Southern hemisphere stratosphere warmings occur in the winter over the polar region. It is not unusual to have a patch of warming in the uppers and associated wave disturbances propagating down to the troposphere where most of us observe the weather. Some years the disruption to the polar vortex is mild and the vortex may wobble from its symmetry. This year, winter 2019. The polar vortex is forecast by GPS to split into two around the 10th of July. This event is not so common in the Southern hemisphere . The repercussions are positive for the snow fields. Cold air and troughing is likely to be pushed northward into the mid latitudes generally about a week after the vortex splits I see this event as a chance to learn more about the dynamics of the event but more importantly for you guys the effect on snow production. So stay tuned..and would to hear your views or answer your questions
In the last few years I've seen a few "unprecedented" cold outbreaks in the US attributed to the "arctic vortex". Is what you refer to our southern hemisphere equivalent? (note, I'm you average untrained skiing punter so excuse the lack of relevant meteorological knowledge inherent in the question...)
Yes Polar vortex split in 2019 in the NH and effected some parts of the mid-latitudes Try this article https://www.slashgear.com/polar-vortex-split-means-winter-is-coming-15562420/
That is correct. It is the same principle. This particular event may not be called a major event compared to the strength of the NH events but exciting because it doesn't happen every year. I need to dig up' some of the information from past events. Happy for anyone to help here.
Do you think it's actually going to split in two similar to sept 2002? I'd be suprised if it did. I've seen these distortions before - probably a result of vertically propagating planetary waves being directed polewards . @70 and 50 hpa there's a serious bit of stretching going on...but it's less pronounced @20hpa. Usually it's spring when this process tends to really get going(a number of sources implicate zonal wave 1 in distortion, 2 with splits). It may be early and perhaps it could mean the vortex is more vunerable to further stressing later on....as you point out the split events(certainly in NH I think) can lead to very serious cold outbreaks. I've just migrated to a new machine and have left a few relevant bookmarks behind - I'll have to catch up- thanks for bringing it to attention.
The GFS forecast showing dumbell shape on forecast on the 10th, 11th July 'Didjman' from AWF gave me a nullschool link showing dumbell shape Not sure if this picture below is forecast or real time though? Anyone got some real time data? You just have to love real time research 70hpa,
I'm not sure it this sort of thing is what you have in mind - or perhaps you already have seen it https://www.pa.op.dlr.de/arctic/ecmwf.php Charts for GPH and Potential Vorticity up to last night. I dont know of any more immediate obs - it's either hindsight or forecast.
It’s not going to split IMO. Not strong enough in terms of planetary waves and momentum flux. But it’s certainly stretching or becoming elongated.
The nullschool map posted above was apparently real time 7pm tonight. Yes . any links like that to real time monitoring of variables would be useful. It would be good to do a case study l thought. with some observation. I am no expert in this area and have many questions. I am all out of 'puff' for today. Thanks all ror your interest and input
There's no question of the tendancy here for a split into two nodes - above about 100 hpa though, there's only sign of a distortion in the pv field. This shot is of pv between 250-200 hPa - I think it's the best shot of the splitting tendancy. I'm reminded that the point should be made that there are two distinct vortices a stratospheric and a tropospheric and the latter can have a significant and dramatic affect where it orbits in an elliptical fashion from it's central polar position towards the equator, or if two nodes of pv are rotating similarly in tandem. In this case though the rift at the troposheric level (temp,gph,pv) seems to be forecast as very breif- for now at least.
Looking simular atm to 2002, August /September 10 hpa/10 and zonal wind plots re reverse friction anom may be v/interesting..A connection between the increase of tropopause height tropospheric warming, and toc depletion might exist already due to events of volcanic eruptions in indonesia No intention to hijack the thread. Just my current thoughts. Leave to you guys to update.
Could you help me 'snowbarbie' or others here to understand what that SH vorticity map is showing.. Vorticity ..Is that rotating air , convecting air? I have seen that term used in storm analysis. ? So what would all those purple patches represent. .............. Also .. if we can try to keep discussion simple as much as possible. Many non weather experts reading and likely to be totally foreign to them. Also if using shorthand like SH. Please state the meaning. ie. SH =southern hemisphere. Would be appreciated also please post a link to source
Thanks for your commentary 'guys',it is very interesting. I need some help re: terminology and suitable links to resources as l would like to snap in real time some of these variables. Do you have a link to zonal winds. . ? I read that the change direction from west to east in a polar vortex split. What layer is the best to check out. the vortex 10 hpa, 70hpa? ( the lower the number the higher the altitude from the earths surface) If their is both stratosphere and tropopause to check out, what hPa layers are recommended? Any information links to the 2002 event? Where there any more after 2002 ? Could anyone provide a link for tropopause height? what is toc depletion? ozone? I think l have some ozone links. More ozone is produced after the warming event l believe Links for geopotential height anyone. Links for stratospheric temps.. Any other variables? Would like to do a before and after obs'...If the event eventuates.
