thread and reading GPs posts as a guide to what we can expect in January. I certainly won't be using the current model output!!

[damianslaw]

All im going to say about the model output is from now into the xmas period it looks dire for those wanting cold, snow. However don't let those fool you by saying this will last into Mid Jan. The truth is you cannot tell how Jan will pan out based on the current model output. I still remember Feb 05 when the model output was dire and then the chart below appeared out of nowhere.

http://www.wetterzen...00120050226.gif

I shall be following the Stratosphere thread and reading GPs posts as a guide to what we can expect in January. I certainly won't be using the current model output!!

Good post - I also suggest many read the strat thread and the more technical thread - longer term developments do look very encouraging for more persistant cold conditions in the second half of the winter and this isn't to rule out the chances of cold and snow before mid january as the last couple of weeks have proven - shortlived cold spells can and do occur even with a strong PV and unfavourable strong heights to our south, I am certainly not dismissing the chance of another decent polar blast either just before or just after new year.

[Weather-history]

As I've said before, we can extend our outlook beyond the so called reliable timeframe where zonality is concerned, I think we can accept that this time with the High pressure surge from the South, that we are going to end up where the 06z and now the 12z puts us at around T240.

I take it you have forgotten about December 2007? Remember when you said it was going to be a zonal fest and possibly a record break mild December and I pointed out that one or two ensembles were showing high pressure having more of influence? Lo and behold as the runs went by the high pressure influence increased and increased and we ended up with about a two week anticyclonic spell and an average December. Not saying that will happen this time but the point is we don't know with any degree with certainty.