Teleconnections - Interactions and Impact

[Dennis]

a nice phase 8-1now MJO

Edited November 21, 2023 by Dennis

[Blessed Weather]

54 minutes ago, Dennis said:

a nice phase 8-1now MJO

Yes, arguably that low amplitude transition of the MJO through Phase 8 during 17-19th November that you show played its part to give us the current model attempts to amplify the Azores High mid-Atlantic block and transition it to a Greenland/Iceland high latitude block around the 25-26th of the month. But this shortlived because not only was it was a rapid transition thru Ph 8 but as @Met4Cast says above, there wasn't enough "oomph" (amplitude).

[Dennis]

AO forecast 21-11

[Dennis]

MJO 21-11

[Dennis]

13 hours ago, Met4Cast said:

Before we look further ahead let's take a look at what's recently happened. 

A strong westerly wind burst (WWB) event has just finished in the Pacific, this wind burst event is responsible for a large uptick in AAM tendency (and subsequent rise in AAM) which can be seen here, the timing correlates well with the 850hPa zonal wind anomalies chart above. The left chart shows the rise in AAM tendency and the second chart shows the subsequent rise in global AAM (GLAAM) which followed.

The WWB has faded and easterlies have returned just west of the dateline, as a result AAM tendency has fallen through the floor and GLAAM will begin falling again, likely back into neutral or negative territory, this can be seen on the above two charts too. The main trigger for this is convection emerging in the Indian Ocean (MJO) scrubbing the atmosphere of westerly inertia from the recent WWB. 

During this timeframe the MJO was emerging into a very weakly amplified phase 8.

Rising AAM tendency signals an increase in westerly momentum within the global wind-flow budget, higher westerly momentum can lead to a more perturbed jet stream with phase 8 MJO roughly correlating to a mid Atlantic ridge, I've posted both the El Nino composite & the neutral ENSO composite below given the atmosphere is behaving somewhere between the two. 

If we compare the above composites with the latest GFS forecast there are some similarities, not an exact match but that's to be expected given the very weak amplitude MJO. The high is a little more amplified in the forecast vs the composites and I suspect this is due to +ve westerly momentum perturbing the jet stream.

Broadly speaking then, no real "oomph" to transition the high from a mid-latitude HP to a high latitude HP and as such despite some over-enthusiastic NWP modelling, the signal for a Greenland high hasn't been particularly well supported when taking into account all models and ensemble suites. Going forward, a fall in AAM and the MJO cycling through phases 1-2-3 suggests a return to zonal/Atlantic driven weather through early December but perhaps with the Azores high occasionally extending NEwards into southern parts of England.

Another thing to consider is the -QBO which is continuing to down well. I suspect this is helping to temper the SPV from properly coupling with the troposphere giving us a small window where tropospheric blocking (albeit mostly mid-latitude due to lack of tropical forcing) is favourable.

Will do a post tomorrow about the likely evolution of the MJO & AAM through December and when things could potentially get a little more interesting. 

see this too

 

Edited November 21, 2023 by Dennis

[knocker]

A short summary of the MJO

MJO_summary.pdf

[knocker]

The links between the Madden-Julian Oscillation and European weather regimes

Abstract

Skillful weather forecasting on sub-seasonal timescales is important to enable users to make cost-effective decisions. Forecast skill can be expected to be mediated by the prediction of atmospheric flow patterns, often known as weather regimes, over the relevant region. Here, we show how the Grosswetterlagen (GWL), a set of 29 European weather regimes, can be modulated by the extra-tropical teleconnection from the Madden-Julian Oscillation (MJO). Together, these GWL regimes represent the large-scale flow characteristics observed in the four North Atlantic-European classical weather regimes (NAE-CWRs), while individually capturing synoptic scale flow details. By matching each GWL regime to the nearest NAE-CWR, we reveal GWL regimes which occur during the transition stages between the NAE-CWRs and show the importance of capturing the added synoptic detail of GWL regimes when determining their teleconnection pattern from the MJO. The occurrence probabilities of certain GWL regimes are significantly changed 10–15 days after certain MJO phases, exhibiting teleconnection patterns similar to their NAE-CWR matches but often with larger occurrence anomalies, over fewer consecutive MJO phases. These changes in occurrence probabilities are likely related to MJO-induced changes in the persistence and transition probabilities. Other GWL regimes are not significantly influenced by the MJO. These findings demonstrate how the MJO can modify the preferred evolution of the NAE atmospheric flow, which is important for sub-seasonal weather forecasting.

