Model Output Discussion - 8th December Onwards

[Gavin Hannah]

ECM mean at T120hrs shows how close we are to serious snowy breakdown.

It's coming, this bad boy is going to slide right under and we are going to be getting plastered. I'm going to positive think it to happen!

[bluearmy]

we may have expected to be further north with the breakdown by now (within T96/120) and some are thinking that there is still time for the models to shift the pattern even further south. anythings possible but that atlantic jet seems awfully strong and i cant see anything getting in its way now. we had our sunday morning 'lift' and tbh, the ecm mean at T120 is encouraging but i fear that upper warm front shown on the fax will introduce high enough uppers to scupper even a soueasterly flow ahead of the precip band. northern england and scotland could still manage a decent fall and beyond next weekend could retain well below av surface conditions. its all a shame but the signs of the next instalment are already looming large on the nwp.

[Hotspur62]

The models have been fairly consistent that the milder from the SW will win out across most areas by the weekend, pressure/heights are not high enough not to hold it back and the strong jet streak charging across the Atlantic later this week from New Foundland will provide the additional impetus for this removal of cold air.

IMO it's just a question of how quickly the cold air will be removed later this week. The flow will be backed to a colder flow from the SE longer across the north with a more -ve angle of approach of the fronts up here, so here we will most likely see the risk of snow preceding the eventual transition to rain. GFS more bullish on the 12z than ECM in breaking down the cold from the SW, so we may see a slower breakdown from subsequent GFS runs, but it's really delaying the inevitable IMHO.

Thanks for that reasoned explanation.Unfortunately,think you will be proved right as Atlantic seems to be shifting through the gears ready to hit us!!

[Snowmad79]

The models have been fairly consistent that the milder from the SW will win out across most areas by the weekend, pressure/heights are not high enough not to hold it back and the strong jet streak charging across the Atlantic later this week from New Foundland will provide the additional impetus for this removal of cold air.

IMO it's just a question of how quickly the cold air will be removed later this week. The flow will be backed to a colder flow from the SE longer across the north with a more -ve angle of approach of the fronts up here, so here we will most likely see the risk of snow preceding the eventual transition to rain. GFS more bullish on the 12z than ECM in breaking down the cold from the SW, so we may see a slower breakdown from subsequent GFS runs, but it's really delaying the inevitable IMHO.

I know you are a pro so no disrespect meant. But I though the Jet Stream energy is also "up for debate" . How do you know the strength and orientation of the jet is nailed later in the week ?

[Matty M]

IMO there is still room for this jet to be directing towards France and at least keep the northern half of the UK locked in cold.

We need things to fall our way, but maybe we are due something.

[bluearmy]

Quite a few sliders in there, 20 runs slide the Low many with the -6 isotherm towards the southern half of the UK.

interestingly, only around half a dozen runs for holland manage to retain the cold into next weekend - friday being the main 'changeover day'. an undercut off the continent may only have a brief window of opportunity, even with a favourable looking undercutting frontal approach.

[shotski]

Isn't it amazing that the difference between a very wintry ending week with lots of snow or a very mild ending week with gales and heavy rain is all down to the low moving a couple of hundred miles to a more favoured position or the position of it stalling against the block.

All the charts, data etc and really it just boils down to something as simple as that.I honestly dont think the charts/METO have a got a clue beyond Thurday,possibly Wednesday.

Is it fair to say to say that most weather data centres struggle forecasting blocking around the UK?

I

Join with me people and I think we can do this, grab your loved ones and together with our mental thoughts, and if we all become

one, we can move this thing. I suggest we start praying when the 18z starts to come out. If Uri Geller can make a ball move on the

penalty spot at Euro 96 vs Scotland why can't all of us move this thing a couple of hundred miles ??

If the output changes over night I will be taking the credit

[billy]

we may have expected to be further north with the breakdown by now (within T96/120) and some are thinking that there is still time for the models to shift the pattern even further south. anythings possible but that atlantic jet seems awfully strong and i cant see anything getting in its way now. we had our sunday morning 'lift' and tbh, the ecm mean at T120 is encouraging but i fear that upper warm front shown on the fax will introduce high enough uppers to scupper even a soueasterly flow ahead of the precip band. northern england and scotland could still manage a decent fall and beyond next weekend could retain well below av surface conditions. its all a shame but the signs of the next instalment are already looming large on the nwp.

