Model Output Discussion - 05/01/2016 18z onwards

[damianslaw]

GFS continues to suggest a different evolution compared to the ECM/UKMO. The differences lie in how they develop heights in the mid atlantic combined with the effects of two opposing camps - energy off the NE USA seaboard and energy coming out of Russian and spilling into Scandinavia.

GFS does tend to perform better with events over the USA, however, the euros trump GFS when it comes to events to our east, especially over Scandi.

Who is likely to be right? - not a clue.

Sticking to the output in the next 96 hours, all models are supporting a shortwave development in the vicinity of Iceland with cold uppers thereafter making their way down to southern parts of the country. Thursday and Friday would see nationwide cold conditions, very cold in the north.

Cold air once established over the country can be a stubborn beast to shift, there is a significant cold pool to our NE, and as winter wears on, traditionally the atlantic has a much harder time edging it away..

[Mark Neal.]

ECM text forecasts can be found here for locations - http://www.yr.no

@Mark Bayley- ECM snow charts at http://www.wunderground.com/wundermap/

 

[chris55]

The sensible discussions on this thread are way more current than the BBC automated forecasts, and sometimes ahead of the chief forecasters advise to the BBC weather presenters. Thats not to say we are correct, just that the nature of our discussions are in real time as opposed to the daily advise/probability that the MET gives out.

The BBC weather app is a good example of this......it runs on raw UKMO data!!!!!! (i think) Since when was that reliable at day 3-4-5? 

Its all a balance of output really. And for Joe bloggs, when the output is changeable, the accuracy of the raw data is questionable. 

 

[bluearmy]

Just browsing the ECM control out to T200 and I had to double check I wasn't looking at the op! 

Though it takes the ridge a bit further north than the op which brings in a sub -10c upper easterly for a time. Expect a frigid looking de bilt control shortly. 

Edited January 9, 2016 by bluearmy

[karlos1983]

ECM ENS

graph is a worry though, bottom end of cold

 

Edited January 9, 2016 by karlos1983

[Liam J]

52 minutes ago, Shuga ice said:

If the ecm verified, the lowest temps and the deepest snow would be towards the south/southeast.   

There are more ECM charts available to the public on Wunderground here - http://www.wunderground.com/wundermap/

Here's an ECM 2m temp chart for the early hours of Thursday morning, very much colder in the north, bitterly cold in Scotland.

There's also a snowfall chart view but it's not lying snow just where snow may be falling. 

Edited January 9, 2016 by *Sub*Zero*

[Mucka]

1 hour ago, chionomaniac said:

The GFS ensembles have never really wavered from an overall cold theme and until they do then the operational run should always be treated with caution. ECM and UKMO show this.

The pendulum swings continue.... it is leading into an epic chase this one  - will it be rewarded?

 

These for SE England will undoubtedly be a fair bit milder than ECM. They really only show a 4 day cold spell as far as upper is concerned and the mean only very briefly drops below -5. I would say they were quite solidly behind the Atlantic coming back in from around the 17/18th albeit that is somewhat slower than the Op has been showing it is a very similar progression that leads them there. Even the Op hasn't wavered from an overall cold theme from mid week.

I do agree though that pendulum has swung in favour of more prolonged cold this evening but that is not really the case within GFS ensembles which if anything have become more supportive of a quicker breakdown - up to the 12z run anyway.

The 2m temps for the SE make this clear 00z, 06z, 12z comparison

I think that is pretty clear evidence the ensembles have more and more got behind a quicker warm up as the Op as I have previously stated and shows they have not stayed solidly behind a longer cold spell at all. It really is not a case of taking the Op in isolation but of course there should be caution when there is not cross model consensus but that works both ways as we have recently been painfully reminded. 

ECM tonight should be much colder and I'm confident the warming trend should be reversed soon given tonight's output.

Hoping to come back to lots of post which should be a sign the 18z has flipped cold.

