Model Output Discussion

[Avain]

The in depth discussion thread Here seems to feel that it is possibly not East that we ought to be looking but West, not for mild but cold, a while away yet but with more of an unsettled picture for us than a cold one for the short term.

Considering the constant seesaw of the current model output it is certainly worthwhile reading the the thread to get a different perspective on the current situation.

Edited January 15, 2010 by Avain

[Climate Man]

That has to be the biggest swing on the GFS in a 6 hour period and that is saying something. This year is different, for whatever reason and neither the models or I suspect the model watchers, know how to handle it.

[Tom D]

The agreement between the models at +144 is good (GFS op and control very similar to the UKMO). Let's see what the ECM throws out.

[Guest North Sea Snow Convection]

Hello Dave - hope you are ok

I'm going to stick my neck out and suggest that the GFS 12z is not implausible at all into FI. The trough ends up in Scandinavia with height rises into Greenland and it might simply be the case that low pressure undercuts as the GFS suggests on this output which draws the Siberian/Scandi High westwards and then the trough sinks behind into Scandinavia as the High retrogresses across Iceland into Greenland. It doesn't necessarily follow that the Russian High has to sink south in order to get the trough across the UK and into Scandinavia.

The polar vortex has been very unstable all winter, and it just could be the case that the models are starting to backtrack with the strength of the vortex back over Greenland and more energy is going south again to undercut the high.

We shall see

[TEITS]

Back to the models and whilst the UKMO isn't a impressive as the GFS 12Z its certainly an improvement over recent runs.

In summary next week there is a fair chance of a snow event occuring. However what happens if the snow event via the SW tracking SE is anyones guess. Could turn milder or colder like the 12Z shows. Like I say fasinating model viewing at the moment.

[Bobby]

GFS ensemble average at +180

Quite different to the OP.

[Methuselah]

As I said yesterday (before I checked the bottom of my vodka glass) the remainder of the winter will be 'average' in 1960s terms... IMO, there will be further snow-events, before May is oot; but, there'll also be spells of mildness, wetness and general dreichness...That's the way it goes...

The models will (IMO) continue to chop-and-change - that's what models do???

[Duane S.]

Whilst I agree there are hardly tangible building blocks being laid which will likely evolve into a meaningful Easterly, the same could also be said of a mild outcome. I'm very interested to see how this will pan out for the 5-10 day period. I don't think it's a straight fight by any means, more like 75/25 in favour of the mild corner but we certainly cannot rule out (as some have already done) a cold outcome!

I think the GFS is a little too fanciful about the medium term BUT it's evolution of a large trough scenario over Scandinavia is, I think, going to become the main talking point in here in about a week's time as the timeframe edge closer. This has a fair bit of upstream support.

Oh and I've just opened my back door and seen this..

Should I invest in more themals??

Seriously though, that is excellent TEITS. These signs are often dismissed as old wives tales etc but I am a firm believer in all of that. My old grandad (a farmer when he was alive) would know what the weather was doing tomorrow far better than any TV weatherman would! Never convinced about the cows lying down = rain one though, more that they are just tired

Anyway, let's see what the ECM throws at us tonight!

[The PIT]

One of the best periods of model watching for a very long time. Since I joined in in Dec 2004 there hasn't been a battle like this once. High pressures all to easily brushed aside was the scenario. Didn't we once declare Scandi highs almost extinct???

A swing either way of not a very large distance could spell major event or major none event. If it wasn't for the strength of the lows the cold air would be coming back right now.

[Barometric]

Thanks for sharing your 'secret'. I love weather lore, think it is fascinating. Having lived in the country all 36 years of my life and coming from a family of farmers, I have heard pretty much all of them except that one!!

Back to the 12z and as was said earlier, tiny changes can produce huge differences in the end result. The models aren't really showing an awful lot different synoptically than they have over the last 48 hours, however a shift in just 300 miles west can make a huge impact on UK weather, especially when the continent is so cold right now. Also we have to factor in the rare beast that is the SH. Modelling such a rare event will have its problems especially when snow cover over almost the whole of Northern Europe is factored in.

Just as the MetO thought it was plain sailing they have another potentially interesting 7-10 days ahead of them and as a result the CF forecast will be 'interesting' if things continue along the 12z lines.

James

[TEITS]

One of the best periods of model watching for a very long time. Since I joined in in Dec 2004 there hasn't been a battle like this once. High pressures all to easily brushed aside was the scenario. Didn't we once declare Scandi highs almost extinct???

I agree pit. Personally im just enjoying the ride and putting aside my preferences. The difference between the 06Z/12Z is extrordinary and I don't think i've seen such a change in 6hrs. This doesn't mean the 12Z is right but it does mean the outlook is far from certain.

We're going to need the ECM to bring some consistency with this.

Edited January 15, 2010 by THE EYE IN THE SKY

[Methuselah]

Aye. I do hope you recover quickly, Dave.

Apologies, for being OT...

