Model Output Discussion

[reef]

Please continue.

[ChartViewer]

quote name='cooling climate' date='04 December 2009 - 18:29 ' timestamp='1259954974' post='1626721']

The shortwave being shown by the ECM may or may not be right, we know what the GFS is like

with shortwaves so one to watch over the coming days.

Even if the ECM is right, as others have said this will only act to delay rather than scupper any

very cold outbreak.

Seriously I would advise any one betting on a white Christmas to get their bets on before the

bookies get a whiff of this otherwise odds will plummet along with the temperatures.

[/quote

Hi,

Thats a massive bold statement to be honest. The NOAA discussion does not back these comments up.

what they said was discard the GFS runs yesterday and stick with the ECM. Now the ECM does NOT get on board entirely and shows shortwaves and a scenario which does not bring in a full blown Easterly.

Regards

CV

I think theres a long way to go before anyone can claim we are in for a White Xmas but I admire your optimism

[Geordiesnow]

Don't blame just GFS , what about the other models , Have you seen No gaps it is brilliant. I think we will be sure of a cold snap as long as we get the pressure rise as is shown on nearly all the models at +144 . It may delay a couple of days but with the blocking signal there then a link up with Greenland is more likely than usual .

ECM in the short-medium term imo is better than the GFS when handling cold complex sets up and i think that the opinion of others - i often hear on here that "i am never happy unless the ecm is on board". GFS tend to be better at picking up dreaded shortwaves but can go overboard with these and we often get quite messy charts.

GFS 18Z is the next run coming up - certainly not been the best recently in the shorter-medium term so bear that in mind, regardless what it shows. However if it shows high pressure taking control of the UK then that is good enough for me, not too bothered at this range if it shows an easterly or not as it's too far out to take runs at face value.

[snowmadchrisuk]

ECM in the short-medium term imo is better than the GFS when handling cold complex sets up and i think that the opinion of others - i often hear on here that "i am never happy unless the ecm is on board". GFS tend to be better at picking up dreaded shortwaves but can go overboard with these and we often get quite messy charts.

GFS 18Z is the next run coming up - certainly not been the best recently in the shorter-medium term so bear that in mind, regardless what it shows. However if it shows high pressure taking control of the UK then that is good enough for me, not too bothered at this range if it shows an easterly or not as it's too far out to take runs at face value.

Well I'm happy as in the Short/Medium term then ECM is on side . I don't think much of the 18z really , i'll be happy if we are still seeing these charts in the morning. Tomorrow Night the Pressure rise will be at +120 and much more certain .

[MR EXTREMES]

quote name='cooling climate' date='04 December 2009 - 18:29 ' timestamp='1259954974' post='1626721']

The shortwave being shown by the ECM may or may not be right, we know what the GFS is like

with shortwaves so one to watch over the coming days.

Even if the ECM is right, as others have said this will only act to delay rather than scupper any

very cold outbreak.

Seriously I would advise any one betting on a white Christmas to get their bets on before the

bookies get a whiff of this otherwise odds will plummet along with the temperatures.

[/quote

Hi,

Thats a massive bold statement to be honest. The NOAA discussion does not back these comments up.

what they said was discard the GFS runs yesterday and stick with the ECM. Now the ECM does NOT get on board entirely and shows shortwaves and a scenario which does not bring in a full blown Easterly.

Regards

CV

I think theres a long way to go before anyone can claim we are in for a White Xmas but I admire your optimism

yep this is my point aswell NOAA do not support the gfs and the ecm is unlikely to follow the trend suggested.

[snowmadchrisuk]

yep this is my point aswell NOAA do not support the gfs and the ecm is unlikely to follow the trend suggested.

But yesterdays GFS was totally different to today's and GFS is now much more inline with ECM out to +168 .

[cooling climate]

quote name='cooling climate' date='04 December 2009 - 18:29 ' timestamp='1259954974' post='1626721']

The shortwave being shown by the ECM may or may not be right, we know what the GFS is like

with shortwaves so one to watch over the coming days.

