Model Output Discussion 17th Dec.2013-12z onwards.

[R.P. McMurphy]

Sorry, but this 'less data' is a complete myth...

 

It's true... Missing Data etc is complete nonsense. It's true there is a few niggles with the 06Z and 18Z, but nothing where we can say "Bin it, it's the 18Z / pub run"

[SMU]

There seems to be a modest trend / pattern emerging within the GFS ops & ens of today which covers the next 6-14 days-

 

day 6 sees pressure building to the NE

day 6-10  Pressure holding firm across Svalbard, Northern Scandi & eastern Greenland-

day 10-14 Amplified jet across the atlantic allows ridging to take hold & join with the modest high pressure over Greenland- allowing low pressure to sink south with fairly solid cold signal moving west across Europe-

 

 

Expect a similar ECM DET 32 update on the next run, the key is how much amplitude we get in the atlantic ridging around day 9-10 if theres sufficient then the UK will be in for its first proper cold spell of the Winter.!S 

[Jason M]

Very good set of ensembles tonight. Some decent 850s as well. Nice way to end Christmas Day :-)

[East_England_Stormchaser91]

Magic FI once again showing! If only them -32uppers came across from Siberia!

[SMU]

The missing data is not a myth im afraid- less data is ingested on xmas day ( manual & Aircraft obs) - however whether it has a significant effect on the output is another argument.

 

Knowing our luck when full data resumes on the 27th the new information will probably be in favour of mild SW winds- lol.

 

 

Anyway- a good days output- the pot beginning to bubble nicely.

 

S

[Neilsouth]

I'll lay my cards on the table....bar December 2010, January 2014 will be the most severe winter month we've seen during the Netweather era.

 

I've added this to my signature

[R.P. McMurphy]

The missing data is not a myth im afraid- less data is ingested on xmas day ( manual & Aircraft obs) - however whether it has a significant effect on the output is another argument.

 

Knowing our luck when full data resumes on the 27th the new information will probably be in favour of mild SW winds- lol.

 

 

Anyway- a good days output- the pot beginning to bubble nicely.

 

S

 

Hi Steve,

 

I always used to think this was true as well, until reading:

 

http://www.americanwx.com/bb/index.php/topic/32149-gfs-12z-and-0z-runs-compared-to-6z-and-18z-runs/

 

Take a look at DTK's post, sums it up nicely.

 

 

In terms of aircraft data, your comment is sort of true if you focus only on a small portion of the globe (i.e. CONUS). I took the liberty to get a rough estimate for the number of aircraft observations that we assimilated, by cycle, from 00z-18z today, and here are the approximate numbers:67610, 52744, 53490, and 72177.....not as much disparity as people think. This is partly because these are global numbers. However, we actually get a lot of observations from package carriers that operate aircraft (think Fedex and UPS).

[weather eater]

Not trying to blow my own trumpet or anything but I was talking about this trend just after mid month along with one or two others so it has been in the output for quite a while as at least a weak signal.

What we are seeing is a gradual firming up of the signal and the possible benefits from any blocking being modelled.

We are not there yet though and still a way to go before we start to see decent snow chances to low levels - I still fancy Northern England will see a good snowfall in the first half of Jan and the South could see some transient snow too but any deep cold, should we get it, will likely come toward and after mid month if blocking establishes itself.

 

GFS ensembles 18z SE England

 

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=288&y=122

 

ECM 12z London ensembles

 

 

Yes I know you have, but with very little really consistent and concrete evidence that a change is going to happen from the model output so far, so I would say keep your trumpet handy but don’t blow it just yet, but a great call if you are on the money. Now I’ve just seen Steve’s post re data at Christmas time and it suggests the jury is out in regards impacts on model output, but I would reiterate what I said, that a couple more days of decent output would give me more confidence that real change is coming, because we have certainly seen dodgy output before at this time of year, In regards the ensembles, I have to say I don’t set a great deal of store by them, I find that they are as likely to muddy the water as clear it or point at everywhere and nowhere, I prefer to use an ensemble in my head of resent operational’s, now these do suggest a trend to height rises across the pole and possible movement, split and weakening of the PV that been stuck over Greenland, all good news that at the least may give us a chance of something more wintery. However, as yet they are not really pointing at the kind of patterns that most of us want to see.

Edited December 26, 2013 by weather eater

[weather eater]

Hi Steve,

 

I always used to think this was true as well, until reading:

 

http://www.americanwx.com/bb/index.php/topic/32149-gfs-12z-and-0z-runs-compared-to-6z-and-18z-runs/

 

Take a look at DTK's post, sums it up nicely.