https://link.springer.com/article/10.1007/s00704-020-03223-2

[rwtwm]

Thanks for sharing this. I'll read down to the correlations, and then realised I'd been distracted from work for some time. I'll update here when I finish absorbing, rather than clogging up the other thread!

[Catacol]

4 hours ago, rwtwm said:

Thanks for sharing this. I'll read down to the correlations, and then realised I'd been distracted from work for some time. I'll update here when I finish absorbing, rather than clogging up the other thread!

And additional to my reply in the model thread, this presentation is probably an easier way into the murky and complex world of the GWO...

GWO.pdf

[knocker]

21 hours ago, knocker said:

The links between the Madden-Julian Oscillation and European weather regimes

Abstract

Skillful weather forecasting on sub-seasonal timescales is important to enable users to make cost-effective decisions. Forecast skill can be expected to be mediated by the prediction of atmospheric flow patterns, often known as weather regimes, over the relevant region. Here, we show how the Grosswetterlagen (GWL), a set of 29 European weather regimes, can be modulated by the extra-tropical teleconnection from the Madden-Julian Oscillation (MJO). Together, these GWL regimes represent the large-scale flow characteristics observed in the four North Atlantic-European classical weather regimes (NAE-CWRs), while individually capturing synoptic scale flow details. By matching each GWL regime to the nearest NAE-CWR, we reveal GWL regimes which occur during the transition stages between the NAE-CWRs and show the importance of capturing the added synoptic detail of GWL regimes when determining their teleconnection pattern from the MJO. The occurrence probabilities of certain GWL regimes are significantly changed 10–15 days after certain MJO phases, exhibiting teleconnection patterns similar to their NAE-CWR matches but often with larger occurrence anomalies, over fewer consecutive MJO phases. These changes in occurrence probabilities are likely related to MJO-induced changes in the persistence and transition probabilities. Other GWL regimes are not significantly influenced by the MJO. These findings demonstrate how the MJO can modify the preferred evolution of the NAE atmospheric flow, which is important for sub-seasonal weather forecasting.

https://link.springer.com/article/10.1007/s00704-020-03223-2

https://confluence.ecmwf.int/display/FUG/Section+8.2.6+Madden-Julian+Oscillation+Output

Edited December 5, 2023 by knocker

[knocker]

 

[rwtwm]

On 04/12/2023 at 14:34, knocker said:

The links between the Madden-Julian Oscillation and European weather regimes

Abstract

Skillful weather forecasting on sub-seasonal timescales is important to enable users to make cost-effective decisions. Forecast skill can be expected to be mediated by the prediction of atmospheric flow patterns, often known as weather regimes, over the relevant region. Here, we show how the Grosswetterlagen (GWL), a set of 29 European weather regimes, can be modulated by the extra-tropical teleconnection from the Madden-Julian Oscillation (MJO). Together, these GWL regimes represent the large-scale flow characteristics observed in the four North Atlantic-European classical weather regimes (NAE-CWRs), while individually capturing synoptic scale flow details. By matching each GWL regime to the nearest NAE-CWR, we reveal GWL regimes which occur during the transition stages between the NAE-CWRs and show the importance of capturing the added synoptic detail of GWL regimes when determining their teleconnection pattern from the MJO. The occurrence probabilities of certain GWL regimes are significantly changed 10–15 days after certain MJO phases, exhibiting teleconnection patterns similar to their NAE-CWR matches but often with larger occurrence anomalies, over fewer consecutive MJO phases. These changes in occurrence probabilities are likely related to MJO-induced changes in the persistence and transition probabilities. Other GWL regimes are not significantly influenced by the MJO. These findings demonstrate how the MJO can modify the preferred evolution of the NAE atmospheric flow, which is important for sub-seasonal weather forecasting.

