Model Discussion January 18th

[bluearmy]

Agree with this.

I think that we are lining up for a cold spell in 10-15 days time starting from the east. This is for a number of reasons.

Firstly we are seeing a considerable warming at 30hPa which will take a little time to affect tropospherically but not as long as if the warming was higher up. We then have the vortex shape lower down which wool be more conducive to blocking to our NE.

Next we have an increase in frictional torque starting to occur which is likely to be followed by a positive mountain torque. The net affect will be removal of westerly winds north of 35°N. With the GWO likely to be around phase 1 then.

I suspect after this any longevity will be determined on the strength of the block and positioning of the PV following this.

On the look out for signs in the FI output in the coming days now.

just took the time to play through the nh plots on the parallel gefs (i prefer the parallel as the normal gefs have been too keen on introducing snow bearing runs post T168 for well over a week now whilst the parallel seems more consistent). there is a general theme to raise pressure markedly during week two and there are plenty of members that would be going cold beyond T384, if not a couple of days before. not sure this is the right pattern but there arent really too many options of the standard zonality we've endured for so long this winter.

[Weathizard]

High looks stronger and further west at T96

Edited January 18, 2012 by Weathizard

[phil nw.]

Following GP`s post regarding the variabiltiy of the operative runs here are the mean hts from both ECM and GFS at Days 8-10 on the left and that forecast of the mean Height Anomolies for Days 8-10.and 8-14.

All indicating building high pressure towards Scandinavia and E.Canada and an upper trough around the UK or a little further South.

As i have said in previous posts when there`s so much doubt in the models have a look at the wider picture over the N.hemisphere.

Refering to the mean hts and anomoly forecasts help towards highlighting the trends in the medium term.

On many occasions they are less likely to jump around day to day.

I have been following the Hts. anomol. forecasts for some time and they have gradually moved the Azores high further west along with those Russian heights.The modelling of our trough has changed little recently too.

Bear in mind these changes are modelled for around days 8-10 not in the next 4-5 days,but we should see the Op runs picking up on these by the weekend as they come within the T96hrs range.

The longer ECM Ens graph

http://www.weerplaza...?type=eps_pluim

picking up on a colder trend later next week.

[Jason M]

18Z looking better at this point. Atlantic low is much further west.

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=126&mode=0

Less phasing of the lows

[The Northern Ramper]

Ahem!!. I've been saying this for a few days. He has stuck to his guns and has not waivered so fair play to him. If he was unsure then i wouldnt be so confident and he sees to know more about all the background signals than anyone else onthis thread with respect.

Rock solid for weeks now

[TEITS]

Latest fax goes with a cold NW,ly on Monday.

http://nwstatic.co.uk/fax/PPVO89.png

So Met O go with the UKMO rather than the ECM.

[nick sussex]

You'd look at this fax chart and think the real cold was very close but the models want to drag the drama out with that troughing over the UK after this point.

[mountain shadow]

You'd look at this fax chart and think the real cold was very close but the models want to drag the drama out with that troughing over the UK after this point.

I look at that chart and see a brief northerly followed by the low pressure on the eastern seaboard moving east towards us on a flat jetstream between the Azores High and the small Greenland High. The centre of the Russian High is so far away it's not even on the chart.

Edited January 18, 2012 by mountain shadow

[Cloud 10]

You'd look at this fax chart and think the real cold was very close but the models want to drag the drama out with that troughing over the UK after this point.

Looks nice,528 dam line clear of the south coast,trough spreading down from the north,certainly

very different to ecm.

[bluearmy]

as soon as we enter low res, we lose the surface high in eastern canada. interesting developments in low res this side of the atlantic but shouldnt analyse them in too much detail. just pleased to see them on the output.

[Grimsby Snow Lover]

Not a million miles off an easterly in the low resolution part of the GFS run. Thats one huge area of high pressure extending over Scandinavia from Russia. If that did reach us we could be seeing one hell of an easterly. Hope so any way,

http://cdn.nwstatic.co.uk/gfsimages/gfs.20120118/18/276/h500slp.png

[Mark Neal.]

Just seen the fax chart, the 528 dam line is well down the country infact near Northern France, i guess any precip would be wintry in nature?

[WhiteFox]

dreaded 'faux cold' (really hate that phrase but needs must

Edit: where is IB? its his job to be negative, not mine

It isn't fake cold, because regardless of how it occurs, it is still cold. 'surface cold' is far more accurate and descriptive. Incidentally, the period from Friday to Tuesday just gone was a good example.

