Stratosphere Temperature Watch 2014/2015

[feb1991blizzard]

I assuming you mean a negative CET anomaly?

A negative CET March has never happened.

 

Yes its a case of wires crossed, I didn't know whether it had happened or not but certainly knew it would be pushing the boundaries as to what is actually possible and impossible.

[KyleHenry]

I assuming you mean a negative CET anomaly?

A negative CET March has never happened.

Apologies I forgot to clearly state below average March CET against average temperatures from 1981-2010. Not sub zero.

[TomDav]

Nice GFS run

 

 

 

 

 

 

[bluearmy]

Nice GFS run

 

splitdis.png

I think that's a decent representation of where a few trop predictions are also headed for the third week feb tom.

[skatefan]

Hmm, awfully quiet over here.

 

 

I might be completely wrong but is there a reversal in the making?

 

 

Temps at 30 hPa are rocketing up like early Januari. At 10hPa less pronounced though.

 

 

 

 

I can imagine that these observations are illustrating the shift of the strat-vortex away from the pole?

 

[lorenzo]

Liking the 10hPa level this morning, that immediate wave activity is followed at the end of the run by another Siberian hit. Always good to see these on Berlin versus the more volatile GFS extended timeframes.

 

Some Wave 2 activity possible later on as W1 peaks at D5.

 

The vortex out to day 10 remains bunched over the Siberian side at 100hPa, toward D10 again making attempts to ET go home back to the Hudsons.

 

Until then plenty of core cold this side of the hemisphere getting topped up and of course that window for Atlantic ridging remains. Re the MJO or Vortex lead, my take is that vortex in charge toward D7-D10 again as it edges across NH, am still not convinced by MJO plots at present, not good agreement here on what it's next step is on CPC discussion vs Roundy Plots. 

 

All in this is the vortex that refuses to die, so wouldn't surprise me to parry another wave 1 hit and turn it from torch to surf zone warming. On the opposite train of thought there is a decent u-wind tightening at D10 which could help carry said wave hit through the strat. Something to follow for how rest Feb pans out..

[Weather-history]

By the fact, the more knowledgable members have hardly posted recently is an indication that nothing is going to happen of note in the near future?

[KyleHenry]

By the fact, the more knowledgable members have hardly posted recently is an indication that nothing is going to happen of note in the near future?

The only thing of note is the GFS 0z at 384 hours/19th Feb, has warming over Eastern Russia at the 10 hPa level, but the signal appears out of no where so at that time frame nothing definite.

[Weather-history]

The only thing of note is the GFS 0z at 384 hours/19th Feb, has warming over Eastern Russia at the 10 hPa level, but the signal appears out of no where so at that time frame nothing definite.

Thanks

That's says to me, stratospheric wise that it is effectively over for this meteorological winter.

[feb1991blizzard]

The only thing of note is the GFS 0z at 384 hours/19th Feb, has warming over Eastern Russia at the 10 hPa level, but the signal appears out of no where so at that time frame nothing definite.

 

I would hardly call it a warming anyway to be honest.

[KyleHenry]

Thanks

That's says to me, stratospheric wise that it is effectively over for this meteorological winter.

There may still be a final warming event to come. Dr Cohen has made musings towards it in last update.

[summer blizzard]

In the meantime, are we looking at average/above average temperatures up there or are we expecting a cooling and possible vortex reformation?

[mountain shadow]

I suppose in terms of the learning for next year, we now know that whether the vortex is strong or weak at the beginning of Winter makes no difference to achieving a HLB in a decent position to bring a proper sustained cold spell to these islands.

 

Still the best thread on here in my view though.

[KyleHenry]

In the meantime, are we looking at average/above average temperatures up there or are we expecting a cooling and possible vortex reformation?

At the 10 hPa level what's left of the PV is to position over Greenland Sea Northern Scandinavia with recorded temps of -72 C which is still at the extreme end. So there is still plenty of cold air circulating. Peak summer temps measure approx -36 C in August.

The PV is on the wind down through natural decay from the increasing solar radiation/ tilt of planet.

Still 3 weeks of Winter left but the mini SSW instead of what should have been a true SSW was the true point of no return on 28th Dec 2014.

This winters waves were just not enough to allow HLB to take root and impress on the Jet stream. There's still March lol

[Duane S.]

