Model Output Discussion

[J10]

Still better agreement for the continent than for here as these ensembles for Berne show

[Duane S.]

I don't like the look of the GFS ensembles, they arn't dire my along way, but there is a majority clustering now keeping things averageish 850 wise. A wobble or a trend. ?

Yep the these are definately a cause for concern. Hopefully just a blip but we need to see other members start to go cold over the next half dozen chart runs or so or I am going to start to get worried.

[damianslaw]

After weeks and weeks of persistantly unsettled weather, it is looking like finally as we head towards Thursday/Friday next week we are going to see some high pressure on the scene and hopefully the return of a spell of settled weather - for the Lake District it will be a major triumph to see some settled weather.

Too far out at this stage to call just how the heights to the east will influence our weather as we head towards the middle of the month, as others have stated it isn't easy to get such heights to play ball and deliver a severe cold spell especially in the early part of the season, if we were into Jan and certainly Feb the likelihood of some proper cold I believe would be much higher.

However, I remain optimistic that the heights will be favourable for a sustained cold period occuring as we reach the middle of the month, the trend for most of the jet energy to be in the southern arm I don't foresee suddenly changing and it is this factor which I feel is key for allowing the heights to advect south westwards and at the same time we see the jet tracking southerly allowing low pressure to the south to undercut the high, hopefully heights will build to the NW at the same.. as I said too far out to place any bets, but the signs are very promising for that cold to the NE to infiltrate our way.

[SMU]

I think we should have a much better idea of where the pattern could eventually go this evening, the first major switch in the ensembles occured yesterday on the gfs 12hrs, we've now had all 4 different runs from the gfs with varying solutions, in terms of verification stats at day 5 currently the gfs 12rs is ahead of the 18hrs followed just behind by the 00hrs and then finally the 06hrs.

Overall i think we can lock in the euro high to deliver some quieter and colder weather especially for the se. Then as Steve M mentions the problem then of getting the cold to back westwards, this in recent years has been very difficult.

Hey Nick- in the last 5 years or so how many times have you & I seen an Easterly get toppled to a slack Northerly- always notably though from low heights & troughing over svalbard.....

Steve

[bluearmy]

the GEFS look at 'sixes and sevens' in the lower resolution. the spread in the latter stages to our west and north is higher than is normal. as much as we want to know what will happen to our mid lat high beyond next w/end, i'm afraid it remains a mystery. as sm says, we need something to advect the cold west. yesterday, it looked as though we could rely on the jet going into the continent to our south. this looks less likely today and we know what recent history says about shortwaves to our north. just need to watch and wait and be thankful that the rain looks like its finally going to stop. (for about a week at least).

[Guest North Sea Snow Convection]

With the early winter patterns unusually setting up a -AO and a split vortex, if we could get a major big stratospheric warming event later this month then that would really be the decisive push to get that cold air west without having to undergo 'tests' along the way.

The vortex needs to take a blow that it can't recover from. It really is there for the taking, so to speak.

[nick sussex]

Hey Nick- in the last 5 years or so how many times have you & I seen an Easterly get toppled to a slack Northerly- always notably though from low heights & troughing over svalbard.....

Steve

Too many times to mention! but surely this must change at some point, looking on the bright side we have come along way since the start of the week when the models had a Noahs Ark Special as the UK's love affair with rain looked set to continue! <_<

[cooling climate]

With the early winter patterns unusually setting up a -AO and a split vortex, if we could get a major big stratospheric warming event later this month then that would really be the decisive push to get that cold air west without having to undergo 'tests' along the way.

The vortex needs to take a blow that it can't recover from. It really is there for the taking, so to speak.

I think a warming is or has already taken place and this is what is causing the ridging and higher heights

over the Arctic and the split vortex to occur.

Edited December 5, 2009 by cooling climate

[Guest North Sea Snow Convection]

What we are seeing is a splitting vortex from the bottom layers upwards towards the top. A full blown SSW will involve a warming propagating from the top of the stratosphere ie through the 10mb layers to the 30mb and so on. I think there is a high chance of one of these following this winter - the question is when. In order to sustain the split vortex it would be ideal to see a top level warming which fully propagates afterwards, before the vortex has time to regroup in any way, plus to stun and sustain negative zonal winds in such a way that retrogression of the pattern can keep occuring.

We need to remember that the atlantic trough is very likely to be a near permanent feature this winter, so we need the pattern 'backed up' as much as possible so that jet energy is held as kept far away from the Uk as possible and that a sustained -AO has a chance to pull the cold air from the NE further and further west. We don't want to see the pattern reset at all following the upcoming potential colder period - so that with each retrogression we stay one step closer to the cold air without having to go back to square one again.