 

[Mark Bayley]

22 minutes ago, Mark N said:

ECM text forecasts can be found here for locations - http://www.yr.no

@Mark Bayley- ECM snow charts at http://www.wunderground.com/wundermap/

 

Cheers Mark. The ECM charts posted by subzero are available on accuweather, around £12 a month. Can report the snow accumulation on the ECM is pretty good by the end of the run. A covering everywhere. The feature crossing the UK at T96 to T120 delivers a decent snow event to Yorkshire, Lincolnshire and central/east Midlands with a dusting into East Anglia and the South East (a 1 to 3inch covering, not that snow accumulation charts should be trusted, in the east midlands and yorkshire). Dewpoints look marginal however, although hard to tell with the chart graphics. Dew points drop as the feature clears south eastwards, so snow on the back edge where sleety at first. Rather too much detail for a chart certain to change. However, it does highlight some good opportunities in the next week!

Edited January 9, 2016 by Mark Bayley

[lorenzo]

As far as daam  / aam is concerned that outrageous off the grid spike has worked through the modelling peaking as we saw the proper eye candy.

Then this tendency chart shows the drop

Bear in mind that the aam is as GP said still running at 'peak Nino' in phase 6 ( see below) , so even the downward tendency in 'relative AAM' ( above) i.e which way the atmosphere is leaning -  is levelled out somewhat by the continuing high base state, in addition a good call to not rely on MJO too heavily - 1 due to variance and 2 due to programmed return to lower amplitudes or it's COD - Circle of Decay / Death / Doom - that middle circle where it doesn't really imprint in a meaningful way.

GWO at the top of it's game / GEFS at well.....

Earlier @Mucka put up the 144 plots across the models, 96-120 may be the watch here as per what @bluearmy noted earlier, the disconnect between the projected AO and where things look wrt. Arctic High. The Arctic High which also has impact on the canadian daughter vortice of trop vortex.

The new 150 hPa strat plots @96hrs have more than a hint of west based NAO, understandably much more volatile than plots from higher in the atmosphere, it takes between 168 and 192 for the vortex at this level to 'bridge the gap'. 

Looking at the GWO firmly in Phase 6  and considering the MJO through phases 7/8/1, whilst also ignoring the GFS on the MJO - seemingly seeing the planet's coriolis force across the worlds biggest ocean enter something of a twilight zone, we are left with a composite that looks like below. Again, as I said previously these are a 'background' and you must consider - not just the composite but also the anom. forecast i.e what is anomaly vs what is 'normal', clearly from the look at present we do not have the strength of low evident in NPAC.

As far as trends go, we have seen how the 'energy' in the Canadian Vortice has in tandem with the earlier rampant AAM caused some degree of variance in the output to extreme, from amazing to boring, then back to - okay are we onto the final trend now?

Still think more runs needed, truly this is a cliche here, but with so many opposing variables, and different variables in decay, no clear lead at this period.

Have added this chart of the trop vortex too to compare with lower in the atmosphere over the locale we are looking at as far as ridging is concerned, certainly is a different spin over Scandi to enhance cold for the continent. Note the teaser filaments on the core of the vortex itself and the crushed zone courtesy of the W1.

In a winter where the Kara High forced through whilst the Siberian vortice was parked on top of it, it is very difficult to predict the strat - trop interactions, this is why I think a definitive MJO pulse shone through in such a stark manner.  Enough to keep the interest going for now, the AAM next steps of much interest.

 

[Captain Shortwave]

Regarding the ECM ens, back to a similar theme as last night. Turning cold during the week and increasingly cold on Thursday and Friday. If anything a better result with the -6C isotherm across nearly all of the UK on Friday.

The -7C isotherm from approximately Birmingham northwards. The best I have seen for the end of the week.

So a few extras from me as others will have more insight into the suite than I can see. Good agreement on a set up cold enough for snow at low levels by the end of the week, turning drier over the weekend as high pressure moves in slowly, the 850s wash out but ultimately the surface conditions should remain cold with widespread hard frosts.

The pattern slowly edges east cutting off the supply of precipitation over the week with the upper trough and cold pool sinking into east and south east Europe.

This certainly isn't set in stone, will the ensembles handle the next system exiting Newfoundland correctly or will we see something similar to the ECM op develop which could extend the cold out further perhaps. One to watch.

De Bilt ensembles

Pretty cold to day 10 though with scatter appearing. Just one outlier which goes mild from Thursday. The control goes sub-zero into the following week.

Longer term I am still looking for an east to north east flow to develop if we can amplify the Atlantic ridge enough to push it towards Scandinavia when the Canadian lobe of the polar vortex does decide to wake up again.

