Winter Model Discussion 18Z 19/1/13 onwards.

[Catacol]

Once the energy gets to us though, the eventual westward progression of all weather types hints that whatever is left behind may well be very favourable for cold.

That's gobbledigook to me. What do you mean by "westward progression of all weather types?" The Canadian energy is heading east. The Siberian lobe was forecast to edge east - most recent run has it staying put. Where is the westward progression here?

[KTtom]

I don't understand this panic over the PV!

It's not a problem seeing a few days of that, the NH pattern doesn't just stay frozen for weeks, things have to move around like the PV.

If the PV leaves Canada and joins up with the one over Siberia how is it expected to get there, it doesn't just teleport itself there!

Before the prozac is needed lets just give it a few days to see what happens after this pattern change. It might look zonal but the AO is still negative so we should bear that in mind.

I Agree Nick, but reading all the posts over the last 3 weeks or so we were lead to believe the PV would be in tatters if it even existed at all. so we have to understand people's pessimism.

[ABCD]

What I don't understand is...when a freeze is shown at 240 on the models people urge caution and act as though everyone on this is 5 years old and are unable to think for themselves. However, when zonal is shown at 240 sheer panic sets in and folk try to push it as being the likely outcome! Very bizarre!

Just a balance of probabilities I think mate. Zonal is more likely than a big freeze so people will more readily accept it when it appears in the models. Also the people that want cold probably try not to get their hopes up when it shows up for fear of having them dashed.

[beefy201]

Well said Mr Frost my sentiments too!!!

[chris55]

Fair point, it may well be that we get plunged into a full on easterly next weekend. I would not discount that at all, but looking at the charts now being churned out I wonder if the SSW impact is wearing off quicker than expected. Chio or GP might have thoughts on that.

I think the strat guys did a great job of predicting the SSW, but nobody could have predicted how this would impact and the view that heights would build to our NW appear to have been incorrect. That's no criticism as whilst it hasn't happened there was clear logic behind the forecast.

Anyway, Greenland heights at day 5 on the 18z run anyone :-)

Jason

I totally don't see that happening (but you never know) I see a more Atlantic based pattern becoming established (briefly) towards next weekend and into the following week. But then, with the pattern shifting further east and the Polar Vortex moving out of Canada, we have the possibility of a renewed cold push from the N.E as the whole pattern moves from west to east.

[Catacol]

I don't understand this panic over the PV!

It's not a problem seeing a few days of that, the NH pattern doesn't just stay frozen for weeks, things have to move around like the PV.

If the PV leaves Canada and joins up with the one over Siberia how is it expected to get there, it doesn't just teleport itself there!

Before the prozac is needed lets just give it a few days to see what happens after this pattern change. It might look zonal but the AO is still negative so we should bear that in mind.

I'm busy on my keyboard tonight...

Nick - agreed... but we have about 5 weeks of proper winter left before we reach bonus ball territory. If the PV reunites in a swathe to our north as modelled now by ALL of the big 4 - and pressure rises to our south in response then there is no quick and easy route out of that. We would need another big wobble in the vortex caused by further strat assaults or even better another splitting episode - but if you watch the progression of each of these kind of events in this winter so far (and we have watched a split in late Nov, a wobble in Dec and then recently another big split) they take a little time to translate into a tropospheric pattern favourable for cold. As I see it we may be looking at a zonal final week to January now and then searching for a reset. Not good news in my book.

[fergieweather]

What I don't understand is...when a freeze is shown at 240 on the models people urge caution and act as though everyone on this is 5 years old and are unable to think for themselves. However, when zonal is shown at 240 sheer panic sets in and folk try to push it as being the likely outcome! Very bizarre!

Although in fairness, given good MOGREPS agreement with EC it's unsurprising UKMO have been fairly bullish about a major pattern change from weekend onwards (to zonal W/SW initially with fair few members later into a milder anticylonic in 15d trend period). But then they can only call things as best the ensemble consensus suggests... reality may prove far less straightforward, but we shall see.

[chris55]

That's gobbledigook to me. What do you mean by "westward progression of all weather types?" The Canadian energy is heading east. The Siberian lobe was forecast to edge east - most recent run has it staying put. Where is the westward progression here?

Sorry, eastward progression of all weather types. s.h.i.t I'm crap sometimes, that glass of red has obviously had an effect. Doh!