One thing to consider is that the Polar regions are still somewhat lacking in Satellite coverage. Data can still be a bit thin.
Hey thanks 'kletterer' that is an excellent link !!!! Would l be right in saying the vortex is forecast to split in 48hrs but only for a day? http://db.cger.nies.go.jp/gem/stras/en/forecast.html?date=20190705&polar=s&k=320 I am of my comfort zone atm.Appreciate your expertise and interest
For a broad spectrum of heights- 1 - 70 hPa i go here to customise your own selection. Forecasts from the GFS
I'm a learner like everyone else - my head is spinning on this stuff just as much. I wont even attempt to explain pv( potential vorticity) but the link below might help those who are interested https://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-15-00212.1 If there's a problem with that link try it on a search- should be accessible
Thanks. for link. I would like to spend a bit more time investigating the upper atmosphere layers in weather because we have a prolonged solar minimum underway for possibly many years,. related to solar minimum and shift in magnetic poles,expected increase in the volcanic activity. There are implications for the SH as time foes on but as you say the historical archives, the research and real time data may be a bit wanting. Most is known about the NH . There are possible links to the ski seasons so it is area of interest for your readers. ..... Here is a snap l took of the next 4days forecast for the polar vortex from the fabulous link you provided. I would like to get all links needed now so they are in one place for future reference.
No worries 'snowbarbie' we all learn together. Thanks for your support and interest. Keep your input coming. Love it !
Those various temp( Kelvin ) plots are based on laws of Entropy so it doesnt take into account( thermodynamicaly speaking) work exchange by the system surroundings.
Credit for the link to National Institute for Environmental Studies ( Japan) plots above should got to @snowbarbie .
In observing polar vortex split. From what l gather. The best variable to watch would be wind stream pattern. A vortex has a roundish, oval shape looking down but a cylinder shape vertically. So c for a split l believe you would be observing the vortex structure which is defined by wind stream pattern. I think that considering the short frame for this event (if any)and broad amount of possible variable to observe , l might initially focus on polar wind pattern , horizontal and vertical.It will be the deciding factor of if in fact there has been polar split. It already been established that there has been a stratospheric warming event. Looking for the implications in the troposphere surface layer could be a little more controversial
EC going for an ear-popping 927hPa (GFS - 920hPa) central pressure low @ 150W Longitude, for Monday. Living proof of the PV displacement and circulation derailment.
From the GFS suite of data you provided #kletterer University of Wyoming. Amazing plethora of data ........ GFS absolute vorticity forecast Showing 2 vortices? The split is underway now .7th July 2019 to the 12th July. I selected 70hpa Absolute vorticity The effect on troposphere ,other layers about a week later. Some time frame to observe the obs http://weather.uwyo.edu/models/fcst/images/2019070618.f240.70.nonenonehghtavornone.ant.gfs003.gif I am having trouble capturing that animation. Can anyone help with that? I will capture a few stills
GFS 50 hPa height and Temp Advection plots seem to be indicating a return to Equilibrium- or am i missing something ?
https://acd-ext.gsfc.nasa.gov/Data_services/Current/seasonal_strat/seasonal_strat.html @K most temp/wind data is collected by meteorological balloons @outposts.
18hrs GFS Absolute vorticity is about as real time as you can get. http://weather.uwyo.edu/cgi-bin/mod...L=70&F1=none&F2=none&C1=hght&C2=avor&VEC=none Might get some confirmation from other models ans other variables.
GFS showing 70hpa split in vortex from 7th July, today. Until the 12th for equilibrium. However the question begs is the split at all layers .How high, how low? Some real time obs' in the next 48hrs going to be useful Wind stream anomalies perhaps?
As i mentioned earlier the satellite coverage is not complete. GOES 16 and 17 cover cover a portion of area and this gets assimilated with the Substantial data the GOES 5 collected previously. Will be interesting to see the outcome .
how about the nullschool windstreams at various heights? what about tropopause height. what variable would you use to observe the height disturbance over the antartic?
@k Nasa has been assimulating data from long duration balloons from the Mcmurdo station into the models for many years now. I really did not want to respond.
