Winter Model Discussion Thread 12Z onwards 5/1/13

[chionomaniac]

Time for a new thread.

So we have some great output to discuss and a great chance of some severe cold as the month progresses.

In favour of this are:

1) SSW and split. The SSW has left the perfect split vortex positioning for Greenland heights demonstrated aptly at 100 hpa:

the latest ECM reinforces the idea of a secondary warming and this is reinforced by Cohen climatology studies following a displacement SSW. Remember this?

2) The MJO is on the move! Latest forecasts suggests that phase 7 is well within reach. Here is the GFS forecast and the ECM and UKMO are now heading the same way.

Phase 7 Jan composite h500 anomaly:

3) Ensemble means for the GFS and ECM are backing the Greenland height rises up:

only up to day 10

4) NAEFS anomalies Day 10 look great

I can't find anything suggesting anything other!

Expect to see some whopper runs and lets just hope that they have it right and winter can really begin!

As always keep relevent, and no trolling. Excitement allowed. Repeated posts warning of caution please hold back on - WE ALL KNOW THAT - we have seen it all before!!!!!

[Bobby]

Yes I totally agree, the SSW is a totally different kettle of fish to the major let down we had with the failed easterly, we had a cold stratosphere then and we were lucky to have a cold snap which lasted a week and gave us a few ice days, the upcoming cold will eventually deliver a much more potent cold spell.

The 2009/2010 winter and Nov-December 2010 big freeze had no SSW before them at all though. So a cold stratosphere doesn't prevent a big freeze / severely cold winter and I guess we'll see over the next few days and weeks what warm stratosphere may produce. Is interesting watching how the models react to it.

It would be nice to get some kind of ensemble agreement at something solid at a somewhat realistic timeframe, say +144 or so, are a while a way from that ATM though.

[weather is fun]

Chio do you think we could be looking at something similar to 1963 or am i getting ahead of myself. Thanks in advance

[johnholmes]

The 2009/2010 winter and Nov-December 2010 big freeze had no SSW before them at all though. So a cold stratosphere doesn't prevent a big freeze / severely cold winter and I guess we'll see over the next few days and weeks what warm stratosphere may produce. Is interesting watching how the models react to it.

It would be nice to get some kind of ensemble agreement at something solid at a somewhat realistic timeframe, say +144 or so, are a while a way from that ATM though.

both those winters showed what I call spikes in the 30mb temperature and in one if not two cases the 15-25 day time lag from 30mb to surface blocking also occurred.

Somewhere in my met files I have the data but I am damned if I can find them at the moment. The penalty of being a weather enthusiast for so many years!

[Ian Brown]

Thanks Chiono, but I feel the last point about holding back on 'it could go wrong' posts is not the right way to go, as many members may not have been here for the classic failures, which are many fold over the last 10 years.

People need to know how a set-up can go wrong, or fail to deliver. for the British Isles.

[chionomaniac]

Thanks Chiono, but I feel the last point about holding back on 'it could go wrong' posts is not the right way to go, as many members may not have been here for the classic failures, which are many fold over the last 10 years.

People need to know how a set-up can go wrong, or fail to deliver. for the British Isles.

Yes, but it is getting to the point where we have more posts in the thread pointing this out than actually discussing the models. And as I say we all know that - so why bother - thanks yet again for pointing it out.

[Isolated Frost]

Thanks Chiono, but I feel the last point about holding back on 'it could go wrong' posts is not the right way to go, as many members may not have been here for the classic failures, which are many fold over the last 10 years.

People need to know how a set-up can go wrong, or fail to deliver. for the British Isles.

I agree but what we usually see is people saying 'it could easily go wrong' without any charts, or back up for their statements at all.

The polar high seems to extend into Greenland in later modelling with Hudson Bay and eastern Scandinavia holding the stratospheric polar vortex. The NOAA 500mb anomaly charts highlight this well- there is also a split forecasted after the original displacement (the secondary warming affecting Siberia, and then Baffin Island and western Greenland.

There is much reason to be optimistic. Take the MJO charts signalling movement into a more phase 7 type shape (I don't have the composite on me but it's cracking)-

Very exciting times when it comes to the current nwp predictions, with colder air likely to dig in from first a continental source, with the potential for east or north-east winds increasing as we move past d8.

[mistyqueen]

I'm enjoying the charts that are appearing here regularly and you can almost taste the expectation too, but what I'd like to know is......what could happen weatherwise to prevent the cold and snow arriving? I'm deliberately not getting my hopes up as they were dashed in December, but I'd just like to know if there's a chance of that happening again in view of the fact that the various forecasts for once all appear to be singing from the same hymn sheet.

