Model Output Discussion - 1st - 7th January

[Grimsby Snow Lover]

Quite a decent pressure build over the pole by the end too. First time I've seen green over parts of Greenland since October I believe

http://hw.nwstatic.co.uk/gfsimages/gfs.20120101/12/384/npsh500.png

[Summer Sun]

Something for the coldies

[shotski]

Quite a decent pressure build over the pole by the end too. First time I've seen green over parts of Greenland since October I believe

http://hw.nwstatic.c...384/npsh500.png

Are you sure thats over Greenland, I'm not to hot on my geography ?

[damianslaw]

Some pleasing charts today especially ECM if you are looking for a pattern change. Also GFS continues to firm up on a pattern change starting second week of Jan with an ever weakening Polar Vortex enabling heights to build north across the country forcing the PV to retreat westwards towards west greenland enabling strong building of heights over NW Russia and a clear path for these to advect westwards in time.

The ECM chart for early next week is very indicative of events in mid Dec 09, when we saw a sudden build of heights northwards over the country and a rapid strengthening of heights to our NE which quickly merged with those heights over the country - definately not an inplausible evolution, yes rather progressive it may appear. ECM does outperform GFS when it comes to heights building from the east - GFS always struggles in such situations, mind GFS outperforms ECM when it comes to developments to our NW.. will wait and see whether ECM is being too progressive or if its on the right theme. In such situations all eyes should be on UKMO and which way it moves, today's UKMO charts wouldn't support the ECM evolution, but still time for plenty of change.

In the short term - quite a wintry week for Scotland with snow showers tomorrow, low level snow later Tuesday and further snow showers wed and thursday. Further south a less mild week than last week with perhaps a local frost this evening and again on wednesday eve, possibly thurs eve with some wintry showers on higher ground tomorrow and perhaps thursday.

I'm left this evening thinking is something stirring more quickly than I first expected, or have the models got blurry eyes from last nights revelry.. whatever the case, at least the outlook is much more seasonal than the last couple of weeks have been.

[Grimsby Snow Lover]

Are you sure thats over Greenland, I'm not to hot on my geography ?

The main high is over the pole like I said, but if you view the very last chart on the GFS you can clearly see green in the top right hand corner. All change on the next run but it just caught my eye.

[chionomaniac]

Something for the coldies

Come on Gavin, we need more than that.

How about another more amplified run from the 12Z GFS which leads to a more blocked scenario which looks to drive the jet stream further south by the end.

All in all a mixed run which again adds to thoughts that the we may be seeing a pattern change come mid month.

[johnholmes]

I think you forgot the gales?

[JP1972]

Some pleasing charts today especially ECM if you are looking for a pattern change. Also GFS continues to firm up on a pattern change starting second week of Jan with an ever weakening Polar Vortex enabling heights to build north across the country forcing the PV to retreat westwards towards west greenland enabling strong building of heights over NW Russia and a clear path for these to advect westwards in time.

The ECM chart for early next week is very indicative of events in mid Dec 09, when we saw a sudden build of heights northwards over the country and a rapid strengthening of heights to our NE which quickly merged with those heights over the country - definately not an inplausible evolution, yes rather progressive it may appear. ECM does outperform GFS when it comes to heights building from the east - GFS always struggles in such situations, mind GFS outperforms ECM when it comes to developments to our NW.. will wait and see whether ECM is being too progressive or if its on the right theme. In such situations all eyes should be on UKMO and which way it moves, today's UKMO charts wouldn't support the ECM evolution, but still time for plenty of change.

In the short term - quite a wintry week for Scotland with snow showers tomorrow, low level snow later Tuesday and further snow showers wed and thursday. Further south a less mild week than last week with perhaps a local frost this evening and again on wednesday eve, possibly thurs eve with some wintry showers on higher ground tomorrow and perhaps thursday.

I'm left this evening thinking is something stirring more quickly than I first expected, or have the models got blurry eyes from last nights revelry.. whatever the case, at least the outlook is much more seasonal than the last couple of weeks have been.

I have to admit that I'm pleasantly surprised at how a pattern change appears to be happening rather quickly. But as you rightly point out December 2009 is proof that a relative rapid evolution can occur. I'm inclined to believe that what we're seeing is what IS going to evolve.

