Model output discussion - 16th Nov onwards

[Man With Beard]

This is getting silly now - yet another wintry Scandi High from the GFS - someone really must tell it that the eQBO and the strat forecasts won't permit such frivolity until at least late January

[Captain Shortwave]

Still hope for something drier, though it would be nice to see this get closer instead of seeing zonal westerlies.

 

GFS

 

GEM

 

GFS ens not really interested

 

Though pressure rises from the south in the extended ensembles, but again it would be nicer to see this in the nearer timeframe. Temperatures look near normal for the foreseeable, differences between the north and the south which is typical given the jet is currently passing through the UK.

[bluearmy]

 

This is getting silly now - yet another wintry Scandi High from the GFS - someone really must tell it that the eQBO and the strat forecasts won't permit such frivolity until at least late January

 

I think height rise to our ene is fine for the dec nino composite. the model may just be over reacting and driving too much amplification with consequential CAA towards nw Europe. 

[cold snap]

ECM is mild ,and slightly less mild right out to 240

Very little change in the next two week I feel

[snowking]

This is getting silly now - yet another wintry Scandi High from the GFS - someone really must tell it that the eQBO and the strat forecasts won't permit such frivolity until at least late January

It's worth pointing out that the potential for a Scandi high is not unprecedented or unexpected in a high SAI year - some of you may even remember back to the December 2012 failed easterly debacle. As the feedback loops resultant from the lower sea ice extent around the arctic continue to deliver high SAI years we should expect this possibility of teaser Scandi highs in December to become more prevalent (remember the theory goes high snow advance > big Siberian high > wave activity > unhappy vortex).

This is what happened back in 2012 too and look at what resulted in Jnauary (and indeed March) of that year. This is never a guarantee of cold later on (especially given other current global drivers) but the appearance in both extended operational and ensemble output of a Scandi high should not be unexpected and may prove to be fruitful from a longer term perspective.

I would, however, caution at this stage that even if such a feature were to verify I would not expect it to make a huge impact on the UK just yet. Then again this season really is analogue-less in real terms taking in to account the usual global drivers.

SK

[Frosty.]

ECM is mild ,and slightly less mild right out to 240

Very little change in the next two week I feel

Actually, the Ecm 12z is cold at times in the north with night frosts & wintry ppn and generally close to average temperatures with just short lived milder blips, especially across the south..it's also a very unsettled run.

Edited November 25, 2015 by Frosty.

[blizzard81]

Actually, the Ecm 12z is cold at times in the north with wintry ppn and generally close to average with just short lived milder blips, especially across the south.

I agree, much less influence from the Euro high.

[Nouska]

It's worth pointing out that the potential for a Scandi high is not unprecedented or unexpected in a high SAI year - some of you may even remember back to the December 2012 failed easterly debacle. As the feedback loops resultant from the lower sea ice extent around the arctic continue to deliver high SAI years we should expect this possibility of teaser Scandi highs in December to become more prevalent (remember the theory goes high snow advance > big Siberian high > wave activity > unhappy vortex).

This is what happened back in 2012 too and look at what resulted in Jnauary (and indeed March) of that year. This is never a guarantee of cold later on (especially given other current global drivers) but the appearance in both extended operational and ensemble output of a Scandi high should not be unexpected and may prove to be fruitful from a longer term perspective.

I would, however, caution at this stage that even if such a feature were to verify I would not expect it to make a huge impact on the UK just yet. Then again this season really is analogue-less in real terms taking in to account the usual global drivers.

SK

 

A good post about the possible reasons for heights being modelled to our NE.

 

May I suggest another one ...MJO modelling takes the activity through phase three before returning to neutral. The composite for >1 in phase 3 (ENSO enhanced) December also shows heights over the UK with focus on Scandinavia. Some have suggested the amplification of the MJO is a false signal but that doesn't mean that the modelling will not respond to strong signals in tropical zones.

 

  

 

There is enormous spread in the extended ensembles for the area north and north east of us. Below the GEFS parallel and current suite.

 

  

[Ravelin]

A quick comparison of the 12z ECM and GFS show they are quite similar up to t120 but start to diverge after that. By T168 they are significantly different from Alaska across to Northern Europe.

Is the GFS right with the strength of that Alaskain high, which never really develops on the ECM?