Hi BA, could you please explain what you mean by the signs looming large on the NWP. Regards Billy

[Summer Sun]

50 / 50 split from the ensembles tonight for another cold spell starting around the 19th going through to the 25th

Away from the UK parts of Europe look like staying in the freezer for another 5 days before warming up

[Nick F]

As Nick F mentioned earlier though this is delaying the inevitable unless there is a monumental turnaround.

It's been a strange week so I wouldn't want to completely say its impossible!

Certainly can't rule out the colder air being more stubborn to remove when the Atlantic attacks later this week - with the potential for a significant and prolonged snow event still possible, but probably for northern Britain.

We can only really base what may happen at a certain timeframe when we see consistency from the models for that period, which we seem to have for the breakdown later this week. But with the breakdown at 72hrs+, there's chance that the NWP could be wrong with the approach of the attack from the west.

[Nick F]

I know you are a pro so no disrespect meant. But I though the Jet Stream energy is also "up for debate" . How do you know the strength and orientation of the jet is nailed later in the week ?

I'm not saying the track is nailed, but when I see model consistency over a certain parameter in the semi-reliable timeframe, like the jet track - I try to point out what's looking to be the most likely outcome, but by no means the definite outcome.

I would also like the models to be wrong, but until the models all do a u-turn, no-one can really say they are likely to be wrong later this week.

Edited December 9, 2012 by Nick F

[OldMetMan]

There must be a broadly similar pattern now for that month to be second top analog.

Yes, but what was particularly significant in 1978 was the intensity of cold over Europe. I wish I still had the thickness charts for back then, I seem to remember the values being well below 510dm over the S of England, which is extraordinary .

Edited December 9, 2012 by OldMetMan

[IDO]

Keep seeing lots of references to zonality on here tonight, but I am not seeing that myself. To me, zonality is lows barreling through the UK into Scandinavia, whilst the Azores high sits to the S and the PV is attached to Greenland. The Russian block is stopping that happening and all the recent model dramas just prove that they struggle with these blocking situations.

Could easily see something very interesting cropping up in the runs this week; this is not a "normal" set up by any means.....

Its a westerly flow on GFS and ECM OPs, bringing cyclonic weather but as you say its not zonal per se, at least while the block lasts. However it is probably worse than raging zonality in the medium term as the lows slow down as they meet the block and the UK ends up in the firing line for high levels of wind and rain. Of course it is synoptically better for cold, as it may allow the Russian high to push back west, however it will need the upstream amplification to trigger this. At the moment nothing conclusive on that front and the GFS op (later stages of FI) has the Russian high migrate to Siberia, giving a more active zonal flow.

[Panayiotis]

50 / 50 split from the ensembles tonight for another cold spell starting around the 19th going through to the 25th

Away from the UK parts of Europe look like staying in the freezer for another 5 days before warming up

If the cold does come at the dates you have suggested,it looks like precipitation is also likely to fall, and if it does looking at the cold side, it would fall as snow.However it is FI and all subject to change. Edited December 9, 2012 by panayiotis

[karyo]

The 72hrs fax chart shows the fine lines between at least a snow event for a few more people and one probably reserved for just northern areas more especially to higher ground.

You can see that shortwave approaching Scotland which phases with the incoming Atlantic low earlier than the 00hrs run. Also the earlier 84hrs chart had the low pressure centre further west.

As Nick F mentioned earlier though this is delaying the inevitable unless there is a monumental turnaround.

It's been a strange week so I wouldn't want to completely say its impossible!

The Met Office must think the UKMO and GFS version of events is more likely than the ECM.

Karyo

[Gavin Hannah]

Its a westerly flow on GFS and ECM OPs, bringing cyclonic weather but as you say its not zonal per se, at least while the block lasts. However it is probably worse than raging zonality in the medium term as the lows slow down as they meet the block and the UK ends up in the firing line for high levels of wind and rain. Of course it is synoptically better for cold, as it may allow the Russian high to push back west, however it will need the upstream amplification to trigger this. At the moment nothing conclusive on that front and the GFS op (later stages of FI) has the Russian high migrate to Siberia, giving a more active zonal flow.

Depends on which Op you look at. The 06Z had us under an easterly. The Siberian High looks to become fairly established and close to us at t.144. That has been on both the 12 and 06z. It's what happens after that I'm looking forward to seeing. I would say it's going to be an interesting week or so.

[John Cox]

IMO there is still room for this jet to be directing towards France and at least keep the northern half of the UK locked in cold.

