Model Output Discussion 1200 hrs 15/11/14

[IDO]

The GEFS for D13 show variations on the upcoming pattern with little sign of HLB in our quadrant:

 

 

But by D16 once the third Atlantic high has taken up close residence there remains a cluster suggesting amplification:

 

 

This has been a background noise for a few runs, with no clear trend yet to evolve this within the ensembles, but I am still hopeful of something like this as we enter the mid-December period.

 

ECM suggests about 10mm of rainfall for London in the next 15 days: 

 

Temps fluctuate from cool and frosty to above average. Surface conditions will be difficult to pin down till nearer the date though a cooler period from next Tuesday once the cold front slides through, till the end of the weekend looks to have good agreement:

 

 

CET is still +1.7c and this may be close to the final figure.

[MR EXTREMES]

HP has been present to the NE and E since the middle of the month. The upper pattern is, as I mentioned, admittedly somewhat ill-defined over N Europe, but currently Atlantic systems are sliding away SE as a result of the high, so I think that constitutes a block.

Such patterns of HP to the NE do have a tendency to recur. Some models have been showing the Azores HP actually linking NE to Scandinavia, but there is too much day-to-day variation in that scenario to put much faith in that happening.

I think the next few days should give us a clearer idea of whether blocking as I mentioned will re-develop.

i think its clear to see all models show a block of sorts.

ne block removed and to be honest good because it allows heights to build elsewhere im just happy there are no above average temps forecast by day and by night.

 

so temps looking likely to be slightly below to average with some white stuff up north.

 

its still a evolving situation because the models are not certain where things will settle although the gem is rather tasty its certain to be wrong although maybe right in the shorter term.

 

the ecm has relaxed its garden path antics to my relief but i think fi stands at 96 hrs across the board but by the end of the weekend where have a clearer picture.

 

until the current changes have taken effect id expect much more flip flops.

but over all pretty normal uk december up and coming.

much better than last year.

[Summer Sun]

For those of you new to the models the beeb have done a video explaining what the forecast models and "postage stamps" are

 

http://www.bbc.co.uk/weather/features/30235229

 

 

[Iceaxecrampon]

Just had a quick look at the GFS 06Z - no time to post a chart but things still looking good maybe for a cooling down of sorts for the 5th  - 7th December just bonkers double figure temps for this Sunday.

 

FI is just eye candy hilarious if anyone wants a look - T372 13th December.

 

Ian

[knocker]

HP has been present to the NE and E since the middle of the month. The upper pattern is, as I mentioned, admittedly somewhat ill-defined over N Europe, but currently Atlantic systems are sliding away SE as a result of the high, so I think that constitutes a block.

Such patterns of HP to the NE do have a tendency to recur. Some models have been showing the Azores HP actually linking NE to Scandinavia, but there is too much day-to-day variation in that scenario to put much faith in that happening.

I think the next few days should give us a clearer idea of whether blocking as I mentioned will re-develop.

 

Yes I misread your post OMM, so apologies for that. My mind has been concentrated on future developments. Well as much as my mind can concentrate these days. From my reading of the anomaly charts I can't see the blocking re-develop unless there is a fairly drastic pattern change shortly. My bet would still be a cold incursion from the NW if I had to place a bet.

[Mucka]

No strong signal as yet for cold weather to affect the UK but we are getting back to the stage where the daily output will become more interesting viewing once more over the next few days as high pressure to our NE relents and we go into a more mobile Westerly flow.

Usually these type of pattern changes are frowned upon and come with dire warnings of the Atlantic driven weather setting up and not relenting for several weeks but with the PV in a weakened state and showing signs of wanting to migrate West it may actually be the pattern change we needed as the Scandi high and Atlantic trough stalemate was getting a bit - well stale. The heights to our NE still come into play though as they reinforce the Arctic high which itself will hopefully have a positive influence on bringing some colder weather down the line.

Of course a nicely rounded cut off Scandi high or far fetch continental easterly can be great but the beast from the East is in fact extremely fickle in nature and while you have low heights to the NW it is always going to be extremely difficult to get the undercut and retrogression of heights required to get the necessary HLB, especially late Autumn early winter where the PV is wanting to flex its muscle. 

That is why my preference is always for blocking to our W/NW, at least initially as this is a much more secure route to cold for the UK and any blocking over Greenland can a;ways transfer to Scandi to prolong a cold outbreak and turn the flow from the N/NE to the E.