Edited January 20, 2013 by chris55

[tvh3382]

I think people read to much in every single chart. If people read the various opinions of the experts then they will see that they are expecting the Canadian vortex to go on a holiday across the Atlantic to our northeast. The ECM 240 chart looks like this may be happening. Secondly if people look at the very consistent Met Office 16-30 day outlook they will also see that they do not see zonal and expect the cold to return from the Northeast.

The slight warm up will happen but it will NOT be mild and every chance of a very snowy breakdown. FI is only 72/96 hours at the moment. Remember what the Met did with their t120 Fax last night, it completely ignoted the UKMO output so we can't take any chart after 96 hours as being correct.

[Dunstable Snow]

My interpretation of Strat Warming (and I am no scientist) is that it does a great job of both reducing vortex energy and putting it into unusual places. That might sound a bit general, but 2 years of reading about it and watching it forecast seems to paint that picture for me.

We have a great situation at present with the split vortex, but energy is still energy... and there are 2 centres of it at present. The forecast Canadian Warming is going to reduce the Canadian lobe and drive it from its current locale... but unfortunately for us this is modelled as slap bang into the centre of the north atlantic rather than anywhere else - and as it then rejoins its Siberian cousin in the more distant medium range it creates a horrible swathe of low pressure to our north.

I'm having trouble equating this with MJO - something I have barked on about in a few posts today. I dont understand enough of MJO - nor of how the MJO phases might be coupled and interact with stratospheric conditions. However it does seem to me that The Vortex (capitals out of respect...) is the single most important feature for weather in the northern hemisphere and so Strat disruption of the vortex trumps MJO phases. Therefore my fears are growing that other teleconnections from the last month or so are about to be overwhelmed by the one simple factor in our weather lives: that The Vortex is The Boss and when it decides to come knocking - even in its current weakened form - it wont be beaten.

To those who would say - "hang on: what about the last week???" - you are right. What about it. Specifically it has been weakened by reverse zonal winds in the Strat, and lost a good deal of its punch. This would be great if it stayed exactly where it is now. But that isnt going to happen - thanks to the Canadian Warming.

In November the phrase "Canadian Warming" made me want to add it to me Xmas Card list. Right now I'm thinking of putting out a contract on it. :-(

Hopefully the swathe of low pressure will be to the NE and high pressure will fill in the gap left by the vortex over greenland/eastern canada. Lets hope that is what happens and such a set up is not too far west. If that is the case we will finally get our -NAO but a west based one which is unlikely to be good. That said , still lots to be positive about. Lets try and enjoy what we have had and what is to come over the next few days. Do try and cheer up, gievn your current state of mind people would think you are spending too much time thinking about the scottish football and rugby teams !

[Mr Frost]

I totally don't see that happening (but you never know) I see a more Atlantic based pattern becoming established (briefly) towards next weekend and into the following week. But then, with the pattern shifting further east and the Polar Vortex moving out of Canada, we have the possibility of a renewed cold push from the N.E as the whole pattern moves from west to east.

Spot on Chris. I think this is what the met office are hinting at in today's update (hopefully Ian F would be kind enough to give us a fleeting thought on this? ) and also what GP and others have alluded too.

Maybe the coldest spell of Winter to come during February? We shall see.

Chin up for those who have had nothing during the current wintry spell. (I have only had a 1 cm covering which lasted 24 hours)

Plenty of Winter left for everyone to get involved!

Edited January 20, 2013 by Mr Frost

[Frosty.]

Well what a let down the ecm 12z is compared to last night, a return to average/mild zonal mush just like the gfs 12z with a fired up atlantic, the cold block is quickly eroded during fri/sat with barely a whimper and then it's turning much milder with wet and windy weather, last night the ecm 12z was showing a cold backlash from the northeast at T+240 hours, now it's flat zonal all the way from next weekend onwards. The message from the ecm and gfs 12z is loud and clear, make the most of the next 4 days before it all goes pear shaped.

[nick sussex]

I'm busy on my keyboard tonight...

Nick - agreed... but we have about 5 weeks of proper winter left before we reach bonus ball territory. If the PV reunites in a swathe to our north as modelled now by ALL of the big 4 - and pressure rises to our south in response then there is no quick and easy route out of that. We would need another big wobble in the vortex caused by further strat assaults or even better another splitting episode - but if you watch the progression of each of these kind of events in this winter so far (and we have watched a split in late Nov, a wobble in Dec and then recently another big split) they take a little time to translate into a tropospheric pattern favourable for cold. As I see it we may be looking at a zonal final week to January now and then searching for a reset. Not good news in my book.