[MR EXTREMES]

Thanks Chiono, but I feel the last point about holding back on 'it could go wrong' posts is not the right way to go, as many members may not have been here for the classic failures, which are many fold over the last 10 years.

People need to know how a set-up can go wrong, or fail to deliver. for the British Isles.

im sorry i dissagree this is the jigsaw falling into place and is as good as it gets for what people on the cold side of the force is looking for just wait and see the models churn out them cold charts now ok we will see upgrades downgrades explosive charts tempting us with 63 snowfall but the reality is its 2013 and its winter and the final parts of the jigsaw are falling into place.

and since 07 we had a few good winters in my opion not seen since 80s and whether we failed back in november december 2012 this is a whole new ball game.

ofcoarse we may not see snowfall country wide but we will see colder weather in one form another just enjoy and sod it get excited because hey this is something evolving and exciting.

[chionomaniac]

I'm enjoying the charts that are appearing here regularly and you can almost taste the expectation too, but what I'd like to know is......what could happen weatherwise to prevent the cold and snow arriving? I'm deliberately not getting my hopes up as they were dashed in December, but I'd just like to know if there's a chance of that happening again in view of the fact that the various forecasts for once all appear to be singing from the same hymn sheet.

The forecasts could be wrong, misty. After all they are only forecasts. Not only that but we could see the NH swamped with cold except for one little bit - you know where!

[The PIT]

Problem is if you look at the uppers from T141 it's not really to T180 until -5 line pushes in. So it's not going to a major cold period shown on the 06 oz GFS. Don't think I'll be looking at a foot of snow sitting in the middle of the road at the moment.

[Kentish Snowman in Yorks]

Re the caution posts...I don't really see the need. If coldies want to get all giddy with the output when things are looking good and then suicidal when things go the shape of the pear surely that's their choice?!

Let's be honest, no amount of nanny state type posts pointing out the pitfalls of general over excitement and past failures is going to make a blind bit of difference anyway...its human nature.

For what its worth all I have seen this morning is a continuation of the general theme that a colder more settled spell of weather will be upon us by the end of the week, and with the SSW forecast to continue into January who knows where we could be cold weather wise in a couple weeks time? Fascinating stuff....

[Bobby]

both those winters showed what I call spikes in the 30mb temperature and in one if not two cases the 15-25 day time lag from 30mb to surface blocking also occurred.

Somewhere in my met files I have the data but I am damned if I can find them at the moment. The penalty of being a weather enthusiast for so many years!

I remember there being some minor warnings but no SSW and it's hard to link to the two I think, minor warmings are fairly common aren't they and those big freezes certainly weren't.

Edited January 5, 2013 by Bobby

[southbank]

chionmanic just a quick question not sure what thread to stick it in ,we currently now have a m- class solar flare being forecast , do youthink this may have an impact if any on the current warming ? just there are some thoughts on how solar activity impacts HLB

[snowking]

The 2009/2010 winter and Nov-December 2010 big freeze had no SSW before them at all though. So a cold stratosphere doesn't prevent a big freeze / severely cold winter and I guess we'll see over the next few days and weeks what warm stratosphere may produce. Is interesting watching how the models react to it.

It would be nice to get some kind of ensemble agreement at something solid at a somewhat realistic timeframe, say +144 or so, are a while a way from that ATM though.

Ummm might not prevent it altogether, but it makes it very very difficult without a huge slice of fortune.

November-December 2010 might not have been an SSW, but it had a WARM stratosphere.

Ditto 09/10.

As for ensemble agreement needed at 144:

So i'm afraid im not entirely sure where your caution is coming from in terms of taking things purely at face value at the moment.

Now of course if you were going down the route of NWP uncertainty given events aloft at present then there might be some concern necessary....but then again, as Chiono pointed out at the beginning of the thread, with Strat-Trop coupling looking very impressive at the moment (along with resultant tropospheric forecasts), and tying in nicely with the MJO, even that is looking less and less of a concern.

Kind Regards

SK

[chionomaniac]

Chio do you think we could be looking at something similar to 1963 or am i getting ahead of myself. Thanks in advance

Whoa, calm down there. I am just hoping to see some snow that settles! But before that we need to get the synotics in place that can deliver cold.

[Frosty.]

Well we had a recent classic failure (cold strat etc) which promised much and delivered nothing in terms of snow but there is definately a change on the way, just looking at the gfs and ecm we can see a colder trend and the latest meto update is still indicating a much colder spell in the 16-30 day range. We require more patience but the trend is towards cold, next week will see temps dropping to normal or just below, but milder in the west and north where the most unsettled will continue, but then a colder pattern is the form horse.