Even if the ECM is right, as others have said this will only act to delay rather than scupper any

very cold outbreak.

Seriously I would advise any one betting on a white Christmas to get their bets on before the

bookies get a whiff of this otherwise odds will plummet along with the temperatures.

[/quote

Hi,

Thats a massive bold statement to be honest. The NOAA discussion does not back these comments up.

what they said was discard the GFS runs yesterday and stick with the ECM. Now the ECM does NOT get on board entirely and shows shortwaves and a scenario which does not bring in a full blown Easterly.

Regards

CV

I think theres a long way to go before anyone can claim we are in for a White Xmas but I admire your optimism

Sorry what I was trying to imply was that any cold spell before Christmas and bookies will slash the odds of a

white Christmas.

I know its way to early to predict a white Christmas, cold spell or not.

[ChartViewer]

Sorry what I was trying to imply was that any cold spell before Christmas and bookies will slash the odds of a

white Christmas.

I know its way to early to predict a white Christmas, cold spell or not.

Hey Cooling Climate I am not knocking your view and actually agree with you in a way...

1. Why is the 12z the 1 run that poured cold water on optimism now coming ON board?

2. ECM now possibly SHOWING higher heights from the South that build north and join?

3. More runs coming in the Mid term showing that N/NE colder opportunity

4. The experts here hinting at a possible optimistic opportunity at a colder view

For me its all up for grabs BUT...NOAA seem to want to continually discard this scenario and I and the form horse is for a High over UK and Cold flooding down Eastern Europe...But I hope it doesnt....Just my view but yours is as valid as mine.....And actually I hope you are right!

Edited December 4, 2009 by ChartViewer

[BLAST FROM THE PAST]

Just a quickie from me. Tremendous thread today and hey....be wary of the models...many experienced folk keep saying this. Great posts by Steve MURR...identified what is needed for real cold blast and I suggest what he saw in the outlook too as a potential development. Excellent posts by many and Iceberg for me too has been on the mark.

Anyway, I believe the real mild outputs seen sporadically are wrong. I'm not saying full on winter Armaggeddon BUT A REAL cold shot is on the cards for mid month on

BFTP

[Cecil Hogmanay Melchett]

Absolutely vital ecm sensembles this evening.We really need to see some support for a cool down .

[NorthantsSnow]

Overall one would have to concede that prospects for a cold easterly developing around mid month have improved somewhat today with strong runs from the GFS, NOGAPS and to an extent the ECM. The ensembles however are a very mixed bag with a peak range of around 20C in the upper temps for southern England next week- illustrating well the two very different scenarios possible. However several members do go for a cold easterly which is good enough for me at this range.

The building blocks are beginning to fall into place just outside the reliable timeframe which is also an important development. I agree with Dave that the pressure ensembles for Iceland are both encouraging and improving, and will be a useful indicator over the coming days.

However- there is still a LONG way to go. The model rollercoaster will continue until Monday at the earliest by which time we should have a clearer idea of the likely eventual outcome. By midweek next week we could be anticipating the most significant spell of cold weather since at least 1997 or drowing our sorrows whilst waiting for Mr. Bartlett to arrive. The possibilities are that wide ranging!

[Shunter]

I hear all this talk about NOAA dismissing GFS but looking at their own track record in relation to MJO forecasting shows just how inaccurate they can be.

I've been watching the 40day mjo forecast for the last 15 days and they have got it wrong every single day.

The latest forecast is linked below for reference.

http://www.cpc.ncep.noaa.gov/products/people/wd52qz/mjoindex/index/diagram_40days_forecast_GEFS_membera.gif

CFS forecast updated today also shows increasingly milder outlook for the British Isles in both December and January. Both months had been showing below average temperature forecast for the past few weeks.

http://www.cpc.ncep.noaa.gov/products/people/wwang/cfs_fcst/images/euT2mMonNorm.gif

Strange considering todays developments, be interesting to see who is on the money

Edited December 4, 2009 by Shunter

[nick sussex]

Just got in and had a look at the model output! Thought i had entered the twilight zone, the ensembles from the gefs had made a big switch, even down here there are some under -15/850s.

