Model Output Discussion - The Start Of Winter

[mushymanrob]

No let up in the cold zonality for the next 10 days

 

eh?.... sorry but that is simply not true!

 

 

yes ive cherry picked the mildest charts , but it proves the point.... some mild, some colder, average id have thought!

 

That at far reaches of model runs, it may be a while before they show clear signs of synthesising change via drivers such as stratospheric warming. The tail-end of 00z EC EPS clusters, for example of inter-run oscillations, return to status-quo with no hint of possible NW heights as signalled in yesterday's 12z. Thus, it now aligns with latest EC32.

 

with respect, the question was 'in basic terms what does that mean' , i have no idea what you mean here and i have some rudementary knowlege of weather jargon. there are i believe alot of people with little or no knowlege of weather terms. can you tell us in very basic terms what is possibly going to happen and where on the models to watch for these signes please.

Edited December 9, 2014 by mushymanrob

[Nick L]

 

 

with respect, the question was 'in basic terms what does that mean' , i have no idea what you mean here and i have some rudementary knowlege of weather jargon. there are i believe alot of people with little or no knowlege of weather terms. can you tell us in very basic terms what is possibly going to happen and where on the models to watch for these signes please.

 

My interpretation in simpler terms:

 

It will take a while for the models to exhibit the effects of any stratospheric warming. The end of the ECM ensembles show little sign of height rises to the NW and is now singing from the same hymn sheet as the ECM monthly.

[492]

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=6&code=0&mode=2

06Z GFS T+78 and T+84 shows a period of snow across the extreme south as a shallow low travels along the English channel.

Edited December 9, 2014 by 492

[mushymanrob]

My interpretation in simpler terms:

 

It will take a while for the models to exhibit the effects of any stratospheric warming. The end of the ECM ensembles show little sign of height rises to the NW and is now singing from the same hymn sheet as the ECM monthly.

 

thanks

[Nick L]

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=6&code=0&mode=2

06Z GFS T+78 and T+84 shows a period of snow across the extreme south as a shallow low travels along the English channel.

 

The ECM has the cold air not digging in until it's cleared the southeast. Air temps will be around 6-7c by the time it clears so I'd say wintry stuff is unlikely.

[chionomaniac]

Just seeing signs on some of the models today as of at day 10 any low Scandi trough is stalling and negatively tilting. I suspect that means that the Russian block is ready to move west.... which could potentially fit in with 40% MOGREPS signal, MJO and strat precurser signals. One to watch.

[Frosty.]

Cold zonal is the main driver but with little mild blips sprinkled in as warm front sectors dive southeast but cold polar Maritimes bordering arctic at times with a generally northwest to southeast aligned jet profile..compared to some of the mushy mild winters of years gone by, this winter has got off to a better start, at least for northern UK

[shaky]

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=6&code=0&mode=2

06Z GFS T+78 and T+84 shows a period of snow across the extreme south as a shallow low travels along the English channel.

are there any ensembles that take that feature further north!!!

[shetland islands]

ECM has temps of around 7C in the south, so I doubt there will be any snow on the south coast. I suspect detail will firm up on the 12Z.

[IDO]

Last two runs of the CFS MJO suggests that the signal is trending to the "circle of death"?

 

 latest: 

 

The composite for phase 5: 

 

So that very much marries with the extended outlook from the GEFS and EC32. The 06z op is consistent as it has been for days. No sign of blocking, a mainly westerly flow with some PM and some TM air. For the south average to above, the north average to below. D16 and no sign of a change:

 

 

The first week of December temp anomaly suggests average temps for most: 

 

So not mild but not cold either. The northerly for later this week is fleeting and it remains a westerly (>NW'ly) for south of Birmingham. This ties in with ECM snow on the ground: 

 

  MarkVogan
Low crossing Scotland Thu could deliver 1-2" of snow even to low levels Thu. ECM 'snow on the ground; forecast @ 96h http://t.co/jkfHIOPrBg
09/12/2014 10:52

 

Still warming at the top of the strat and at 30mb it's continuing:

 

Edited December 9, 2014 by i'm dreaming of...

[Bristawl Si]

Cold zonal is the main driver but with little mild blips sprinkled in as warm front sectors dive southeast but cold polar Maritimes bordering arctic at times with a generally northwest to southeast aligned jet profile..compared to some of the mushy mild winters of years gone by, this winter has got off to a better start, at least for northern UK

Standard Winter weather IMO, for the UK - yes, even in December. The North often sees pre-Xmas snow - esp over the mountains and hills.

 

It may be better compared to some winters, but i think it really represents more of the 'norm' for December. If not the 'norm' certainly nothing unusual.

