[Stratosphere Temperature Watch 2011/2012]

Chio - can you help me with that graph? It is an average over a wide range of latitude and doesnt seem to show the warming that I understood had occurred this time last year to help destabilise the vortex. Is it much use as a graph with such a wide range of latitude? Should we not be looking at temperatures in more precise areas, and seeing how tropospheric trends emerge from more specific upper atmospheric conditions?

Or perhaps I am barking up the wrong tree. Is such a wide average useful?

Cheers

Al

[Stratosphere Temperature Watch 2011/2012]

Take a look at this link:

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/northpole/index.html

Very interesting table from lots of angles.

While these are running monthly averages for cold in the stratosphere, it does look as though we are entering a period of extreme stratospheric cold. GP cryptically alluded to the possibility of overspin of the vortex...

Is there a more detailed historical breakdown of weekly/daily stratospheric temps on the net? Apologies if that is a dull question - I am a lurker in a learning phase.

Is there any analogue data for what happens to temps in the stratosphere if it gets severely cold? There has to be a bounce back at some point, but if the cold is the severe is the bounce back "bouncier"? If the cold is so severe that wind speeds up there get very high, is there any data for what happens next? What is the out and out measured record for stratospheric cold?

So many questions... :-)

[Winter Forecast - 2011/2012]

Re Feb and snow it very much depends where in the country you are.

by the last week in feb the sun gets pretty strong in the far south(i.e dorset), because of this a very very cold air mass is needed to stop it from melting over a few days.

In December though there probably isn't enough sun strength to actually melt fallen snow down here, hence when it does fall it tends to stay around longer, particularly so in Jan.

I've got a feeling futher north and definately in scotland the sun doesn't make much difference in Feb.

... and yet my memory of Feb 1996 in Dorchester was quite exceptional. Woke up to about a foot on snow in the Piddle valley, and all week Thomas Hardye school was at a virtual standstill as snow and ice stuck around for ages.

[The Winter 2011/12 Forecast Thread]

I was merely stating that I would not put much faith in

a winter forcast that included a prediction for November

that went titicus verticus so quickly.

I rarely post, but this has promtped me to respond. Please point me to a part of RJS's forecast which has gone wrong already. My calendar says 17th Nov. The forecast talked about a mild fortnight (which we have had) and then cooling off - which seems likely enough. Maybe it is the historian in me, but downright inaccuracy flung at someone else who has put together a forecast in reasonable detail strikes me as pretty bloody poor. Are you sure you are a weather fan at all?

[Model Output Discussion - 14th - 20th November]

Yes, more of the same. Average temps with mild not far to the SW and the promise of cold that never really crosses over to us. Sounds familiar and a recurring theme this Winter I suspect.

Have a look at some other threads, especially the stratospheric thread. The consensus from the knowledgeable community would seem to be that cold weather in January is becoming more likely than not, though how cold obviously remains to be seen. A pressure rise over Scandy later in winter is the form horse, but probably not until after the New Year. Until then pretty average, with the mid atlantic ridge become a player in December and bringing us at least a different type of scenario from now.

[Rjs And Bftp Winter 2010/11 Lrf]

Roger

I doubt too many people would demand precise daily accuracy for a lrf to be worthwhile. So far your forecast has the patterns spot on, although the cold in the first third of Janaury was not as bad as expected with the trough obstructed somewhat. I am impressed purely by the general pattern accuracy, and would agree that for industry/business this would be an excellent asset for useage - and if the cold or warm or whatever arrives a day or two early/late then so bet it, but the knowledge that the overall pattern was accurate would be sufficient.

It will be interesting to see if you can score a near 100% on this in the second half of winter - lots of suggestions around that high lat blocking and/or easterlies will not be on the cards - getting that pattern correct is the key.

I am new on Netweather this year: I note you spoke of posts as far back as 2005. Over the last several years how would you rate your accuracy in getting the overall patterns right? Do you keep data like that?

[Rjs And Bftp Winter 2010/11 Lrf]

Btw, looks like the January forecast has gone tits up.

Hmm - that seems a bit premature. The forecast pointed to cold to start - and for much of northern Britain that is exactly what has happened. For the south continental HP stopped the trough digging as far south as it might, but the pattern was picked up correctly. We are now approaching the energy peak and rising temps that were also specified in the forecast. That looks correct again to me.

The jury is out on the final third - recently BFTP has made comments suggesting that the models will come back around to cold from the NE soon... I am not so sure about that, but Jan 20 (date picked out in the forecast as the end of the mild spell) is still out over T+240 so I think we should wait before stating that anything has gone awry.