This is particularly important if we don't manage to get the cold air past the German border in the next 10 days or so. At the very least we want it to remain there ready to arrive on our doorstep with the next push. So the sooner that push comes the better, before the atlantic has a chance to send it back bottled up into NE europe again.

Edited December 5, 2009 by North Sea Snow Convection

[nick sussex]

What we are seeing is a splitting vortex from the bottom layers upwards towards the top. A full blown SSW will involve a warming propagating from the top of the stratosphere ie through the 10mb layers to the 30mb and so on. I think there is a high chance of one of these following this winter - the question is when. In order to sustain the split vortex it would be ideal to see a top level warming which fully propagates afterwards, before the vortex has time to regroup in any way, plus to stun and sustain negative zonal winds in such a way that retrogression of the pattern can keep occuring.

We need to remember that the atlantic trough is very likely to be a near permanent feature this winter, so we need the pattern 'backed up' as much as possible so that jet energy is held as kept far away from the Uk as possible and that a sustained -AO has a chance to pull the cold air from the NE further and further west. We don't want to see the pattern reset at all following the upcoming potential colder period - so that with each retrogression we stay one step closer to the cold air without having to go back to square one again.

Hi Tamara

If i'm reading this right, with each warming the pattern retrogresses , isn't the initial model trend to back the pattern west and with it the Arctic high a response to the initial PV split coming up within T-96 hrs and this causing those reverse zonal winds. So we can only hope they've underestimated the reverse zonal winds, this way that pesky trough to our west will be blown further west and this gives a little insurance.

Edited December 5, 2009 by nick sussex

[Guest North Sea Snow Convection]

Hi Tamara

If i'm reading this right, with each warming the pattern retrogresses , isn't the initial model trend to back the pattern west and with it the Arctic high a response to the initial PV split coming up within T-96 hrs and this causing those reverse zonal winds. So we can only hope they've underestimated the reverse zonal winds, this way that pesky trough to our west will be blown further west and this gives a little insurance.

Hi nick - yes, I think we need as much insurance (a good way of describing it) as we can get . I'm not sure that we will get the cold air this time myself, and that is why I keep going on about a follow up full blown warming to really retrogress the pattern our way before the westerlies return and undo the good work that looks like it is about to happen

[Snowyowl9]

The trend for most of the jet energy to be in the southern arm.

This is the link I remember seeing in february 2005 when I first heard about the southern arm of the Jet it was Steve Murr who first introduced it and I seemed to of only got the atlantic side now,can`t seem to find the american loop.

Which I first got,showed the jet more clearly going more south or north.

http://www.stormsurfing.com/cgi/display_alt.cgi?a=natla_250

Can you provide a link Steve M if anyone.

[cooling climate]

From what I have read this is a warming from the top down or at least 20-30mb heights

the warming rises to these heights then due to lower density the warming expands and starts to

descend again.

Anyway quite agree that we do not want a pattern reset ( I'm thinking Jan 82 no good the pattern

collapsed and that was basically it).

That is why I am hoping the ECM 0z run is correct in as much that at t240 we still have 1050 heights

over the pole where as the GFS has the vortex returning to the pole.

[David-kig]

not bad i have to say im looking forward to winter now!!!!

[snowmadchrisuk]

Well going into the 12z's we have the MJO slowing down a bit but still looking likely to enter phase 8 .

http://cawcr.gov.au/bmrc/clfor/cfstaff/matw/maproom/RMM/phase.Last40days.gif

The Met office talk about an increasing likely hood of getting into a cold easterly flow next weekend and into the following week.

http://www.metoffice.gov.uk/weather/uk/em/em_forecast_weather.html

The Ecm ensembles have been good this morning and will hopefully mean a good ECM run this evening. High pressure looks like building over the country late Wednesday or Thursday so we don't need to see this being delayed.

Chris .

P,s If anyone is from Nottingham then the ref is a crook.

[MR EXTREMES]

Well going into the 12z's we have the MJO slowing down a bit but still looking likely to enter phase 8 .

http://cawcr.gov.au/....Last40days.gif

The Met office talk about an increasing likely hood of getting into a cold easterly flow next weekend and into the following week.

http://www.metoffice...st_weather.html

The Ecm ensembles have been good this morning and will hopefully mean a good ECM run this evening. High pressure looks like building over the country late Wednesday or Thursday so we don't need to see this being delayed.

Chris .