I understand your concerns and of course we'd all rather not see that swathe of low heights to the north.

But we just have to deal with it, you are right though re the Canadian warming it didn't really do us any favours as the PV is sent packing, of course had we been lucky it wouldn't have wanted to meet up with its old chum in Siberia!

So I'm happy to give it a few days to see what happens if the models solidly get behind moving the whole chunk of the PV to Siberia.

The problem isn't so much the ECM 240hrs its what happens next, I'm keeping an open mind and will be interested to see exactly how the SSW downwells into the troposphere re any HLB's.

[That ECM]

I'm busy on my keyboard tonight...

Nick - agreed... but we have about 5 weeks of proper winter left before we reach bonus ball territory. If the PV reunites in a swathe to our north as modelled now by ALL of the big 4 - and pressure rises to our south in response then there is no quick and easy route out of that. We would need another big wobble in the vortex caused by further strat assaults or even better another splitting episode - but if you watch the progression of each of these kind of events in this winter so far (and we have watched a split in late Nov, a wobble in Dec and then recently another big split) they take a little time to translate into a tropospheric pattern favourable for cold. As I see it we may be looking at a zonal final week to January now and then searching for a reset. Not good news in my book.

A lot of what you say makes sense. I would add though, you are looking at the output and making a judgement for the rest of the winter based on ten day charts. Previous experience of it being difficult to get out of the pattern. However we know a lot has happened to the NH and more still go on. Wait ten days and see if there is a trend a lot of people including the meto do not think winter is over.

Just seen NS has similar thoughts.

Edited January 20, 2013 by That ECM

[TEITS]

Yes, it would be quite nice if the SSW would deliver a chart like this one below rather than the ECM at T+240.

Fully aware of what its bringing now because I have heavy snow outside. My post was referring to the poor ECM run which coincides with the period when the SSW could have its greatest impact. The ECM output is very poor and far from what has been suggested by some.

[Catacol]

Although in fairness, given good MOGREPS agreement with EC it's unsurprising UKMO have been fairly bullish about a major pattern change from weekend onwards (to zonal W/SW initially with fair few members later into a milder anticylonic in 15d trend period). But then they can only call things as best the ensemble consensus suggests... reality may prove far less straightforward, but we shall see.

Oh dear - now we have MOGRAPS and EC also backing a zonal final week to January, azores high dominated at best. There was me hoping for one of our "big guns" (Ian - you are now officially a "big gun" on here, a bit like being a member of the Magnificent Seven) to come riding in and putting an end to fears of "winter's over" posts. Instead we have the opposite. Mexican "zonal" bandit in charge. :-(

It has been an officially dreadful weekend here - not helped by the fact that I have Year 11 reports to write tonight now - and I am not heading into the final phase of my weekend any happier now. Sigh. See you all later. I'll probably revert to lurker status now that I have vented my fears and frustrations on various parts of this wonderful Netweather community across today.

[The PIT]

Wow monster zonal flow in deep FI with the ECM. Very stormy looking. Very little chance of getting in the reliable time frame like that but if it did it would certainly be interesting wind wise.

[Summer Sun]

Alex Deakin just said on country file hints of something milder as the week ends but take that with a gritter full of salt

Goes to show how much uncertainty there is with the model at the moment

Edited January 20, 2013 by Gavin.

[chionomaniac]

It is actually quite straight forward what is being modeled on the hemispheric scale.

We have had a large SSW that has displaced the PV to the Atlantic side with a large ridge based on the Pacific sector. Following this, the Atlantic PV has been cut in half leaving the two vortices seperated but still based towards the Atlantic sector. Further upper warming is destroying the stratospheric Canadian vortex but leaving the tropospheric vortex intact. The underlying upper Pacific ridge is maintained whilst the tropospheric Canadian vortex tries to join with its Siberian counterpart, thus removing the small wedge of increased strat and tropospheric heights keeping them apart.

Meanwhile, the Siberian stratospheric vortex (10 hPa) will slowly increase in strength and eventually make its way back to the pole (over the next 2-3 weeks). What occurs to the tropospheric vortex during this timeframe is unknown, however we know that its starting position is Atlantic based and that the tropospheric vortex is unlikely to regain full strength for a long time yet, and, as the upper Pacific ridge wanes so will the lower Pacific ridge, allowing heights to build elsewhere tropospherically at high latitudes. We don't know where yet.

