Jump to content
Cold?
Local
Radar
Snow?

Stratosphere and Polar Vortex Watch


Recommended Posts

1 minute ago, northwestsnow said:

Quite, i wonder if Glosea has factored in the Dec SSW...

Obviously the 1st part relies on the 2nd part coming to pass..

 

Well glosea was showing a strong Weak flow anomoly high up and the opposite low down on a chart I saw so maybe yes, it did and for whatever reason, it doesn’t want to propagate the slowing/stalling/reversal (whichever verifies) 

  • Like 5
Link to post
Share on other sites
  • Replies 3.9k
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

Some useful tropospheric developments upcoming which are likely to have stratospheric impacts towards the end of November and more particularly into December. A strong convectively coupled tropic

so after many days the GFS & FNMOC & canadian finally now follow the Euro with 44 out 64 Members with a split at day 9- The ECM is day 8. We will call it - SSW & Split for 1st Ja

For all that watch the zonal winds. Let me urge you to look at the geopotential heights more. At least as far as weakening/strengthening trends go. Because as the polar vortex cries for help, you migh

Posted Images

2 minutes ago, bluearmy said:

Well glosea was showing a strong Weak flow anomoly high up and the opposite low down on a chart I saw so maybe yes, it did and for whatever reason, it doesn’t want to propagate the slowing/stalling/reversal (whichever verifies) 

What is a strong weak flow anomaly, please BA?

  • Like 1
Link to post
Share on other sites
7 minutes ago, Tim Bland said:

Does what is shown on the 12z GFS op qualify as a SSW?

Yes...

but this is a forecast for day 10>

that's the first step

the second step is will it displace or split the pv

thirdly,will we benefit from it,we will see. 

Edited by Allseasons-si
  • Like 3
Link to post
Share on other sites

The warming of 22-24 November will lead to a Canadian Warming and a wave 1 of exceptional magnitude for the time of the year. As a consequence the SPV will be displaced to the Russian side of the North Pole. That's where it begins to be really interesting. By the end of the month and the Russian High (troposphere) will intensify again (mainly because of the long lasting AO+). For the beginning of December a huge heat flux is being calculated, due to the all known wave breaking. 

I would like to know something more about this wave breaking. Is this wave breaking taking place in de troposphere, over East Siberia (picture 2)? Secondly: is it purely a coincidence that the heat flux in the stratosphere shows itself at the transition of the Canadian wave1 and the Russian wave2. What kind of mechanism is taking place?

The early December heat flux leads to a wave2 at the upper levels of the statosphere over East Siberia (Picture 3). West of this second wave is an area of intense heat flux, but at the east side of the Candadian wave also strong heat flux is taking place. Is this second one a downward heat flux?

Knipsel2.PNG

Knipsel8.PNG

Knipsel4.png

  • Like 4
Link to post
Share on other sites
4 minutes ago, Tim Bland said:

Does what is shown on the 12z GFS op qualify as a SSW?

Well it would qualify if zonal winds reverse at 10 hPa and 60N, which I haven't seen charts for, but I would expect probably not.  What is important from my experience having 'watched' a number of SSW events unfold on the models is a sense of momentum building, and we are seeing this now, a few days ago the first GEM ensembles went for it, now the GEFS (a much more reliable set) are too.  The trend is your friend!  If you are looking for a SSW that is, even if one happens the jury hasn't even sat for the impacts on UK after!

  • Like 5
Link to post
Share on other sites
5 minutes ago, bluearmy said:

There is no ssw on the gfs 12z ruN

Zonal wind is 18m/s by day 16

Closest  point to a reversal approx 7hpa 50N 

But gefs shows mean speed at only 5m/s by day 16 

Interesting.  I'm putting more faith in the GEFS than the op this year (re the strat), as we have seen some divergences already, the GEFS is as it always was, but the op is now the FV3 and I read at the time of its introduction that there were some question marks over the models performance in the strat.

Edited by Mike Poole
  • Like 3
Link to post
Share on other sites

Judah Cohen's latest blog update includes his thoughts on the stratospheric goings on 

aer_logo_300x300.png
WWW.AER.COM

November 11, 2019 - Dr. Judah Cohen from Atmospheric and Environmental Research (AER) embarked on an experimental...

