Model Output Discussion

[Nick F]

These small changes on a global scale make a big difference, chance now for some snow as the fronts try and push eastwards.And now because of this the ridge is further west with low pressure to the south, this forces some disruption to the trough with another shortwave heading se'wards.

This is a very good example of such a small feature much earlier causing a massive domino effect. It's the gfs so i'm not going to overplay this but certainly adds to the interest for next week.

Really? I agree that shortwave on the 12z GFS looks more favourable to bring snow across the UK as it shoots SE and drags in colder air with the precipitation. But with regards to a small surafce feature causing a massive domino effect, I disagree, as the Altantic is shown again to kick back in with mider air flooding back in and the colder air getting pushed back. I don't think the shortwave will have a great enough effect on altering the upper flow to stop the Atlantic from taking over into the medium range, unless something changes with the flow upstream over the Atlantic, i.e. Atlantic trough becomes negatively tilted and allows upper flow to undercut the block to the NE. No sign yet of that occring from NWP.

[PB22]

I suspect that after a quiet day, the coldies will be back in force tonight after the GFS and UKMO 12z runs!

UKMO T+120:

Shows what a knife edge situation next week is, and it will be interesting to see the ensembles later.

[winterof79]

slowly but surely, realism seems to be settling over this thread. there really is no indication of the russian high exerting its influence over us re deep cold apart from hopecasting. now hopecasting will be right every now and again but i think a few are hanging onto this block by their fingernails, desperate to pull it in our direction. doesnt look like its coming, looking at all available output. i see BF has, like GP, seen the same indicators that the trough may get to our east by the back end of Jan.

GFS 12z saysUKMO 12z says

Edited January 15, 2010 by winterof79

[PB22]

Really? I agree that shortwave on the 12z GFS looks more favorable to bring snow across the UK as shoots SE and drags in colder air with the precipitation. But with regards to a small surafce feature causing a massive domino effect, I disagree, as the Altantic is shown again to kick back in with mider air flooding back in and the colder air getting pushed back. I don't think the shortwave will have a great enough effect on altering the upper flow to stop the Atlantic from taking over.

I'd concur, merely delaying the inevitable I'd suggest.

[TEITS]

Really? I agree that shortwave on the 12z GFS looks more favorable to bring snow across the UK as shoots SE and drags in colder air with the precipitation. But with regards to a small surafce feature causing a massive domino effect, I disagree, as the Altantic is shown again to kick back in with mider air flooding back in and the colder air getting pushed back. I don't think the shortwave will have a great enough effect on altering the upper flow to stop the Atlantic from taking over.

I disagree.

Look at +174 on the GFS. Note the block is further W. Why is this?

Well the answer is because the SW systems track underneath the block allowing it to back further W. Clearly see this at +192.

http://www.wetterzentrale.de/pics/Rtavn1921.png

[nick sussex]

I suspect that after a quiet day, the coldies will be back in force tonight after the GFS and UKMO 12z runs!

UKMO T+120:

Shows what a knife edge situation next week is, and it will be interesting to see the ensembles later.

It was always a knife edge situation at least for next week, even if the Siberian high implodes later theres still the chance of some snow beforehand. Does that mean we won't have put up with all the droning on about mild wet blah blah blah! :o at least until tomorrow. By the way the UKMO 144hrs is close to disrupting the trough with pressure higher to the ne!

[MR EXTREMES]

What I said above last night is already beginning to show its hand.

http://www.wetterzen...cs/Rtavn901.png

Considering this is the 12Z which is by far the most likely run to blast any blocking away.

I will add im not promising bitterly cold upper temps with snow showers but we might be able to pull enough colder air in to bring a few snow events. I wonder if those who were so confident of a mild week next week are so confident after seeing the 12Z!

as much as i hope your right it does not make sense,

the gfs although not the worst model like some think is still on its own.

most likely outcome will be brief cold then return to milder alantic.

id be very suprised if any of the other models prog the outcome you suggested,

and im not ramping up mild,

it would seem the most likely out come.

remember the jet is tracking back for a visit add in talk of a pos nao then any cold that does come next week is likely to be fleeting.

if the alantic flow really gets going then its going to be awhile for cold to return.

but the alantic pressure rise sounds good to me,

last year the alantic high pressure was a player in settled cold with blasts of arctic air straight from greenland.

[Bobby]

UKMO +144 isn't as good though

[cooling climate]

Well the twoing and frowing of the models looks likely to continue for a while yet but I am quite sure

we will see at least a couple of cold days next week here in the east.

