brogdale

Any links BA?

I'm not at all certain about that ba, just put it out there However if you look at the progged downward propagation the underlying air column is +ive :- http://strat-www.met.fu-berlin.de/cgi-bin/ecmwfzm?alert=1&forecast=f96&var=u etc.

Agreed Pete The tornadic analogy is a good one Chiono, and I now get what you were saying over in 'the other place'. I've gone back and had a look at a number of the 3D animations here:- http://www.appmath.columbia.edu/ssws/index.php and the propogating vortices do appear to naturally drift eastwards (going down through +ive zonality?) so maybe the progged position over us could come good if the trop effects are shunted eastwards of the upper PV...hence the model propensity to Northerlies?

Apologies if this has been posted before, but it seemed an appropriate complement to Chiono's explanation above:-

Yes, still interesting and still with the potential to surprise us For the benefit of any followers of this thread who are not able to see the Strat thread on TWO I thought I'd post an edited version:- As the cold spell receeds (temporarialy?) some may start to look for factors capable of bringing some more winter weather, so I thought I'd attempt a Strat update. Outwardly the signs for a SSW(MWW) event may look encouraging from this data:- http://strat-www.met.fu-berlin.de/cgi-bin/times?plot=temps&alert=1 with NH strat temps forecast to rise quite steeply in the near future. But there are few signs that this warming, even if it did develop into a definable SSW, would be one that significantly affected the zonal winds of the Trop; ie. I suspect it would not become a downward propagator. I base this assertion on findings outlined in this piece from two Japanese researchers, that attempts to establish why some SSW events propagate downwards to affect the troposphere and others don't. http://center.stelab...mazaki_koji.pdf Nakagawa & Yamazaki highlight we need to be looking out for if we hope to see a Splitting SSW capable of driving some cold our way later in the season is the following:- a) Increasing Wave 2 energy flux B) Less strong wave 1 energy c) Poleward EP flux d) Decreasing zonal wind velocity in the high trop. http://acdb-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/z2n_50_2009.pdf showing the Wave 2 energy flux to be fairly unexceptional this year (red), certainly compared with the massive peaks that hepled to precipitate last year's event (blue) http://acdb-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/z1n_50_2009.pdf showing significantly high Wave 1 flux (red) which, according to the Japanese, is unhelpful to propagation ( and note last January's much lower values in blue) http://ds.data.jma.go.jp/tcc/tcc/products/clisys/STRAT/html_e/ep_12z_nh.html showing some healthy flux up into the Strat, but with very little of the poleward component associated with propagator type. http://acdb-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/u60n_150_2009.pdf showing (in blue) last years 'textbook' dramatic rise, then fall in high trop zonal winds either side of the key day (point of max warming @10 hPa). This year's red line does not show that pattern. I'm afraid therefore that the current state of play does not really indicate that we're in for another whopping (splitter) SSW(MWW), nor do I think that any event that did occur would significantly affect the Trop. Sorry to report that, and i hope really that i may be proved wrong, but I think we may well have to look elsewhere this year for the cause of our next cold spell. Lack of SSW doesen't seem to have hindered us thus far

Hi Chionomaniac I agree that any 'key day' is going to be some way off, but i do sense that we might be embarking on a 'growing stage' for another SSW. Based on the paper I posted above, there are signs to indicate that any SSW that did develop over the next few weeks might well be a downward propagator. This forecast:- does appear to show the 'pre-conditioned' +ive zonal anomalies (50 - 80N) in the strat that preceed day -5 in a propagator There also appears to be good indications of another pre-condition for propogation; negative zonal anomalies in the upper trop. Taken with the Wave 2 increases I thought it looks to be a situation of some hope?

