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

[Dunstable Snow]

Cross-model agreement between GFS, UKMO and ECM at +120. GFS holds the low pressure off more at +144, but it would still be less cold. Confidence of a breakdown is increasing.

http://www.meteociel...M1-216.GIF?20-0

http://www.meteociel...H1-240.GIF?20-0

EDIT: Horrible. Horrible. Horrible. Is there anything possible we can get from these charts?

No expert -far from it but that 240 chart looks like the vortex is on the move from Canada to Siberia. With heights already evident across the pole perhaps we would start to see height rises in the greenland area in the following days. Just hope it doesnt set up too far west. If I have interpreded correctly this does fall in line with what more learned members have been suggesting. Thats about it for positives on the later part of the ECM Im afraid.

[Tamara]

Cross-model agreement between GFS, UKMO and ECM at +120. GFS holds the low pressure off more at +144, but it would still be less cold. Confidence of a breakdown is increasing.

http://www.meteociel...M1-216.GIF?20-0

http://www.meteociel...H1-240.GIF?20-0

EDIT: Horrible. Horrible. Horrible. Is there anything positive we can get from these charts?

That is about as likely in the present circumstances as some of the fictional cold scenarios that appear 9 and 10 days away when the polar vortex is at full capacity. Ignore it - the vortex is going to take until at least the end of February till (and if) it reorganises anything like that

[nick sussex]

Taking all the output into account very good agreement for an end to the cold by the end of next week.

The GFS has at least a more interesting end whereas the ECM and UKMO run energy over the top with no snowy breakdown.

The UKMO update suggested a rather unusual end synoptically, somehow they had a positive tilt trough pivoting with some snow in the east before it turned milder but looking at their operatonal output the mild air has already got in before the precip.

There is still a chance of a more favourable tilt to that troughing but regardless it does look very much like energy heading east as the PV moves out of Canada isn't in the mood to make a detour near the UK.

To get back to cold really depends on whether the models can shift the whole PV east with the UK on the western side of those low heights with pressure rising to the nw.

If the SSW is going to deliver higher latitude blocking then this milder spell shouldn't last too long.

It will be interesting to see whether we will finally get rid of the PV from eastern Canada because so far this winter its been reluctant to depart from there.

Edited January 20, 2013 by nick sussex

[Yozzer]

Would that bring snow all the way across the atlantic because its soooo cold ?

not in Weymouth it won't, unless you are at about 1500m! Lots of surface layer modification takes place over the 2500 miles of ocean it's travelled over, despite the very cold air that spawned it.

[stewfox]

Well very disappointing ECM. The most disappointing isn't just the break down of the cold spell but if we cast our minds back we had GP referring to a very cold blast from the NE and then we had the Strat thread suggesting the main potential from the SSW will be end of Jan. So combined with that we have the ECM showing this chart below.

http://www.meteociel...H1-240.GIF?20-0

Oh dear.

Im not for one minute having a pop here or dismissing the effects of the Stratosphere. However it does show that despite all these various technical forecasting methods, long or even medium range forecasting is impossible for the UK.

Your posting a T240 chart , suggesting various technical forecast methods dont work based on events that havent happen yet ?

I'm sure there was no pop intended

[Yozzer]

Well, this map doesn't show anything nice

Strong vortex and zonal

I think we will see a more zonal spell in a week or so's time, and a chart like that would bring very heavy snowfall to many upland areas of northern Britain. The Spey valley for example can get feet of snow from such a set up.

[chris55]

Well very disappointing ECM. The most disappointing isn't just the break down of the cold spell but if we cast our minds back we had GP referring to a very cold blast from the NE and then we had the Strat thread suggesting the main potential from the SSW will be end of Jan. So combined with that we have the ECM showing this chart below.

http://www.meteociel...H1-240.GIF?20-0

Oh dear.

Im not for one minute having a pop here or dismissing the effects of the Stratosphere. However it does show that despite all these various technical forecasting methods, long or even medium range forecasting is impossible for the UK.

Look at the displaced vortex though!! Surely this is just the energy transferring from the (diminishing) Canadian segment over towards the Siberian segment.

To me the ECM 240 chart shows the PV on it's travels. Look to the far north west. The PV is moving out of that region, this is a very good thing for a cold Feb IMO. Although at this range it's prob not worth to much.

[nicknacknoo]

Evening all, I'm new to all of this but a keen enthusiast none the less.

Has anyone got a brief synopsis (sorry) of the acronyms and technical terms you all use?. I know I can find most on the met sites but I sense also some 'forum specific' stuff.

[weather eater]

what an insightful piece of analysis!

Yes - operationals coming together for something of a breakdown for next weekend, but that's about all we can say at the moment. May be mild, but more likely to be just less cold. For how long is the million dollar question. Operationals again flying around with all kinds of solutions. good to see some sort of tentative agreement around 120 even if it's not quite what we want. But wasn't the last time we had perfect agreement at 120 on December 6th...