https://link.springer.com/article/10.1007/s00704-020-03223-2

It's taken me a long time to get round to looking at this I know. Lots of new terminology to internalise with the regime classifications! I'm gonna need a few more passes to really understand it, so what follows might be based on a misinterpretation.

I think the state models at the end are really useful. I have one hesitation around the correlation matrices though. Whenever a composite is posted, it's normally for a specific month. Phase 1 in January can look quite different to the same composite in March for example (and I haven't checked so that example might be rubbish!)

The paper seems to correlate the MJO with a lagged regime regardless of when the phase occurs. Nor is it mentioned as a follow up activity, suggesting that in the eyes of the authors at least, it's maybe not that important?

Is it possible then that the sample size of the composites is too small to be useful? Or are the authors overlooking an important aspect? Or have I missed something?

FWIW - The best Phase 1 (Our current place in the cycle I think) correlation I can see in the paper is for the SA, and SWZ regimes. That's the top right and bottom left on the below. Not quite nirvana?

 

 

 

[Met4Cast]

Given the recent discussions around teleconnections/AAM & the broader GSDM framework I thought I would begin posting in this thread, hopefully we can build up something of a more technical discussion here & separate from the usual chaos and ups and downs of the model output thread. Winter is coming to an end now so I suspect the forum will be quietening down so it's perhaps a good idea to start and see where we go through summer. 

I've been delving into the GSDM and broader teleconnections for just over a year now after DMing Tamara & asking for some guidance. I'd still consider myself a novice but I do think this is the way forward in terms of mid-extended range forecasting despite recent comments from some. I wonder if @Paulor another mod could move this thread to the model output section? It seems a better fit vs here. My main goal is to try and get broader teleconnections discussed more by those who have an interest in the science & in forecasting vs just wanting a particular weather type. 

Late February

I've posted elsewhere re: late February prospects but figured I would discuss the current situation here too. The MJO is currently dwindling through phase 7 and into phase 8 which if taken into isolation correlates to a mid Atlantic ridge/amplified Azores high.

The up-coming stratospheric warming can be linked back to the MJO passing through the Maritimes and into the Pacific Ocean (Phases 4 > 5 > 6) through mid-late January, this created +ve Frictional Torque which in turn creates Rossby waves that amplify northwards, the impact of this was a very strong +ve mountain torque event in late January leading to a Pacific jet extension, this created further Rossby wave packets that have led to anti-cylonic wave breaking into southern Europe helping to strengthen the Iberian/S European high over the past couple of weeks. You can see these Rossby wave packets on the ECM time longitude plots.

Back to the SSW (technical or not), the strong +ve East Asian Mountain Torque (EAMT) essentially deflects waves from the troposphere up into the stratosphere, this has been sustained more or less since late January with wave activity impacting the stratospheric vortex & now resulting in it's collapse. You can see this heatflux on the stratosphere plot from stratobserve, it's no coincidence that this is showing strongly downstream of the Himalayas (this is the EAMT at work)

North American mountain ranges have also helped to generate heatflux (namely the Rocky mountain range) albeit to a lesser extent and now we're in a position where we're expecting significant deceleration of u-wind speeds in the stratosphere. 

AAM anomalies and indeed flux direction plays a part in the Iberian high mentioned above & subsequent anticylonic breaking. I wont go into too much detail on this in this post as there's always a lot of information here, but in summary;

 

+ve anomalies have been broadly equatorward since late January (between 30S and 0) with little momentum propagating poleward, this (from my understanding, happy to be corrected) tends to drive energy into sub tropical ridges (Hadley cell inc. the Azores high) and this broadly has been the dominating pattern through February so far. 