[Guest North Sea Snow Convection]

As the models come into the t120 area they are reducing the amount of energy thrown NE against the block and starting to disrupt it SE against it. Both GFS and UMO show this at t120. Both models for the last 36 hrs or so have been suggesting that the atlantic returns after t144. This is proof that they have so far been overcooking the estimated northern arm strength of the jet and vortex strength to the NW.

It is still conceivable that the block might be fully undercut by low pressure and this pushes an easterly further west into the UK. With suggestions of the AO going negative again it also gives cautious credence to the FI solution of GFS in terms of retrogressing the high to Greenland and dropping the trough into Scandinavia. It is just that the method is different (and colder) than the one outlined on the Strat thread for eg.

Edited January 15, 2010 by North Sea Snow Convection

[TEITS]

Unsurprsingly the 12Z was an outlier in F.I. However look at how some of the colder members are returning for 21st Jan.

http://charts.netweather.tv/ensimages/ens.20100115/12/t850Cambridgeshire.png

However in saying this its the operationals that will lead the way with this one.

Cheers Pete.

Edited January 15, 2010 by THE EYE IN THE SKY

[chionomaniac]

As the models come into the t120 area they are reducing the amount of energy thrown NE against the block and starting to disrupt it SE against it. Both GFS and UMO show this at t120. Both models for the last 36 hrs or so have been suggesting that the atlantic returns after t144. This is proof that they have so far been overcooking the northern arm of the jet and vortex strength to the NW.

It is still conceivable that the block might be fully undercut by low pressure and this pushes an easterly further west into the UK. With suggestions of the AO going negative again it also gives cautious credence to the FI solution of GFS in terms of retrogressing the high to Greenland and dropping the trough into Scandinavia. It is just that the method is different (and colder) than the one outlined on the Strat thread for eg.

And certainly not unfeasible, Tamara. It is as you say a different way of getting to the same end result but will depend heavily upon the exact positioning of the residual energy of the PV as the main body initially displaces to Eastern Siberia. Too much and the trough migrates eastward knocking over the block leaving the opportunity for NW height rises , too little and the block possibly retrogresses to Greenland. But somewhere in the middle leaves us where we are!

With the GFS being an outlier the first option still looks favourite!

Edited January 15, 2010 by chionomaniac

[sandstorm2]

Phenomenal charts in FI but with the recent chopping and changing its still in the lap of the weather gods. Is +96 FI? I think it is coming into the reliable timeframe, a few days ago I posted that the easterly would suddenly appear on our doorstep T +24.

Thank you for sharing your secret sign with us TEITS and I hope your health improves soon.

SS2

[Guest North Sea Snow Convection]

And certainly not unfeasible, Tamara. It is as you say a different way of getting to the same end result but will depend heavily upon the exact positioning of the residual energy of the PV as the main body initially displaces to Eastern Siberia. Too much and the trough migrates eastward knocking over the block leaving the opportunity for NW height rises , too little and the block possibly retrogresses to Greenland. But somewhere in the middle leaves us where we are!

Yes - I get the impression that the models are starting to perhaps try to redefine the balances of that energy as you suggest. Although the nowhere land continues to be a possibility, as well as proper atlantic return (in terms of discussing next week after the 'battle') there is the potential for some model chopping and changing over the next day or two I think, and we just could be looking at a different scenario to what may be currently assumed as the end product. Might still come to nought, but the possibility is very much there

Again, regarding the ensembles - I am very sceptical of these in the current situation. As I have said before they can all flock in one direction like lemmings overnight. How many times does it happen that the operational starts a new trend?

Edited January 15, 2010 by North Sea Snow Convection

[Geordiesnow]

Does look like that we are going to get some sort of continental air flow early next week, never all that cold until the shortwave/trigger low moves SE and brings in a slightly stronger flow for a brief while.

Interesting output and the battle is far from over.

[Tom D]

http://charts.netweather.tv/ensimages/ens.20100115/12/prmslLondonderry.png

http://charts.netweather.tv/ensimages/ens.20100115/12/prmslNorth~Lanarkshire.png

That's an outlier if I ever saw one!

[phil nw.]

The toing and froing between the Atlantic and Continental air continues to be modelled through the next week.

I think many of us realised before todays thaw set in that this wasn` t a straightforward return to Atlantic domination.

12Z GFS has made more of the colder return towards next midweek.

http://www.wetterzentrale.de/pics/Rtavn1201.png

http://www.wetterzentrale.de/pics/Rtavn1441.png

Extending it by a further day compared to prevoius output.

However as regards a snow event although the surface would be near freezing as the perc. moves in from the West dewpoints start to rise ahead of the rainband and this may scupper any chance of lying snow.

The ukmo is more in line with recent runs and minimises any return of the block.

http://www.wetterzentrale.de/pics/Rukm1201.gif

http://www.wetterzentrale.de/pics/Rukm1441.gif

All the recent Ens.have suggested something like a 2day dip in temps. around that timescale as the Block inches West a little and then retreats again.

GFS Ens.(Warks.)

