Model Output Discussion

[bluearmy]

the continental flow is coming. the strength of it by T180 will depend on where the blocking is centered and its orientation. by day 10 it will be strong though - whether it comes a bit faster is dictated by the shortwave activity off the easern seaboard.

the trend from the nwp this morning is to send more enegy south which just adds to the possibilities by mid feb. i think part 3 will be better than parts 1 and 2 - the continent will be snow covered east of south and the north sea SST's are lower.

[Lewis]

The last time I looked Lewis it hadn't even occurred yet!

T72 and within is reliable time frame, heres the 12z on the 26th;

Compare;

06z Today

26th 12z

Quite a difference if you ask me, as we get closer to the time frame, it downgrades...

Edited January 28, 2010 by Storm Force Lewis

[Southender]

I have rarely seen such an extensive cold pool over Central Europe as is projected in GFS 06z FI - This pool has escaped direct from the Artic - I think now that some sort of Easterly is on the cards - it's a matter of fine tuning

Yeah, looks like part of the PV has gone walkies!

Let's hope..

[chionomaniac]

T72 and within is reliable time frame, heres the 12z on the 26th;

Compare;

06z Today

26th 12z

Quite a difference if you ask me, as we get closer to the time frame, it downgrades...

That is a longer term upgrade if you look at the WAA into Greenland.

Any way it is good to see that the pattern suggested by the ECM lower stratospheric charts this morning has been played out to T+240 by the 06Z GFS.

Edited January 28, 2010 by chionomaniac

[snowmadchrisuk]

That is a longer term upgrade if you look at the WAA into Greenland.

Any way it is good to see that the pattern suggested by the ECM lower stratospheric charts this morning has been played out to T+240 by the 06Z GFS.

Yes the -5's that were over Greenland are now 0 deg at 850mb . I would still say the second week of Feb is likely to have a cold to very cold flow , either from the North / North East or East.

[Guest North Sea Snow Convection]

The models have continued their evaluation of the energy distribution, especially wrt to the MMW. They may now be picking up on the downwelling negative zonal wind anomalies (easterlies) as well as pinpointing the displacement (another splitting?) of the polar vortex. All of this is bound to create model uncertainty and hence the colder and then milder model solutions we have been seeing. Mainly in the operationals.

On this basis the very good analysis that has been going on this morning by Dave (TEITS) Nick F and others lends a lot of credence for looking at the model output in FI. There are very good reasons for believing that an easterly is possible by about the second week of Feb or so and no hopecasting on the basis of looking several days out can be levelled at anyone in this respect.

In terms of other possible outcomes, these too have been much discussed in recent days. This again comes back to the jet stream energy which has see-sawed in the modelling and yesterday the models were suggesting greater emphasis on the northern branch - hence high pressure perhaps being closer to the UK as an outcome.

An easterly is quite likely imo, with the patience required to wait for several days. Assuming this is what happens - the type (ie dry frosty/ convective snow showers) is not going to be known for an even longer time until the trend is completely fleshed out.

Edited January 28, 2010 by North Sea Snow Convection

[NorthantsSnow]

A better easterly on the 06z that would be potent enough to bring UK wide snow showers. Still FI though. Not going to be very sustained however if the block immediately heads east.

As others are saying however the building blocks are encouraging early on. The detail beyond that will change. Overall then, the chances of a cold snowy easterly occurring in early Feb have increased to about 20%. But it might be shortlived.

[full_frontal_occlusion]

T72 and within is reliable time frame, heres the 12z on the 26th;

Compare;

06z Today

26th 12z

Quite a difference if you ask me, as we get closer to the time frame, it downgrades...

Surely the model evolution within the nearfield is a direct consequence of realtime data accuracy? Each new timestep compounds the errors but from your example - given the positioning of all the high and low centres, 850 distribution, heights etc - the limited error differences between those charts is pretty impressive.

ffO.

