Model Output Discussion

[Duane S.]

Thanks Phil

Yes the ensembles don't look too bad, having looked at those for eastern europe and Russia there is good support there for a very cold plunge, now the problem of how to back that cold westwards,its always a tall order!

Sometimes we see the coldest air miss the UK to the south but just going off the ensembles and overall pattern any high looks like being at least orientated favourably as we see very few much colder ensemble members for southern europe, so its a question of it extending far enough west. We have to bear in mind the amount of near misses in the past and so the success rate is low, i think more so with the Arctic high although the pay off is of course this brings the coldest possible air.

Yep, that's pretty much how I see it. Whenever cold air plunges southwards much more often that nor we miss out. The fabled true Arctic high sees us miss out even more so, but as you say, on the flip side, if we do get lucky when this rare beast delivers its payload, it would likely be the jackpot. High risk Arctic high, big payday or lower risk Scandi/surface high smaller dividends. I know which one I would plump for!

[Duane S.]

Also, whilst I do agree -AO does not mean the UK has cold weather, the forecast still is for this to drop through the floor. I really do expect to see many more decent Arctic high appearances over the coming couple of weeks or so on the charts. NAO still progged to drop further negative as well at present. I think we will see the charts take on a more promising appearance over the coming days.

[Eugene]

Tentative signs of the jet buckling later next week onwards as pressure builds from the south giving us some faux cold, mid to late december IB's christmas pudding winter forecast might go t*ts up, lets hope so

[osmposm]

Just when you thought it was safe to go back in the water....the beast is back (but never seems to get any closer in time, alas).

Edited December 3, 2009 by osmposm

[VillagePlank]

The cold run still looks like a cold outlier, to me; which is a shame. The best, at this stage that we can hope for is for a run of negative temperatures at 850hPa starting on the 14th Dec; however the below -5 850hPa are now within one standard error between the 15th onwards which is encouraging.

Still FI, though, so usual caveats apply

(This is the first season where I've seen standard error and a min/max range applied to ensembles. I think it will be interesting to see if it makes a difference when looking out at FI. In theory, it should ...)

EDIT: It might be worth mentioning what this 'standard error' business is. Essentially standard error is the same as 1 standard deviation. This is the green bars around the red mean.

This means, colloquially, that 68 times out of 100, what occurs will occur within those green bars. The odds on favourite, in fact. It's a shame that it doesn't go as far as 1.96 std-dev: that would be 95 out of 100, which means that we would almost certainly know the temperature range of FI forecasts (likely to be a large range!)

Edited December 3, 2009 by VillagePlank

[Frosty.]

A fair attempt by the GFS 00z to give the coldies something to smile about this morning, a large anticyclone building to the northeast in FI drawing very cold air towards the uk so at least we would have a frosty settled spell but probably not the snow showers. There are big differences between the gfs & ecm at T+240 hours with the ecm very unsettled throughout the run whereas the gfs 00z shows high pressure pushing north across the uk with some inversion cold resulting but for the next 6-8 days it looks like remaining unsettled with the north being generally a bit colder than the south and the south does look like being fairly mild for a time next week.

[Nick F]

Still encouraging to see the +ve heights over the polar region to our N in the 00z 8-10 day H500 comparisons, this still supports the shift southwards of cold pools and the PV for once not making home over Greenland:

The trouble is, will that cold air that sinks S into Nern Russia back west sometime this month? We really need the Atlantic jet to play ball to get that cold air to retrogress, a difficult task for us at the end of the Atlantic conveyor.

One thing seems more certain though, the trough looks like sitting just to our west until mid month at least and perhaps beyond too, so northerlies look very unlikely - so we need to look east for cold prospects. 00z GFS FI satisfies us once again in that respect.

[Rollo]

Worth remembering that we had to wait until the 26th December in 1962 — I can't remember what the autumn or first few weeks of December was like, so it was probably unremarkable. I do remember as an 11 year old staring through the french windows on Boxing Day evening and watching the first of the snow that was going to last until 8th March 1963.

For your information,Up North we had snow for 3 or 4 days in November 62' after a mild wet October,regrettably a winter like that seems a million miles away.

[cooling climate]

Model output this morning is a lot more positive with height rises to our north which

as Steve Murr, myself and one or two others have said is the first and most important

stage to a much colder pattern for the UK and Europe.

