Model Output Discussion

[MR EXTREMES]

http://www.wetterzen...cs/Rukm1441.gif

UKMET in....

not bad at all

Steve

nice chart as long as the low pressure system steaming across south of green land towards us,

does not shunt our high pressure out the way.

but at the same time if it did come up against us if cold enough could be a battle ground setup so not all bad.

00z's horrid massive pressure outlier, coldish outlier, GEFS control mild all through, no cold ensembles, I wouldnt be surprised if the settled spell only lasted 3 days, and back to unsettled on 14th

this is what ive been thinking maybe a few day event.

but still its a start and regardless cold in europe is very good news the longer it sticks around the better.

Edited December 6, 2009 by badboy657

[MR EXTREMES]

sorry this fax looks pretty ugly.

[disco-barry]

They usually only are ever 3day events anyway, wrong country for prolonged spells of cold. Rare.

[Eugene]

LOL.....Well for starters that is last nights T+120 hrs fax and secondly its in line with what models are showing for that timeframe before HP ridges northwards like on most models this morning

[snowfish]

LOL.....Well for starters that is last nights T+120 hrs fax and secondly its in line with what models are showing for that timeframe before HP ridges northwards like on most models this morning

Yes, coffee is required! looking good I'd say...let's hope that the next runs show all the models in agreement with each other - that would be nice!

Edited December 6, 2009 by snowfish

[Eugene]

00z's horrid massive pressure outlier, coldish outlier, GEFS control mild all through, no cold ensembles, I wouldnt be surprised if the settled spell only lasted 3 days, and back to unsettled on 14th

Good models this morning, ECM, UKMO and GFS all showing HP taking over just to our northeast and are obviously the best three models so are the ones to side with, even on TWO they are optimistic of some low level cold by T+144 hrs onwards and so am i

[nick sussex]

The ecm freebie info today is all 50 ensemble members upto 168hrs and these have quite a few colder scenarios.

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2009120600!!/

[MR EXTREMES]

LOL.....Well for starters that is last nights T+120 hrs fax and secondly its in line with what models are showing for that timeframe before HP ridges northwards like on most models this morning

yeah i agree and i did think this myself after i posted so this to is a step in the right direction.

[Shiny_Bottom_1]

Agree with Eugene, Badboy. It is not showing anything that wasn't already being projected by the big models.

Some advice on viewing the ensembles when watching for this potential cold spell.

Those who read my posts know that I don't dismiss FI. In fact, I don't buy in to the term...I just see it as a probability chart.

Anyway, mid to long term, which is the time frame we are looking at, the key is to ignore the 850's/2m temps for the moment. Focus on the pressure ensembles, as these will give the best accuracy of all in terms of what we are looking for.

We know that the high pressure will be close by, potentially feeding us the cold air. Position, orientation, and shape of this high are going to be crucial.

If you see the pressure ensembles start agreeing more in terms of pressure rise, it is the first key. As this moves more from long range into the mid range (lets say for example, T+120-T+240) then start to look more so at the 850's, but keep a close eye still on the air pressure.

We need the agreement here first before making judgement on whether the cold will hit us or not.

You then need air pressure and 850's starting to agree in the above time frame to increase the probability, and then as you get in to the <T+120 time frame, detail can then start to be analysed with more confidence.

Then, if you want to look for snow (you need the cold first remember!), then I would advise the best time frame to make a judgement on that is <T+96.

Those who have seen the 00z air pressure ensembles from the GEFS will see that the agreement is not there for a pressure rise. However, there is also not an agreement on the pressure to remain low. Its quite a scatter this morning, which when looking at the potential both systematically and from a probability point of view, I would still not give any confidence that it will go either way at the moment.

Previous runs have shown the potential, which should offer some hope.

Either way, some warmer weather on the way next week. No what we want, but time frame left for wintry weather is so long, its not really worth worrying about.

The ecm freebie info today is all 50 ensemble members upto 168hrs and these have quite a few colder scenarios.

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2009120600!!/

Thanks Nick. Quite amazing how many, whilst not over the UK, have the cold weather (-6oC Isotherm) not a million miles away.

[nick sussex]

The extended ecm ensembles show a change from yesterday with milder members diminishing. For days 8-10 the operational run was one of the mildest.

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

I think the ecm ensembles are run at a higher resolution than the gefs and this might explain why the ecm is much more bullish about something colder, shortwaves are difficult to model and the higher resolution might make the difference.

Edited December 6, 2009 by nick sussex

[TEITS]

Well after yesterdays disappointment we start today with an improvement with the UKMO at +144 being the best chart for this timeframe. However there is so much uncertainity in what happens afterwards and the 3 outcomes I mentioned yesterday all remain possible.

At the moment the most likely outlook in my opinion is we might miss out on the true beast but some E/SE areas might just tap into -5/-10C upper temps. Now whether the energy goes under the block or over the block in F.I remains uncertain. In my experience the models in F.I will always try and blast any blocking away and have a tendancy and moving this energy NE rather than SE. If we are to see LP systems undercutting our blocking then this won't be modelled until its within the reliable timeframe.

The pick of the charts today is most certainly the GFS parallel run.

http://91.121.94.83/modeles/gfsp/run/gfs-0-252.png?0

[Duane S.]

00z's horrid massive pressure outlier, coldish outlier, GEFS control mild all through, no cold ensembles, I wouldnt be surprised if the settled spell only lasted 3 days, and back to unsettled on 14th

Ah well, that's that then.

I suppose it's all about your take on things. If you go looking for positives you will find them, if you go looking for negatives they are there too. In all honesty we probably need glass-half-empty posters like yourself to keepmost members' feet on the ground at times like this.