[Man With Beard]

In between the events of this week and the end of the month ... I sense a possible northerly for next week. GFS / GFS(P) / ECM at T192 are consistent in placing the surface low in the North Sea off the coast of Norway. Now this set-up is just begging a late-developing low to shoot across the North Atlantic and join this North Sea low on its southern flank, which would lead to a pull of colder northerlies over us once again as it clears. With heights low over Europe at this timeframe, there would be nothing to stop this secondary low on its journey SE-wards. This is not showing on the models but is the kind of thing that often appears at around T144, isn't it?? A possibility, anyway.

 

[mountain shadow]

To enforce the reality of no longer term cold spell the NAO forecasts remains positive throughout across all members. Any short potent Notherly/North Westerly will be determined upon how far North and West the Azores ridge can get.

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/new.nao_index_ensm.html

 

I would say the chances of white Christmas in the South are pretty remote with Northern and Western areas best in with a shout based on the latest output and potential of brief topplers.

 

Looking further ahead with the likely SSW towards the start of January, the downwelling can take a couple of weeks or more and then a further lag before it can impact our wee islands. So perhaps a lengthy cold spell might occur from mid January onwards.

[Summer Sun]

What time does GFS P update for the 06z? meteociel is still stuck on the 00z run

 

ps the version on netweather is stuck on yesterdays 12z

[johnholmes]

Looking at what we have and what indicators over the next 2 weeks and perhaps beyond

Yes you will have to put up with me using the 500mb anomaly charts. But they do give usually fairly good indications of what the upper air pattern is going to be in the 2 week period. From that one can then use the synoptic models to see which one best fits with that predicted upper pattern. We have to remember that the anomaly charts are averages or means over the period they indicate. But, it is pretty unusual for the pattern to be dramatically different on a day to day basis.

At the moment we are in a fairly mobile westerly average upper air pattern. The actual direction for the UK has and will swing between a touch south of west and about as far round as north west. The latter behind major surface weather systems developed as a result of the upper pattern NOT the other way round. Over and just east of the UK we have and are predicted to keep an upper trough. This is at times what forecasters call a diffluent trough and is a feature that causes surface systems to deepen, sometimes quite rapidly.

The anomaly charts do not suggest any major change in the 2 week time frame. The pattern of some ridging in the Atlantic with troughing east and west of this feature is also shown on the GFS MJO equivalent chart for MJO 6 which is the pattern currently showing. Sometimes the MJO can give some advance guidance on how the upper main trough-ridge pattern may change. Sometimes it is not so good. You have probably seen the phrase ‘circle of death’ or something similar. All this means is that the MJO orbit is being predicted to have little momentum and is shown close to the origin. In these situations we have little to help with what may happen beyond the 15 day time scale after the anomaly charts. Of course we get snippets of information from those with access to the longer range ECMWF outputs but that is about all.

So at the moment, pretty much a continuation of the present set up, air from a fairly cold start point over Canada, and little sign of any major input of really mild air for the south of the North Atlantic on these charts. Details of when any major surface low and changes in how cold from normal will as always come from the nearer range synoptic outputs, remember to follow the model most closely aligned in the upper air with the anomaly charts. So disregard some of the larger differences from this pattern, they are very unlikely to turn out to be correct.

What happens after 2 weeks, maybe 18 days or so I have no real insight into.

Below are the links to the anomaly charts and the MJO actual and forecast phases using the GFS output. I only ever use that as it saves me having even more data to try and decide what is most relevant. I do not pretend to be an expert with this part but it does seem to be fairly useful over the past 3 years or so that I have used it. I also give the link to what the average 500mb height anomalies are for December using the MJO data.

Not the same as last December that is for sure, how much the polar vortex will decline, or not, is something we have to wait and see as is any major Stratospheric warming. Just be careful of anyone who promises deep cold etc be it within the next fortnight for lowland areas south of the main Scottish mountains, and also for beyond it. No intention to knock anyone just a note of caution.

500mb anomaly links

http://www.cpc.noaa.gov/products/predictions/610day/fxus06.html

 

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

 

MJO charts using GFS

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml

and the link for December 500mb anomalies using the actual and predicted MJO GFS outputs

http://www.americanwx.com/raleighwx/MJO/MJO.html

 

enjoy whatever the weather sends us.

 

I forgot to add a comment about using AO, NAO etc

Remember that these are not drivers but charts showing what the models already suggest; they are helpful when used in conjunction with other teleconnections but do become pretty unreliable after 7-10 days in my view

sorry gap in posting as phone rang!

Edited December 9, 2014 by johnholmes

[ItNeverSnowsInWindsor]

To enforce the reality of no longer term cold spell the NAO forecasts remains positive throughout across all members. Any short potent Notherly/North Westerly will be determined upon how far North and West the Azores ridge can get.

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/new.nao_index_ensm.html

 

I would say the chances of white Christmas in the South are pretty remote with Northern and Western areas best in with a shout based on the latest output and potential of brief topplers.