I have looked at meteociel at the gfs 06hrs gefs ensembles and this must be one of biggest changes from that to the 12hrs, the ecm doesn't look quite as good but still is an improvement, i think its a case now of whether the main trough can back far enough west and where the jet energy goes, southern arm and unbelievably this output could verify, northern arm then its not good news, initially though its crucial we get the euro high forced northwards ahead of the trough.

I'm still in post gefs ensemble shock! still a long way to go with the real interest still too far out.

In relation to shunters post the MJO mystery deepens, the MJO on the Australian site you would think would be the more accurate as its from observations not forecasts, could it be a case that the models are lagging behind and their starting conditions are wrong, if this is the case could this explain the sudden developments this evening or am i barking up the wrong tree?

Edited December 4, 2009 by nick sussex

[Paul]

Quick request - while you're waiting on the 18z's to start rolling, please take a minute to give your thoughts on the model threads on the forum:

[J10]

The latest Ski/Snow Forecast for the Alps and Pyrenees is now out and is available here. Link

However I have also attached a Word Document with the same info below.

[ChartViewer]

Quick request - while you're waiting on the 18z's to start rolling, please take a minute to give your thoughts on the model threads on the forum:

Hi Paul,

Well done opening a debate, discussion on the matter of Model Thread...think/hope everyone posts in Model Thread Thoughts as will give the Site oppoRtunity to think about how they set out things in the future.

Well done Netweather for being open.

CV

[MR EXTREMES]

this is what im saying massive changes to much so in my opion.

GP post yesterday where a warning to be cautious to be honest one day at a time although exciting thing could change in a big way tomorrow.

and in anycase only the gfs is suggest anything really exciting.

[Thundery wintry showers]

Having seen the latest models I think the chances of a cold easterly or north-easterly incursion around midmonth has increased from 10% to 20-30%.

GFS and ECMWF both agree on high pressure building from the south and high pressure then cutting off the continued stream of depressions and heights building to the north. From there it is still quite a tall order to get the cold air as far west and south as Britain, which is why I am implying 70-80% chance that it won't happen. But we are closer.

[Cloud 10]

The ecm 12z ensembles are out,the operational run is one of the coldest,although a general cooling trend overall.

[nick sussex]

The ecm de bilt ensembles for the Netherlands show the operational run as a cold outlier.

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png

The freebie ecm ensemble this evening is for Jersey, again we can see here a cold outlier later on.

http://www.ecmwf.int/products/d/sampler/epsgrams/europe/page.html

We should bear this in mind, it might gather support over the coming days but certainly this might temper the excitement in here for a while, myself included.

[bluearmy]

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png

thats an outlier at T216 to t240 in holland (especially in an impending easterly). That surely shows the GFS 12z to be too quick.

http://www.ecmwf.int/products/d/sampler/epsgrams/europe/page.html

and in the channel islands although can be misleading due to any flow not east or south east tempered by seatrack

EDIT: sod it - beaten by 2 mins - better concentrate harder for the extended ecm ens

Edited December 4, 2009 by bluearmy

[ChartViewer]

To be honest IF we get a Euro High joining up with a High further North 2 people should be congratulated here

Nick Sussex who called it early and GP who has called a late Dec colder spell from day 1....If it comes up Mild as I hope Ill be coating them hehe....Only joking.....They are near the mark and fantastic to see to be honest that they can call this so early

Me ill stick with NOAA for a not so cold scenario and stick with ECM at moment

[cyclonic happiness]

The ecm de bilt ensembles for the Netherlands show the operational run as a cold outlier.