Noted as well, as I said in my first post I don’t know the right and wrong but I do know that some iffy runs have turned up Christmas day and Boxing Day before, I am not saying disregards today’s output, just  that I would wait and see if it keeps showing before reading much into it.

[That ECM]

http://images.meteociel.fr/im/9839/ECH1-168_zpa4.GIF

Nice looking chart. Blocking north and north east. Low can only dig into mainland Europe. Not cold at this point for us but from there it would get very interesting.

http://images.meteociel.fr/im/3331/ECH1-216_hzj7.GIF

Oh well, shows you how much I know. Still blocking ne but also south SW. Which will give way first?

http://images.meteociel.fr/im/3010/ECH1-240_qug3.GIF

No ECM, not the answer we want. Please try harder.

Edited December 26, 2013 by That ECM

[Captain Shortwave]

Sigh, the ECM again being a total scrooge. Builds heights to the north and north east, then follows it up with an attrocious upstream pattern which its only consequence is to push the Azores high over Iberia and then close to the UK.

From this

To this

Hope the next run is better. Day 6+ consistency has been non-existent to be honest.

Edited December 26, 2013 by Captain shortwave

[Frosty.]

The Gfs 00z op run is showing some wintry weather at times through early to mid Jan with a higher risk of snow as rather colder air is drawn southeast across the uk, so there could be marked changes on the way but in the meantime, the gfs remains very disturbed with a sequence of vigorous depressions sweeping in off the atlantic but there is very little in the way of mild weather, temps look close to average, yes there are a sprinkling of slightly milder days but generally it looks rather on the cold side if anything, and average at this time of year feels chilly...so that's my usual positive spin, the gfs at least offers some colder shots with occasional frosts and a wintry mix of rain. sleet and snow, again the highest risk of snow in the reliable timeframe is for northern hills & mountains but that could change through early 2014 with more in the way of trough disruption working in our..I mean coldies favour for a change!

[Weather-history]

I'll lay my cards on the table....bar December 2010, January 2014 will be the most severe winter month we've seen during the Netweather era.

I'll lay my cards on the table....bar December 2010, January 2014 will be the most severe winter month we've seen during the Netweather era.

HmmmI hope you haven't been sucked in by CFS with this prediction. Nothing in the GFS ensembles to indicate this during the first third of January at the moment.

[Jason M]

Very poor output this morning. As per weather history above GEFS are also really poor and are now favouring continuing zonality.

Looks like the PV is just too strong tbh.

[Gibby]

Good morning everyone. Here is the Boxing Day morning report on what to expect as predicted by the midnight outputs of NWP for today Thursday December 26th 2013.

 

All models show a weak ridge crossing East today with a new deepening depression crossing the Atlantic towards NW Britain tonight and tomorrow carrying thick cloud, rain and severe gales across the UK. The winds look likely to be less severe across Southern Britain though this time round. By tomorrow morning a cold front crosses quickly East bringing all of the UK under a strong and showery Westerly flow with this weather lasting well into the weekend. On Sunday a weak ridge crosses East damping down the showers ahead of the next series of troughs with rain and strong winds returning later on Sunday and into Monday. Temperatures will range from average levels in the South and a little below in the North where snow may fall from the showers on the hills at times.

 

GFS then shows the last few days of 2013 with Low pressure out to the NW with rain at times, especially towards the North and West before clearer showery weather turns up for New Years Day itself with more of a Westerly breeze. Into the first week of 2014 and the weather remains very unsettled and rather colder as depressions take on a more SE track across the UK enhancing the colder element on the rear of each depression and allowing snowfall to reach lower levels at times in among the continuing large amounts of rainfall.

 

UKMO closes it's Boxing Day morning run with Low pressure well established South of Iceland on New Years Day with a broad SW flow with rain at times carried on troughs moving NE on a strong SW wind. It would feel relatively mild, especially in the South.

 

GEM also continues very unsettled weather into the first week of 2014 though the influence of High pressure to the South and SE is drawing nearer with the emphasis of the very heaviest of the rain shifting more towards NW Britain later with all areas feeling rather milder temperatures at times.

 

NAVGEM enters 2014 showing a depression crossing East over Southern Britain with chilly and showery conditions with a longer spell of rain crossing East on New Years Day.

 

ECM today shows an unsettled start to 2014 with rain at times followed by chilly and showery conditions for a day or two in the first week. At the end of the run High pressure from the SW reaches Southern Britain for a time with frost and fog possibilities in a quiet and dry spell here with an attached ridge drying things up in the North too.