Yes. Thats correct . Are you saying thats the major or only source ? Happy to be corrected. Am i missinterperating something here- GMAO - Global Modeling and Assimilation Office Research Site
This journal link that #snowbarbie has provided WHAT IS THE POLAR VORTEX AND HOW DOES IT INFLUENCE WEATHER? https://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-15-00212.1 is excellent. It is not hard to read and suitable . It contains all the information we need to assess this polar vortex perturbation. It saves a lot of time and is a recommendation from a reputable source Here are the variables recommended to assess the horizontal extent of the vortex. so might use these for verification purposes. Anything else is a bonus EDIT add to that zonal wind anomalies re recommendation from journal The variables they use and their associated units of measurement are potential vorticity. (pvu) geopotential height (hpa) Keep in mind please that only diagram A and B apply to the POLAR VORTEX
OK. Now for the recommended observational variables... I proceed with trepidation. Please feel free to correct me. This reminds me when l saw my first ultra sound. It needs an expert to interpret accurately. Here is my attempt First variable...ZONAL WINDS This map below shows zonal winds vs pressure at 70to 90s latitude (from pole out to 70s) which is called the polar region It also shows the height of atmosphere from surface 1000hpa to upper stratosphere 10hpa which is a vertical profile of the winds from the surface to about 30km , l think. The colored area on the map is what we are looking for. Strong wind anomalies and a reversal of wind direction The dates are there......Important. From the 9th to 19th June the wind anomaly from the surface to the top of stratosphere was anomalously strong (west or east?) Then importantly , today, the day of vortex split we have a change in wind direction? which is also very strong Tick..Confirmation number one l believe? Source..link provided by ..ski forum member ..trophy for you for this link https://acd-ext.gsfc.nasa.gov/Data_services/Current/seasonal_strat/seasonal_strat.html.. I want to point out that this anomaly is through the troposphere to the stratosphere. 30km.Hard visualize
There's a cheeky dive for a few days around the 29th too. But yeah, neg Zonal anoms are Easterly. Positive would indicate Westerly, which is situation normal for the SH Pole.
What would really be interesting is the Meridonal shift in the mid-lats at tropo levels, as a result of the above.
...And there we have it; officially a SSW event, on paper. Quite a significant event IMO. Anyone checked up on Solar activity impacting the SSW event here? I haven't but know that Solar Flares can disrupt thermal layering in our Strat.
Thanks #POW_hungry for for input and assessment. I look forward to the discussion as to the hows' and whys'. I am just collecting some data while the 'iron is hot' .and then of course the most interesting part for the skiers and snow lovers is what if any effect on our surface weather in the weeks to come. Below is a graphic on 70hpa temp from late May to (July 7th.2019.. Date of vortex split.) Noticing a warm anomaly late May and cold anomaly commencing 25th July. Gets stronger at the split .The forecast is for this 70hpa anomaly to get even colder.!!!! I believe the vortex is COLD. I gather what has happened is that the stratospheric warming started late May and was strong enough to instigate a vortex split commencing around the 25th June and was split on the 7th july. That would make the process from start to finish..6to 8weeks. and then. the split continues for? and then the effect on the midlatitude? How long My point being is this.. It seems quite a drawn out process The only thing l can say here is that there has been some serious energy input to shake the otherwise stable vortex Capturing these time series graphs allows connections with possible causes , like solar, volcanic or surface mslp anoms' etc etc source https://acd-ext.gsfc.nasa.gov/Data_services/Current/seasonal_strat/zmplots/T___time_lat_70hPa_zm.pdf
Which makes strong westerlies forecasted at 60S at the upper stratosphere level more intriguing. This is even more intriguing: -AAO from a tropospheric perspective, but an increasingly +AAO in the upper stratosphere. GFS** is even more extreme, showing a propagation of +AAO into the troposphere around the 20th of July. To me, this seems to be a result of the -AAO event in the mainstream stratosphere in mid-June, that resulted down the line, plus planetary waves via extratropical momentum flux and the Brewer-Dobson circulation*, into the lower stratospheric event that is propagating into the troposphere. The tropospheric event in many ways looks stronger than the stratospheric one, from my view. But there also seems to be some other factor to add to the equation. Interesting. *I'm at Buller so don't have access to all of the resources, but they are the factors that typically cause these sorts of events. ** noting a upper stratospheric bias in GFS.
Ok, what can we expect from the southern version? I would assume that because we don’t have a landmass between us and the poles unlike the northern hemisphere, that any impacts would be less (even far less) dramatic. Models don’t indicate anything of note? But given it’s a poorly modelled area, I’d take that with a grain of salt. Cheers for all the tasty info.
the last vortex split and only one recorded l believe was 2002. Maybe some could check that 2002 SSW event on google and then perhaps BOM seasonal reports for winter 2002 perhaps We are in somewhat uncharted territory. Was 2002 solar minimum as well?