As for next weekend and behond is still very much open to question.

[SussexmarkyMark]

What I said above last night is already beginning to show its hand.

http://www.wetterzen...cs/Rtavn901.png

Considering this is the 12Z which is by far the most likely run to blast any blocking away.

I will add im not promising bitterly cold upper temps with snow showers but we might be able to pull enough colder air in to bring a few snow events. I wonder if those who were so confident of a mild week next week are so confident after seeing the 12Z!

I don't think that changes much to be honest. The LP to our NorthWest is likely to link up with further LP over northern Scandinavia and Svaalbard. In turn this is likely to push the Russian HP further south and that may well start linking across the Alps to a HP building over the Canary Islands. If that happens, the UK will be left with HP to the south and LP to the north and in a generally mild South Westerly. Not guaranteed, but seems the most likely outcome to me.

[conor123]

UKMO +144 isn't as good though

Looks like a big snow event to me

The lower resolution part is enough to send the forum into meltdown, beast from the east with -12 850Pha's covering England & Wales at 240hrs

[nick sussex]

I'd concur, merely delaying the inevitable I'd suggest.

Does a 5 day cold spell with chances of snow count as delaying the inevitable! I think most people in here would take that, its always inevitable that the Atlantic will eventually win unless the earth starts spinning in the opposite direction!

[Frosty.]

I suspect that after a quiet day, the coldies will be back in force tonight after the GFS and UKMO 12z runs!

UKMO T+120:

Shows what a knife edge situation next week is, and it will be interesting to see the ensembles later.

I'm a coldie and don't see anything to be optimistic about, a few scraps might be thrown our way but it still looks less cold with a significant thaw ahead. 4c already and thawing fast, 6c tomorrow,

Edited January 15, 2010 by Frosty039

[bluearmy]

To my untrained eye, another reason the 12z evolves favorably re retrogression is the assisitance of an arctic ridge which shows its hand over eastern greenland and takes the sting out of the momentum of the flow to our north. as we know, modelling up there isnt great run to run. cant say it was something i was expecting to see. if it repeats then all bets may well be off. fi polar developments do look rather yummy though. just a tease or something more substantial???

[MR EXTREMES]

UKMO +144 isn't as good though

http://www.meteociel...44-21.GIF?15-17

yep thats what i mean its a fleeting visit of cold.

the building blocks for sustained cold are not there.

[TEITS]

I suspect that after a quiet day, the coldies will be back in force tonight after the GFS and UKMO 12z runs!

UKMO T+120:

Shows what a knife edge situation next week is, and it will be interesting to see the ensembles later.

Despite a sudden shift in the 12Z im still going to be cautious as we may find the model output varies between what was shown on the 06Z and 12Z. Whatever the outcome its makes fasinating viewing.

Time for me to reveal my secret forecasting tool. However let me explain something first.

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.wetterzentrale.de/pics/Rtavn2402.png

[weather eater]

As I alluded to earlier the cut off low was important, on the gfs 06hrs run this headed nw and became absorbed by the main Atlantic trough which reduced the ridging westwards, here this doesn't happen and so we see colder surface air pulled nw into the UK.

These small changes on a global scale make a big difference, chance now for some snow as the fronts try and push eastwards.And now because of this the ridge is further west with low pressure to the south, this forces some disruption to the trough with another shortwave heading se'wards.

This is a very good example of such a small feature much earlier causing a massive domino effect. It's the gfs so i'm not going to overplay this but certainly adds to the interest for next week.

Hi Nick, without a doubt it is possible that we could see a change round, we have after all seen stranger things happen, but the odds still seem to me to be pretty much stacked against any meaningful easterly setting up. Out to the 160hr range today's 12z GFS is perfectly summed up in my earlier post, but the general trend has been for an initial Atlantic incursion, followed by a brief period of influence by the Siberian high and then a return to a normal UK westerly based regime Of course we see detail changes but the overall pattern remains the same. As I say it could be that as we get closer to the event we will see upgrades but that's a hope rather than a realistic prognosis.

[Bobby]

Looks like a big snow event to me

The lower resolution part is enough to send the forum into meltdown, beast from the east with -12 850Pha's covering England & Wales at 240hrs

In the East possibly.

Best to wait for the GFS ensembles before people get carried away.

