skatefan

As far as I can see this historic SSW is in fact (slowly migrating into) the final warming. I don't see any significant restoration happening coming weeks. The stratospherical reverse flow has dropped but is still very neutral. I am asking myself what this dynamically quiet context will mean for the coming weeks and spring. Lingering LP's and shallow HP's don't sound good to me, and don't produce much trop-strat effects. Do we have comparing years?

Too fast retrogression of the HP creates a level playing field for the LP's. Impossible to say what will happen but the charts don't promiss much!

Always good to keep positive! But a westbased -NAO is almost bound to happen as I see it.

I don't believe that, how much I would like to: the SSW and secondary warming determined the positioning of the HP's: and that gives too much retrogrssion and a free game for the LP's.

I would love to have this but Navgem over-estimates the HP above Greenland. ECM, UKMO and GFS don't see this.....

Nope! The HP above Greenland retrogresses too fast and LP's coming in from the SW will create a big mess of changing conditions, merely S to SE driven.. Although the ECM12 was at the end clearly a warm outlyer, it presents the trend in the models. After next weekend it is clearly gone with the cold.

What do you mean?????

And more! Great to have someone aboard this thread who can take some distance and describe the beauty!!!!

Epic poetry to an epic development.........

Well, the first week cold will be there, whether or not delayed by a day or so! Then we go to FI-watching: will the Greenland high hold itself and tilt clockwise due to the energie on the Asian side or will there be a new pressure-rise from the south? Both scenarios open the door for a new invasion of cold. Obviously there are numerous other scenarios but i like to look at it from the cold side......

I want to pay my respects to Chionomaniac, who has tried so long to bring the effects of a SSW on the tropospheric conditions to attention! We are currently seeing what that means! CHIO gave the first signals on the stratosphere thread and: Yes, we are seeing an incredible SSW and we are seeing incredible tropospherical response. Let us remember how long it took for the models to take a grasp on this and, certainly with this kind of events, Keep the eyes on the large-scale movements when SSW events occur and a lot off uncertainty from models wil take a place!

Yeah textbook. Currently the second wave is happening: but where will this lead us? It looks like this SSW is slowly moving into the final warming? I have never seen this before.

Don't forget that the second blow on the remnants of the split strat. vortex is currently taking place. Anything beyound T144 is therefore soo uncertain! It will take some time again before the models get a hold on this...... but that is what makes model-watching great!

Fantastic runs today! I don't believe, as I argued earlier, that shortwaves will change the large-scale synoptics caused by the SSW: - Ridging N/NE of the UK and HP across the pole - PV energy slowly transferred to the Pacific side What you see today is that when the models grasp the large-scale developments without to much disturbances from small to medium scale waves, the crossmodel agreement becomes clear. Obviously, shortwaves can have a big effect on local development in cold and snow but the big picture is quite clear now....

As I tried to point out yesterday: the developments are dominated by the largescale movements due to the SSW: as a consequence of the revearsal in the Stratosphere the tropospherical vortex-energie above Canada/Geenland is bound to move to the Pacific side. It is strange to see that most models see this in the longe range but fail to incorporate it in the short-range. It is still my opinion/question that this is because hi-res models are mislead by shortwave activity! The positioning of the HP across Europe is an example of this: it will occur because of the large scale dynamics, the only question is: where will it land.

Maybe this has been discussed on this forum before, I don't know. But I was pondering about the role of shortwaves in the models in situations of large-scale stratospheric changes like the SSW we have at this moment. In my meteorology-classes I have learned that this kind of changes generally are dominated and driven by longwave activity/movement and that shortwaves are a consequence of those large-scale movements. The essence of my "pondering": could it be that the high-res parts of the NWP models (specifically the OP's) in these situations inherently over-estimate the effect of short-waves and could lead to short-term fluctuations? I think that is what we are watching continiously! As a consequence you could say that in these situations relatively low-res (ensembles, means and low-res models) is essentially better because it keeps focus on the large-scale development?

Yes. It was interesting to see how GFS low-res played with the Greenland-scenario. We'll have to wait and see whether this develops in a FI-trend...

T240 reaching out for Greenland.......

Yes, and you can see that very consistently in the modelled position of the Scandi-H: it systematically tends to be placed much higher, even elongated. Wether that is good or not remains to be seen but it is a big difference with the december situation! Back then it was always the question: will it be MLB or HLB.

It seems to me that in most models a slight HP zone above Greenland steers the energie more southward and thus creates a delicate balance between the heavy atlantic and HP above the continent. I can imagine that a small difference in the upstream modelling will create a large difference in the downstream battle...

Yep, saw that too. The big 3 are also fairly agreeing on this (T144) although ECM has, again, the most N movement.

Models are what they are: models! They take into account what their creators know about the atmospherical processes and that is a lot. But there is also a lot they don't know or are unable to bring into the models. There is a lot of uncertainty, exponentially increasing after D1. When you can't stand this uncertainty don't look at models!

An excellent wrap-up of developments i think. But it still strikes me as strange that ECM and GFS model so differently in a situation where there are, as you say, few major forcings taking place. In a relative quiet environment every model should be down to basic airo-, thermo- and other dynamic models..?

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?