2m temps. http://charts.netweather.tv/ensimages/ens.20100115/12/t2mWarwickshire.png Getting cold after midweek for 3days then milder again.

850hpa http://charts.netweather.tv/ensimages/ens.20100115/12/t850Warwickshire.pngtheop.-- a cold outlier midterm.

pressure. http://charts.netweather.tv/ensimages/ens.20100115/12/prmslWarwickshire.png Outlier after next week suggesting it`s on it`s own bringing the High closer.

[R.P. McMurphy]

The GFS 00z ensembles sum it up for me to be honest:

http://www.wzkarten...._London_ens.png

http://www.wzkarten...._London_ens.png

http://www.wzkarten....chester_ens.png

http://www.wzkarten....chester_ens.png

http://www.wzkarten....berdeen_ens.png

http://www.wzkarten....berdeen_ens.png

No sign of anything notably cold, and look at all those precipitation spikes, starting from tomorrow.

I don't think anyone can really say whats going to happen for sure. The models are changing within 6 hours!!! Seems like something different everytime. At the moment, It's the cold thats winning :blush:

[LomondSnowstorm]

And certainly not unfeasible, Tamara. It is as you say a different way of getting to the same end result but will depend heavily upon the exact positioning of the residual energy of the PV as the main body initially displaces to Eastern Siberia. Too much and the trough migrates eastward knocking over the block leaving the opportunity for NW height rises , too little and the block possibly retrogresses to Greenland. But somewhere in the middle leaves us where we are!

With the GFS being an outlier the first option still looks favourite!

None of these solutions look particularly mild, not even the third one to any large extent. This is a really interesting spell of model watching for an inexperienced poster like myself with so many slight changes on the models giving very different outcomes for the UK. Incredible to see this after an already fantastic winter, with weather and synoptics I've never experienced first hand before becoming almost everyday occurances. All eyes on the ECM 12Z, though this is still likely to prove inconclusive in the long run. Anyway, the GFS control run is quite interesting also, with a colder flow for eastern Scotland and it also comes very close to being a very cold run later on -

http://charts.netweather.tv/ensimages/ens.20100115/12/t850control-120.png

LS

[cooling climate]

Hello Dave - hope you are ok

I'm going to stick my neck out and suggest that the GFS 12z is not implausible at all into FI. The trough ends up in Scandinavia with height rises into Greenland and it might simply be the case that low pressure undercuts as the GFS suggests on this output which draws the Siberian/Scandi High westwards and then the trough sinks behind into Scandinavia as the High retrogresses across Iceland into Greenland. It doesn't necessarily follow that the Russian High has to sink south in order to get the trough across the UK and into Scandinavia.

The polar vortex has been very unstable all winter, and it just could be the case that the models are starting to backtrack with the strength of the vortex back over Greenland and more energy is going south again to undercut the high.

We shall see

From the northern hemisphere charts of the 12z GFS it looks to me that the easterly and Scandinavian heights are

bolstered by heights over the high Arctic moving south into the block.

Without this I think the block would have sank or retreated east.

[gottolovethisweather]

My obsession with E,lys started during the winter of 78/79 as the blizzards left a lasting impression as I was only 8yrs old. During my childhood days my Grandad would often tell me stories about 1947 and how the Siberian winds always brings heavy snow to this part of the world. Now my Grandparents used to say to me that during the winter if you see a mass of Seagulls this is a sign of the weather coming from Siberia. Apparently this is a well known saying in E Anglia.

Recently my mother informed me of a huge number of Seagulls in this area which I have also witnessed first hand. Now the combination of the model output showing a battle and the Seagulls is what makes me believe the E,ly is on its way. This has proved very accurate in the past especially prior to 1987 & 1991. However this time I have never seen so many in Peterborough!

What a chart this is!

http://www.wetterzen...s/Rtavn2402.png

Indeed, a lovely chart in what may well be a sign of things, so I was not so far out in my Bittern invasion theory either then. I wonder if the models should and subsequently the forecasters incorporate mass migration movements be it the wildebeest, painted lady butterflies, 260+ % increase in numbers of fieldfares n redwings etc. Nature has to react to conditions in their backyard and move ahead, also ultimately if the atmospehric conditions follow them it will eventually help them back to whence they came.

Now back to the models as I fear this will be binned, I must admit GFS 850's seqeunce did not look favourable for coldies when I looked earlier this pm. So gut feeling suggest the east may still see the beast for a few days and then raging zonality enevitable maybe a few days on down the line.

Off to measure the last of my snow cover.

Good discussions guys n gals.

STORMBOY

[Guest North Sea Snow Convection]

From the northern hemisphere charts of the 12z GFS it looks to me that the easterly and Scandinavian heights are

bolstered by heights over the high Arctic moving south into the block.

Without this I think the block would have sank or retreated east.

Yes - the Greenland arm of the vortex splits away towards Baffin and the other arm over Siberia drops south into Scandinavia

There are more members going more deeply negative on the AO forecasts once more. GFS onto something?

Edited January 15, 2010 by North Sea Snow Convection