Edited November 25, 2015 by Ravelin

[Paul]

In case you haven't spotted it, the winter forecast has been issued this evening:

 

Summary:

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

 

In depth version:

http://www.netweather.tv/index.cgi?action=winter-forecast-2015;sess=

 

Discussion thread (please don't discuss it in here):

https://forum.netweather.tv/topic/84508-netweather-winter-forecast-201516/

[Cloud 10]

Looks like another soaking for some Western parts of the UK over the next week with over 4 inches of rain forecast for Cumbria (again) and plenty of wind to go with it.

 

 

 

Also another FI Scandi high from the GEFS (p) control run.

 

[Cheshire Freeze]

It's worth pointing out that the potential for a Scandi high is not unprecedented or unexpected in a high SAI year - some of you may even remember back to the December 2012 failed easterly debacle. As the feedback loops resultant from the lower sea ice extent around the arctic continue to deliver high SAI years we should expect this possibility of teaser Scandi highs in December to become more prevalent (remember the theory goes high snow advance > big Siberian high > wave activity > unhappy vortex).

This is what happened back in 2012 too and look at what resulted in Jnauary (and indeed March) of that year. This is never a guarantee of cold later on (especially given other current global drivers) but the appearance in both extended operational and ensemble output of a Scandi high should not be unexpected and may prove to be fruitful from a longer term perspective.

I would, however, caution at this stage that even if such a feature were to verify I would not expect it to make a huge impact on the UK just yet. Then again this season really is analogue-less in real terms taking in to account the usual global drivers.

SK

 

Steady on SK, although I agree whole heartedly with what you're saying, you may get accused of leading people up the garden path- just like I did last night...ahem.....

 

In the mean time, Scandi high trying to form once again on the 18z

 

 

Ends beatifully with -10 uppers across the country and some advection towards Greenland

 

Edited November 25, 2015 by CreweCold

[SMU]

Again the 18z pub run comes up trumps if its cold your looking for -

2 key ingredients -

* an arctic high - supporting SOME cross polar flow

* a weak signal for a 2 wave pattern trying to develop - 1 from the atlantic ridging NE & another in the far east of russia ....

The 18z is almost identical to the 12z control, there are also a handful of ECM solutions with a similar evolution..

Also the good news is that its a fairly cold high to start with ( around 192 )

Best

S

[Singularity]

Again the 18z pub run comes up trumps if its cold your looking for -

2 key ingredients -

* an arctic high - supporting SOME cross polar flow

* a weak signal for a 2 wave pattern trying to develop - 1 from the atlantic ridging NE & another in the far east of russia ....

The 18z is almost identical to the 12z control, there are also a handful of ECM solutions with a similar evolution..

Also the good news is that its a fairly cold high to start with ( around 192 )

Best

S

 

The Arctic High features on the ECM 12z det. run too, the first det. run from this model in a while to have it in place, and the polar vortex does look a little fragile and prone to splitting as of +240:

 

 

What GFS has been putting on the table does seem to be a fairly direct interference with the polar vortex by the Arctic High, with a corresponding drop-off in the intensity and 'flatness' of the polar jet. By two week's range the vortex has fallen apart at the tropospheric level and the main blocking high taking advantage of this happens to be over Scandinavia - which based on Snowking's post earlier today is a supported location in relation to the high SAI this year, though it wouldn't usually be so far west at this early stage in the season.

 

All this happens despite the stratospheric vortex only looking a little bit troubled, as wave breaks surf the periphery but lack the strength to really cause it trouble. One has to wonder whether anomalously high heights in the Arctic can really counter the stratospheric forcing so effectively. That may well depend on the level of support from the distribution of sea ice deficits and perhaps even the way in which the anomalous warmth in the subtropical E. Pacific (north of the usual El Nino warmth) affects the waveguide over the N. Pacific. Once again I find myself speculating about the possible effects of a situation for which we have no analogues.

 

As a footnote, it's nice to see the Netweather Winter Outlook calling for a change at a very similar time to what I've been starting to see as a probable outcome (mid-Jan, following a major strat. warming event early in the month), albeit far from certain. I'm very big on my caveats in this experimental field of meteorology. Recent GFS output has been inconsistent with the level of strat. warming this month but as long as the overall configuration persists - particularly the wave breaking being sourced from Eurasia rather than the Western Hemisphere - there ought to be little reason to panic regarding January's prospects. Fingers crossed!

[Peter H]

Notice the latest models have the Scandinavian high back again at the end of the period, with very cold air to the east, but it'll probably flip flop back again in the morning.

[Captain Shortwave]

No real change this morning in the output, aside from the usual variation in the low resolution of the GFS. Still looking predominantly westerly but with the chance of the heights over Europe becoming more influential.