[Polar Continental]

Yep quite agree, including the northern hemisphere charts. The high to the northeast is the dominant

force and it is this that is dictating the pattern. IE where shortwaves and lows move etc, also on the

t150 northern hemisphere charts the Siberian high is pulling much colder air into its circulation.

Mm, the charts are becoming very interesting. It does seem that the Siberian high is now so powerful, that its become in effect an easterly bull dozer, what happens upstream to the west is probably not so important now, because this high is just going to keep on pushing westward with relentless force. What happens after?, that I will leave to the imagination?

[TEITS]

Excellent 06Z GEFS mean at +168.

http://91.121.94.83/modeles/gens/run/gens-21-1-168.png?6

If we can get this at +72/96 with agreement from all models then the Siberian express is on its way. Even if the cold pool is expected to arrive a few days later.

[Frosty.]

Beyond the Northerly it looks like nerve shredding times ahead next week with the bitterly cold airmass over northeast europe edging southwestwards towards the uk but will we feel the full force of it or just a glancing blow, I much preferred the GFS 00z to be honest because the 6z makes more of a meal of getting there and struggles to maintain it. Looking at all the output though, a very good chance we will tap into that very cold air building up to the east but the middle of next week looks like the crunch period for us.

Edited January 28, 2010 by Frosty039

[Alister]

I have rarely seen such an extensive cold pool over Central Europe as is projected in GFS 06z FI - This pool has escaped direct from the Artic - I think now that some sort of Easterly is on the cards - it's a matter of fine tuning

The Alps are really starting to see the cold air move in!

[Guest North Sea Snow Convection]

Mm, the charts are becoming very interesting. It does seem that the Siberian high is now so powerful, that its become in effect an easterly bull dozer, what happens upstream to the west is probably not so important now, because this high is just going to keep on pushing westward with relentless force. What happens after?, that I will leave to the imagination?

Morning Paul

I suspect that the extra early development of the eurasian snow cover was one of the main triggers for the eventual strength and backing westwards of the high further than usual - in tandem with the favourable NH atmospheric conditions that have allowed stable high latitude blocking such as we have seen so much this season. No surprise that there has been such a strong -AO feedback with all these factors and very extensive snow over over so many parts of the NH. This has not been seen for some time and we are being reminded quite emphatically what can happen as a result.

The Siberian/Scandi High has been allowed to play a role she hasn't been able to since the 60's,70's and 80's

Edited January 28, 2010 by North Sea Snow Convection

[TEITS]

Morning Paul

I suspect that the extra early development of the eurasian snow cover was one of the main triggers for the eventual strength and backing westwards of the high further than usual - in tandem with the favourable NH atmospheric conditions that have allowed stable high latitude blocking such as we have seen so much this season. No surprise that there has been such a strong -AO feedback with all these factors and very extensive snow over over so many parts of the NH. This has not been seen for some time and we are being reminded quite emphatically what can happen as a result.

Spot on Tamara.

The lack of snow cover has been a factor in recent winters wrt to the Siberian HP.

The GEFS mean continues to be very consistent.

http://91.121.94.83/modeles/gens/run/gens-21-1-216.png?6

Longer term it seems that pressure builds around Greenland and we see LP systems tracking into S Europe especially into Spain.

[chionomaniac]

Morning Paul

I suspect that the extra early development of the eurasian snow cover was one of the main triggers for the eventual strength and backing westwards of the high further than usual - in tandem with the favourable NH atmospheric conditions that have allowed stable high latitude blocking such as we have seen so much this season. No surprise that there has been such a strong -AO feedback with all these factors and very extensive snow over over so many parts of the NH. This has not been seen for some time and we are being reminded quite emphatically what can happen as a result.

The Siberian/Scandi High has been allowed to play a role she hasn't been able to since the 60's,70's and 80's

Yes T, It is good to see that these factors that we played around with in Autumn and suggested could play an important part in the winter have already done so. There were some ( and a bit of me included!) that thought that we could be talking about how the El Nino has ruined winter so far, but the opposite is true. And I have a sneaky feeling that this MMW is going to produce the goods. If you look back propagation is better in winters that have already had good blocking spells.