I would say consistency wise the models are as good as they are ever likely to be, that’s not to say a breakdown of the block is inevitable, but at the moment I would say its odds on. All the models point to that outcome yes there are some differences in timing but they all agree on a breakdown.

[chionomaniac]

Well very disappointing ECM. The most disappointing isn't just the break down of the cold spell but if we cast our minds back we had GP referring to a very cold blast from the NE and then we had the Strat thread suggesting the main potential from the SSW will be end of Jan. So combined with that we have the ECM showing this chart below.

http://www.meteociel...H1-240.GIF?20-0

Oh dear.

Im not for one minute having a pop here or dismissing the effects of the Stratosphere. However it does show that despite all these various technical forecasting methods, long or even medium range forecasting is impossible for the UK.

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

[Jason M]

When's the first meeting of Straw-Clutchers' Anonymous, then?

Oh, I think there will need to be a bit of the old straw clutching in the next few days if the medium range output is to be believed. Mind you, can it be believed?

One danger though is that we all discount a strong zonal set up or a stalemate as per December on the basis that we should be seeing northern blocking. Despite the teleconnections, SSW, MJO etc it doesn't look like happening so the best we can hope for is that scandi heights come to the fore and the models are making too much of the PV.

I do get the sense that the models are just starting to get some consistency back.

Jason

That's not to say the SSW didn't impact as it clearly did. The effects may not last as long as we hoped though.

Edited January 20, 2013 by Jason M

[chris55]

Oh, I think there will need to be a bit of the old straw clutching in the next few days if the medium range output is to be believed. Mind you, can it be believed?

One danger though is that we all discount a strong zonal set up or a stalemate as per December on the basis that we should be seeing northern blocking. Despite the teleconnections, SSW, MJO etc it doesn't look like happening so the best we can hope for is that scandi heights come to the fore and the models are making too much of the PV.

I do get the sense that the models are just starting to get some consistency back.

Jason

It's only because they are showing a westerly type, the models handle this well, the question is how long this lasts. If it's a transitory pattern then expect the models to falter once again.

[full_frontal_occlusion]

Oh dear.

Im not for one minute having a pop here or dismissing the effects of the Stratosphere. However it does show that despite all these various technical forecasting methods, long or even medium range forecasting is impossible for the UK.

It ain't over till the fat lady sings.

All the popular models had unprecedented trouble settling on this current cold spell even a few days beforehand. If that is also transpiring for long range events between the stratosphere and troposphere, then the outputs used to base next weekends 'potential' breakdown could also be woefully in error.

The modeling of the vortex reformation is part of the story - but is it correct?

ffO

[Catacol]

ECM needs to pull something out the bag tonight. The 00z run frankly was awful for longer term prospects, with the Siberian shard declining and shifting further east, and no end to atlantic energy from the displaced Canadian side. I'm out for the next 90mins or so... hoping for an about turn in medium term prospects when I return...

Back home... and it is a catastrophic ECM run. 9 days from now:

and thereafter true zonal dross. This is the MJO phase 1 composite image for February leaping out of the models for us. Something's got to give: either the MJO is going to race through phase 7 and 8 and into phase 1 as forecast by the GFS op today and give us a terrible final phase of winter if you like cold, or the ops are suddenly going to "pop" and reveal height rises soon with MJO remaining in 7/8 going into February.

Leads me to another question with regards to my desire to learn more: it seems to me that the MJO phase is a driver of patterns rather than a symptom of them. Am I right in this? If so can anyone more knowledgeable than I analyse what is going on there? GP occasionally does it, but he has gone quiet...

Can anyone cheer me up and point me to a teleconnection that is going to pull us away from this medium range signal? Something other than the projected Canadian warming. I am aware of that... and what it seems to be doing is making matters worse by pushing the energy there at present straight for us. I need another straw to clutch.

Edited January 20, 2013 by Catacol_Highlander

[Snowman.]

When's the first meeting of Straw-Clutchers' Anonymous, then?

Next weekend I believe!

[nick sussex]

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.

[Snowman.]

Oh, I think there will need to be a bit of the old straw clutching in the next few days if the medium range output is to be believed. Mind you, can it be believed?

One danger though is that we all discount a strong zonal set up or a stalemate as per December on the basis that we should be seeing northern blocking. Despite the teleconnections, SSW, MJO etc it doesn't look like happening so the best we can hope for is that scandi heights come to the fore and the models are making too much of the PV.

I do get the sense that the models are just starting to get some consistency back.

Jason

That's not to say the SSW didn't impact as it clearly did. The effects may not last as long as we hoped though.

I do believe February will be a good month in terms of cold just a little hunch I got the 7th pops into my head!

[chris55]

Back home... and it is a catastrophic ECM run. 9 days from now:

and thereafter true zonal dross. This is the MJO phase 1 composite image for February leaping out of the models for us. Something's got to give: either the MJO is going to race through phase 7 and 8 and into phase 1 as forecast by the GFS op today and give us a terrible final phase of winter if you like cold, or the ops are suddenly going to "pop" and reveal height rises soon with MJO remaining in 7/8 going into February.