 

The GFS Ensembles show a very flat pattern over the next two weeks showing changes in the pattern over the next few weeks will be slow and not very noticeable to the majority of folk on the ground. The Atlantic bandwagon remains well in control carrying depressions across the Atlantic to the North throughout with just the hint of a temporary more SE track to the Jet flow deeper into Europe for a time with the risk of colder injections at times before the pattern resets late in the run.

 

The Jet Stream shows no change in the orientation of the flow for the foreseeable future carrying it West to East across the Atlantic and close to or over the UK. The flow does dig South across Europe later in the outputs but remains high across the Atlantic maintaining the milder feed across the UK.

 

In Summary the weather remains Atlantic driven with a continuing changeable pattern alternating between rain bands crossing East and a sunshine and shower mix in between. With winds generally from a Westerly point the weather looks never overly cold with just polar maritime air delivering some wintry showers to Northern hills at times. There is some suggestion that High pressure could edge up closer to Southern Britain later removing the deeply unsettled weather of late to something drier and much less windy and still not cold though this theory is balanced with the chance of Low pressure slipping SE over Europe and bringing the UK into more cold northerly components and attendant wintry weather for a time.

[Cloud 10]

The ECM ensemble mean at day 10 is a country mile better than the operational,with the op

run looking way to far east with the pattern. 

 

op run...  ens...

[Summer Sun]

I think its fair to say this morning's ECM is an outlier at the end

 

Op

 

 

Ensemble

 

[nick sussex]

The ECM ensemble mean at day 10 is a country mile better than the operational,with the op

run looking way to far east with the pattern. 

 

op run...ECH101-240.gif  ens...EDH101-240.GIF

I agree the mean is more in line with whats to be expected given the upstream pattern and the signal for higher pressure to the ne. However the problem across the outputs is the lack of a clean break with energy over Greenland.

If that remains the case then there needs to be a large westwards correction in the output to keep theUK in with a chance of some snow on the eastern flank of any low that runs se, the best outcome is the Azores high ridges north to the west and high to ne working together to clear low pressure se into the continent then the ridge to the ne backs sw towards eastern Greenland.

In line with my post last night I'm still on the fence here, I think it will turn colder but extent of that and how much if any snow very uncertain, but I do feel that we need to see the quickest cold conclusion here because the Arctic high is primed and ready to help if that damn PV to the nw would just take a hike for a few days to allow the ridge to extend in, after that you're in a much better place to fight off the next wave of zonal bombs sent in with a better chance of energy disrupting further south.

Edited December 26, 2013 by nick sussex

[winterof79]

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=120&mode=10&carte=1

The srat warming showing up in the near future now and has been consistantly modelled by GFS.

 

At 144z  UKMO and ECM and GEM all playing with a push of heights to our e/ne

http://www.meteociel.fr/ukmo/runs/2013122600/UN144-21.GIF?26-06

http://www.meteociel.fr/modeles/ecmwf/runs/2013122600/ECH1-144.GIF?26-12http://modeles.meteociel.fr/modeles/gem/runs/2013122600/gemnh-0-144.png?00

 

GFS not a million miles away but things will change in about 30 mins anyway

http://modeles.meteociel.fr/modeles/gfs/runs/2013122600/gfsnh-0-144.png?0

[Frosty.]

Yep changes are afoot with a colder more wintry tone through jan with increasing trough disruption and better jet alignment, hoping the latest met office update carries on with their more wintry outlook as per yesterday. :-)

[IDO]

The ECM ensemble mean at day 10 is a country mile better than the operational,with the op

run looking way to far east with the pattern. 

 

op run...ECH101-240.gif  ens...EDH101-240.GIF

 

Yes, and just to make it even more confusing, the D10 mean for:

 

GFS:   ECM: 

 

Both show the upper Arctic High weakening, whereas the GFS is more progressive, sinking the surface high into the East Conus, the ECM maintains that high longer. However both have different perspectives on the upper ridging, GFS now renews the Upper Pacific Ridge, and maintains this till T384: 

 

 

The ECM weaker upper ridge is more Scandi based.

 

The GFS solution will push the mean vortex east and re-establish the mean Icelandic surface low, muting any troughing (only one run and hopefully wrong):  

 

Whilst the PV is so strong, and assuming the models are now hinting that the Arctic High is only temporary, the ECM solution would be better for medium term cool/cold. However till the PV drains (or the strat helps) we are really going to struggle to see any prolonged wintriness without a lot of luck (IMO).