 

with that in mind the ensemble mean 10 day charts are quite favourable for the prospects of an Atlantic ridge forming and the PV around Greenland to shift West with low pressure dropping into into Scandinavia and Central/Eastern Europe as we go into the second week of December.

 

 

Looking at the NH ECM ensemble mean above we can just intuitively feel the low heights over Greenland dropping SE as a cross polar split forms, the only fly in the ointment is our old enemy the Azores high. Any trough to our East will need to be deep enough to keep the pattern amplified behind and far enough West to prevent the AH riding in and forcing a flatter pattern with a westerly jet. The more defined the trough to our East is the more we squeeze the pattern and AH West and the stronger any Atlantic ridge and WAA toward Greenland will be.m Naturally we are also relying on an amplified pattern upstream but given the NH profile predicted around that time we should have a fair shot at it.

 

Usual caveats apply to all this because we are likely talking 10 days+ for a favourable pattern to develop but at least we can see if such a pattern is becoming more or less likely day to day.

What I don't see is raging zonal conditions setting up with the UK being battered by low pressure through December because the spoiler will likely be the AH which would mean any storms are forced North of the UK so even then we would probably have a spell of fairly benign weather with the possibility of a UK high forming or blocking reforming to our E/NE a little further down the line.

So, in my mind at least, typical zonal mush is probably the most unlikely weather type to set up though we will have some unsettled weather to get through as the low heights around Greenland try to push East and lows pass to our N and attempt to dig SE..

Edited November 28, 2014 by Mucka

[A.J]

The last two posts have been moved to the following thread as they are not model related

 

https://forum.netweather.tv/topic/69782-weather-in-the-general-media-newspaper-features-etc/

 

Please remember that this thread is for model output related discussion only, and there are far more suitable threads for met office forecasts and other media forecasts......thanks

[OldMetMan]

Yes I misread your post OMM, so apologies for that. My mind has been concentrated on future developments. Well as much as my mind can concentrate these days. From my reading of the anomaly charts I can't see the blocking re-develop unless there is a fairly drastic pattern change shortly. My bet would still be a cold incursion from the NW if I had to place a bet.

No problem Knocker.

It's a very tough call at the moment really. The only other thing that has caught my attention today is the tendency for a more amplified hemispheric 500mb pattern. But that in itself only hints at possible future blocking. So much depends on the long wave locations. But it sure looks a lot different from this time last year!

[Severe Siberian icy blast]

Yes I misread your post OMM, so apologies for that. My mind has been concentrated on future developments. Well as much as my mind can concentrate these days. From my reading of the anomaly charts I can't see the blocking re-develop unless there is a fairly drastic pattern change shortly. My bet would still be a cold incursion from the NW if I had to place a bet.

The thing about the anomaly charts is like all computer models , once they pick up on a new signal , they do change drastically , Iv seen lots of times the anomaly charts showing a Scandi high for example for a time period of say 6-10 day period , then a few days later they pick upon new signal and they change accoranly, before the Scandi hight rise was even due to take place , so it picked up a false signal .

Not saying thats gonna happen now of course , particuarly as we are expecting a more Atlantic type period , but I wouldn't be surprised at all to see the Scandi high become big player again in the 7-12 day range from now , especially as December progresses with the SAI feedback propergation moves forward a fase .

This is the other point I wanted to make , considering the vortex is at a weakened state this year , especially higher up the strat , it means the vortex is not doing the same dictatorship this time round like it was last year , so we can have a major pattern change that's trop led rather than strat led. So if we can get some decent amplification downstream , pump some WAA into the polar regions then there's nothing to say that warm air can infiltrate the strat from the bottom up , as a suppose to top to bottom . So we really just need to keep watching for signals in the models , knowing its only a matter of time untill we see the wave activity pick up again and this time the Scandi high should force itself further west with cold air much more likely on the second round to put Europe in the freezer .

Tick tock tick tock

Edited November 28, 2014 by Severe Siberian icy blast

[winterof79]

Shannon Entropy shown at its best by the control

http://www.wetterzentrale.de/pics/MT8_Manchester_ens.png

 

Somethings brewing for mid December methinks.

[Dancerwithwings]

Shannon Entropy shown at its best by the control

http://www.wetterzentrale.de/pics/MT8_Manchester_ens.png

 

Somethings brewing for mid December methinks.

The consensus is pretty much there, but after the 5th its all over the place! just shows how they are stumbling at just days 5-7... Agreed and hopefully something is brewing!

Very interesting model watching in the next coming days methinks.