I suppose in terms of the learning for next year, we now know that whether the vortex is strong or weak at the beginning of Winter makes no difference to achieving a HLB in a decent position to bring a proper sustained cold spell to these islands.

Still the best thread on here in my view though.

I would completely disagree. There is plenty enough evidence to show a strong vortex at the beginning of winter makes HLB less likely ( at least until the latter stages of winter). Conversely a weakened vortex does make HLB more likely. BUT when combined with other factors/drivers, this propensity for HLB (or not) can be muted or completely over ridden. Edited February 3, 2015 by s4lancia

[polar vortex]

I think it is quite obvious the vortex is a lot more durable than we give it credit for both higher up and lower down.

Also warmings that just circle the surf zone tend to tighten and strengthen the vorticies (which make sense when

you think about it). That was the main problem last winter and to a certain extent has been the problem this 

winter.

[Snowman.]

I think it is quite obvious the vortex is a lot more durable than we give it credit for both higher up and lower down.

Also warmings that just circle the surf zone tend to tighten and strengthen the vorticies (which make sense when

you think about it). That was the main problem last winter and to a certain extent has been the problem this 

winter.

 

Actually last year it was less reluctant to move or power down.

At least we have seen that this year it has been knocked around a lot and powered down with the rest of Feb left and recent runs show that it isn't without interest.

[Weather-history]

Cohen update

https://www.aer.com/science-research/climate-weather/arctic-oscillation

What do they mean by sensible weather changes?

[karyo]

Cohen update

https://www.aer.com/science-research/climate-weather/arctic-oscillation

What do they mean by sensible weather changes?

Not sure, For me this paragraph is the most interesting: 

• Several large-scale climate factors suggest that the AO will average more in the negative phase through February and into early March. However, recent model behavior about the salient features responsible for this negative AO forecast lowers our overall confidence.

He also mentions the possibility of a -NAO but the CFS forecast goes for positive NAO from next week till early March.

[Nouska]

Cohen update

https://www.aer.com/science-research/climate-weather/arctic-oscillation

What do they mean by sensible weather changes?

 

I think your Manchester index would be a good example - it is weather we see and feel on the ground. 

[sebastiaan1973]

As part of our interview with Judah Cohen Paul and I asked last week some final questions for him.

-We are in the middle of the winter. In october we saw a high SCE and > SAI, so expectations we could see a negative AO, NAO in januar. But altough not extremely positive, these indeces proved to be positive. NA0 + 0,42 en de AO +0,23. What is your opinon about the first two months? Where did it go 'wrong'?
-What can be the reason for the strength of the tropospheric polar vortex so far, despite last years exceptional SAI/SCE?
-What are your expectations for the AO/NAO of the next two months?
-Do you expect this winter to have implications for the validity of your theory, despite a still possible favourable outcome of the temperature forecast?

Every winter forecast is challenging and this one is no exception. Applying our research to operational forecasts does allow us to improve on our ideas and to understand better the predictability skill of our model. And we learn more from our failures more than our successes. However to be clear I do not consider this winter a failure. I am surprised that the AO has not been more negative this winter given the high values of the October SCE and SAI. But what is more important are the surface temperatures and that is looking quite good. For the US, our model predicted a warm December but cold January and February in the Eastern US and that is looking excellent.

Also based on the six-step model that we discussed earlier, the first hemispheric atmospheric response due to snow cover variability is observed in the stratosphere followed by a downward propagation and a similar tropospheric response. High October SCE (as this past October) favors a sudden stratospheric warming in early January followed by a negative AO, cold temperatures in the Eastern US and northern Eurasia and even possibly more snowstorms. I have attached a plot that shows the polar cap height anomalies for this winter so far (top; ignore what follows the sold black line on February 2 that is the forecast) and the composite polar cap heights based on high minus low October Eurasian SCE. I think the match is pretty remarkable (but also note the difference in scale). So physically what has happened this winter was pretty much as expected based on snow cover alone, except the AO has not been that negative.

So why has the AO/NAO preferentially been in the positive state? I don’t really know. One thing that was unusual about this winter the sea ice extent in the Barents–Kara seas has been more extensive than in the recent past. I do think that this favors a positive AO/NAO. There are other possibilities that I am hoping to pursue. I would just conclude by saying that the dynamical models universally predicted a mild winter across the Northern Hemisphere. I would argue that using October SCE as a predictor has great value.