UKMO is actually my favorite with a niece clean split of the vortex allowing heights to

readily build to the north.

Stage two of where the main heights will build will develop over the next couple of days

or so and the rest is just detail which will take several days perhaps for the models to work

out.

Hopefully the models will continue this positive trend towards a much much colder outlook.

[weather eater]

As I expected the GFS has another stab at the easterly, the ECM is not keen this morning. I do think this will come and go over the next few days as the models try to get to grips with further evolution, we shall just have to wait and see.

[TEITS]

Well im very pleased with this mornings outputs. Some of the models continue to suggest blocking developing to our N from around +240 onwards.

The most interesting chart is the Iceland SLP ensembles.

http://charts.netweather.tv/ensimages/ens.20091203/00/prmslReyjavic.png

Compared to a few days ago there seems to be more members going towards pressure rising in this area. A few days ago there was huge scatter with 50% suggesting a deep icelandic LP system.

Now compared to a few days ago im probably less confident that a severe cold spell will reach us. However I still remain convinced that N blocking will develop around mid month and a bitter cold aitmass will push S out of the arctic. The question is will this cold airmass then move S,SE,SW,W.

[nick sussex]

Overall this morning the pattern looks a stalemate with the Atlantic never allowing a chance for high pressure to edge sw'wards, the ecm is a disappointment in that it shows an elongated trough running sw/ne to the north of the uk.

The gfs slightly better, the gem maps a plausible scenario with trough to the west and pressure rising from the south, also pressure building sw'wards from the ne, i'm beginning to think that this might be a way out of the current stalemate.

http://www.wetterzentrale.de/pics/Rgem2401.html

Often the euro high can be seen as a negative but i feel we might need it's help to move forward.

Edited December 3, 2009 by nick sussex

[Turnedoutniceagain]

Just when you thought it was safe to go back in the water....the beast is back (but never seems to get any closer in time, alas).

Looks like the mythical Feb' 05 "Beast of Beasts" that came so tantalisingly close.

(still in therapy from that one - *sob*)

[Guest North Sea Snow Convection]

I think overall that there are just starting to show tentatively better signs of the Gulf Stream shutting down the trough to the west backing off just a little, allowing pressure to rise a little over western europe as well as pushing down from the arctic (which is the most important thing).

It is quite conceivable that an initial euro high type situation could become a much colder one as any ridge is absorbed from the north, much as the winter in 1947 began. Of course I am saying it is going to happen, I am not saying it is going to happen but this looks to me like the best opportunity so far for a change in the weather for a winter long freeze the better.

[pyrotech]

Well im very pleased with this mornings outputs. Some of the models continue to suggest blocking developing to our N from around +240 onwards.

The most interesting chart is the Iceland SLP ensembles.

http://charts.netweather.tv/ensimages/ens.20091203/00/prmslReyjavic.png

Compared to a few days ago there seems to be more members going towards pressure rising in this area. A few days ago there was huge scatter with 50% suggesting a deep icelandic LP system.

Now compared to a few days ago im probably less confident that a severe cold spell will reach us. However I still remain convinced that N blocking will develop around mid month and a bitter cold aitmass will push S out of the arctic. The question is will this cold airmass then move S,SE,SW,W.

I agree with all that you posted, but must emphasise that the trend all the models are hinting at is what any cold hunters are looking for.

The GFS, ECM AND ASSMBLES all hint at blocking although still in Fi. The good news is they are all playing with this ideas so although timing is in question, the likely hood is increased.

How far south west this cold air comes is another matter, but surely everyone agrees that the best foundation block that we can get for a prolonged cold spell is for Europe to cool significantly. A northerly for the UK is normally too short lived and an easterly is the best for prolonged deep cold.

Too me this is what is needed for a better chance of cold snowy weather and although the GFS in fi is really the only one showing what we want to see in Fi for the UK , they all show the likely hood of Europe GETTING MUCH COLDER, which is the first positive step.

Models will struggle as too many factors iE EL NINO V SOLAR MINIUMUM. The models have never had to account for a prolonged solar minimum before which is why many parts of world have recently had record cold temperatures. It takes the human touch to add this effect.

Fi is just that and overexcitement over any chart beyond 72hrs just silly, but trends by models are a little better even well into Fi, Maybe not for uk just yet but the foundations are likely for step 1, very cold europe

[chionomaniac]

I think overall that there are just starting to show tentatively better signs of the Gulf Stream shutting down the trough to the west backing off just a little, allowing pressure to rise a little over western europe as well as pushing down from the arctic (which is the most important thing).