As for IB, I'll take the mantle for now. I can sympathise with his standard position on this. Time and again over the years we have seen the Russian high displaced over Europe but nevet quite reaching the shores of the British isles. I asked earlier in the winter (around December I think) when the Russian high would move west and tease us. Bear in mind that many times it never delivers and we stay on the warm side of the block. Such is the risk with no blocking to the north.

In this case we may be in danger of getting reasonable synoptics which do not persist long enough for the really cold uppers to reach our shores. That Russian high is strong, but right now not very cold. If it moves slightly north and west it would take a few days for really cold air to be dragged across. Ideally we'd want to to see a trough dive down SSE through Scandinavia to bring in some very cold air, and the high to build in behind. Without any ridge further west to cause this however, we are left with systems pushing west and over the high.

This is why Nick S rightly maintains an obsession with viewing the NOAA discussions. We need to see changes to the 500 charts which will allow a better alignment of the Atlantic lows. High pressure ridging far enough north, forcing an Atlantic system to travel over the top through Greenland and then dive south-south east over Scandinavia, then the Russian high spreading west whilst the low cuts off and advects the cold air west. At the same time, a mid Atlantic high building further north preventong a breakdown from the north west. That would be ideal in this setup, but it will take a lot of ifs and buts to get there, hence model uncertainty. The first piece of the puzzle is a weakening northern jet...

[Grimsby Snow Lover]

Just seen the fax chart, the 528 dam line is well down the country infact near Northern France, i guess any precip would be wintry in nature?

You would of thought it would be that easy wouldn't you. Areas with elevation should see snow with most low lying areas near the north and west seeing a wintry mix. If dew points and the 0 degree isotherm allow more areas could see snow showers. Snow in this country is harder to achieve than you think.

[TEITS]

I look at that chart and see a brief northerly followed by the low pressure on the eastern seaboard moving east towards us on a flat jetstream between the Azores High and the small Greenland High. The centre of the Russian High is so far away it's not even on the chart.

I don't mean to be funny but what else are you expecting to see.

At the moment the outlook is relatively straight forward. A colder NW,ly flow this weekend into Monday. This likely to be followed by LP centred over the UK.around midweek. The uncertainity is what happens afterwards and whether we see the blocking to our NE becoming influencial.

[damianslaw]

Latest fax goes with a cold NW,ly on Monday.

http://nwstatic.co.uk/fax/PPVO89.png

So Met O go with the UKMO rather than the ECM.

I like the look of this FAX chart showing sub 528 dam air across most the country and troughs running down on the N/NW wind - suspect these would deliver snow to many places. But caution - the FAX charts were showing a similiar outlook on Monday for this Friday/Saturday with sub 528 dam air making inroads into central/southern england - but then backtracked as the longwave trough over the atlantic began to phase quickly towards us killing off the chances of any arctic blast. However, the longwave trough on this occasion appears to be further west with more favourable mid atlantic ridge development. Yes the trough will quickly attack us from the west by Tuesday but there is a potential for a window of 24 hours of pure arctic air and for precipitation to be quite widely of the snowy variety especially in the north.

Back to the models - the PV is ruling the roost at present but the upstream signals continue to suggest it will weaken. The ECM output is very plausible - azores high ridging NE across the country and into scandi - but unlike the last few days would be a more robust affair - with trough forced to track SE - result undercutting and easterly/northeasterly airstream, this does appear to more obvious evolution to a colder period rather than greenland heights building, the PV remains too strong for this to happen anytime soon, but is more likely to occur as we head into February as the heights to our NE gradually retrogress south and west towards Iceland and into east greenland possibly.

Edited January 18, 2012 by damianslaw

[Grimsby Snow Lover]

I don't mean to be funny but what else are you expecting to see.

At the moment the outlook is relatively straight forward. A colder NW,ly flow this weekend into Monday. This likely to be followed by LP centred over the UK.around midweek. The uncertainity is what happens afterwards and whether we see the blocking to our NE becoming influencial.

TEITS, having seen the outcome of the 18z run should we be concerned about lack of any cold pooling over the continent? If those charts were to verify and I know there is a very low percentage chance the only really cold air is still over Russia. Thanks GSL

The trend I would like to see is the continuation of the block to our east forcing the jet further south as was seen in FI tonight.

Edited January 18, 2012 by Grimsby Snow Lover

[nick sussex]

I look at that chart and see a brief northerly followed by the low pressure on the eastern seaboard moving east towards us on a flat jetstream between the Azores High and the small Greenland High. The centre of the Russian High is so far away it's not even on the chart.

The upstream pattern is expected to amplify and NOAA preferred the more amplified solutions aswell as this the low is negatively tilted and should at least be delivering some WAA into Greenland.