There's no real sign in this fluxing switching to poleward fluxing and as a result there isn't much forcing to amplify Atlantic ridging into high latitude blocking later this month, hence the forecasts (and this is well represented within NWP modelling) generally favouring an amplified Atlantic ridge sending energy SEwards, for the UK this will likely bring colder weather than the anomalous warmth we've been seeing/will see in the coming days but probably wont be enough for a notable cold spell or widespread snow risks. 

Any questions please feel free to ask, the idea of re-igniting this thread is to get more people interest in the science & forecasting aspect this can provide, the more people joining in and being open to background teleconnective forcing the better in my opinion. It is a shame the GSDM data is locked away and it does somewhat limit potential learning on the topic but I think we can get around that via discussions/sharing of data where possible on this forum.

 

Edited February 14 by Met4Cast

[Metwatch]

I imagine many are now looking for any signs of something warmer / settled heading into the first half of spring following how much rain there has been recently. A 2020 repeat is probably unlikely or even 2018 for later spring, but I was wondering what would the AAM, MJO, GWO etc need to do to get heights over or just east / North east of the UK during spring as Nino weakens? The 850mb wind anomalies in the tropics and velocity potential chart discussions would prove useful as well.

Analogues are are of less use now with AGW, but we are coming out of a strong Nino, which was last seen in 2016, 2010, 1998, 1992, 1983 etc. A lot of those springs weren't great for dryness (2010 was drier and May can some years be an improvement), but ENSO on its own isn't very indicative of much.

I wonder what the IOD forecasts look like and if that has much bearing on what it does. Below I found the IOD index since the 90s, but I can't see much correlelation with settled springs. Any links to other IOD forecast charts would be useful!

The North Atlantic is in uncharted territory at the moment, and that may not bode well for something drier heading into spring but a question mark on that.

 

Also any idea where I may find those MJO reanalysis charts which i've seen posted by a fair few recently?

Edited February 14 by Metwatch

[Blessed Weather]

26 minutes ago, Metwatch said:

Also any idea where I may find those MJO reanalysis charts which i've seen posted by a fair few recently?

I'm unsure exactly what you're after (I can't recall seeing reanalysis charts posted), but maybe the NOAA MJO archive going back to January 2006 may help? Don't look at the "file last updated" date, but go by the date embedded within the pdf file name.

Files in /products/precip/CWlink/MJO/ARCHIVE/PDF

WWW.CPC.NCEP.NOAA.GOV

 

[Metwatch]

 Blessed Weather

Thanks, that is helpful, but specifically looking for charts like this below which Met4cast posted. I've seen them for years going all way back to the 80s.

On 13/02/2024 at 14:41, Met4Cast said:

Here is the complete MJO cycle, the blue line represents Decembers progression & then subsequent collapse.

@Derecho posted a lot of them above the other week.

Edited February 14 by Metwatch

[Metwatch]

https://ds.data.jma.go.jp/tcc/tcc/products/clisys/mjo/monitor.html

Got this now, goes back to 1980!

[Met4Cast]

1 hour ago, Metwatch said:

Thanks, that is helpful, but specifically looking for charts like this below which Met4cast posted. I've seen them for years going all way back to the 80s.

They’re available here; 

http://www.bom.gov.au/climate/enso/#tabs=Tropics&tropics=History-to-now

[Metwatch]

 Met4Cast

BOM just doesn't work for me, phone or laptop or any browser

Edit: i've got it working for the time being, thanks!

Edited February 14 by Metwatch

[Blessed Weather]

7 minutes ago, Metwatch said:

BOM just doesn't work for me, phone or laptop or any browser

Strange. The link works for me on my laptop (using Firefox browser). From your image it looks like the https protocol might be messing it up. Try copying in and pasting the link from Met4Cast into the url address line. It should look like my screen shot and not have 'https' showing on the address.