P,s If anyone is from Nottingham then the ref is a crook.

yes but the met office are putting the possible cold spell into a cold snap,

so we could be looking at a 2day event,

although be nice to see europe get sustained cold something for january maybe.

but winter is really hitting alot of america very hard,

does this have a effect on our side of the world?

Edited December 5, 2009 by badboy657

[snowmadchrisuk]

yes but the met office are putting the possible cold spell into a cold snap,

so we could be looking at a 2day event,

although be nice to see europe get sustained cold something for january maybe.

but winter is really hitting alot of america very hard,

does this have a effect on our side of the world?

Yes . Think Positive

[sundog]

If i was a betting man i would say late dec/early jan will be very cold. I think that is when we will get the real cold,just a hunch but thats my guess.

[Thundery wintry showers]

For now I'm inclined to agree with the Met Office. I think there are too many variables riding against this possible easterly shot for it to be likely to amount to more than a brief snap with HP too close by to enable widespread snow showers, and the Atlantic should win the battle in the long run. However I am hopeful that repeats of this kind of scenario later in the season may succeed in bringing that cold air as far west as Britain.

[Downpour]

For now I'm inclined to agree with the Met Office. I think there are too many variables riding against this possible easterly shot for it to be likely to amount to more than a brief snap with HP too close by to enable widespread snow showers, and the Atlantic should win the battle in the long run. However I am hopeful that repeats of this kind of scenario later in the season may succeed in bringing that cold air as far west as Britain.

But is there any sign of the Pest from the West actually coming back any time soon? From what I read on here, there's not.

BTW, Chris, I'm from Nottingham, the red half. You can't blame a 5-1 defeat on the ref old chap!

[osmposm]

...The Met office talk about an increasing likely hood of getting into a cold easterly flow next weekend and into the following week.

http://www.metoffice.gov.uk/weather/uk/em/em_forecast_weather.html

I'm sorry, Chris, perhaps I'm being dense....but where does it say that? All I can see is that 11-13th they forecast North & West wet, South & East drier with 'some' fog/frost - but clearly not a cold flow, since they reckon "temperatures mostly near normal but mild at times in the south". There's a suggestion of "colder later in parts of the north" - from an Easterly? - and then 14th-18th they go with "staying unsettled with further rain at times".

Hmmm. If they are talking about such a likelihood, they're doing so very secretly so far!

EDIT: OK, found it now - must have been looking at an older version of the 6-15 day. Sorry.

Edited December 5, 2009 by osmposm

[MR EXTREMES]

I'm sorry, Chris, perhaps I'm being dense....but where does it say that? All I can see is that 11-13th they forecast North & West wet, South & East drier with 'some' fog/frost - but clearly not a cold flow, since they reckon "temperatures mostly near normal but mild at times in the south". There's a suggestion of "colder later in parts of the north" - from an Easterly? - and then 14th-18th they go with "staying unsettled with further rain at times".

Hmmm. If they are talking about such a likelihood, they're doing so very secretly so far!

cold easterly flow in the southeast.

[chionomaniac]

I'm sorry, Chris, perhaps I'm being dense....but where does it say that? All I can see is that 11-13th they forecast North & West wet, South & East drier with 'some' fog/frost - but clearly not a cold flow, since they reckon "temperatures mostly near normal but mild at times in the south". There's a suggestion of "colder later in parts of the north" - from an Easterly? - and then 14th-18th they go with "staying unsettled with further rain at times".

Hmmm. If they are talking about such a likelihood, they're doing so very secretly so far!

It's on the 6-15 day forecast, Ossie.

http://www.metoffice.gov.uk/weather/uk/uk_forecast_weather.html

[SMU]

This is the link I remember seeing in february 2005 when I first heard about the southern arm of the Jet it was Steve Murr who first introduced it and I seemed to of only got the atlantic side now,can`t seem to find the american loop.

Which I first got,showed the jet more clearly going more south or north.

http://www.stormsurfing.com/cgi/display_alt.cgi?a=natla_250

Can you provide a link Steve M if anyone.

Its prob this your after-

http://wxmaps.org/pix/hemi.fcst.html ( 200 mb jet)

Although im sure net weather extra has the same info-

S

[Frosty.]

If i was a betting man i would say late dec/early jan will be very cold. I think that is when we will get the real cold,just a hunch but thats my guess.

I'm inclined to agree that something is brewing from mid month onwards but it could just be a near miss for the uk although mainland europe looks set for a freeze up. I still think we will get a settled spell from next weekend onwards with frosty nights and some freezing fog, anything more than that will be a nice bonus.