Edited January 5, 2013 by Frosty039

[MR EXTREMES]

Yes, but it is getting to the point where we have more posts in the thread pointing this out than actually discussing the models. And as I say we all know that - so why bother - thanks yet again for pointing it out.

it was also over ten years and im sure if net weather was around in the 60s 70s and 80s there would have been failures this is not a new thing the climate changes with sun cycles and many other factors i really dont want to go down the route of climate change im just enjoying the model evolution to something people are looking for.

in summer i like heat thunderstorms in autumn i like storms wind and rain in winter snow in spring the mixture this is climate and enjoyable it is and even better when you have the luxury of models and great posters who have incredible experience and expertise.

cant wait for tea time bring on the weather evolution.

[chionomaniac]

chionmanic just a quick question not sure what thread to stick it in ,we currently now have a m- class solar flare being forecast , do youthink this may have an impact if any on the current warming ? just there are some thoughts on how solar activity impacts HLB

I haven't done enough research on instant impacts on the sun's activity to be able to give you an answer, I am afraid.

[virtualsphere]

I'm enjoying the charts that are appearing here regularly and you can almost taste the expectation too, but what I'd like to know is......what could happen weatherwise to prevent the cold and snow arriving? I'm deliberately not getting my hopes up as they were dashed in December, but I'd just like to know if there's a chance of that happening again in view of the fact that the various forecasts for once all appear to be singing from the same hymn sheet.

Looking at recent model output, perhaps the biggest risk is for the block to be positioned wrongly and for the coldest air to be deflected south of the UK. The signals are there for blocking to set up to the north so what we need to look for as the colder synoptics near the reliable timeframe is for lower pressure to dig SE under the block which will allow the cold air to flood in from the continent. The other favourable resolution would be for the high pressure to back west allowing in low pressure from the east.

There seems to be no evidence of a zonal pattern developing so getting a block set up in a favourable position is going to be what to look for in the next couple of weeks I think to avoid disappoment - which hopefully we will.

[Frosty.]

And with a potential second stratospheric warming event from the ecm as chio mentioned, surely we will strike gold with one or the other..or both, all of us coldies just need to hold our nerve for another week or so and then our rewards should come, we have endured some pants weather for the last few weeks and the winter has been mostly rubbish so far with all the flooding, time for a cold fix.

[phil nw.]

Yes all the available outputs from the top(Strato.) to the surface are pointing to a cold outlook now.

Those anomalities that Chiono.posted if anything have strengthened the -AO signal in the last few runs so all trending good for cold.

Another plus is the MJO forecasts which are showing movements to Phase 7 and maybe even 8 later indicating a probable lengthy cold spell.

We have seen the phase 7 chart so here is the phase 8 outlook

The milder spell is now approaching it`s end game and by midweek we will see surface temperatures falling and the return of night frosts as the High starts it`s build north across the UK.

Thereafter we can start to anticipate the approaching colder upper air from the east.

It will feel cold enough at the surface under the High by the end of next week but when it moves further north and we start to see those cold uppers easing this way we can anticipate some real cold days/nights with sharp frosts and low single figure max`s,maybe ice days later.

Finally the 2mtr London temps ens.

Plenty of evidence to show the change to cold coming quite soon now.

[Ian Brown]

Looking at recent model output, perhaps the biggest risk is for the block to be positioned wrongly and for the coldest air to be deflected south of the UK. The signals are there for blocking to set up to the north so what we need to look for as the colder synoptics near the reliable timeframe is for lower pressure to dig SE under the block which will allow the cold air to flood in from the continent. The other favourable resolution would be for the high pressure to back west allowing in low pressure from the east.

There seems to be no evidence of a zonal pattern developing so getting a block set up in a favourable position is going to be what to look for in the next couple of weeks I think to avoid disappoment - which hopefully we will.

Yes, I think that is the crux of it. We are seeing solid agreement on the end of zonality, but the tendency for the NWP at the moment is to build HP over or very close to the UK just beyond the reliable timeframes, we want to see subsequent runs start developing higher latitude blocking.

[MR EXTREMES]

chionmanic just a quick question not sure what thread to stick it in ,we currently now have a m- class solar flare being forecast , do youthink this may have an impact if any on the current warming ? just there are some thoughts on how solar activity impacts HLB

indeed this has been something ive been watching for few years now and i believe there is cause for concern with the suns impact and it certain has become very lively on the sun right now lets just hope we get colder before it impacts out amosphere.

but this said i do believe theres a lagtime.

[Methuselah]

chionmanic just a quick question not sure what thread to stick it in ,we currently now have a m- class solar flare being forecast , do youthink this may have an impact if any on the current warming ? just there are some thoughts on how solar activity impacts HLB

Can't imagine that it'll have any effect whatsoever, SB. IMO, if things do go the way-of-the-pear (not impossible) then it'll be down to mundane terrestrial factors.