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Model output discussion - 1st December onwards

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Some signs of a change upstream in the USA and Canada with troughing working eastwards from the eastern Pacific. The issue currently is the amplitude of this troughing. This does effect high pressure ahead of it and the angle of the jet in towards western Europe.

If this troughing does verify then a lobe of high pressure is likely to track eastwards ahead of it, this of course does open up a window for a colder snap as the high exits eastern Canada.  Of course with these types of set ups the amplitude might fall too far west so the wrong side of any low pressure.

However an extended western based negative NAO is unlikely , so its a case of making the most of this temporary more amplified set up.

 

 

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Surely this is a good sign, still doesn't dip to far below as a mean though!!

image.png

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Well the GEM has officially stopped pulling phantom Euro height rises....

gem-0-240.png?12

Now we are back in the cold ramping runs :)

Probably the best of the output so far given this is a ten day chart. Though being the GEM it is probably a very optimistic output.

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15 minutes ago, Captain Shortwave said:

But again the seasonal norm is for high pressure to be over southern Europe, so a shallow positive anomaly will still mean strong heights in that region, the reason I highlight this again is the 850 and T2M anomalies suggest a more Euro/Scandi ridge rather than a blocking high to our north east and the jet pushing underneath it. You need to see those blue colours widespread over southern Europe to suggest unsettled conditions and hence the chance of an easterly flow for the UK.

The same caveats apply when looking in other places, for example a weak positive anomaly over Greenland still overall represents low heights in that particular location.

 

18 minutes ago, Captain Shortwave said:

But again the seasonal norm is for high pressure to be over southern Europe, so a shallow positive anomaly will still mean strong heights in that region, the reason I highlight this again is the 850 and T2M anomalies suggest a more Euro/Scandi ridge rather than a blocking high to our north east and the jet pushing underneath it. You need to see those blue colours widespread over southern Europe to suggest unsettled conditions and hence the chance of an easterly flow for the UK.

The same caveats apply when looking in other places, for example a weak positive anomaly over Greenland still overall represents low heights in that particular location.

But not throughout the whole month though - the proof is in the pudding - this is the Daily chart from that exact run!

 

cfsnh-0-1254.png?18

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2 hours ago, northwestsnow said:

Interestingly the ECM control looks very cold and snowy as we hit mid December.

If nothing else a block over Canada may well promote a more SE trajectory of the lows spinning towards the UK medium term.Hopefully starting the demise of that horrid Euro high!

 

Yes the signal for any MLB or HLB that would drag in any cold polar air to our shores is very muted but the signal for some form of cold zonality is much stronger after mid month.

As you say cold zonal flow generally has a southerly tracking jet so hopefully that will erode the Euro high but all so far out.

Currently I would say the second half of December will be of more interest to those in the North and with some elevation than the South but this pattern is still developing and more changes likely.

 

Mods.

New site layout is a pain in that it doesn't give posting times, just x hours ago which isn't that useful.

Edited by Mucka
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GEM with a nice northerly further down the line. High pressure to the NW, suggesting the movement of the vortex from this quarter. 

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1 minute ago, Mucka said:

 

Yes the signal for any MLB or HLB that would drag in any cold polar air to our shores is very muted but the signal for some form of cold zonality is much stronger.

As you say cold zonal flow generally has a southerly tracking jet so hopefully that will erode the Euro high but all so far out.

Currently I would say the second half of December will of more interest tot hose in the North and with some elevation than the South but this pattern is still developing and more changes likely.

I think thats a very reasonable post mucka. No sign of any major blocking where we want (Greenland or Scandinavia),but enough amplication to force the jet further south in the longer term. :)

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Rest of this week largely unsettled for England and Wales, some respite at times further into Scotland and Ireland, Temps average to colder than normal in spells up the North, milder than usual down South. Mild wet and windy for most parts of the UK at the weekend.