It is quite conceivable that an initial euro high type situation could become a much colder one as any ridge is absorbed from the north, much as the winter in 1947 began. Of course I am saying it is going to happen, I am not saying it is going to happen but this looks to me like the best opportunity so far for a change in the weather for a winter long freeze the better.

You still having trouble with that computer of yours, Tamara!

[Reefseeker]

I think overall that there are just starting to show tentatively better signs of the Gulf Stream shutting down the trough to the west backing off just a little, allowing pressure to rise a little over western europe as well as pushing down from the arctic (which is the most important thing).

It is quite conceivable that an initial euro high type situation could become a much colder one as any ridge is absorbed from the north, much as the winter in 1947 began. Of course I am saying it is going to happen, I am not saying it is going to happen but this looks to me like the best opportunity so far for a change in the weather for a winter long freeze the better.

I'm a fully paid up lurker, never post, but love following your discussions on here and have learnt a lot after a year of so of reading what you all say (although A LOT of it is hard to follow without a lot of thinking and reading). I love this post from Tamara: Let's hope the stuff under the lines comes true More below the line stuff please....

[TEITS]

So far the 06Z is rather different to the 0Z. The LP system is much further E at +162 just off the W coast of Scandi. Whereas the 0Z had this sitting to the W of Iceland!!

Such changes within the reliable timeframe makes what happens after pretty pointless to be honest.

[nick sussex]

Quite a departure here from the general model output with the gfs 06hrs run being much more progressive with the pattern, most guidance suggests the trough remaining slow moving near or to the west of the uk.

I wonder if this has something to do with the MJO perhaps moving more quickly through phase 7 and perhaps strengthening more than initially thought by the models.

What we don't want is the trough right over the uk, so we want the models to either edge this west or do as the gfs 06hrs run is doing this morning by pushing this eastwards.

Edited December 3, 2009 by nick sussex

[Guest North Sea Snow Convection]

You still having trouble with that computer of yours, Tamara!

For some reason the graemlin is only on the n-w website, all others work fine!

Looks like the latest GFS is doing what the afternoon output usually more progressively does.

I'm a fully paid up lurker, never post, but love following your discussions on here and have learnt a lot after a year of so of reading what you all say (although A LOT of it is hard to follow without a lot of thinking and reading). I love this post from Tamara: Let's hope the stuff under the lines comes true More below the line stuff please....

Welcome along Reefseeker

There are some good experts to learn from on here

[Cecil Hogmanay Melchett]

I feel very deflated by the outputs again this morning!

Yes its only the 3rd of Dec but we really are stuck in the most awful rut and i just cant see a way out

of it at the moment.Fingers crossed things improve after the first week of Dec,but thats just an aspiration

in my eyes.Cold charts remain firmly in FI,and even their number have decreased on gfs ens.

[D KARLSON]

Although the models are stuck in a rut at the mo ,this is not our typical souwesterly pattern as we still have blocking to our east and northeast which is stopping the progress of our low pressure systems and there does seem a lot of uncertainty in the models past the 140 hour mark with regards to how this pressure is displaced or not as the case may be.

As always you never really see a proper cold outbreak coming ,but perhaps there may be a bite at the cherry from this current set up as i dont think the models are handling this hgh pressure very well or the atlantic for that matter ,one to keep an eye on this although it may take 2 weeks to resolve or just a break in the atlanitc to allow other factors to play in ,possible cold spell for christmas !!!!!!!!!

[stewfox]

Fi is just that and overexcitement over any chart beyond 72hrs just silly,

For cold lovers on here maybe. However the BBC and papers always seem to predict the next 5./6 days i.e. up to T144 with a good degree of accuracy.

[weather eater]

Such changes within the reliable timeframe makes what happens after pretty pointless to be honest.

A good point Dave, overall the 06z looks rather more plausible to me, but this is going to run and run lots more options to come I think.

[Turnedoutniceagain]

For cold lovers on here maybe. However the BBC and papers always seem to predict the next 5./6 days i.e. up to T144 with a good degree of accuracy.

Apart from the D'Express, which has new "Ice-age" warnings out every 2 weeks in the winter !!