Stratosphere Temperature Watch 2012/2013

[Isolated Frost]

ECM consistent with it's expected temps- at 240 (30 Dec), looking at roughly -9c as the highest temp around, v close to breakdown warming-

latest GFS suite consistent with a strong prolonged warming 192 onwards, with 0c and 5c being passed at 10hpa, and zonal 10hpa winds across the arctic, with a squeezed vortex around svalbard

at 100hpa we see the mean vortex over siberia, with an elongated ridge moving energy into svalbard/scandi, symptoms shown by the current nwp, notably the ec op

[feb1991blizzard]

Can not for the life of me understand why there is so much emphasis on the ECM 32 dayer

when it has been flapping around like a fish out of water the last few weeks, Even the update

a few days ago suggested more in the way of northern blocking and has now changed back

again. Treat it the same you would treat any other model.

A few bad weeks does not make it poor in general, it seems more consistent than using the even the ECM and GEFS ens in the 10-15 day range, admittedly not great towards the 30 day range but seems to outperform the CFS, i cannot back that up admittedly because i don't get to see the data and try to paint a visible pressure pattern in my head based on Matt, Snowking and fergie's updates, agree to a certain extent with treating it like any other model but its no good saying that and then +1 ing a post to death when someone posts an FI chart on another model showing a stonking easterly.

[mcweather]

Met office hinting at possible colder weather in mid Jan with their 30 day update, rare of them to go against the EC32, particularly at a range where they could easily wait until another 1, maybe even 2 runs before deciding whether to alter their wording, its not like they would be overly criticised as long as they changed as any colder weather crept into the 20 day range, the only thing i can think of is that they are factoring in a warming strat.

EDIT : beaten to it!!

met 30 dayer finally recognises the upcoming warming. hints yesterday from ian re this and now on the website.

More likely they've just taken a peak at GP'S winter forecast and didn't want to get caught out. lol

On a more serious note it would seem that they have seen something that is giving them reason to do this,especially so far out. As others have said they would lose no credibilty if they waited a while longer especially when they are normally so very cautious in their approach.and wording.

[chris55]

Not being a Strat expert! What do the pro's make of the GFS extended forecast? It looks like the warming (quite a good one) is squeezing the Strat PV and nearly causing a SSW (reversal of winds at the pole). But doesn't look to split the PV at a Strat level.

How does this correlate to the Troposphere, to the untrained eye the Strat PV is getting pushed towards Greenland/Canada with the warming on the other side of the Globe. Do we need to see this continued and the PV to disappear for anything good to feed down to our part of the world?

[AWD]

One things for sure, there is going to be a hell of a battle above our heads come the new year;

Who are you supporting? The red corner or the blue corner?

[BLAST FROM THE PAST]

The Red, it has the sun on its side

BFTP

[-uksnow-]

The Red, it has the sun on its side

BFTP

Can't tell if thats serious or not? Haha. Also seems like as hoped, the warming is moving foreward in timeframes rather than staying stagnant in FI and its nice to see such a strength of warming still predicted not becoming watered down.

[Recretos]

192h sounding on the exact location where EC had its Tmax at 10mb.

Edited December 22, 2012 by Recretos

[chris55]

We are this close - still a little way to go.

But at this point we would only go one way. ( We still have not had a forecast SSW yet.)

Are we now seeing a SSW officially being forecast??

[chionomaniac]

Are we now seeing a SSW officially being forecast??

Morning all,

c55 that is just a temperature forecast - it looks good but there is no way that we can tell whether there is a forecast SSW from that.

I've been very busy recently in the run up to Christmas so will go and look and see what we have on offer this morning. Back soon!!!

[chionomaniac]

Morning all,

c55 that is just a temperature forecast - it looks good but there is no way that we can tell whether there is a forecast SSW from that.

I've been very busy recently in the run up to Christmas so will go and look and see what we have on offer this morning. Back soon!!!

And the answer is not quite yet.

Impressive warming (up to 7ºC) at 10 hpa now at an earlier time frame

leading to this by the end of the run - close to reversal

[cooling climate]

I known this is at the far realms of FI but I would have thought

the temperature profile of the chart below at 100 hpa is not what

we would want to see with warming south of the UK.

[bluearmy]

I known this is at the far realms of FI but I would have thought

the temperature profile of the chart below at 100 hpa is not what

we would want to see with warming south of the UK.

given the odd nature of the gfs op 00z fi wrt to trop feature placement, not sure that 100hpa chart is worth anything CC

[chionomaniac]

Pretty much a SSW forecast on this run. Possibly <5m/s mean zonal winds.

[cooling climate]

given the odd nature of the gfs op 00z fi wrt to trop feature placement, not sure that 100hpa chart is worth anything CC

Very true not expecting the chart to verify just saying we would not want to

see warming similar to what the chart depicts south of the UK,we want it up

north. Cheers.