Next week, a more settled picture at least on a couple of days nationwide resulting in a patchy frost in places and hopefully some much needed sunshine for a few of us. Never cold perhaps near average for most and possibly milder than normal again in the South during the latter part of the week. After a potentially troublesome Monday for folk in the South, Thanks to strong winds and prospects for further flooding rain, things will dry out for most of us nationwide as the week goes by.

Beyond this, placing confidence in any surface conditions and corresponding surface features would be folly, which stands to reason. Whilst the default SW to NE Jet flow up above us in the atmosphere may well be a fair bet once more, I think an Atlantic driven Jet based set up with a higher incidence of NW'rly incursions is more likely than not. NO changes broadly speaking before D10 then but mid December from perhaps as early as the 12th is where I'll be focussing my thoughts about any potential major pattern change.

 

Things to watch.

 

  • fluctuating Pacific Jetstream activity and associated troughing and just how this in turn effects the US weather situation
  • Where next week's developing HP cell positions itself over our part of Europe and how long it might hang around for
  • Whether this in turn allows for upper High development in the Greenland region
  • Stratosphere changes affecting the longer-term signal for the 2nd half of December and whether something more traditional might pop up just in time for Christmas

 

Will tonight's ECM backup these thoughts of mine or will I be facing prison time for wrongful forecasting tendencies?

 

Cheers all and do play nicely, whatever the weather.

 

 

Edited by gottolovethisweather
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3 hours ago, warrenb said:

So eyes down for the new GFS coming to you live with the 12Z run.

 

2 hours ago, Ali1977 said:

We also have upgraded GFS ens to come  after this run...maybe we can have a little more confidence on any future pattern change than with the last lot.

Just a heads up-as Ali has inferred it is just the GEFs(ensembles) that have been upgraded today as from the 12z run.

Link here-  http://www.nco.ncep.noaa.gov/pmb/changes/

As far as i know the GFS Op is unchanged.:)

 

Edited by phil nw.
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29 minutes ago, phil nw. said:

 

Just a heads up-as Ali has inferred it is just the GEFs(ensembles) that have been upgraded today as from the 12z run.

Link here-  http://www.nco.ncep.noaa.gov/pmb/changes/

As far as i know the GFS Op is unchanged.:)

 

Yep, just ensembles being updated. New 12z is in and looking good - we'll add some of the extra data / times next week. 

http://www.netweather.tv/index.cgi?action=ensviewer;sess=

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ECM really latching on to those Canadian height rises now.

 

ECH101-240.GIF.thumb.png.47a9a8fc9a60c1b

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The NH profile at 240 looks really good, vortex breaking, and considerably weakening over the pole...If this model ran another few days on there would be some cracking charts I think. Things look like getting interesting to say the least, maybe from around the 13th onwards!!

The high building over Labrador at 240 may have an easier migration north if the Vortex continues to break.

image.png

Edited by Ali1977

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A weather eye needs to be kept on this fella as it deepens to 960mb on it's travels. It could bring winds in excess of 75kts into Scotland as it passes to the north

ecmwf_z500_mslp_eu_6.png

ecmwf_z500_mslp_eu_7.png

Edited by knocker
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1 hour ago, Mucka said:

 

Yes the signal for any MLB or HLB that would drag in any cold polar air to our shores is very muted but the signal for some form of cold zonality is much stronger after mid month.

As you say cold zonal flow generally has a southerly tracking jet so hopefully that will erode the Euro high but all so far out.

Currently I would say the second half of December will be of more interest to those in the North and with some elevation than the South but this pattern is still developing and more changes likely.

 

Mods.

New site layout is a pain in that it doesn't give posting times, just x hours ago which isn't that useful.

Just scroll your curser over the time last post made and it will show the time of posting.