 

Looking further ahead with the likely SSW towards the start of January, the downwelling can take a couple of weeks or more and then a further lag before it can impact our wee islands. So perhaps a lengthy cold spell might occur from mid January onwards.

Still too early to be predicting xmas weather with so much happening in the nearby timescales. We could all easily be in a potent N' / NW' blast as shown in the GFS 0Z output.

[mountain shadow]

Still too early to be predicting xmas weather with so much happening in the nearby timescales. We could all easily be in a potent N' / NW' blast as shown in the GFS 0Z output.

Well, it is certainly to early to call it accurately, but based on the current tropospheric signals as John alludes to above, there is nothing to support low level Southern snowfall for Xmas, but of course things can change.

[SylvainTV]

What time does GFS P update for the 06z? meteociel is still stuck on the 00z run

 

ps the version on netweather is stuck on yesterdays 12z

 

I think there is still some maintenance, there is no data at all, even not data from parallel GDAS 06z.

 

It is probably linked to this :

"Tuesday 12/9 :  NCO will run a single-cycle parallel production test on

Gyre to test functionality post-Phase 2 integration.  No developer

access to the system during the test."

[bluearmy]

IDO, if the MJO does enter the 'COD', then I don't expect the composites will be relevant. Other drivers wil take precedence.

Ed, I did note on Sunday that there were the first sniffs of the Russian high pushing west and perhaps cutting off the trough to our se but tbh, there has been little momentum in that regard since then.

[nick sussex]

Well the plot thickens, both the GFS 06hrs and NAVGEM 06hrs runs trend towards the GEM 00hrs which to be honest I thought had gone AWOL once again.

 

Whether this trend lasts more than 6 hours we'll see tonight but certainly although not offering anything very cold at least they look more likely to keep temps on the cold side.

[Barry12]

The Stratospheric warming continues on the GFS 12z, and is now starting at day 13.

 

 

 

The Christmas period continues to show interest.

 

[bluearmy]

The NAO is only the representation of the pressure patterns in the ens.

If the ensembles are wrong then so is the NAO forecast. Xmas is over two weeks away. - impossible to make predictions yet - could be be steamy, could be frigid but likely something inbetween.

[IDO]

Massive 'broad brush' comments for Christmas 16 days away, not to mention what will happen in mid Jan. Wow. Do you have access to the METO's new super computer?! 

 

Hi. Statistically according to the UKMO there is about an 8% chance of snow being on the ground on Christmas Day. That is for 40% of weather stations so about 3% chance for any one location and probably less than that for the south. So a reasonable statement and bearing in mind all LR Forecasts are painting the same picture where the south has little chance of snow for the foreseeable then no super computer is really needed. However its not like last year, so of course the models could easily flip in the next 2-3 weeks, but at this moment in time the models are poor for snow in the south (different story of course for up north and on mountains).

 

ECM Jan temp anomaly highlights this: 

 

 

  WSI_EuroEnergy

Latest ECMWF January seasonal forecast colder Scandinavia, above normal mainland Europe, nearer normal UK. http://t.co/wdqYoetpJq

09/12/2014 13:55

 

Interesting tweet showing how important the SSW will be to our whole winter (if cold is what you are after):

 

 

  chionomaniac

@antmasiello @scotlandwx Look how important SSW could be for rest of winter http://t.co/joGJhRM0F5 http://t.co/qJFvmsIP8u

09/12/2014 11:12

 

(UKMO data source: http://www.metoffice.gov.uk/learning/snow/white-christmas)

Edited December 9, 2014 by i'm dreaming of...

[Recretos]

Now I am working quite a bit with GEFS for the strat., but I work with the bias corrected version of the GEFS, while meteociel and wetterzentrale I think use the normal one. So,.. if anyone is interested what kind of a difference that makes, here is a comparison of the 6z GEFS, the bias corrected vs the normal one. I usually always prefer the BC one, because it removes some of the known bias or a false tendency of the GEFS, compared to the normal one. Differences are not that big, but are meaningful.

 

This basically shows where the BC version of the GEFS is higer/lower in heights, and where the BC version is warmer/colder than the normal one. 

 

 

 

Cheers

[OldMetMan]

Just seeing signs on some of the models today as of at day 10 any low Scandi trough is stalling and negatively tilting. I suspect that means that the Russian block is ready to move west.... which could potentially fit in with 40% MOGREPS signal, MJO and strat precurser signals. One to watch.

My feelings exactly Chiono. I was waiting to see what later runs come up with, but current runs do show the Russian HP a little closer. Once any LP over Scandinavia finally fills, now that is the time when HP can form with a vengeance. I have seen such on a number of occasions in the past. Zonal W to NW flows don't often stay as such for long, usually the cold air will win but occasionally, as hinted by the last GFS, there's a pressure build in our area as the pattern amplifies in mid-Atlantic. Cue the (sometimes quite rapid) emergence of the Scandinavian HP, pushing westwards!