[Met4Cast]

On 14/02/2024 at 13:23, Met4Cast said:

There's no real sign in this fluxing switching to poleward fluxing and as a result there isn't much forcing to amplify Atlantic ridging into high latitude blocking later this month, hence the forecasts (and this is well represented within NWP modelling) generally favouring an amplified Atlantic ridge sending energy SEwards, for the UK this will likely bring colder weather than the anomalous warmth we've been seeing/will see in the coming days but probably wont be enough for a notable cold spell or widespread snow risks. 

Just over a week on & indeed transient Atlantic ridging seems the most likely weather pattern through this month, certainly a departure away from the recent anomalous warmth across the UK (and indeed Europe) but nothing overly sustained or notable as largely expected. Any snowfall in the coming week or two will be mostly restricted to higher ground in the north. 

Going forward I'd not be surprised to see this pattern repeat a few times, i.e Atlantic ridging before collapsing. The MJO signal has now decayed into the Circle of Death (COD) and is not currently driving global weather patterns, a result of this is an abrupt loss in westerly inertia triggered by a strong -MT event, led particularly by very strong -EAMT. 

There is now evidence of poleward propagating +AAM anomalies which should help to generate Atlantic ridging and amplify it away from Iberia (the opposite to the recent equatorward fluxing helping to strengthen the Iberian high). The forecast going forward is quite uncertain, the MJO seems likely to emerge into phase 4/5/6 but the direction of travel & amplitude is very hard to ascertain at the moment. A major and sustained (perhaps final warming) SSW looks to take place during early March helping to destabalise the polar field but there's currently little sign of these -ve anomalies downwelling to impact tropospheric patterns before the middle of March, again though this is a large uncertainty within the forecast period.

I'm still of the opinion that early-mid March will feature an increasingly -NAO regime albeit probably not notably cold across the UK with the high never really gaining much in the way of amplitude due to the lack of tropical (MJO) forcing.

Looking beyond the early March period is difficult, much will depend on the outcome of the major SSW (and any downwelling impacts) & the trajectory of the MJO, again currently uncertain. 

Edited February 21 by Met4Cast

[Rain All Night]

10 hours ago, Met4Cast said:

destabalise the polar field

What does this actually mean?

[Met4Cast]

 Rain All Night

Wind reversal. Westerly winds are inherently more stable than easterly winds. Descending easterlies disrupts the usual westerly flow in the troposphere which can lead to blocking.

[MattH]

 Met4Cast

19 hours ago, Met4Cast said:

There is now evidence of poleward propagating +AAM anomalies which should help to generate Atlantic ridging and amplify it away from Iberia

Just a quick one, but some caution here...If you're after amplification to the pattern and a more buckled jet stream then you don't want +ve AAM anomalies propagating to higher latitudes, you want -ve E'ly AAM anomalies. This is where some of the GSDM plots can be misleading, on the MT plot you're statement is "correct" but in the grand scheme of things, if you look at the AAM transport plots, along with the Total AAM plot, relative AAM plot then it is the other way around. +AAM through the mid-latitudes would help to reinforce a westerly flow.

I recommend cross-checking the following - https://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/hgt.ao.cdas.png with the likes of relative AAM transports plot and you'll see the key links as to when the AO became both -ve and +ve based on the poleward propagation of E'ly AAM anoms and W'ly AAM anoms.

Matt.

[Met4Cast]

6 hours ago, MattH said:

Just a quick one, but some caution here...If you're after amplification to the pattern and a more buckled jet stream then you don't want +ve AAM anomalies propagating to higher latitudes, you want -ve E'ly AAM anomalies. This is where some of the GSDM plots can be misleading, on the MT plot you're statement is "correct" but in the grand scheme of things, if you look at the AAM transport plots, along with the Total AAM plot, relative AAM plot then it is the other way around. +AAM through the mid-latitudes would help to reinforce a westerly flow.

Thanks for the correction, appreciate that!