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Please can we keep discussion around the new forum / feedback to the topic that's been made specially for it. It'll get lost if it's posted in random places, your questions are more likely to be answered, and feedback acted upon if it's posted over there.

https://forum.netweather.tv/topic/84553-forum-upgrade-please-read/

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gfs-0-144.png

Here's GFS with the trough digging down in the central North Atlantic, this allowing a ridge to build ahead of it, across the UK.

 

UW144-21.GIF

ECM1-144.GIF

Here's UKMO and ECM doing no such thing. They keep the pattern flatter at this time and this is what leads to all of the low heights ending up over Scandinavia by +192, around which time there is some amplification taking place in the Atlantic-NW Europe sector which then places us on the cold side of a 'tall' ridge in the Atlantic. This is in stark contrast to GFS which has the amplification unfolding while that trough is in the middle of the North Atlantic, placing the UK on the 'warm' side of things - though with the ridge influential enough to allow a surface chill to feature by night in particular.

GEM is a kind of GFS/UKMO+ECM hybrid in that the trough seeks to drop down in the mid-Atlantic, but is unable to do so due to the jet taking longer to weaken and take on a more meridional behavior. The model then disrupts the jet so much in a short space of time that a cut-off low occurs off the coast of Newfoundland, propping up a strong high over Greenland - the end result being suitably dramatic in terms of conditions going forward. For once the 'halfway house' solution appears not to be the best guide in the longer-term. Or is it? I can't go around ruling things out no matter how low the odds are!

 

Posted at 19:56 on 2nd December. Yes - I agree that it's good to have the posting time and not 'X hours ago'.

Edited by Singularity
figured out how to make images attachments
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Is it me, or since this upgrade happened this forum has gone quiet - or is it a lack of any cold signals in the next few days!!

Anyway, we now have interest showing on the ECM and GEM , not way out in GFS FI!! 

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Extended ECM ens drift that high anomoly just south of Greenland which is enough to get the trough just to our East. Barely would be a fair description but that's better than to our west where we would see a west based neg NAO.  The control is very cold again, this time with a huge Greenland/Arctic ridge in far off fi.  I'm not really inspired from a cold perspective but then again, some pretty cold operationals so wouldn't be much of a surprise over the next few days. 

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4 minutes ago, bluearmy said:

Extended ECM ens drift that high anomoly just south of Greenland which is enough to get the trough just to our East. Barely would be a fair description but that's better than to our west where we would see a west based neg NAO.  The control is very cold again, this time with a huge Greenland/Arctic ridge in far off fi.  I'm not really inspired from a cold perspective but then again, some pretty cold operationals so wouldn't be much of a surprise over the next few days. 

Is there anywhere to view these extended charts?

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After what looks like a stormy weekend the ECM ens shows winds should start and ease down with high pressure to the south pushing up for during Wednesday and Thursday so for the midland's south it should become calmer and drier the far north though remains prone to some rain

Reem1441.gifReem1681.gifReem1921.gifReem2161.gifReem2401.gif

 

Temperatures look around average though feeling colder overnight during any quieter periods

Edited by Summer Sun

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Both the GEFS and ecm anomalies at T240 feature the ridge NE Canada which downstram has a tendency to restrict Atlantic incursions to the north of the UK with HP pushing up from the south with perhaps some more settled weather.  In the ext period ithe GEFS weakens and re-orientates the Canadian ridge resulting in the trough(s) to the east once again becoming more influential resulting in generally unsettled weather over the UK with some wintry incursions of Pm air. The ext ecm also weakens the ridge, perhaps more so, and also introduces a weak low pressure area NW Greenland with similar results downstream.

Charts weatherbell and http://www.tropicaltidbits.com/

ecmwf-ens_z500a_nhem_10.png

gefs_z500a_nh_41.png

gefs_z500a_nh_65.png

Edited by knocker
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The ensembles for Winnipeg give an idea of the unusual "warmth" associated with those anomalous Canadian heights.

 

MT8_Winnipeg_Kanada_ens.thumb.png.48b3e8

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