Well after the exhausting business of model watching, its good to get back to the 'sanity' of the strat threads I've really been trying to get my head around this piece from two Japanese researchers, that attempts to establish why some SSW events propagate downwards to affect the troposphere and others don't. http://center.stelab...mazaki_koji.pdf Now do forgive me if I make any glaring errors with this attempt at simplification, but here we go:- Nakagawa & Yamazaki looked at 51 SSW events from 1957 to 2002 and defined 28 as downward propgating events (affecting the tropopause) and 23 as non-propagators. (They actually described them as Trop 'warm' and Trop 'cold' respectivly indicative of whether polar warm anomalies reached down below 500hPa). They used the normal 'key day' definition of max rate warming ' 10 hPa, with -days before the key day and +ive days after. So as we approach the point in the year when we might expect to witness the 'growing stage' of another SSW what signs should we be looking for if we are to get a downward propagator? To start with both types appear to be characterised by preconditioned +ive anomaly winds above 10hPa, with the propagator type perhaps showing more intense +ive anomaly preconditioning till day -5. Both types also see a decrease in (50 - 80N) zonal winds @ the key day, and -ive zonal wind anomalies by day +5. But crucially it appears that the propagator type is determined in the growing phase (-10 to key day) with propagators having reduced zonal wind velocity in the high trop to the key day, and the non-propagators seeing high trop zonal velocities increase. Also in this growing phase the propagators see Wave 2 > Wave 1 with EP flux exhibiting poleward propagation, whereas the non-propagators see Wave1 stronger and equatorward EP. So there you have it ( ) What we need to be looking out for if we hope to see a Splitting SSW capable of driving some cold our way later in the season is the following:- a) Increasing Wave 2 energy :lol: Less strong wave 1 energy c) Poleward EP flux d) Decreasing zonal wind velocity in the high trop. Shall we have a look? a) & B) http://ds.data.jma.g..._12z_wn_nh.html looks promising with the Wave 2 rising, and wave 1 declining. c) http://ds.data.jma.g.../ep_12z_nh.html looks like there's a healthy poleward element to the EP flux? d) http://strat-www.met...cast=f192&var=u some encouraging signs of decreasing/reversing high trop zonal winds there. So all in all looking rather interesting for those of us keen to see another SSW this year, and hopefully one capable of producing effects way down into the trop for up to 40 days after the key day!

Hi Chionomanic Shucks those report and assessment deadlines have really been stopping me from paying enough attention to matters straty. As ever, thanks for the updates. What's happening with those zonal wind forecasts? It looks as though there's very little reversal forecast up within the strat, but quite a lot down with us in the Trop...is that right? So we've got those trop reversals without a preceeding SSW/MWW? BTW have you seen the encouraging poleward burst of EP flux shown here:- http://ds.data.jma.go.jp/tcc/tcc/products/clisys/STRAT/html_e/ep_12z_nh.html now that is a good sign for your 'ripe' strat

Well if its wave 1 you're after, have you seen the blocking forecast two weeks hence here:- http://www.cpc.noaa.gov/products/precip/CWlink/blocking/real_time_nh/mrf3.nh.shtml

Hi Azores 92 Do you know of this site? http://www.appmath.columbia.edu/ssws/ if you use "View Events" on the blue toolbar you can then select a notable SSW event and explore many aspects of its features. Unfortunately not many of the featured events tie in neatly with Cold Winter events that we have experienced in the UK, but the Dec 1981 event did preceed our 3rd coldest DJF CET since the war (2.6C). I think Chiniomaniac will be interested in the wave flux component pattern that preceeded the SSW:- Hmmm...lots of Wave 1 early on in the season. If you then use the animations button you can view the event in 2 or 3D. Enjoy.

Thanks OK, I'll try a little input, but bear with me ....marking, reports and real ale are taking their toll of the old cognitive processes! Here's the really interesting Japanese paper that got me thinking about propogation last winter:- http://center.stelab...mazaki_koji.pdf Now in their summary they appear to be suggesting that for propogating events we would need to be looking for Wave 2 flux? Do you think i've got that right? So how much notice should we take of the Wave 1 anaysis? Back to the reports......

Hi Chionomanic Thanks for the swift reply (and over on the other side). You've given the TWO brethren a very clear, succinct account of the season so far and the inticing prospects. As yet not many over there appear very keen on Straty matters, but a bit of splitting in the offing should raise the level of engagement. I have to say I'm very impressed with the thread you've got going here, and I'm in the process of working through the links, papers and graphics that have been posted already. WRT to the Middle Atmosphere lectures I was certainly drawn to Newman's decadal cyclical analysis, but a bit disappointed with Long's consideration of the impact of the Jan event. I'd have liked a little more of the Japanese type research into propogation factors...but hey, I suppose you had to be there. Anyway, its good to chat again, and keep up the good work...I'll certainly be a regular visitor this way from now on.

Hi Chionomaniac Long time no speak! Just thought I'd ask if you're going to come and have a chat on the 'other forum' 'bout this. I've already kicked a thread off and posted some links to a CPC conference site with illustrated talks from the pros! I think you might enjoy them if you haven't already found them. Well waddaya make of this early upper warming? And the EP veering poleward? Good to be back in straty business eh?