Edited January 9, 2016 by Captain Shortwave

[Weather Observer]

The models last night were all over the place, and the anxiety in here is understandable given the lean years and last December to cap it off.

I feel that what is on offer tonight is some decent winter weather if you like cold. Ecm looks to be toying with an easterly. In the time I have been viewing the computer models I have come to see that model as first amongst equals. Before that I relied on television and radio and charts in the post. And also weather instinct, often wrong. This tells me to expect a proper easterly blast coming soon.

Watch "War and Peace" on the Beeb for a preview

[bluearmy]

 

the favourite is the upper ridge from the sw (see the blue bump )  and the cluster against the mean retrogresses the block to Greenland (see the orange over greeny).  The uppers spread at day 10 shows a strong n plunge headed s to our North which ties in with the Greenland cluster. 

[bluearmy]

The extended eps definitely signalling an end to the strongly neg AO/NAO combination. gfs probably too progressive but also likely headed in the right direction.  Hopefully for the saturated ground of the UK, we can end up with a mid lat high within a less amplified pattern. 

[Lukesluckybunch]

Hi all I'm new here and also not an expert,but I do try.my view on tonight's charts its quite positive at the end of the ecm do we try and see heights strengthen further,my guess is it will!as others have said will be interesting to see which way the gfs trends...so I'm happy with the ecm,some really cold uppers close by particuarly towards the southeast!

[Ali1977]

1 minute ago, bluearmy said:

The extended eps definitely signalling an end to the strongly neg AO/NAO combination. gfs probably too progressive but also likely headed in the right direction.  Hopefully for the saturated ground of the UK, we can end up with a mid lat high within a less amplified pattern. 

Looking like after this cold spell it may be a few weeks Atleast before we see another - if at all that is.

[BLAST FROM THE PAST]

 

Chart of the day, cold to reload and as I said this is FAR from over

 

BFTP

 

[Lukesluckybunch]

2 minutes ago, BLAST FROM THE PAST said:

 

Chart of the day, cold to reload and as I said this is FAR from over

 

BFTP

 

Hi there where is the reload here,does not seem strong enough!?

Edited January 9, 2016 by Lukesluckybunch

[john mac]

2 minutes ago, BLAST FROM THE PAST said:

 

Chart of the day, cold to reload and as I said this is FAR from over

 

BFTP

 

Agreed mate, I think,people need to remember the background signals and also what Tamara and Stuart were talking about the other day.

[snowangel32]

So it seems in general apart from the gfs today has upgraded our chances of a cold spell, still worries me that gfs is the one who sees something different to the rest and we also know it was the one who picked out the shortwave near Iceland a few days ago. So until gfs joins the rest  it's hard to get excited. ECM is a peach of a run prolonging the cold spell and increasing snow potential all over the UK. Next week all models agree winter is finally coming to the UK I hope we all see. Some of the white stuff and when the cold does set in it's hard to shift as 2010 demonstrated.  Going to grab a beer now ready for the pub run will the gfs give us drama or a stellar run. 

[BLAST FROM THE PAST]

1 minute ago, john mac said:

Agreed mate, I think,people need to remember the background signals and also what Tamara and Stuart were talking about the other day.

And what were they talking about  John...please come o n and explain?

 

BFTP

[Vorticity0123]

After a record-crushing warm December month, January has so far delivered much more seasonable temperatures. In the Netherlands, some parts in the northeast have experienced a rather weird winter. Days of freezing rain made it possible to go ice skating on roads. Read more about it in my previous post here. Nevertheless, the southwest of the Netherlands, and most parts of the UK as well, have seen very little in the way of winter. Yet, changes may well be on their way, as possibly northerlies are going to set up shop. How does this look like, and what about possible uncertainty? Time to read on!

Here I mention the 500 hPa level. I assume this level is located about in the middle of the troposphere. I use this level here because the 500 hPa level is less influenced by surface features (like friction) than the surface level.

Troughing into Europe - High pressure towards the Atlantic?

Let's start with the current weather pattern.

GFS 500 hPa heights (colours) and surface pressure (white contours) as of today 12Z.

The chart shows little in the way of winter for the UK as of yet. Low pressure (and 500 hPa troughing, blue) in the Atlantic to the west of the UK is causing mostly unsettled weather there. Behind this low pressure area, we can see a ridge (yellow colours edging northward) buidling near Newfoundland. The ridge is forecast to move into the Atlantic, whereas the low pressure activity is expected to move into Europe towards Scandinavia.