We need things to fall our way, but maybe we are due something.

Hi Matty,

I would love to see this evolving but just don't see it happening with the GFS and ECM charts in the short to medium term.

However, with such a cold pool building over mainland Europe, I think it is just a question of time before this moves west. It may take the New Year and it may well be only the UK that gets it but I would be hopeful that it will indeed happen.

[nick sussex]

The Met Office must think the UKMO and GFS version of events is more likely than the ECM.

Karyo

Yes I'd agree, also looking at the countryfile forecast that looked like they were using old data from the 00hrs output unless they decided to modify the 96hrs on the 12hrs.

When Louise Lear showed Thursdays chart it looked like that was off the 00hrs operational run. Strange, I'm not sure when they actually record those forecasts.

[Matty M]

Will the 18z see a gargantuan shift. Make that block to our north stronger against the initial push from the west near 72hrs and then slide the lows into France?

I think the trend is our friend but unsure whether the 18z GFS will be onto this yet.

Get your seatbelt fastened because i feel the next 24hrs will be huge.

There is potential for a serious snow-event to hit some location in UK mid-week.

Hi Matty,

I would love to see this evolving but just don't see it happening with the GFS and ECM charts in the short to medium term.

However, with such a cold pool building over mainland Europe, I think it is just a question of time before this moves west. It may take the New Year and it may well be only the UK that gets it but I would be hopeful that it will indeed happen.

We should know by tomorrow evening whether the slider is possible. I think it is not only possible but, likely.

Edited December 9, 2012 by Matty M

[Gavin Hannah]

Will the 18z see a gargantuan shift. Make that block to our north stronger against the initial push from the west near 72hrs and then slide the lows into France?

I think the trend is our friend but unsure whether the 18z GFS will be onto this yet.

Get your seatbelt fastened because i feel the next 24hrs will be huge.

There is potential for a serious snow-event to hit some location in UK mid-week.

We should know by tomorrow evening whether the slider is possible. I think it is not possible but, likely.

If its as good as last nights 18Z, this forum will probably explode.

[patrickshere]

50 / 50 split from the ensembles tonight for another cold spell starting around the 19th going through to the 25th

Away from the UK parts of Europe look like staying in the freezer for another 5 days before warming up

50/50? Only ~4-5 of those runs go below -5 in your London diagram...

[John Cox]

Will the 18z see a gargantuan shift. Make that block to our north stronger against the initial push from the west near 72hrs and then slide the lows into France?

I think the trend is our friend but unsure whether the 18z GFS will be onto this yet.

Get your seatbelt fastened because i feel the next 24hrs will be huge.

There is potential for a serious snow-event to hit some location in UK mid-week.

We should know by tomorrow evening whether the slider is possible. I think it is not only possible but, likely.

If you are right Matty, I will be following you rather than Met Eireann.... Keep up your great posts

[nick sussex]

Will the 18z see a gargantuan shift. Make that block to our north stronger against the initial push from the west near 72hrs and then slide the lows into France?

I think the trend is our friend but unsure whether the 18z GFS will be onto this yet.

Get your seatbelt fastened because i feel the next 24hrs will be huge.

There is potential for a serious snow-event to hit some location in UK mid-week.

Matty have you been on the Guinness?

I admire your optimism but unless you can find a way of diverting the jet and doing something with that nuisance shortwave then it's going to need a huge turnaround of Biblical proportions!

I think for those in the north a chance of some snow, perhaps if we get a more favourable angle then some snow a little further south.

At absolute best and this is me feeling all festive we may see a delay to the less cold conditions in the far north, anyway the GFS 18hrs awaits!

[bluearmy]

Hi BA, could you please explain what you mean by the signs looming large on the NWP. Regards Billy

there is a consistent signal in gfs low res to disrupt the trough and sink it south. this at a time when the vortex is relocating to siberia so we should hopefully not expect too much residual energy over canada to end up feeding the atlantic jet. the removal of the vortex should also mean that the jet over the states will ease off a bit in intensity as the temp gradient reduces. there is a general rise in heights across our side of the hemisphere on the ens mean output beyond day 8. i would expect the good gfs fi op charts to remain plentiful over the next few days and ecm/gem should begin to show some decent fi runs also. then we can begin 'hunt the shortwave'.

[Summer Sun]

50/50? Only ~4-5 of those runs go below -5 in your London diagram...

I counted all the lines and I get more than 4 or 5 I must be going wrong some where then?