Stratosphere Temperature Watch

[UV-RAY]

I think for this blocking episode it is a case of everything tropospherically and stratospherically coming together at the right time. That didn't really happen in 2009 - it was much more as if the SSW interrupted what would otherwise have been a milder pattern.

I'm not that convinced about SSW events, for me it's equivalent to which comes first the chicken or the egg. You need height rises for SSW events to take hold, and then SSW leads to blocking. All seems a little vague too me.

[Cheshire Freeze]

To be honest, it's all well and good quoting the teleconnections mantra but as far as I am concerned we don't have enough knowledge or enough sophistication in computer models to understand how certain variables will interact with one another. We tend to use a simplified method whereby we isolate variables; a kind of reductivist approach whereby a cold stratosphere= strong PV a kind of black and white approach. However what about the effects of low solar activity when interction takes place between this and a cold stratosphere? Truth is no-one knows, and even though people like GP and Chiono can have their best guesses, it's not a given by any stretch of the imagination.

Edited December 11, 2010 by CreweCold

[Glacier Point]

The question I'm asking myself is why the upcoming northerly blocking is more impressive with stratospheric conditions as they are then they were after that large warming event back in early 2009?

It's worth considering the presence of downwelling and upwelling waves through the stratosphere and upper troposphere tied into the state of the QBO as a having a strong influence on lagged impact of anywarming or sustained cooling.

QBO 'switches' from east to to west and vice versa generate waves. These waves tend to have a periodicity of 3 months and are associated with anomalous upwelling (warming) waves which are reflected back down through the stratosphere and troposphere and also take around 3 months. Upwellng and downwelling waves are particulalry identified during transitions from east to west phase QBO during the autumn and winter months. West phases tend to start with downwelling waves which propogate and are reflected back upwards 3 months later. These can lead to 3 months where there is a noticeable 'trace' in zonal wind anomalies. The transition from an east to west based QBO can provide optimal conditions for blocking through -ve zonal wind anomalies, peaking at the transition point.

We can see the trace of upwelling and downwelling this autumn, the transition to a west QBO taking place during August but not manifesting iteself in the polar atmosphere until late September.

The blocking signal (enhanced -ve zonal wind anomalies) peaked during October and I suspect the cold outbreak that took place then was heavily influenced by this although the blocking signal at 500 hPa and above has remained favourable since October. Looking at the periodicity, the blocking signal should come under pressure at 200hPa around the turn of the year, and then progressively weaken to a minimum in February and March as the downwelling of +ve zonal winds (weakest upwelling waves) reaches its peak intensity. This underlines the extremely long time scales for stratospheric events to impact the troposhere.

During Feb 2009, the west QBO was well establihsed and downwelling waves had penetrated low down into the troposhere with +ve zonal wind anomalies prevelent.

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_UGRD_ANOM_ALL_NH_2009.gif

The warming event (downwelling easterly winds) had difficulty in manifesting in widescale blocking becauase of the the tropospheric - stratospheric coupling for west winds due to La Nina and downwelling waves. It literally had to fight its way down and work against the grain. Any warming event in February this year will likely have a similar task.

Stratospheric impacts on the troposhere during November and December are less probelamtic because +ve zonal wind anomalies have yet to stir sufficiently to interfer with any other signal.

[lorenzo]

QBO charts from ECMWF - first highlights October and the second is from 1957 to date - if anything this illustrates how far a deviation from the past 2 decades this winter has been.

[BLAST FROM THE PAST]

As regards to changes in outputn its worth looking at what drives rthe telconnections. RJS and I came up with a forecast similar to GP to start but absolutely for sure the teleconnections do not influence the solar, lunar or planetary signals. Look for a prolonged siganl of blocking anmd cold.

BFTP

[chionomaniac]

I am still of the opinion based on the stratospheric forecasts, that we are going to see an end to blocking soon. I know that a lot of people are sceptical of how important the stratsosphere is in determining our own weather pattern, judging by the support that TEITS got in the model thread saying just that. The blocking is likely to be replaced by an Atlantic based pattern for a while before La Nina influences more mid latitude blocking. I will hopefully be able to update in more detail this evening.

[phil nw.]

I am still of the opinion based on the stratospheric forecasts, that we are going to see an end to blocking soon. I know that a lot of people are sceptical of how important the stratsosphere is in determining our own weather pattern, judging by the support that TEITS got in the model thread saying just that. The blocking is likely to be replaced by an Atlantic based pattern for a while before La Nina influences more mid latitude blocking. I will hopefully be able to update in more detail this evening.

Yes i would agree C.

Just looking at GFS and ECM output over recent runs there`s a sense of inevitability about it.

Those heights gradually diminish as they move further away towrds Canada later.

The Arctic cold uppers that we receive soon will slowly modify over time as our piece of the vortex gradually weakens and splits and the pattern mixes out the real cold .

I suppose without a renewal of cold air from somewhere north or east of us then this process is bound to happen although providing we keep a reasonably slack flow along with snow cover then we may hang onto tothe cold untill Christmas especially further North.

Edited December 14, 2010 by phil n.warks.

[chionomaniac]

I still see the same medium term pattern todaywith the polar vortex slowly residing in a position where we have become accustomed to seeing it. Here is the T+240 100 hPa chart showing a reformed lower stratospheric vortex situated more centrally.