I think it's a small step forward in terms of the fact we are another day on and there have been no significant downgrades, certainly no major upgrades but every day that passes by that shows a potential cold scenario getting closer increases the chances of something happening.

Although, expect to get very frustrated with that Euro high before it finally produces something a few days before Xmas.

[Cloud 10]

The extended ecm ensembles show a change from yesterday with milder members diminishing. For days 8-10 the operational run was one of the mildest.

http://www.knmi.nl/e...agse/index.html

I think the ecm ensembles are run at a higher resolution than the gefs and this might explain why the ecm is much more bullish about something colder, shortwaves are difficult to model and the higher resolution might make the difference.

yesterday today

Quite a big change from yesterday.

A very promising start this morning from the models,lets see what the 06z throws at us.

[snowfish]

Well after yesterdays disappointment we start today with an improvement with the UKMO at +144 being the best chart for this timeframe. However there is so much uncertainity in what happens afterwards and the 3 outcomes I mentioned yesterday all remain possible.

At the moment the most likely outlook in my opinion is we might miss out on the true beast but some E/SE areas might just tap into -5/-10C upper temps. Now whether the energy goes under the block or over the block in F.I remains uncertain. In my experience the models in F.I will always try and blast any blocking away and have a tendancy and moving this energy NE rather than SE. If we are to see LP systems undercutting our blocking then this won't be modelled until its within the reliable timeframe.

The pick of the charts today is most certainly the GFS parallel run.

http://91.121.94.83/...gfs-0-252.png?0

TEITS

A superb chart - would be nice to see that materialise - and tbh it has been shown on the charts for a good few runs to date... fingers crossed! :excl:

[Lewis]

Hi,

Sorry mods if this is off topic,

but can anyone let me know which model has been the most consistent with outputting colder conditions in FI, the GFS too me has been rather inconsistent, is it the ECM?

Regards

Lewis

[Shunter]

Interesting update from Joe B******* over on Accuweather.

Seems our potential cold spell is attracting interest from the US.

Apologies but I could not get the link to work properly.

Edited December 6, 2009 by Shunter

[Duane S.]

Interesting update from Joe B******* .......

http://www.accuweather.com/ukie/laminate floori-europe-blog.asp?partner=accuweather

Seems our potential cold spell is attracting interest from the US.

Due to the swear filter that link won't work.

The best bet is to go to http://www.accuweather.com/ukie/index.asp

and click on the 'Check out Joe's European Column' link on the left hand side

[cooling climate]

Encouraging signs as heights and WAA building further west at t108.

[Guest North Sea Snow Convection]

The first good news is that this dreadful stormy unsettled south westerly spell is finally very shortly coming to an end - that in itself is very well received by me whether we get a cold spell as such or not.

Secondly, the UKMO model is often the one that says 'nyet' to seemingly promising cold spell situations and this morning it has a very nice t144 chart indeed - the best of the three main models. Of course it doesn't guarantee anything, but taking into account the overall picture in regard the splitting vortex and -AO etc it is a perfectly feasible one. We should remember that the pattern is being moved west at this time, so the usual expectations of surplus energy coming off the main vortex area should apply less than has been the case. In that respect it is not unreasonable to expect the models to be too progressive with this energy, and indeed we have seen a step back from that this morning. Another reason to give some credence to high pressure being able to set up in the Icelandic/Svalbard region.

All this is still several days away, so of course a cold spell is not a certainty by any means - but at the very least there is going to be an advection of arctic air souhwards and westwards across Europe, and very close to us, at a time when in so many recent years it has been a long way off bottled up in the arctic. That makes all other developments during December that bit more interesting still.

Edited December 6, 2009 by North Sea Snow Convection

[Lewis]

its ok having an easterly, the metoffice have mentioned it in there further outlook, and they just state, "becoming cold and dry with a cold easterly air flow". That to me sounds like sharp frosts by night, chilly by day and nice and dry.

I cant remember the last time an easterly brought snow.

Its either dry cold air, or damp squibble.

Lewis

[Gowon]

Interesting update from Joe B******* over on Accuweather.

Seems our potential cold spell is attracting interest from the US.

Apologies but I could not get the link to work properly.

His European winter forecast which was done in early November, might be spot on.

[TEITS]

I cant remember the last time an easterly brought snow.

Its either dry cold air, or damp squibble.

Lewis

The last time was actually this year for some areas.

http://www.wetterzentrale.de/archive/ra/2009/Rrea00120090202.gif

[Lewis]

The last time was actually this year for some areas.

http://www.wetterzentrale.de/archive/ra/2009/Rrea00120090202.gif

Oops, thanks for making me reminisce :excl: I got a few cm from that.

lewis

[weather eater]

Can anyone give me a quick update on the model runs since the 06z on Friday, had to go to Norwich on Friday and London on Sat so haven't seen any runs until this mornings 00Zs. These both seem to want to go with some kind of easterly, has been the general theme.

[Harsh Climate]

On the GFS 00z the big spoiler clearly is that low pressure developeing near iceland and pushing east over northern scandanavia, making it very difficult for heights to to develope in that area thus pushing the high south...

http://www.wetterzentrale.de/pics/Rtavn1681.png

The problem is, with the potential cold spell being so far out there is plenty of time for one of them spoilers to develope.. :excl:

Its either guna go 1 of 4 ways:

1. The most likely scenario is we get a scandi high develope just too far south, giveing france/germany/eastern spain a cold easterly while we miss out

2. The next most likely scenarion, greece, bulgaria, romania get our cold/possible snow.

3. nothing really happens and it gets gradually colder in eastern europe while we endure murky dry conditions.

4. things go our way and we get a cold easterly!

Edited December 6, 2009 by Jed Bickerdike