[Polar Continental]

Morning Paul

I suspect that the extra early development of the eurasian snow cover was one of the main triggers for the eventual strength and backing westwards of the high further than usual - in tandem with the favourable NH atmospheric conditions that have allowed stable high latitude blocking such as we have seen so much this season. No surprise that there has been such a strong -AO feedback with all these factors and very extensive snow over over so many parts of the NH. This has not been seen for some time and we are being reminded quite emphatically what can happen as a result.

The Siberian/Scandi High has been allowed to play a role she hasn't been able to since the 60's,70's and 80's

Hi Tamara,

Yes indeed, reading through some of my old books from the 60s and 70s, Gordon Manley talks extensively about the great Siberian anticyclone making at least one appearance, during most winters to our shores, usually during February.

Sadly, as we all know, that scenario died many years ago now, but this winter has been special and a throw back to those times.

In my opinion we will see the models continue to project this easterly now, the ECM I am sure will be much improved regarding the easterly tonight.

Edited January 28, 2010 by Polar Continental

[weatherjunkie]

0z GEFS NAO Outlook

Similar to the 18z run, and a little more robust than the 12z run.

[BLAST FROM THE PAST]

Anyone getting the idea that we are about to see model cold/blocking upgrading next few days? I don't even think Monday on is sorted yet.

BFTP

[cooling climate]

Hi Tamara,

Yes indeed, reading through some of my old books from the 60's and 70's, Gordon Manley talks extensively about the great Siberian anticyclone making at least one appearance, during most winter to our shores, usually during February.

Sadly as we all know, that scenario died many years ago now, but this winter has been special and a throw back to those times.

In my opinion we will see the models continue to project this easterly now, the ECM I am sure will be much improved regarding the easterly tonight.

Have to agree with the last bit especially. The models seem to be getting to grips with the residual troughing over

Scandinavia and I am quite sure we will start to see some really mouthwatering charts over the coming days with

cries of 87,47 the next ice cometh etc lol.

[TEITS]

Anyone getting the idea that we are about to see model cold/blocking upgrading next few days? I don't even think Monday on is sorted yet.

BFTP

Interesting you say that Fred.

I was just thinking to myself that normally the GFS has a tendancy of underestimating blocking. Yet here we are with the GFS/GEFS being very bullish with regards to blocking.

I wiah the ECM would stop messing around though!

[Bobby]

GFS ensembles aren't as good as last night... any easterly seems to be pushed further back and/or downgraded and generally less support. Still some support though, such as this chart.

It looks a messy picture though.

[Joe Bloggs]

00z ECM ensembles for London

http://www.meteogroup.co.uk/uk/home/weather/services/ensemble_forecast.html

Still look rather promising to me.

[Severe Siberian icy blast]

It seems to me once again ppl are looking for detail , the trend is a bitter easterly by next wkend and has always ben , the 06z is an upgrade if we'r looking for very col heavy air , -15uppers never far away from the east and most the country under -12/13 , which would bring heavy snow to many .

Its all to play for and this feb will be one to remember .

[stewfox]

00z ECM ensembles for London

http://www.meteogrou...e_forecast.html

Still look rather promising to me.

Yes as we know nothing mild in the reliable time frame or even into extended F1

I think what we are seeing is ‘cold’ its always relative into next week max 3/5c CET zone , we get a further drop in F1 Feb 5^th onwards

Nothing really cold in the early /mid time frame

[Severe Siberian icy blast]

A better easterly on the 06z that would be potent enough to bring UK wide snow showers. Still FI though. Not going to be very sustained however if the block immediately heads east.

As others are saying however the building blocks are encouraging early on. The detail beyond that will change. Overall then, the chances of a cold snowy easterly occurring in early Feb have increased to about 20%. But it might be shortlived.

Your lookin at the wrong chars then , il put money on a sustained bitter easterly and a snowy feb . The signs are there .

Edited January 28, 2010 by shaun wilmer