Leads me to another question with regards to my desire to learn more: it seems to me that the MJO phase is a driver of patterns rather than a symptom of them. Am I right in this? If so can anyone more knowledgeable than I analyse what is going on there? GP occasionally does it, but he has gone quiet...

Can anyone cheer me up and point me to a teleconnection that is going to pull us away from this medium range signal? Something other than the projected Canadian warming. I am aware of that... and what it seems to be doing is making matters worse by pushing the energy there at present straight for us. I need another straw to clutch.

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

Edited January 20, 2013 by chris55

[beefy201]

The weather since Thursday has been incredible for many and most models show a cold week ahead! Breakdown next weekend who knows!! There has been a few surprises this weekend with snow falling in areas not predicted 12 hrs ago so come on peeps cheer up ! Who knows what tommorow brings let alone next weekend !!!

[Jason M]

It's only because they are showing a westerly type, the models handle this well, the question is how long this lasts. If it's a transitory pattern then expect the models to falter once again.

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

[Catacol]

Im not for one minute having a pop here or dismissing the effects of the Stratosphere. However it does show that despite all these various technical forecasting methods, long or even medium range forecasting is impossible for the UK.

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 my Xmas Card list. Right now I'm thinking of putting out a contract on it. :-(

Edited January 20, 2013 by Catacol_Highlander

[Gibby]

Good evening folks. Here's the report of tonight's 12z output from GFS, UKMO and ECM for tonight Sunday January 20th 2013.

All models continue to show a cold and unsettled pattern over the coming two or three days. With Low pressure trapped in cold uppers engulf the UK there will be various pockets of snow floating about over the UK. The NE of Britain seems at greatest risk of disruptive snowfall over the coming day or so as today's snowfall in the SE and Midlands tracks slowly North overnight and tomorrow driven on by a strong SE wind. Elsewhere are at risk from snow or sleet at times too, especially in the SW of England around Tuesday as another surge of milder air attempts to break down the block and fails as it shears away SE to France on Wednesday. Towards the end of the week the models show pressure rising over the UK with some welcome sunshine by day and a slight thaw but with very cold and frosty nights with some very low temperatures over the snowfields.

GFS then shows that by next weekend a pattern change commences as Low pressure in the Atlantic will make a more concerted attempt at dislodging the cold pool over the UK. Cloud will move in from the West with a further spell of snow likely but with a more general likelihood of it turning to rain as milder air advances slowly across the UK from the West. Thereafter and through FI details are irrelevant but the trend is shown for milder Atlantic based weather with rain and strong winds at times for all.

The GFS Ensembles show a warm up in uppers at the weekend with things maintained near average thereafter with rain at times as the Atlantic gains momentum.

The Jet Stream shows the flow maintained South of the UK or the first half of the week before the flow moves North later in the week and beyond over the Atlantic and the UK.

UKMO for midday on Saturday shows milder Atlantic SW winds having developed on Friday with milder air moving in across the UK preceded by a spell of rain and hill snow for some.

ECM shows milder air reaching the NW on Friday while England and Wales stay cold and frosty but dry by then. Over the weekend pressure falls away everywhere and a band of rain preceded by snow in places crosses the UK leading into a milder and windy spell of weather with spells of rain and showers through the week that follows.

In Summary its a full house between the models tonight in that our cold spell will be coming to an end at the end of this working week. In the meantime there are a few more snow opportunities over the next 72 hours before a rise in pressure brings several days of cold, settled weather with severe night time frosts and freezing fog patches before milder air preceded by a short spell of snow crosses the UK next weekend leading us into a more traditional Atlantic mix of showers or longer spells of rain with strong winds at times in the week that follows with temperatures well up to the seasonal normal by then.

[Mr Frost]

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!

[-uksnow-]

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

Chio do not dispair! It's all coming in March...

[lorenzo]

Here is the Canadian Vortex, draining itself and going for a wander over to meet it's Siberian vortex, which by way of the Arctic High bossing the NH view has been spinning over and mildly fuelling the Canadian side of the hemisphere, energy dragging round the High then spinning onboard within the Canadian Vortice.

So, the key thing is what happens next after this period, what could logically fill the void after the Canadian vortex has moved home, and also at that point where is the big ball of cold situated?

During this GIF Run at about 216 hours you see something of an undercut that mirrors the pattern of late on the models and at 240 minimal energy left. Just an observation of how this is reflected at both levels.

Given the Meto cited the last transition of vortex energy across the Atlantic as kicking the models into new realms of confusion - it is hard to trust the output. Mild period, or interlude I think are 2 different things here, mild in terms of the ebb and flow of the cold spilling vs the jet deceleration. Interlude in terms of the vortex repositioning.

Fascinating where we go from here..