[nick sussex]

Hi Nick, without a doubt it is possible that we could see a change round, we have after all seen stranger things happen, but the odds still seem to me to be pretty much stacked against any meaningful easterly setting up. Out to the 160hr range today's 12z GFS is perfectly summed up in my earlier post, but the general trend has been for an initial Atlantic incursion, followed by a brief period of influence by the Siberian high and then a return to a normal UK westerly based regime Of course we see detail changes but the overall pattern remains the same. As I say it could be that as we get closer to the event we will see upgrades but that's a hope rather than a realistic prognosis.

I'm not disagreeing with you. Earlier I was just saying lets try and get the most out of the Siberian high before the Atlantic basically tries to nuke it, even if the lower resolution part of the gfs implodes its still an upgrade . I said earlier we should concentrate on at least trying to get enough surface cold to give a chance of some snow, the gfs does, the ukmo almost so theres still some uncertainty.

The odds are against the block but sometimes even the old donkey can beat the thoroughbred if it unseats its rider!

[Paul White.]

Despite a sudden shift in the 12Z im still going to be cautious as we may find the model output varies between what was shown on the 06Z and 12Z. Whatever the outcome its makes fasinating viewing.

Time for me to reveal my secret forecasting tool. However let me explain something first.

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.wetterzentrale.de/pics/Rtavn2402.png

That is brilliant EITS. But for gawds sake dont mention larks and whatever you do dont bring the winter cut off date outof the wood work alas D Allan on snow watch. OOh remember them dark days of model watching lol. Todays 12z in my eyes is defo a step in the right direction if your blend of Tea is of the cold type.

[Bristawl Si]

Some people on here never learn do they?!

The models always chop and change in this type of 'transitional' period. Last night it looked like there was no sign of cold in the next 10 days, but the latest runs offer some hope for coldies. Things won't settle down for another 2/3 days IMO on the direction of our weather, for say, a week to 10 days time.

The likes of TEITS and Nick S have seen and studied these situs many times before.

Hark back to late Nov and all the gloom posts from numerous members about a mild winter, no snow, blah, blah - then almost in an instant in 1st week of Dec a cold outlook was starting to appear in the model runs. It's only 15th January - in my book there's 6 weeks of 'primetime winter' left + March, which can often produce snow in parts of the UK.

[Nick F]

I disagree.

Look at +174 on the GFS. Note the block is further W. Why is this?

Well the answer is because the SW systems track underneath the block allowing it to back further W. Clearly see this at +192.

http://www.wetterzen...s/Rtavn1921.png

Yes, but that is nothing really do with the surface shortwave dropping SE early next week, that's a change in upper flow pattern upstream thereafter in FI, as the jet drops further south, that was the point I was making.

[weather eater]

I would say model accuracy is very low past a certain point at the moment with such a monster siberian high hanging around, too much counting their eggs before the chickens have hatched going on in here, its quite offputting to read.

No model accuracy is pretty good, as we are not seeing real divergence until the post the 144/160hr mark, traditional FI territory. Great FI on the 12z which I'm sure will be seized on as evidence that a meaningful easterly is just around the corner, however we have seen over the last few days a kitchen sink of ideas thrown at the post 160hr evolutions, so its not a trend yet, unfortunately.

Edited January 15, 2010 by weather eater

[nick sussex]

Some people on here never learn do they?!

The models always chop and change in this type of 'transitional' period. Last night it looked like there was no sign of cold in the next 10 days, but the latest runs offer some hope for coldies. Things won't settle down for another 2/3 days IMO on the direction of our weather, for say, a week to 10 days time.

The likes of TEITS and Nick S have seen and studied these situs many times before.

Hark back to late Nov and all the gloom posts from numerous members about a mild winter, no snow, blah, blah - then almost in an instant in 1st week of Dec a cold outlook was starting to appear in the model runs. It's only 15th January - in my book there's 6 weeks of 'primetime winter' left + March, which can often produce snow in parts of the UK.

I would love the gfs to be right but everyone knows my thoughts on it especially with easterlies! It's earlier stages though look plausible but the UKMO is more lukewarm although its 120hrs chart is close to being very good. The UK is at the end of the line in terms of cold being advected west in these set ups so whatever the output shows we have to factor in a margin for error. We'll have to see what the ECM does, thats crucial IMO.

At least theres a chance of some wintry weather next week so a little upgrade this evening so far.

[cooling climate]

If the GFS is correct then that would be fantastic but what is more fascinating to me is the

amount of northern blocking being shown again and a tanking AO.

I would fully expect to see the ECM to start showing this in its output at t192 onwards as this would

fit in with another northern hemisphere cold pattern to appear.