 

  • Like 3
Link to post
Share on other sites
1 hour ago, bluearmy said:

Well glosea was showing a strong Weak flow anomoly high up and the opposite low down on a chart I saw so maybe yes, it did and for whatever reason, it doesn’t want to propagate the slowing/stalling/reversal (whichever verifies) 

This does just generate the image of the stuff of nightmares!  To think GloSea5 has been right all along, and to boot, we get our SSW, in mid December, and despite all people like us have written about it on here, it does absolutely nothing to unseat the (by then) raging +NAO pattern.  If that happened I really would need to cower under a giant toadstool....

Fortunately, it was just a dream.

Edited by Mike Poole
  • Like 3
Link to post
Share on other sites
39 minutes ago, bluearmy said:

There is no ssw on the gfs 12z ruN

Zonal wind is 18m/s by day 16

Closest  point to a reversal approx 7hpa 50N 

But gefs shows mean speed at only 5m/s by day 16 

Isn’t a reversal a major SSW? It doesn’t need to be a reversal to be a SSW, only to be a major SSW.

  • Like 1
Link to post
Share on other sites
8 minutes ago, MattStoke said:

Isn’t a reversal a major SSW? It doesn’t need to be a reversal to be a SSW, only to be a major SSW.

This is my understanding also. 

Major =reversal 

Minor= no reversal but slowing 

Link to post
Share on other sites
JOURNALS.AMETSOC.ORG

"A stratospheric warming is called minor if a significant temperature increase is observed (i.e., at least 25 degrees in a period of a week or less) at any stratospheric level in any area of the wintertime hemisphere, measured by radiosonde or rocketsonde data and/or indicated by satellite data; and if criteria for major warmings are not met. Less extreme warmings will be referred to as warming pulses. 2. A stratospheric warming can be said to be major if at 10 mb or below the latitudinal mean temperature increases poleward from 60 degrees latitude and an associated circulation reversal is observed (i.e., mean westerly winds poleward of 60° latitude are succeeded by mean easterlies in the same area). Yet a WMO CAS report (WMO CAS 1978, p. 36, item 9.4.4) published two months later, while stating the same definition for minor SSWs, states: “‘major’ warmings [occur] with a temperature increase of at least 30 degrees in a week or less at 10 mb or below, or by at least 40 degrees above 10 mb.” No criteria about the circulation reversal are mentioned in this WMO CAS report."

didnt link properly but on google it is the document called - Defining Sudden Stratospheric Warmings - AMS Journals

Edited by Kirkcaldy Weather
  • Like 3
Link to post
Share on other sites
14 minutes ago, MattStoke said:

Isn’t a reversal a major SSW? It doesn’t need to be a reversal to be a SSW, only to be a major SSW.

 

4 minutes ago, ALL ABOARD said:

This is my understanding also. 

Major =reversal 

Minor= no reversal but slowing 

A technical ssw is a reversal of zonal flow at 10hpa at 60N

warmings/slowdowns/reverse flows .... unless you get a tech ssw then it ain’t a ssw

Whilst a tech ssw at 9 hpa or 61N would still have the same consequences high up in the strat, we do need to see it get down to both 60N and 10hpa if we want to see it downwell to the trop 

Link to post
Share on other sites
14 minutes ago, bluearmy said:

 

A technical ssw is a reversal of zonal flow at 10hpa at 60N

warmings/slowdowns/reverse flows .... unless you get a tech ssw then it ain’t a ssw

Whilst a tech ssw at 9 hpa or 61N would still have the same consequences high up in the strat, we do need to see it get down to both 60N and 10hpa if we want to see it downwell to the trop 

''Major SSWs occur when the winter polar stratospheric westerlies reverse to easterlies. In minor warmings, the polar temperature gradient reverses but the circulation does not, and in final warmings, the vortex breaks down and remains easterly until the following boreal autumn".

 

Butler, Amy H.; Sjoberg, Jeremiah P.; Seidel, Dian J.; Rosenlof, Karen H. (9 February 2017).

 

  • Like 2
Link to post
Share on other sites
17 minutes ago, bluearmy said:

 

A technical ssw is a reversal of zonal flow at 10hpa at 60N

warmings/slowdowns/reverse flows .... unless you get a tech ssw then it ain’t a ssw

Whilst a tech ssw at 9 hpa or 61N would still have the same consequences high up in the strat, we do need to see it get down to both 60N and 10hpa if we want to see it downwell to the trop 

Not sure about that tbf, i just cannot see that tiny margin making a huge difference in the overall scheme of things, certainly not on every occasion anyway.