[snowking]

Only have time for a very brief post off of my phone but the ensembles (primarily ECM EPS) continue with the theme that had been hinted at by the Fi range of recent det. runs, that is weak HP across the pole and the low heights draining away from Greenland....the trick to the pattern for little old us in the UK now is to what extent those heights drain away from Greenland, and that is where it would be wise to remain VERY cautious until we get things in to a more reliable timeframe.

The tendency over the last couple of years (especially from the ECMWF last winter and so far this winter) is for it to drain those Greenland heights far too much (vs the eventual outcome) in the day 6-10 range.

Should this prove to be the case again then it's going to take us a while longer yet to develop something colder.

The overall N Hemisphere pattern continues to look encouraging as a whole but obviously it's a big step from there to getting the right pattern to advect any colder air to our little corner of the NE Atlantic.

Merry (belated) Xmas to all!

SK

[Duane S.]

I agree the mean is more in line with whats to be expected given the upstream pattern and the signal for higher pressure to the ne. However the problem across the outputs is the lack of a clean break with energy over Greenland.If that remains the case then there needs to be a large westwards correction in the output to keep theUK in with a chance of some snow on the eastern flank of any low that runs se, the best outcome is the Azores high ridges north to the west and high to ne working together to clear low pressure se into the continent then the ridge to the ne backs sw towards eastern Greenland.In line with my post last night I'm still on the fence here, I think it will turn colder but extent of that and how much if any snow very uncertain, but I do feel that we need to see the quickest cold conclusion here because the Arctic high is primed and ready to help if that damn PV to the nw would just take a hike for a few days to allow the ridge to extend in, after that you're in a much better place to fight off the next wave of zonal bombs sent in with a better chance of energy disrupting further south.

 

Agree as well Nick. What we need is something like a strong Wave 1 event to help displace the vortex away from Greenland.

 

Aha!...

 

There is of course no guarantee it will verify at that amplitude nor instantly setup a path to bitter cold for the UK but it will make for some interesting weather chart watching going towards Mid Jan.

[nick sussex]

Just to add to my earlier post I've done a couple of NH maps to show what you need to see to have a better chance of seeing some snow and colder weather.NH Map 1 shows the Azores high ridging north further to the west, the high to the ne shown also, these two work together basically draining the energy away from the low over the UK, this stretches and disrupts and then in map 2 the ridge to the ne has backed further west towards eastern Greenland, at this point even if the PV continues to throw lows eastward you have a good chance of these being forced se under the ridge:Now in map 3 you have the set up where you don't get a clearance of energy from Greenland but the pattern is further west, low pressure continues to form but is directed se, often in this case you'll see snow on the eastern flank of these.Map 3As it stands the models are generally going for map 4:Low pressure is further east, the flow into the UK will generally be more PM type, so colder but more marginal.The uncertainty going forward is whether the pattern evolves into one of the first two options or whether its a stalemate with the ridge to the ne never getting enough of a let up from the PV to extend much further west/sw.

Edited December 26, 2013 by nick sussex

[EML Network]

I can't see why the sudden dispondency this morning. 

 

It's not been looking favorable for cold all winter long, I see no sudden change this morning ??

 

nearly every time you find High Pressure lurking to the South of the UK in set up's like this, you'll find it hard to get a route to cold that lasts more than a few days. 

 

As soon as the Jet Stream weakens , that high pressure looks ready to move up from the Azores, and tbh the High pressure that has taken up residence for I don't know how long in Western | Southern  Russia hasn't helped our cause either....when those two pressure systems link up like they have done since Winter began, then the low pressure systems rolling into the UK have only one way to go which is to ride over the top.

 

It's constant presence has meant that all the bombs of Low pressure we have been getting are all taking the same route all winter long. 

 

What is interesting is the formation of the Arctic High, what this essentially means is that the lows now have very little room to go anywhere, they are likely to disperse all of their energy over Northern Europe, and NW Russia. 

 

I would be expecting some biblical rainfall totals over those areas if things come off as modeled.

 

It's difficult to see a route out of all of this, I think the first step is to await the Jet stream to become less intense , so perhaps we need to see the temperature gradient just south of newfoundland to be wider. I.E instead of having -20 uppers to + 10 uppers in the space of 75 miles, it would help lessen the power of the jet stream if that gradient was over a MUCH longer distance. 

 

Once the Jet stream dies down a little, it might give a window of opportunity for everything else to re order .Apologies if all of the above sounds like complete hog wash, it's just my take on things and it's probably complete rubbish, but hey ho I'm still trying to figure it all out :-)

Edited December 26, 2013 by EML Network