GFS at day 10

 

GEM

 

The ensembles of both the ECM and GFS do seem to want to push the high further north albeit slowly with the south of the UK becoming drier as we enter week 2. A Scandi high would seem potentially possible for a couple of weeks time but at the moment remains an extreme and less likely option. It will be interesting to see if we can see anything develop in a more reliable time frame in the coming days.

[knocker]

 

 

The ensembles of both the ECM and GFS do seem to want to push the high further north albeit slowly with the south of the UK becoming drier as we enter week 2. A Scandi high would seem potentially possible for a couple of weeks time but at the moment remains an extreme and less likely option. It will be interesting to see if we can see anything develop in a more reliable time frame in the coming days.

 

The GEFS and ecm anomalies have been hinting at this for a while whilst maintaining the classic Nino pattern upstream. The 18z GEFS(P) certainly in the latter part of the run also supported by the ECM although one has to say NOAA has reservations although edging in that direction

 

As already stated this morning's gfs continues the well established interplay between the Pm and Tm airmasses.

Charts weatherbell

Edited November 26, 2015 by knocker

[bluearmy]

The amplification around dec 5th. Gfs consistent with this and gem makes a lot of it today. We know that ECM is capable of doing the most with such a solution so it's a relief that it doesn't want to for the time being. Otherwise we would be in danger of getting ahead of ourselves. Then further west this amplification takes hold, the easier any CAA will find it to get this far. I haven't seen enough ens support for this amplification to occur to our west so for the ops to do this at 8-10 days would be questionable.

[Ali1977]

No signal of a change in pattern on the latest METO long range so struggling to believe it will happen, although the potential is always there I guess, maybe we need to wait till later in the weekend for a better idea and when not quite as far in FI.

[Summer Sun]

A mixed run from ECM this morning with some milder days and some cooler days so temperatures probably balancing out around average for the south but cold enough in the north for some hill snow

 

 

At the end of ECM's run the high starts and influences more

 

 

ens suggests the south will fair best for the drier weather with rain more restricted to the north and west

 

Edited November 26, 2015 by Summer Sun

[fergieweather]

No signal of a change in pattern on the latest METO long range so struggling to believe it will happen, although the potential is always there I guess, maybe we need to wait till later in the weekend for a better idea and when not quite as far in FI.

A bit of caution required however, given growing signs of amplification and equally anticyclonic bias for S'rn areas with time (and dropping temperatures in EC-EPS as a result). Note too that latest GloSea5 has -ve temp anomalies in all members across most of NW Europe into w/c 21/12. So we need to watch for any continuity in this emergent (v tentative) signal.

[mountain shadow]

A bit of caution required however, given growing signs of amplification and equally anticyclonic bias for S'rn areas with time (and dropping temperatures in EC-EPS as a result). Note too that latest GloSea5 has -ve temp anomalies in all members across most of NW Europe into w/c 21/12. So we need to watch for any continuity in this emergent (v tentative) signal.

If you don't mind me asking Ian. Are the neg anomalies due to a UK high or of more Arctic origin with upper heights more towards Greenland or Scandi?

Thanks

Ms

[fergieweather]

If you don't mind me asking Ian. Are the neg anomalies due to a UK high or of more Arctic origin with upper heights more towards Greenland or Scandi?

Thanks

Ms

Latter. Stress emergent/tentative. Given current set-up, such a major change in just 4 weeks would take some mammoth turnaround. So a 'watching brief' until stronger continuity emerges (or not).

[Ali1977]

So, tentative signs later in Dec from the professionals suites. This would be a great time for a cold spell, continent colder, seas cooler, days are shorter and potential SSW to follow...Monday's ECs could be interesting, hopefully the signal doesn't fall away.

[johnholmes]

Interesting inputs from Fergie.

In the time scale I try to forecast for the anomaly charts are somewhat mixed, The ECMWF-GFS version, back again this morning, show two differing ideas, one with a flattish westerly flow the other with one south of west with a marked trough into the far west of Europe. NOAA 6-10 last evening was a bit more like GFS. Overall the outputs over the last few days do seem to suggest that the flow is tending to be a shade south of west not the shade north of west of a few days ago. The NOAA 8-15 also supports this idea. With the relatively strong flow at 500mb across the Atlantic into the UK it does suggest some deepish surface lows at times which seems likely to lead to quite large variations in surface temperatures ahead of and behind these systems. No sign on these charts, yet, of any marked change in pattern.

links below

sorry the EC-GFS will not open again= I will copy the image I got earlier and post it shortly

NOAA

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