  • Like 2
Link to post
Share on other sites
28 minutes ago, feb1991blizzard said:

Not sure about that tbf, i just cannot see that tiny margin making a huge difference in the overall scheme of things, certainly not on every occasion anyway.

My point being that if it doesn’t get down to 10hpa, it ain’t influencing 100hpa! 

  • Like 1
Link to post
Share on other sites
14 minutes ago, bluearmy said:

My point being that if it doesn’t get down to 10hpa, it ain’t influencing 100hpa! 

See what you mean but it could still have some effect, the average wind speed might be still above 0 m/s but that could have the effect of dramatically reducing the average wind speed lower down, technically you could (however unlikely) have a 100mb pattern (which imprints on the trop) with lower than average heights most of the way around the globe at 60N but the one place they are above average could be Iceland but if there has been a shift in the trop pattern you would bet your bottom dollar it has been influenced by what has gone on above.

Link to post
Share on other sites

Daniela Domeisen is currently presenting at the ECMWF workshop. She's talking about trop impacts of SSW. A couple of notes:

1. There is, on average, a -NAO response to SSWs. However, this average is dominated by a strong -NAO signal in 2/3rds of cases. In the other 3rd, there is no signal at all. 

2. The likelihood of a downwelling (and a subsequent -NAO) depends on the state of the troposphere at the time of the onset of the SSW. If there is a strong Euro block in the trop at the onset of the SSW, then this is much more likely to result in downwelling and a -NAO.

  • Like 4
Link to post
Share on other sites
16 minutes ago, Yarmy said:

Daniela Domeisen is currently presenting at the ECMWF workshop. She's talking about trop impacts of SSW. A couple of notes:

1. There is, on average, a -NAO response to SSWs. However, this average is dominated by a strong -NAO signal in 2/3rds of cases. In the other 3rd, there is no signal at all. 

2. The likelihood of a downwelling (and a subsequent -NAO) depends on the state of the troposphere at the time of the onset of the SSW. If there is a strong Euro block in the trop at the onset of the SSW, then this is much more likely to result in downwelling and a -NAO.

Well it would seem a Euro block is here for the stay so maybe....

  • Like 1
Link to post
Share on other sites

 

According to Cohen we -here in NW-Europe shouldn't expect much of the possible SSW.

Impacts

In my opinion it is crunch time for the Northern Hemisphere (NH) winter. A minor sudden stratospheric warming (SSW where a warming of at least 25°C occurs in the polar stratosphere) is likely and a major mid-winter warming (MMW where the zonal mean zonal wind at 10hPa and 60N reverses from positive to negative) is possible in mid-December. I include in Figure i the temperature animation of the stratosphere and impressive warming is being predicted by the GFS, enough to at least qualify for a minor warming.  Based on the GFS forecast, some regions of the polar stratosphere could see a 70°C (126°F) jump in temperature in a matter of days!  I saw that some members of the GFS ensemble showed an MMW as early as early December, but I think this is likely too soon.

I believe regardless of the timing and magnitude of the event it will have impacts on the NH weather.  I would argue that some of the predicted features in the tropospheric circulation are related to the anticipated PV disruption.  The models are predicting a mid-troposphere low pressure over Northern Siberia starting next week.  This is very close to the predicted location of the stratospheric PV starting this week.  The other predicted main feature in the polar stratosphere is ridging/high pressure centered near Alaska.  This will likely be associated with a tropospheric feature/reflection as well.   Something similar occurred last December with ridging in the interior of North America and very mild temperatures across the continent.  A repeat is possible but my sense of the trends this fall is that the ridge will likely setup further west, forcing a colder solution but admittedly it’s a tough call.

In last week’s blog, I argued that the increase in the vertical energy transfer and the PV disruption is looking more like an “absorptive” event and less like a “reflective” event and that seems to be even more true this week.  Leading up to an “absorptive” event while the stratospheric AO trends negative the tropospheric AO trends positive with milder temperatures across the mid-latitudes and colder temperatures in the Arctic.  Though many of the trends are not particularly strong, based on today’s forecast plots included in today’s blog all those trends are apparent.  The forecast for Europe is consistent with these expectations with an increasing westerly flow and milder temperatures. Milder trends are also predicted for eastern North but those trends might run into more resistance due to record low sea ice in the North Pacific sector of the Arctic and the well above normal sea surface temperatures (SSTs) in the eastern North Pacific especially in the Gulf of Alaska.  Those features could help to promote ridging near Alaska/Gulf of Alaska with downstream troughing in North America with colder temperatures bucking the trends from the vertical energy transfer.