[johnholmes]

An interesting run from the 12z GFS upto the point of the lower resolution part of the run. Just a quick question and I mean nothing by this but Brian Glaze over on TWO mentioned possible lack of data due to less trans atlantic flights etc. Is this correct? Thanks GSL

that crops up every year, or at least lack of data in the northern most areas. I have exchanged e mails on more than one occasion with NOAA and they refute that idea saying there is no data shortage over the holiday periods. But like I say it is raised by someone every year.

[Tim Bland]

"Come on Gavin, we need more than that."

MORE! I'd settle for that! - 5 850s south of channel islands, low pressure, heavy snow showers pulsing across us as the cold air rushed across the mild Atlantic! Are we being greedy now!

Edited January 1, 2012 by Tim Bland

[Jason M]

It all looks a bit similar to this time last year. I'm still going for a near miss (possibly multiple near misses) with the high sat smack over the top of us.

The one constant on just about every chart we see is that dirty great high to our SW. The 'beast from the east' may come knocking but my money is on the displaced Azores high to once again prove its by far the biggest beast in our part of the jungle. We need low pressure to our South as there is no trigger to back the cold air west. High pressure to our South = no snow!!

Despite my own views though, its nice to see some interest again and i suspect that the next few days might throw out some really good runs before things settle down again.

Jason

[chionomaniac]

"Come on Gavin, we need more than that."

MORE! I'd settle for that! - 5 850s south of channel islands, low pressure, heavy snow showers pulsing across us as the cold air rushed across the mild Atlantic! Are we being greedy now!

I meant analysis rather than posting charts over two weeks away!

[Cecil Hogmanay Melchett]

Interesting gfs operational,shows how critical it really is to get the azores high far enough north to allow some WAA.

UKMO doesn't look quite as promising however.

[Wales123098]

These charts are a million times better in my opinion than a week ago. Could be in for a nice cold snowy period mid month onwards. We'll see though.

Edited January 1, 2012 by Wales123098

[leicsnow]

If I remember rightly some charts thrown up on Christmas Day pointed to cold synoptics on the 9th January too (until they became mild after then until now). Now that they are showing for a potential easterly on that date it is a good sign of a trend.

Edited January 1, 2012 by Tellow

[Cecil Hogmanay Melchett]

Hum vast majority of 12z GEFS ensemble suite look to be suggesting HP over or very close to the UK which is more obvious checking the precipitation spikes than say the 850's.The likelihood of drier and cooler weather under an inversion remians the form horse right now.(which i personally be very happy with after another vile wet grey day here)!!

UKMO at 144h is not going to bring about an Easterly any time soonafter IMO with the jet still in a thouroghly active mode still.

[Thundery wintry showers]

"Come on Gavin, we need more than that."

MORE! I'd settle for that! - 5 850s south of channel islands, low pressure, heavy snow showers pulsing across us as the cold air rushed across the mild Atlantic! Are we being greedy now!

In fairness I don't think lying snow would be particularly widespread from that chart as a glance at the 850hPa values and surface temperatures points to a pool of milder air in the north. We'd probably see scattered wintry showers from the Midlands northwards but with lying snow confined to northern hills.

A rather boisterous spell of weather coming up during the first week of January with frequent NW incursions bringing sunshine and showers, wintry on northern hills, and some longer outbreaks of rain, most especially on Tuesday when gales still look likely in the north. I can see strong hints of pressure rising over Scandinavia after the system at T+144-168, but as the evolution to the Scandinavian high falls outside of the reliable timeframe it is doubtful whether we will evolve into a Scandinavian high setup at the first attempt- let alone have the high far west enough to bring us continental air. However, a change to an anticyclonic and possibly colder outlook has fairly strong support for around the 10th January or so.

I don't think snow lovers should get too excited even if we get continental air at the first attempt as the cold pooling amounts to 850hPa values of around -5 to -7C- I think we'd struggle to get much convection over the North Sea off that airmass, though of course any reloads further down the line could be a different story.

[damianslaw]

It all looks a bit similar to this time last year. I'm still going for a near miss (possibly multiple near misses) with the high sat smack over the top of us.

The one constant on just about every chart we see is that dirty great high to our SW. The 'beast from the east' may come knocking but my money is on the displaced Azores high to once again prove its by far the biggest beast in our part of the jungle. We need low pressure to our South as there is no trigger to back the cold air west. High pressure to our South = no snow!!

Despite my own views though, its nice to see some interest again and i suspect that the next few days might throw out some really good runs before things settle down again.