Edited November 28, 2014 by Dancerwithwings

[Gael_Force]

Shannon Entropy shown at its best by the control

http://www.wetterzentrale.de/pics/MT8_Manchester_ens.png

 

Somethings brewing for mid December methinks.

 

That looks like the members out of sync in a fast moving pattern of lows swinging through.

[johnholmes]

The thing about the anomaly charts is like all computer models , once they pick up on a new signal , they do change drastically , Iv seen lots of times the anomaly charts showing a Scandi high for example for a time period of say 6-10 day period , then a few days later they pick upon new signal and they change accoranly, before the Scandi hight rise was even due to take place , so it picked up a false signal .

Not saying thats gonna happen now of course , particuarly as we are expecting a more Atlantic type period , but I wouldn't be surprised at all to 

 I have to say I have rarely, maybe once or twice in 3-4 years seen any dramatic change in the anomaly charts as you suggest. Like any other output they have to be used carefully. Best in my view to ignore the anomaly bit until very well used to using them and concentrate on the 500mb pattern shown.What you need are all 3 of the main charts showing the major wave pattern to be pretty close to one another in position, depth etc, and over preferrably a minimum of 2 better still 3-4 days. If so used then they will be close to the mark on 70+% of occasions. Exceptions I have outlined several times=N hemisphere change over season, spring and autumn and also the input of Tropical/Hurricanes into the N Atlantic. Outside those exceptions then I would bet them against any other 6-15 day time scale outputs. I know my, obsession as some suggest is not agreed by some on here. One last point they are just as accurate if they predict continuation of the present upper air pattern and a marked change.

Below are the current outputs for folk to muse over.

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

 

Please do give them a try, note what the upper air pattern they suggest in the 6-10 day frame then check 6-10 days, or the same with the 8-14.

Remember they are 'average' charts, the pattern on any one day may be slightly displaced from what you have saved but it is pretty unusual, with the caveats given, that the upper air pattern will show markedly different.

 

They do need to be used in conjunction with other outputs at that time scale, MJO, AO, NAO etc.

Edited November 28, 2014 by johnholmes

[knocker]

The thing about the anomaly charts is like all computer models , once they pick up on a new signal , they do change drastically , Iv seen lots of times the anomaly charts showing a Scandi high for example for a time period of say 6-10 day period , then a few days later they pick upon new signal and they change accoranly, before the Scandi hight rise was even due to take place , so it picked up a false signal .

Not saying thats gonna happen now of course , particuarly as we are expecting a more Atlantic type period , but I wouldn't be surprised at all to see the Scandi high become big player again in the 7-12 day range from now , especially as December progresses with the SAI feedback propergation moves forward a fase .

This is the other point I wanted to make , considering the vortex is at a weakened state this year , especially higher up the strat , it means the vortex is not doing the same dictatorship this time round like it was last year , so we can have a major pattern change that's trop led rather than strat led. So if we can get some decent amplification downstream , pump some WAA into the polar regions then there's nothing to say that warm air can infiltrate the strat from the bottom up , as a suppose to top to bottom . So we really just need to keep watching for signals in the models , knowing its only a matter of time untill we see the wave activity pick up again and this time the Scandi high should force itself further west with cold air much more likely on the second round to put Europe in the freezer .

Tick tock tick tock

 

You could say that in spades regarding surface analysis but the 500mb level does 'drive' surface conditions and are a more accurate guide to the latter. These maps are very good for getting a large-scale picture of the "weather pattern" over the United States, North America, or even the Northern Hemisphere. and are probably most useful for studying winter time weather patterns in the middle latiutudes (between about 30° and 60° latitude). So when you can establish some cross model consistency with the 500mb charts the more likely you are on the way to better surface analysis.

 

Whoops didn't notice John had already answered that rather makes my post redundant.

Edited November 28, 2014 by knocker

[Allseasons-Si]

Well look at the difference between ukmo and gfs @144hrs

 

ukmo gfs

 

look at the amplification just off the eastern seaboard,love to see a couple more frames from 144hrs,maybe an atlantic ridge joining up with the arctic high there bringing a northerly sooner.

[Mucka]

GEM 12 goes for a strong Atlantic ridge again though looks like a toppler.

 

 

It is different in key areas to GFS output in that it has a stronger arctic high and is not as keen as bringing the Azores high into play in the shorter range.

 

 

 

UKMO 7 day would have some potential down the line.