Generally the forecast's ability to pick out the general pattern weeks in advance has been very very good. February is looking under pressure though - some esteemed voices gonig for mild - GP for one.

Alastair

[Rjs And Bftp Winter 2010/11 Lrf]

A very clear disagreement is emerging on the net - BFTP and Roger's forecast along with TWO's official forecast and Gavin P over on TWO - - all going for renewed cold. GP has said early spring; Joe B'di has now gone for no return of cold for N, NW or central Europe. Fascinating. 2011 and we are no nearer being able to read the long range signals effectively. One group is going to end up disappointed.

I'm still rooting for cold. My own expertise, after 8 years of lurking and learning, encouraged me to lean towards sustained cold before the winter started - the general alignment of the jet over the last couple of years plus the clear tendency for high latitude blocking over the same period was my rationale, ie using observations of recent past rather than any particular ability to predict the future by using sun or stratospheric signals for example.

If it does end up mild then I would see GP as being most likley to be right - HP centred in the atlantic allowing warm air over the top and the strengthening sun to melt early morning frost. Dry. But we shall see: I want to see snow one more time this winter at least, so I hope that mid atlantic block can set up further north and perhaps pressure might rise over Scandy as the respected pundits over on TWO suggested might happen in Feb in their long term forecasts.

Either way BFTP and Roger - I gather you are expecting the models to turn in your favour in the next 5 - 7 days. Do you still think it is all on track, or are doubts increasing as to any renewed cold spell in late Jan/Feb?

Alastair

[Rjs And Bftp Winter 2010/11 Lrf]

Well at the moment I think the models are at a loss and are struggling what pattern to pick up. Now hints of a scandi high forming.

Going back to the forecast I've just checked and the 13th was a "mild spell" so basically bar the over all cold the forecast is bust however people will read into it what they want. It's not a criticism just an observation. Overall a much better jobby than last year. So next year who knows.

By "bust" you mean wrong I presume?

Not sure how you can back that up. This Dec forecast was released way out beyond FI on the models. It picked up the pattern spot on, got the swiftly retrogressing GH spot on(which was part of the forecast update), picked the snow that stranded a good few in Scotland on the 5th, picked the developing low on the 21st pushing up from the SW (but got the track a bit too far south), seems to have picked the HP that is going to largely sit over us over the Xmas weekend and again on towards the NY (if the models are to be believed) and as far as I can see only missed on the 12th/13th.

That's pretty good in my book. If you are looking for long term accuracy to within 50 miles or 24 hours then I would suggest you are going to be waiting a very long time.

I, for one, have been impressed by the forecast. Have not read any other out there which was more accurate.

[Rjs And Bftp Winter 2010/11 Lrf]

Met O update today calls for return to near normal temperatures in January. Thus far Fred you have been spot on - even the snow event you called for on 21 Dec looks about right: snow hitting the SW and W tomorrow (Mon) and then further east on Tuesday. I'm impressed.

Your Jan forecast called for continental arctic air for the first half before an atlantic charge mid month for a few days. The Met O, having been in line with this, now seem to see a mid latitude block with presumably warm air being dragged over the top with the jet also looping around the northern edge giving dry, often frosty but average temps. Your forecast indicates easterlies, presumably caused by height rises over Scandy rather than somewhere west of Ireland. Are you still confident in this?

Fascinating watching this unfold. I have become less interested in watching the flip flops of the models in recent days and much more interested in the long term trend-casting that is going on. I continue to hope you have it right - we have not had too much snow in Somerset yet: perhaps 2 to 3 inches where I am at present - but I would very much like to experience a February such as you are predicting.

[Rjs And Bftp Winter 2010/11 Lrf]

What I will say about the stratosphere is that its like the ENSO signal. It has a part to play but it does not decide where blocking or PV actually sets up. Winter 08/09 is a very good example of no high latitude blocking but no blow torch conditions. The solar cycle and lunar cycle have set the jetstream on a southerly course...a longterm southerly course and we are and have been seeing the consequences of this. This current set up we see approaching isn't [particularly in our view] a wild guess from us....it is what we see being the responses to such influences on the atmosphere.

We may be wrong down the line, we may be right....but a heck of a start...and as Roger says towards the lower end of our parameters. The blocking looks very strong and seems to be just re-inforcing itself.

BFTP

Evening Fred

Well one thing is for sure - 21/22 Dec is a crucial point. You flagged it up weeks ago as a key moment in Dec; the models are now picking it up as the key point that will determine the next pattern. If the low being modelled does not undercut the block, and instead plows straight through it on a NE tack then it will blow holes in this forecast.