As this pattern slowly evolves I would expect that warm air will slowly work it way north as the Atlantic pushes through more in the way of troughs. Scotland may stay cooler for a little while longer. I know that by looking at the GWO that GP expects the breakdown to come from the north with any high latitude blocking setting up further south, but I feel that this could be at odds with the stratospheric signal. What we could see though is a mid latitude block setting up after an initial Atlantic disturbance.

Further up in the stratosphere the forecasts are showing cooling and a more centrally placed and less distorted vortex.

There is still some peripheral warming forecast so all is not lost for January yet!

[kold weather]

Yeah we are heading for a period where a stronger PV develops and this will be sure to wake the Atlantic up...

However with that being said I'm far from convinced the Atlantic becomes as flat as the models want to suggest and even though the Stratosphere would suggest thats the case I think there are other factors that will at the very least delay the milder return for another 3-5 days longer then some of the models are suggesting.

I agree with GP though, the breakdown wil lnot come from the south, expect any such attempt to get shunted southwards into France over the next few model runs, I think a breakdown from the north or west is far more probable.

I suspect a midatlantic ridge will try and form but the jet will try and flatten any attempt, eventually leading to a surface high building over the UK and if we have a weaker Atlantic like I expect it may take several attempts to shunt away that high.

I bet it works ther otherway round, the south stays colder for longer...but who knows!

[cooling climate]

Stratospheric profile starting to look favorable again at the 10 hpa

level in the extended range t240.

[beng]

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_ANOM_OND_NH_2010.gif

Biggest warming event at the top of the stratosphere so far this winter - very early days though.

[chionomaniac]

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_ANOM_OND_NH_2010.gif

Biggest warming event at the top of the stratosphere so far this winter - very early days though.

Looking at the 10hPa level it seems that every time it tries to cool down another minor warming event comes along and disrupts things slightly. Here we see another at T+240:

However by this time the vortex shape is already having a more familiar look to it.

If we can keep the average speed at 10hPa below 40m/s and at 30hPa below 20m/s then we still have a case for a slightly weaker than average vortex.

I always find the average a little misleading because the extreme warming events will have risen the average significantly. I would like to see what the average zonal mean speeds and temperatures are with every extreme event omitted. I bet if we compared this year to that average then we would be doing very well.

One glimmer on the ECM 100hPa forecast at T+240 is the suggestion of a weak Scandi High. Nothing like that on the GFS though.

c

[chionomaniac]

Well this needs watching at 10 hPa!

That would be the greatest warming of the season!

[karyo]

Well this needs watching at 10 hPa!

That would be the greatest warming of the season!

That's good news! There were fears for a (near) record breaking cold stratosphere this December thanks to the strong La nina so I am happy to see those warmings continue.

Karyo

[Cheshire Freeze]

Very good news indeed. That should serve to disrupt the vortex, could be a get out of jail card from the strengthening vortex we are likely to see over the next week to 10 days.

[greybing]

look ,from a ignorant point of view from me are you guys saying in light of cold weather events continuing thta it i s kind of undecided

[ZONE 51]

What it signals is more periods of what we got now, just a milder or less cold pattern trying to break the cold one now and then, further extreme cold to come for sure, im new to the PV and stuff but thats how i understand it from the expert posts.

Edited December 20, 2010 by nimbilus

[chionomaniac]

look ,from a ignorant point of view from me are you guys saying in light of cold weather events continuing thta it i s kind of undecided

As ever I wouldn't say too much at present from 1 warming chart forecast in 10 days plus. What I would say from previous charts is that we are likely to see some kind of breakdown in the next week or so. Back at the start of November I suggested that we could get the high latitude blocking right up until Christmas and this is coming more or less to an end as expected. That leaves us at a junction and it is the next path that we take that hasn't been fully decided yet. Looking at the ECM 100hPa charts I would suggest that we are due a milder interlude with a thaw. But after that again, the next pattern for me would be a mid Atlantic high forming with a cool mixed North westerly air stream. The Latest ECM 100 hPa chart for T+240 hints at this and this would fit in with GP's longer term low GWO thoughts.

Moving on we will need to monitor the stratosphere mid to upper levels in the next week or so as I think that this will have a large bearing over January's weather pattern.

I will try and update after the next GFS stratospheric charts update.

Edited December 20, 2010 by chionomaniac

[chionomaniac]

GFS keeps the warming strong at the 10 hPa level. All eyes on the ECM and lower levels in the coming week. This forecast warming is strong enough to cause vortex disruption.

[Great Plum]

How long does it take for stratospheric warming to affect the vortex?

[johnholmes]

How long does it take for stratospheric warming to affect the vortex?

how long is a piece of string Plum? Not meant to be unkind but different people will give you different time periods.

I reckon on a minimum of 15 days sometimes nearer 25 for the effects to move into the Troposphere?

More knowledgeable folk-what is your take please?

[chionomaniac]

I would say there is no set time and depends exactly on how the warming affects the vortex. But generally at tropospheric level the minimum time between a warming and any distortions felt at the surface would be two weeks.

Lets say we see today a warming forecast at around 60ºN in ten days time. This will then create a different stratospheric pressure field throughout the following week. This is slowly translated through to the troposphere throughout that week. I am talking minor warmings here, not a complete destruction of the vortex as seen in a SSW. So one could expect to see an effect within the second week of January on the surface.

Edited December 20, 2010 by chionomaniac

[ICETAB]

Where can I find the stratospheric model output?

[chionomaniac]

Where can I find the stratospheric model output?

All the links are in the first post.

[ICETAB]

All the links are in the first post.

Thank you sir.

Edited December 20, 2010 by ICETAB