 

[IDO]

Again I am liking the FI of GFS. This time the op. Once the third Atlantic high arrives after around D13, the westerly flow is stalling and it allows the whole pattern to amplify. Details are going to change, it's the synoptic that interests me. Hopefully more ensemble members will come on board:

 

Edited November 28, 2014 by i'm dreaming of...

[blizzard81]

The UKMO 12z is a major upgrade for a cold outlook imo. For once I suggest people view this on the Europe view as opposed to the northern hemisphere one. Now compare this run with yesterdays 12z and the first thing you will notice is the air still comes in from the continent in todays run, whereas yesterday, the theme was for the azores ridge to be dominant. The change brought about by today's run is the low over southern Europe being a bigger player than previously anticipated - The importance of which Carinthian has been at pains to point out these last couple of days. This draw from Europe should make it easier for the high in our locale to retrogress and join forces with the high off the eastern seaboard and then hopefully complete the retrogression and bring our northerly.

[gottolovethisweather]

Next week's weather summary looks fairly straight forward, most parts rather cold and dry, especially so in lingering fog and mist. The NH view is a changing slowly though and just which region of the globe, the deepest cold wants to infiltrate as we head into D10 and beyond remains an open and most pertinent question.

 

The starting point for December is as modelled some days ago and illustrated in my post here as BATTLEGROUND UK, so it is a trend that stuck and looks like holding, come December 1st.

 

From the latter part of next week, it may well be a case of looking towards the NW for anything wintry, as other members have alluded to in recent days. Will the ECM provide us with any further clues from the 4th December onwards, as this is still the timeframe where differences between the various outputs, will make a huge difference in determining actual surface conditions in your own locale. 

 

See here for my views on yesterday's ECM 12z.

 

Another link worth following for any changes to surface detail in the coming days is the one highlighted below.

 

http://www.weathercharts.org/ukmomslp.htm

 

 

In summary, a rather benign dry start to December, aside from the weakening cold front on Monday which may bring some hill snow for a while, HP takes over and looks like remaining in charge for the best part of next week. The latter part of the week is where things could change though. 

Edited November 28, 2014 by gottolovethisweather

[Nick F]

Not often the 06z and 12z GFS ops churn out a very similar evolution out at T+360 right towards the end of the run, I know it's 6 hrs difference, but both have a strong cold Nly flow on Sat 13/12 as the flow amplifies:

 

06z T+360

 

12z T+360

 

Sheer coincidence at that range, but what's possible if we see a wave amplify and slow upstream over Ern N America, provided we see the core of low heights shift off Greenland more.

[Polar Maritime]

The chance of snow pushing further South on this evenings GFSP run around the 11th. Giving blizzard conditions for the Highlands as a deep low skirts N/Scotland from the N/W, A possible stormy period coming up for the North.

 

Edited November 28, 2014 by Polar Maritime

[492]

http://meteocentre.com/analyses/map.php?lang=en&map=eur_full&area=eur&size=large

Big contrasts in temperature across Europe this morning from 20 C in western France to 2 C in parts of Denmark and Germany. The colder low level air is continuing its trek westwards and as the low now approaching Iberia extends east the flow over S UK should continue to back eventually dragging in some of this colder drier low level air. It remains to be seen how quickly the low to the south loses its influence and latest output if anything keeps the extreme south in the ENE'ly from this low a little longer. Further on the atlantic ridge extends across the UK marginally further north on some of the latest output hinting more towards a frosty spell than yesterdays output. Some evidence of low pressure to the south is also more prominent than yesterday which effectively helps to prop up the ridge even if only in a modest way.   

12Z UKMO expands the low to the south until end of the run at T+144 holding the southern portion of the country in a NE'ly. Consequently the ridge is held further north. Looking up wind it looks like it could get pretty cold fairly soon with lower dewpoints already into parts of the low countries.

http://www.meteociel.com/modeles/ukmo2.php?ech=6&carte=1021

Edited November 28, 2014 by 492

[knocker]

The GFS ops has the HP eastern seaboard at 132 moving east and for a time ridging just to the west and north of the UK before settling into the usual pattern. Really not that important regarding the future outlook

Charts courtesy weatherbell

 

 

[Mucka]

It is a rather sad affair watching GFS ensembles try to model an Arctic high in low res so I won't be looking there for guidance until they are a little more consistent/realistic.

[Dancerwithwings]

How long the UKMO Fax charts have been on Meteociel i have no idea.... Liking it Only out to 120h though naturally.   http://www.meteociel.com/modeles/ukmo2.php?carte=2000&ech=0