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png

The freebie ecm ensemble this evening is for Jersey, again we can see here a cold outlier later on.

http://www.ecmwf.int/products/d/sampler/epsgrams/europe/page.html

We should bear this in mind, it might gather support over the coming days but certainly this might temper the excitement in here for a while, myself included.

Trouble is each run has been flopping back and forth between cold outlier and warm outlier for the past week, no wonder no-one knows where they stand.

Personally I think that given the gfs's aptitude at forecasting mild winter weather, the uncertainty can be see as a good sign, especially as now the colder runs are creeping into a more reliable timeframe?

[Frosty.]

Amazingly, the potential evolution of a monster cold spell is only a week away and the next few days will be a major test of the models credibility, the ECM 12z T+240 chart has stunning potential and the GFS 12z is simply awesome and would surely give the uk it's most wintry spell for several years, it's good that these stonking charts are not just buried deep in FI as they could be dismissed as nonsense but I just have this horrible feeling that it could all implode by tomorrow or sunday because we have seen huge potential evaporate before many times.

Edited December 4, 2009 by Frosty039

[Glacier Point]

Taking the wider view..

Another westerly wind burst is taking place, already with +6m/s speed 140W - 180 in the Pacific:

This is likely to force deep convection along the convergent line centred around 180 degrees longitude, most probably shifting eastward over time. Already we see deep convection around the Dateline which is likely to increase the amplitude of the MJO wave in phase 7/8.

http://cawcr.gov.au/...m/OLR/m.3d.html

Negative zonal wind anomalies are prevelant in parts of the southern and northern hemispheres although these are competing with westerly wind additions from positive frictional torques and poleward transfer of mean zonal westerly wind anomalies.

http://www.esrl.noaa...s/aam/glaam.gif

The global wind oscillation has started to shift back towards phase 4 and the combination of poleward transfer of westerlies plus the westerly motion across the tropics will ensure this. This means a trough solution for NW Europe is the most likely in the long term (and I'm talking inter-monthly here):

http://www.esrl.noaa...gcm/gwo_40d.gif

What I think has happend over the last few days is the shift towards phase 0 has generated Rossby Wave dispersal bringing about the transient loop in the jetstream programmed over Texas t96.

In the upper atmopshere we see a downwelling mean east zonal wind anomaly sufficient to bring about the split polar vortex, possibly with the aid of an upwelling wave (see the winter bulletin) which is bring about a strong blocking signal throughout the troposphere:

http://www.cpc.ncep....OND_NH_2009.gif

All long range guidance is now programming the split vortex and a 200m height anomaly over the Arctic with a characteristic 3-wave pattern of upper lows generally retrogressing with a solid -AO signature to the high latitude flow.

http://www.meteo.psu...2z/hgtcomp.html

http://raleighwx.eas...htAnomalyNH.gif

http://raleighwx.eas...htAnomalyNH.gif

http://www.cpc.ncep....y/814day.03.gif

This has the look of a very stable and prolonged -AO / -NAO pattern evolving.

Putting this together, I suspect that the ridge over the UK is going to be a transient feature. However, it does appear that it may act as a trigger for the -AO to really impact the middle latitudes with retrogressing upper lows across the northern hemisphere bringing colder air into much of mainland Europe before Christmas.

The longwave trough looks like being a candidate evolution for the UK and western Europe. Whether this happens after cold Arctic air has managed to work its way as far west as the UK is a case for monitoring in the medium term. What does seem likely though is that the return of any jetstream will be displaced southwards with genuinely cold 850s to our east and NE setting up battleground type situation for the Christmas period. This is the likely appetizer for January. The really intriguing aspect here is that we have genuinely cold uppers to work with c/o that displaced vortex and a continued prospect of a -NAO / -AO into January where the changing wavelengths (plus any further increase in global momentum) will favour height rises over Greenland and Iceland.

Edited December 4, 2009 by Glacier Point