 

The interview can be found over here http://www.vwkweb.nl/index.php?page=1325 

 

[mountain shadow]

in summary...

 

So, even though it was wrong and I don't yet know why it went wrong, it's still right?

[Interitus]

in summary...

 

So, even though it was wrong and I don't yet know why it went wrong, it's still right?

 

Lol, to be fair the warming was significant and according to the GEOS-5 values in the MERRA data, set a number of daily temperature records for 10 and 30mb levels around 6th January which is reflected in the geopotential height chart above, but clearly this has been overwhelmed and hasn't persisted and downwelled as per the SCE composite.

[bluearmy]

I think that come the end of feb, the eastern side on n america and e europe will feel they have had a v cold second half of winter. the NH is more than just the UK

[MattH]

Just my final two pennies worth, firstly how quickly has the last 3 to 4 months gone?...Doesn't seem two minutes since this thread was bustling back in October and November with such potential and interest given the initial drivers. Starting by quoting the above;

 

"So, even though it was wrong and I don't yet know why it went wrong, it's still right?" - Before I even saw that post the same thought came to me as well. Clearly the guy is a respected scientist for many reasons, but these winter updates this year, in my opinion, have done him no good at all. They have often been rather specific and calculated to what he believes will happen using specific words and phrases. He has certainly had a 'bashing' at times over on Twitter this year, especially regarding this on-going Barents-Kara sea 'get out clause'. Anyway, that's a different conversation and of which no doubt some will agree and disagree regarding his thoughts and forecasts this winter.

 

What has been the most disappointing thing about this winter, regarding the stratosphere, is how the overall 'potential' at the beginning of the winter has not be realised in anyway, again in my opinion. Clearly we saw what happens when we are in a +QBO state in 13/14 and how relentless and damaging that winter pattern can be once it sets up shop. Clearly with such a significant -QBO pattern this winter, amongst all the other variables, there was clearly a lot of expectations and scientific expectations too for a SSW this year. Clearly the period of interest was early January and whilst one could say we were close, it was a case of 'close but no cigar' in my opinion. It is another learning curve and no doubt if this had been 'another winter' then a full blown SSW would have occurred. Clearly this is the second year running now without an official one and with the QBO likely to be in a +QBO phase next year then, in very brief summary, I would imagine the odds of one next winter will be quite low as well, but clearly that's just a broad suggestion. Out of interest can anyone tell me when was the last time 3 years did pass without a SSW?

 

In terms of local and regional weather this winter the strat hasn't influenced things at all really. You could argue that the highly displaced vortex through the second half of January into Siberia has aided, amongst other features, the Atlantic ridging and far more meridional pattern of late, but clearly the main drivers this winter have been troposphere based like the AAM and MJO for example, which have been discussed at times through the winter on the Model Thread I believe. Here in Lancashire this winter has been far, far better than last year in terms of cold weather. With a decent 'festive' cold spell between Christmas and New Year and certainly a decent amount of snow within the last two weeks along with cold days and persistent frosts. Essentially a very 'typical' and 'average' UK winter really and no doubt by the end of February the stats will confirm just that with temperatures and rainfall totals generally not too far away from the norm.

 

Clearly whilst not the be-all and end-all, *IF* we had achieved a SSW this winter then who knows what would have resulted. The years continue to tick by without a 'proper' Scandinavian block and an easterly flow with 850mb temps below -10C to -15C, the last time is now many years ago and clearly we have not had one prolonged spell of HLB over Greenland this winter with that text-book pattern on the wetterzentrale charts in which the 500mb charts suddenly go all 'yellow' over Greenland rather than deep blue and purple.

 

So, in summary not a complete loss that we didn't get a SSW, but there's a lot more that needs discussing as to the reasons why in my opinion. Why hasn't the HLB developed as per forecasts given such a strong SAI, I think the OPI can be thrown out of the window too, or at least taken with far more caution this coming October. The weather will always do what it wants, no matter what the signs and signals may well indicate and we got a first-hand example of that this winter really as despite the seasonal models from the UKMO, for example, I think most were expecting a SSW this winter and at least some prolonged spells of HLB, but of which clearly neither has materialised.

 

Anyway here's to more 'learning curves' next winter and I wish everyone the very best for the rest of the year and look forward to re-appearing on the strat thread come October and November, as from the strat point of view it's all over bar the 'shouting' now really given latest guidance through the rest of February.

 

Regards, Matt.