Question is it just me (hopecasting) or do others see the warming being

forcast screaming of easterly potential again but even stronger than

what we saw earlier this month.

If I had to make a forcast going on what the strat forcasts are showing

us that is the way I would lean as we head on into January.

Edited December 22, 2012 by cooling climate

[Isolated Frost]

GFS 06z sees the warmth penetrate into the upper vortex at 10hpa by 7th January- as chiono notes, it's very much SSW territory- hopefully the upcoming runs can maintain this trend for a warming around 7th-9th January.

[Recretos]

I almost feel sorry for the guy. (the vortex that is)

[bluearmy]

Assuming that the fi ncep charts are overdoing the temps by approx 15c, will the warming out of the vortex be as impressive as shown on the last two runs?

I suspect it will be a slightly better fight than shown today.

[snowking]

Assuming that the fi ncep charts are overdoing the temps by approx 15c, will the warming out of the vortex be as impressive as shown on the last two runs?

I suspect it will be a slightly better fight than shown today.

Sorry to ask BA, but is that figure of 15c based upon anything in particular?

I only ask because I may have missed something but I don't recall seeing any official or unofficial inaccuracy records on the NCEP Strat charts

Kind Regards

SK

[Weather-history]

Is this normal warming for 1mb? 36C at 1mb?

http://www.instantweathermaps.com/GFS-php/showmap-strat.php?run=2012122212&var=TMP&lev=1mb&hour=384

[cooling climate]

Split now forcast at 10, 30 and 50hpa level on the GFS 12z strat forcasts.

[John Badrick]

I almost feel sorry for the guy. (the vortex that is)

Never feel sorry for it, he's the bully in the play ground, that's just about to get a taste of his own medicine

[bluearmy]

Sorry to ask BA, but is that figure of 15c based upon anything in particular?

I only ask because I may have missed something but I don't recall seeing any official or unofficial inaccuracy records on the NCEP Strat charts

Kind Regards

SK

Just a bit of basic checking back over the predicted fi 10hpa temps and those now forecast much closer to the time. Also, there a few charts posted on earlier thread pages that can be verified.

[Recretos]

I wrote a post or my opinion about GFS stratosphere accuracy a few days ago, but I will further address that matter.

I will add skill scores and observed vs. forecast, for the PVO, or the Polar Vortex Oscillation.

So what's this all about. This is a part of abstract from Ren & Ming:

"The EOF and regression analyses indicate that the PVO can be described by a pair of poleward and downward propagating modes. These two modes together account for about 82% variance of the daily potential vorticity anomalies over the entire Northern Hemisphere. The power spectral analysis reveals a dominant time scale of about 107 days in the time series of these two modes, representing a complete PVO cycle accompanied with poleward propagating heating anomalies of both positive and negative signs from the equator to the pole. The strong polar vortex corresponds to the arrival of cold anomalies over the polar circle and vice versa. Accompanied with the poleward propagation is a simultaneous downward propagation."

Basically we are going to look at GFS 16-day skill for PVO in two winters, 06/07 and 05/06 (which featured a split-type SSW). PVO is kinda like a polar vortex strength index, with positive values featuring stronger and organised vortex, and negative values indicate a weak vortex or an SSW event if the values are more negative (look at it kinda like a stratospheric AO). So PVO is derived from the polar vortex and is following its dynamics, so we cant really use the PVO index as a forecast index, because it only reflects polar vortex dynamics. But it is possible to try and forecast the PVO index. Sounds complicated?

"It describes a polar vortex oscillation (PVO) between a strong polar vortex (a positive phase event of the annular mode) and a weak polar vortex (a stratosphere warming event ). In spite of using daily data, the time series of PVO (the PVO index) has a remarkable long time scale and exhibits only 1-2 PVO events within a winter season. The interannual variability of the PVO index is associated with both the duration variations of PVO events and their intensity variations."

Ok. Down to the charts. So basically since PVO index is derived from the state of the polar vortex, a model needs to forecast the stratosphere polar vortex activities correctly if it means to accurately forecast the PVO. Logical, isn't it?

First is the comparison between the 06/07 analysed PVO and 16-day forecasts (The 2006 looks like 2008, due to lower graphical resolution). Each red spot represents the forecast of the PVO for the specific date, issued 16 days (384h) prior to its analyse.

And the average skill score for the 0-16 day period.

Basically a 16-day (384h) skill of 0.8 is the same accuracy as the GFS and ECMWF have for the 500mb height in the 7 day range.

The overall GFS skill for the troposphere in 06/07 Dec/Jan, was not really that impressive.

Next up is the 05/06 winter, with an SSW in mid Jan-early Feb.

The GFS 16-day accuracy of the PVO was quite phenomenal, to say the least, with very good prediction of the oncoming SSW. Notice the fast decline, corresponding to the P.V. disruption and an SSW.