If the models have overblown that low then theres a better chance you'd get some disruption to it even if it still manages to get to the UK by then it would be more negatively tilted and better able to eject energy se'wards, as for the GFS 18hrs it makes a hard slog of bringing the Russian high in because it throws a shortwave north into Scandi off the main trough thereby delaying the westwards push of the high, without that shortwave the low would have already been yesterdays news and the easterly would be in much earlier.

I don't want to flog a dead horse but its essential to get the negative tilt this makes any easterly much easier to attain.

Edited January 18, 2012 by nick sussex

[BLAST FROM THE PAST]

Here's how I see it. Always thouht we look NE for this winter cold when/if it comes. The block is massive to the east and in place. What i see is that trough will be over UK but where will it move. I think the Greenalnd HP scenario is somethin further down the line and NOT the starting point or the place to look for the blockin...not yet. Trough to be in situ, Block to east hold strong, AZH to ridge NE and with cut off shortwave dropping on SSE angle the AZH gets absorbed into the retrogressin Russin HP. This then will retrogress towards Greenland during Feb as pressure rises upthere. Indeed the ECM is IMO picking the trend up nicely, for me its a classic build up to a cold spell...and a classic sympton to prolonged cold setup.

BFTP

Edited January 18, 2012 by BLAST FROM THE PAST

[Mark Neal.]

Looks like a large depression/ pressure system near the north next Thursday....

Also seems to have a face!! :o Lol

Edited January 18, 2012 by Mark Neal Ballooning

[TEITS]

TEITS, having seen the outcome of the 18z run should we be concerned about lack of any cold pooling over the continent? If those charts were to verify and I know there is a very low percentage chance the only really cold air is still over Russia. Thanks GSL

The trend I would like to see is the continuation of the block to our east forcing the jet further south as was seen in FI tonight.

No im not worried.

Encouraging 18Z because after chasing many E,lys over the years the one thing I have noticed is how keen the GFS is to blow away any blocking as though it didn't exist. The 18Z shows the block putting up one hell of a fight and ever so slightly winning the battle.

[Jason M]

Hi Whitefox.

I'll ignore the first couple of sentences of your response

I tend to actually agree with you re the Russian high. I'm not convinced its our friend at the moment for the reason I explained earlier this evening. We could easily end up stuck with southerlies. If we could get a seperate disctinct pressure rise over Scandi however things would look better.

I tend to not pay too much heed to post 192 on GFS when low res kicks in, as outside of very zonal situations it is pretty useless and I tend to give it the same weighting that I would an individual ensemble member.

Edited January 18, 2012 by Jason M

[Zakos]

No im not worried.

Encouraging 18Z because after chasing many E,lys over the years the one thing I have noticed is how keen the GFS is to blow away any blocking as though it didn't exist. The 18Z shows the block putting up one hell of a fight and ever so slightly winning the battle.

Fully agree. The GFS only a few days ago continually modelled the Russian high to randomly collapse as soon as the low res starts. The gfs is no longer doing this, and is now showing the Russian high to remain stubborn throughout FI. This is a big step forward. All we need now is for it to be orientated in a position in order for us to benefit from it. I suspect there will be many "beasterlies" on the ensembles tonight

[BLAST FROM THE PAST]

Not a good ECM!

http://www.meteociel...map=0&archive=0

The high pressure in Russia is too far south and unfavourably tilted. As for the Atlantic, the lows keep riding the high pressure effortlessly.

Karyo

Incorrect, its perfectly poised and could/would develop nicely into an easterly...as indeed it does head that way.

BFTP

Edited January 18, 2012 by BLAST FROM THE PAST

[Zakos]

Here's how I see it. Always thouht we look NE for this winter cold when/if it comes. The block is massive to the east and in place. What i see is that trough will be over UK but where will it move. I think the Greenalnd HP scenario is somethin further down the line and NOT the starting point or the place to look for the blockin...not yet. Trough to be in situ, Block to east hold strong, AZH to ridge NE and with cut off shortwave dropping on SSE angle the AZH gets absorbed into the retrogressin Russin HP. This then will retrogress towards Greenland during Feb as pressure rises upthere. Indeed the ECM is IMO picking the trend up nicely, for me its a classic build up to a cold spell...and a classic sympton to proloned cold setup.

BFTP

Agree with this very much. I remember you saying long ago that any cold is likely to come from the NE, and I agreed. I cannot see any blocking to the NW. the Russian high is very large, and definitely an ally IMO. Its definitely possible we could see some HP over Greenland, but its going to definitely be from the east initially. The met also think its going to be a NE block (presumably)

Edited January 18, 2012 by Zakos