If the ridge near Newfoundland would be able to amplify enough (that means that it is able to extend far enough northward), it may allow for cold air to flow from the north to the UK. Will this happen? That appears to be the main question for now. It should be stressed that the situation as described above is a severe simplification from reality, as many other minor developments are bound to change the details. For simplicity and clarity reasons, I will only focus on the large scale developments, and NOT on the small-scale features.

What about the differences and uncertainty?

Here we make a jump of 6 days. In order not to get a too messed pattern, I use an ensemble map instead of the operational run. Since the GFS run did not work on my computer, below are the ECMWF ensembles.

GFS 500 hPa heights (colours) and surface pressure (white contours) as of today 12Z.

At the large scale, we see a 500 hPa trough over Scandinavia, whereas some ridging at 500 hPa is evident over the Central Atlantic. The ridge is extending northwards all the way towards Greenland (yellow and green colours extending northward, red arrow). All models roughly agree on this pattern, but once again the devil is in the detail. Though we can also extract some more large-scale differences as well. Below are the ECMWF, UKMO and GFS operational runs for the very same timeframe as given above (for 6 days out):

ECMWF

UKMO

GFS

One clear difference in the models is the degree of amplification (northward extension) of the ridge over the Mid-Atlantic. The ECMWF and UKMO tend to amplify the ridge more than the GFS. The result of more northward-extension would be a higher likelihood of a more northerly base flow instead of northwest or west, with more chances on wintry weather.

Furthermore, we also see a myraid of solutions concerning the shape of the trough (blue colours) over Scandinavia. Nevertheless, the presence of this feature is quite certain. It is yet too early to talk about surface features, though, so to what extent a cold spell will develop or not over the UK is still in debate. A good guide for that are the ensemble forecasts as posted by Captain Shortwave.

Mid-Atlantic or Greenland ridging persisting?

In the long term, it seems that we will see a continuation of ridging over the Mid-Atlantic towards Greenland and beyond.

NOAA 500 hPa heights (green) and anomalies (red and blue) for 6 to 10 days out.

The map above shows a 'kink' in the green lines towards the north in the center of the Atlantic (also indicated by the red arrow). This 'kink' is indicative of the presence of ridging (high pressure activity). With this kind of ridging present, one could suggest that a northerly component is likely in the flow over the UK (see black arrow over the UK which runs parallel to the isobars). Therefore, I expect the temperatures during that period to be below average. This statement is in agreement with the ensemble forecast shown by Captain Shortwave. To what degree these below average temperatures will end up remains to be seen, but a somewhat more cool (fore some parts even wintry) spell appears to be quite likely in the medium-to long term.

I hope this post gives an understandable overview of the weather to expect in the coming days and also the uncertainties still present at large scales. If anything is unclear with respect to this post, just ask!

Sources:

http://www.wetterzentrale.de/topkarten/fsecmeur.html

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

 

 

 

Edited January 9, 2016 by Vorticity0123
Added sources to post.

[Lukesluckybunch]

Hay again all newbie,also would be worth a look at navgem ,absolute stunning charts!

 

[john mac]

2 minutes ago, BLAST FROM THE PAST said:

And what were they talking about  John...please come o n and explain?

 

BFTP

Well, I'm not pretending to be a weather expert but it was along the lines that cold weather will prevail through the second half of Jan, also the negative nao becoming less west based as we move forwards. Lost of fun and games to come. 

[bluearmy]

17 minutes ago, Ali1977 said:

Looking like after this cold spell it may be a few weeks Atleast before we see another - if at all that is.

That's a bold statement Ali. I suspect that it wouldn't be too long until we arrived at a similar model evolution as we've been through the past week.  just have a retrogressive feeling. 

Edited January 9, 2016 by bluearmy

[BLAST FROM THE PAST]

18 minutes ago, Lukesluckybunch said:

Hi there where is the reload here,does not seem strong enough!?

The ridge in Atlantic is rebuilding and the Low Pressure NW UK is moving on a NNW to SSE angle

to this

and this

 

And could go on to better...could being operative word.....that's why I like the t144

 

 

BFTP

Edited January 9, 2016 by BLAST FROM THE PAST