Edited January 20, 2013 by chionomaniac

[Gibby]

We can only base our analysis of the outputs from what we see and that is overwhelming support for a warm up and a return to Atlantic mobility in 5 days time backed by GFS, it's ensembles, UKMO, ECM and with Ian's input above strengthening that outcome still more. What is more unsavoury is the thought of a milder Anticyclonic spell which is shown on both GFS and ECM late in their runs indicating a strong West or SW flow with dry or dryish weather in the South with High pressure over France sending ever milder SW winds our way. Once in that sort of pattern it can become set for a while. Still a long way off with plenty of swings through the coming week I'm sure.

[Frosty.]

Alex Dekin just said on country file hints of something milder as the week ends but take that with a gritter full of salt

Goes to show how much uncertainty there is with the model at the moment

Even an amateur like me can see there are more than mere hints of a pattern change back to mild zonal, the cold block looks done for by the end of next weekend unless there is a miracle.

[chionomaniac]

Fully aware of what its bringing now because I have heavy snow outside. My post was referring to the poor ECM run which coincides with the period when the SSW could have its greatest impact. The ECM output is very poor and far from what has been suggested by some.

I agree Dave, not a great ECM FI. The SSW is having a great impact with a tremendous HLB - the problem is that it is currently forecast over the bloomin' Pacific and it will take a little time for that to change position.

[OldMetMan]

This is becoming one of the most interesting winter weather scenarios I have seen for a long time, made even more interesting by the way the models are handling it!

At present, the models seem to agree on a return to Atlantic weather within a week or so. Interestingly, the GFS backed off a bit on the 12Z run and the GEM has been the slowest to break down the block. But, as ever, the degree of certainty I would call very low indeed in the mid- to long-term, given the chopping and changing we've had recently.

The 500mb flow is particularly interesting. The guidance coming from the US has been mentioning the upper ridge over the E Pacific quite a lot, and the fact that the models are collapsing it with renewed cyclonic activity entering the Pacific NW. At the moment, the ridge is showing no signs of going anywhere:

This predicted collapse seems to be the key to changing the pattern downstream. The Canadian vortex has most of it's energy well to the E and SE, the collapse of the Pacific ridge would likely allow it to return further W as the predicted cyclonic development moves in and joins it.

Meanwhile, there is a persistent upper high to our N and an extended upper trough running to its S well SE almost to N Africa, hence the succession of LPs sliding SE into the Mediterranean. The remarkably persistent weakish HP to our N associated with the upper high is showing no signs of immediate change. It is an offshoot of the Arctic HP which is still feeding cold air SE into Europe.

Historically, these patterns can be VERY persistent and it is clear the models are pretty hopeless at predicting their development beyond the short range. On that basis, I am putting very little trust in anything beyond T+96 at the moment. The overall upper long wave pattern looks very stable to me so I see no immediate reason for it to change.

The jet has spread a little further E but it still is running on quite a low latitude so unless and until the US pattern changes as described above I don't foresee any big shift in its trajectory and thus the UK remaining in the cold air, although we may see some less cold air pushing into southern counties for a bit, before the north-easterlies reassert themselves.

So, the snow risk remains for the foreseeable future as far as I am concerned. One major concern I have if milder air does filter into the south of the country is the potential for freezing rain, but I hope I am wrong on that score!

All in all, a fascinating week's weather - and model watching - ahead!

[TheHumph]

Even an amateur like me can see there are more than mere hints of a pattern change back to mild zonal, the cold block looks done for by the end of next weekend unless there is a miracle.

Alex Deakin must have some reason/evidence to support what on the face of it is a bold statement from such a high profile forecaster. Not sure he would be sticking his head above the parapet like that otherwise. I agree with you Frosty that the mild appears to be a done deal at this stage but I would love to know what made Alex say this.

[BurwellWeatherWatch]

even if a raging zonal flow does become implemented, it does not mean that winter is over. I'm not sure why all the manic depression tonight - we're in the middle of a serious cold spell and the garden is currently filling up with snow.

~Very likely that from next weekend we are going to enter a less severe/benign/milder phase but that does not lock in anything for February. I wonder if this is going to become a winter of three months, each roughly of two halves.

1st half of December - very cold; 2nd half of December - very mild

1st half of January - exceptionnally mild; 2nd half of January - exceptionally cold.

February - which way round?