I am a quiet lover of cold and hope that does not happen... I am very lacking in knowledge as to how models are programmed, but I am hoping against hope that they have indeed been adjusted and tweaked over the last 10-15 years to understand weather in the "modern" era - ie low pressures rule the roost and blocking highs and cold are only there to be merrily batted out of the way.

If your forecast comes off for the 22nd - and I am rooting for you - then I would suggest it is a turning point for the whole winter. Undoubtedly the models are struggling with it - not every run is seeing the mild air win out, but tonight there seems to be some consistency as to the prediction at 144 hours across the board, namely that the cold will be pushed aside.

Fascinating times... you must be shaking in your shoes waiting to see what Tues-Thurs will bring!

[Stratosphere Temperature Watch]

CH - these long distance forefasts for the Stratosphere: how accurate are they? If they are accurate and are clear precursors to pressure changes lower down in the atmosphere, why do climate models have such difficulty predicting patters even out to 6 days or sometimes less? I hear your gloom, and perhaps the logic and the outcome will prove to be correct, but I cant help thinking it must be much more complex than this, otherwise weather forecasting in general would surely be much easier.

And while the Met Office are not always right, they have come out with quite a cold outlook right up to 19th December at present, so surely gloom need not be too great.

[Stratosphere Temperature Watch]

Welcome Alastair.

There are multiple factors associated with (1) warming events and (2) generally elevated stratospheric temperatures. What causes these is a continuing area of research, however, I would pick out a couple of drivers.

The fact that warming events tend to occur in Nino winters tells us that there is a relationship with the troposphere and the meridional circulation. During El Nino years, angular momentum is enhanced which favours tropical activity in parts of the Pacific which develop high pressure systems generating poleward dispersing Rossby Waves. El Ninos favour low pressure systems in the North Pacific and Atlantic so this probably does suggest that an absence of blocking around the edge of the Arctic does allow for penetration of Rossby Waves into the polar stratosphere deccelerating the polar jet and releasing energy.

Generally warm stratospheric years are also associated with west QBO phases during solar maxima and east QBO phases during solar minima. There is also a relationship between the northern and southern hemispheres. This suggests a second factor (via the Brewer Dobson Circulation) which makes a warming event much more likely.

Then there is 2008/9 polar winter. A low solar / west QBO / Nina winter but where we witnessed a massive mid winter warming event. What caused that ? I remember that there was a strong +ve mountain torque preceeding the event. Maybe the stratosphere got so cold it became unstable, maybe there was a solar influence through the Ionosphere ?

So chicken or egg is difficult to answer for SSW because all of the factors are so interrelated. For seasonally warmer stratospheres, definately egg.

Thanks GP - so uncertain. Do I get the impression from your post that the effects of a Nino in terms of low pressure development and eventual disruption of the PV are better understood generally than the impact of a Nina? I am relatively new to building up a knowlege base on this, but a number of forum threads I have been scanning seem to be really rather confused about any links between Ninas and "weather" as such, especially in our part of the world.

How far back does our data on such links go? I dont have anything bookmarked, but are we talking a very recent detailed dataset or have the QBO / Solar/ Nina / Nino links you mention above been catalogued for a fair while?

I'm going to need to go and read more about Brewer - Dobson. That's totally caught me unawares!

Many Thanks

Alastair

[Stratosphere Temperature Watch]

Thanks, and fixed.

No coincidence that all of your cold selections were east QBO and all bar one were Ninos.

I think that it is very significant that there is a large weighting of Ninas on the cold list. Look at the 500mb plots for both cold and warm. They are typical patterns associated with La Nina (cold strat) and El Nino (warm strat) in the troposphere w/r/t pressure anomalies in the Pacific and Atlantic - Pacific and Atlantic ridges for La Nina, troughs for El Nino.

First post here...

GP - a quick and punchy question on SSW. Do you believe it is the chicken or the egg? Doing some recent reading I have come across some strong arguments stating that SSW is caused by blocking patterns, and not, as would seem to be implied by much of what I am reading on NW, the creator of such patterns. I am sure the analogue data of La Nina to SSW does match either way - it would have to.. But in my attempt to increase my understanding of weather drivers surely the key is to try and get a handle of what causes blocking in the first place. I apologise if this is OT for this thread...

Are you of the belief that SSW warming is the key to blocked or unblocked patterns? How does it fit alongside other suggested drivers such as a weak sun? In our part of the world is it a more important factor than SSTs in the atlantic?

Curiously

Alastair