And the skill score. A score of 0.97 is really high, especially when considering the time span.

When compared to 07, GFS had a better 5-day skill of the 500mb heights in the NH (20N-80N) in the period prior to the SSW (Nov-Jan). This is important, because it had a slightly better idea of the dynamics and consequently a better idea of the coupled trop-strat dynamics.

This year, the model skill is fairly good, with ECMWF having a very decent average day-5 score. You can notice a skill drop in late November, around the time of the great Blocking/Highs moving around the pole and into the pole, giving models a bit of a hard time, figuring out their exact position. Keep in mind that this is a day-5 skill, meaning that the weak skills in the late Nov. belong to the forecasts issued/run in the mid November.

Now I will try to write a summary based on all above. I am first going to add an abstract from Shin&Cai:

"The NCEP operational GFS still has a remarkable prediction skill of (stratospheric) polar vortex oscillation (PVO) index at the lead time of day 16, despite a very poor skill in forecasting tropospheric circulation anomalies beyond day 7.

The largest gain of prediction skill w.r.t. the persistence is over the stratospheric polar region. The remarkable skill comes from the signal of systematic poleward propagation of thermal anomalies from the equator to the pole in the stratosphere associated with the global mass circulation variability (intensity/time scale)"

So to try and simplify all above: GFS stratosphere gph,temp. and wind forecasts in the 336h-384h period, are in average as "accurate" as the 500mb forecasts on day 5. I first wrote 6-7 days, but after doing some of this "research" I noticed it is actually better. The PVO is/was forecasted from more layers of the stratosphere, so basically it means that the forecasts for a single layer should be just as good. But as we have seen in just two cases, the skill or accuracy has its variance from year to year. It depends how well the model picks up the tropospheric dynamics and processes that affects the stratospheric polar vortex.

So the GFS FI for mid and upper stratosphere would be,... well... lets say from 336h on. Now I am not saying that the strat. forecasts beyond 240 are still very accurate and reliable, but I am saying they are decent, because they usually pick up trends fairly good, and show highly likely scenarios. There is always variance from run to run in such a time extent, but looking in general, GFS has a good idea of the overall dynamics in the 12-16 day range. Of course I say overall, because details like warm core or cold core max/min temperatures are something to be more accurately shown under 192h range. And even tho the runs are jumping from split to displacement and vice versa in the 13-16 range, the overall idea is constantly the same, and it has little "delaying", meaning when the model shows a certain scenario in the works, but then it keeps delaying it, like it usually happens with snow scenarios down here in the troposphere.

All non quoted text above and especially the summary, is just based on my observations and a little research. You can easily do some verification yourself. Just go a few pages back, like around 50 for example, and search for GFS charts for the 384h, and compare them with latest runs.

If I can do one myself. Besides the slightly less warm Canada, the overall idea is very similar. And this is basically quite amazing, when considering the left graphic is a 384 forecast, and the right one only 72h. 13 days have passed, and a resolution increase, but the original idea was very much in place. The warming at this period seems to be even slightly more intense than the original forecast and the Canadian High a bit more defined. But given the fact it was a day-16 forecast on a low resolution, I think it did a great job, with very little delay, not moving the scenario away into the future.

That's about it. I thought I was going to write this in like 30 minutes, but it actually took me 4 hours and 5 cans of beer. I guess that's the downside of being a perfectionist. But I must say that I really enjoyed every minute of it. I really like writing posts like this, because it also helps me to gain some more knowledge along the way. And I must add that I only have around 6 months in total of "stratosphere expertise" gathering, in contrast to some of the pros in here who are following stratospheric activities for a few years now. http://forum.nwstatic.co.uk//public/style_emoticons/default/smile.png As I said in a post a few days ago, this time last year I didn't even knew what and SSW is. I only had the idea that there is some sort of a cyclone high up in the stratosphere, but no clue just how important it is. So basically I am really trying to learn things fast to keep up with the pace and to try and compensate for my stratos. experience deficit. But a big part of my strat. education process is basically this thread itself. There are some really knowledgeable people in here that I learned from (and to which I would like to say Thank you), besides other sources. I guess my data assimilation system is much better than that one of the GFS. http://forum.nwstatic.co.uk//public/style_emoticons/default/biggrin.png I also have around 4 years of "general meteorology" experience, which helps me to understand things a bit faster and to put them into the big picture. Of course all those 4 years are sadly or luckily self learned too. I never had the will to go to "meteo school". The "learn through experience" motto worked fine for me I guess. I am going waay off topic here.

Cheers. http://forum.nwstatic.co.uk//public/style_emoticons/default/smile.png

Edited December 22, 2012 by Recretos

[Midlands Ice Age]

My first post on this thread. Felt I had to congratulate Recretos on a fantastic post.

So easy to read and understand for me as a relative newcomer to the subject.

Hope you leave this mods as I feel it had to be said.

MIA