Jason

Take a look at the charts from 9 dec 09 - you don't need low heights to the south for a quick evolution to something much colder and snowier. However, what you do need is a weak polar vortex to our NW and perhaps even more importantly building heights to our NE - these are two developments being shown by the ECM and GFS this evening.

[phil nw.]

Quite a decent pressure build over the pole by the end too. First time I've seen green over parts of Greenland since October I believe

http://hw.nwstatic.c...384/npsh500.png

I think the real change is likely to come from the other side of the pole but not within the high resolution modelling.

I will try to explain but you will have to indulge me as i am going to use charts from the later part of the 12z output.

The pressure from the Greenland low hts. and the attendant n.Jet is still too strong to maintain ridging very far north around the UK. for a while yet.

Here from UKMO 12z T144

and running on through the GFS12z

However later on,although low resoultion,we see something stirring

showing the vortex in a weaker state,the sort of thing that`s showing up more now in the later output.

The High to our south being squeezed and the low heights becoming displaced south and east.

The best way to cold from this Zonal pattern would be Atlantic ridging getting established behind the piece of Greenland vortex diving SE in the later frames.

However we need more buckling of the flow from upstream which would drive the Canadian low heights south creating deeper troughing into the E.Seaboard,thus sucking up those heights from the Azores high.

GFS 06Z toyed with this -

I don`t think an Easterly in the nearer term is a goer because of the strong jet pattern running over the top,Untill the core of the Vortex shifts and starts to fragment from the Greenland area anything from the East will flatten under the pressure.

but once the vortex weakens further as modelled again in the low resolution then we should see a different outcome.

If the pattern doesn`t buckle into FI as i am looking for then we would still see a colder pattern with the jet further south as shown on 12zGFS.

I should add at this range the modelling of the PV will change many times but it will certainly add to the interest in chart watching through the next couple of weeks.

Edited January 1, 2012 by phil n.warks.

[Grimsby Snow Lover]

Thanks Phil, you have explained the possible developments very clearly. At least now I know what to look for in future runs.

[phil nw.]

Thanks Phil, you have explained the possible developments very clearly. At least now I know what to look for in future runs.

Thanks GSL-i am glad you said possible-with the energy across the north at present it will take time as i have said.

The ECM will probably now show a raging Easterly in it`s later frames just to show me up.

[kold weather]

Better model runs today, the trend for the height rises to our north looks solid, but nothing too impressive being forecasted yet, still a little far out yet.

Anyway ensembles are interesting, looks like a real mixed bag, some members do give us some cold weather, quite a few more produce a mid latitude block and hold it fairly close to the UK. That wouldn't be a bad solution IF we can get another wave of warming to totally finish the vortex.

MUCH better prospect then this time last week...

[Frosty.]

The Gfs 12z op run shows a very anticyclonic outlook for southern britain once we get past friday but the north of the uk probably remaining changeable or unsettled, although it's still unclear whether the high will push into northern areas but that currently seems unlikely and the high could end up being centred to the southwest of the uk with cloudier skies pushing down it's eastern flank. There are some very wintry synoptics towards the end of the run with a southerly tracking jet and lots of frigid arctic air not far to the west, north and east of the BI so the models are starting to look like they should with the downwelling effects of the moderate strat warming. The polar vortex is going to come under immense pressure to split during the next few weeks and there are potential northerly blasts not to be ruled out but a calmer and colder spell is now looking more likely for the south at least after the next 5 days but it probably won't stay settled for long.

[mountain shadow]

ECM backs off from the 0z. Less amplified and looks like we will have the HP over us.

http://www.wetterzentrale.de/pics/Recm1441.gif

[Snowmadsam]

The Gfs 12z op run shows a very anticyclonic outlook for southern britain once we get past friday but the north of the uk probably remaining changeable or unsettled, although it's still unclear whether the high will push into northern areas but that currently seems unlikely and the high could end up being centred to the southwest of the uk with cloudier skies pushing down it's eastern flank. There are some very wintry synoptics towards the end of the run with a southerly tracking jet and lots of frigid arctic air not far to the west, north and east of the BI so the models are starting to look like they should with the downwelling effects of the moderate strat warming. The polar vortex is going to come under immense pressure to split during the next few weeks and there are potential northerly blasts not to be ruled out but a calmer and colder spell is now looking more likely for the south at least after the next 5 days but it probably won't stay settled for long.

Thank you frosty you have presented this in a nice basic way . Totally agree with your own words.