Regardless of the amplitude, I expect some cold weather from the SSW most likely in eastern North America and Northern Asia.  However, if the predicted SSW is relatively minor with a quick recovery in the stratospheric AO, even possibly becoming strongly positive, would favor a positive tropospheric AO.  Then an extended mild to very mild period across the NH mid-latitudes could ensue from late December through much of January.  I would expect at some point another PV disruption that would reverse the weather to colder but by then an overall mild winter would be almost a certainty.

Last December (before the AO blog was archived), I did analyze some MMW that were of the displacement variety.  First, event to event variability is large but there are two PV displacements that occurred relatively recently in mid-December – December 15, 1998 and December 16, 2000.  These are calendar dates close to when our polar vortex model predicts as the time most likely for an MMW this upcoming December.  If the SSW occurs mid-December then it takes about two weeks for the related circulation to propagate down from the stratosphere to the troposphere with a colder weather regime to follow, starting around the holidays.

The winter of 1998/99 and 2000/01 are two very different winters with winter 1998/99 being relatively mild and winter 2000/01 being relatively cold in eastern North America and Northern Asia.  There was also an MMW in late December 2001/early January 2002 followed by a mild winter.  However for now, I am leaning towards a colder solution more similar to 2000/01 more so than 1998/99 given the low sea ice in the North Pacific sector of the Arctic (though based on the weather forecasts, I expect a lot of ice to form over the next two weeks) and the very warm SSTs in the eastern North Pacific.  Also, in general the Arctic is warm.  I wrote many blogs last winter on the surprisingly cold Central Arctic that may have interfered with the downward propagation of a negative AO.  So far this fall, the central Arctic has not been cold.   Also the QBO (quasi biennial oscillation) is easterly or at least trending east.  An easterly QBO favors a more negative AO than a westerly QBO  (see Labe et al. 2019).

The following is some of the relevant text and figures copied from last December: “I have included in Figure ii the stratospheric PV a week or longer prior to when an MMW was observed and then in Figure iii the observed temperature anomalies across the NH the month when an MMW was observed and the following one or two months.  Winters included are 1998/99, 2000/01, 2001/02, 2003/04, 2005/06 (in the Cohen and Jones paper this is listed as PV split - the cold Europe and blockbuster February snowstorm along the mid-Atlantic are consistent with this - but at least the beginning resembles a PV displacement), 2006/07 and 2007/08.  Prior to 1998, the most recent stratospheric PV displacement was in 1987. My personal preference is not to use analogs prior to the era of amplified Arctic warming (pre-1990) for current winters.

  In all of the stratospheric PV displacements since 1998 the stratospheric PV is displaced towards northern Eurasia with the exception of February 2007 when the stratospheric PV was displaced towards Greenland.  Also, the flow around the stratospheric PV in all winters was directed from Siberia towards eastern North America (5 winters) or to Europe (2 winters).  The predicted stratospheric PV displacement (see Figure 13 below) is consistent with all the previous stratospheric PV displacements of the past two decades.

Looking at the surface temperature anomalies during and following all seven stratospheric PV displacements shows more variability.  Temperatures across eastern North America are below normal four of seven two or three winter months during and following the stratospheric PV displacement.  Temperatures across much of Europe are below normal really only once for the two or three winter months during and following the stratospheric PV displacement.  Temperatures across Asia are below normal three of seven two or three winter months during and following the stratospheric PV displacement.” https://www.aer.com/science-research/climate-weather/arctic-oscillation/

  • Like 3
Link to post
Share on other sites

@sebastiaan1973, we expect too much of a ssw, I checked most of them since 1958 and only 1985 (actually new years eve 1984) and 2012 brought could to our region (I looked at hellmann numbers for de Bilt), most ssw  however were actually preceded by marked cold periods 

Link to post
Share on other sites
Guest
This topic is now closed to further replies.
×
×
  • Create New...