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Snowy Hibbo

Teleconnections: A More Technical Discussion

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2 hours ago, Bring Back 1962-63 said:

The further 10 to 14 time lag between FT and MT is even clearer.  The peak in FT on Nov 10th was followed by a peak in global MT on Nov 20th.  The fall in FT from Nov 15th to its low point around Nov 25th is currently being matched with global MT still falling steadily and with the 10-14 lagged window it should reach its lowest point around Dec 5th-9th. It looks like it will only go slightly -ve overall before rising again. Then it should be rising for about a week but as FT is expected to fall sharply this week, then global MT should fall sharply again around mid-Dec.  Now if the big fall in rel GLAAM tendency is followed by a big bounce back imminently, then FT should rise strongly after mid-month but the next "big" rise in global MT should not be until around of just after Xmas (with only that modest and brief rise around Dec 9th-15th). I won't go into the regional torques this time.

And that was really what I was trying to say on the previous page :) 

 

We shouldn't see big rises in the MT until around Xmas or just after. 

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2 hours ago, Isotherm said:

Recall, too (this is just directed to everyone), that total AAM is multifactorial, and independent intraseasonal AAM anomalies can arise via extratropical mountain torque forcing, in addition to the tropical convection related FT which propagates poleward on the time-lag schedule of 7-10 days. The tropically emanating torque anomalies may be  somewhat insignificant, but the disparate, extratropical MT can also modulate the AAM. So, while I concur that tropically generated torque will take longer to manifest, that doesn't preclude rises from other extratropical source.

 

"Oscillatory forcing by the extratropical mountain torque in the 20–30-day band was also proposed (e.g., Lott et al. 2004; Lott and D’Andrea 2005). The idea of independent intraseasonal global AAM oscillations, one forced by mountain torques in the extratropics and the other by convection in the tropics was postulated and the former process was studied by Marcus et al. (1994) and Jin and Ghil (1990)."

 

https://journals.ametsoc.org/doi/10.1175/2008MWR2686.1

 

Hi Tom, thank you for this very useful additional information.  The 2008 paper that you refer to was one of the first that I placed into the Research Portal in early April.  It is a superb read and written by Ed Berry and Dr Klaus Weickmann. It's essential for anyone learning about or increasing their AAM knowledge.  I need to re-read some of these papers several times to get more of it to sink in and it really helps to return to it (or them) once one's knowledge of the basics has increased. Here's a direct link to the portal entry:   The tropical Madden-Julian oscillation and the global wind oscillation with the abstract and link to the full paper.  I copy the entry here:

 

The tropical Madden-Julian oscillation and the global wind oscillation

 

Authors:   Klaus Weickmann and Edward Berry

 

First Published:  June 12th , 2008

 

Abstract:

The global wind oscillation (GWO) is a subseasonal phenomenon encompassing the Madden-Julian Oscillation (MJO) and mid-latitude processes like meridional momentum transports and mountain torques. A phase space is defined for the GWO following the approach of Wheeler and Hendon (2004) for the MJO. In contrast to the oscillatory behavior of the MJO, two red noise processes define the GWO. The red noise spectra have variance at periods that bracket the 30-60 day band generally used to define the MJO. The MJO and GWO correlation accounts for 25% of their variance and crossspectra show well-defined phase relations. However, considerable independent variance still exists in the GWO. During MJO and GWO episodes, key events in the circulation and tropical convection derived from composites can be used for monitoring and for evaluating prediction model forecasts, especially for weeks 1-3. A case study during April-May 2007 focuses on the GWO and two ~30 day duration orbits with extreme anomalies in GWO phase space. The MJO phase space projections for the same time were partially driven by mountain torques and meridional transports. The case reveals the tropical-extratropical character of subseasonal events and its role in creating slowly evolving planetary-scale circulation and tropical convection anomalies

 

Link to Paper:

https://www.esrl.noaa.gov/psd/map/clim/wb08_final.pdf

 

David :)  

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11 hours ago, Snowy Hibbo said:

And that was really what I was trying to say on the previous page :) 

 

We shouldn't see big rises in the MT until around Xmas or just after. 

Given that FT started to rise about 5 days ago I'm expecting MT to follow mid month and not later. It seems to me on his tweet that Masiello is simply reading the pressure anomalies, with positive anomalies forming around all 3 major mountain ranges at around the same time and creating the spike in torque. Reading those forecast anomalies, unless the forecast proves wildly incorrect, I'm not sure how his interpretation can go awry. 

 

Which leads me back to where my musing on all this started. Given that Glaam remains high - how can we have another interaction of torques and another predicted rise in tendency? Given that we are still above +2SD in total momentum it seems bizarre to me that we have not experienced a fall in momentum, but have instead witnessed a best fit line that has projected upwards consistently. This in the context of a Nino that is not huge. But as Zac says - it may not be intense but it is a widespread phenomenon that reaches north as well as a long way west. And the Siberian High Aleutian Low combo is allowing all that energy to be channelled onto a destructive path for the winter vortex.

 

It's a fascinating season beginning to unravel. The timing of Nino's arrival in early autumn on the back of a Nina that had maintained broad control for around 2 years and a transitioning E to W QBO last month, may prove in the end to be of critical significance in how this season progresses. The timeline context of every event is surely as important as the snapshot blueprint of that event itself.

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1 hour ago, Catacol said:

Given that FT started to rise about 5 days ago I'm expecting MT to follow mid month and not later. It seems to me on his tweet that Masiello is simply reading the pressure anomalies, with positive anomalies forming around all 3 major mountain ranges at around the same time and creating the spike in torque. Reading those forecast anomalies, unless the forecast proves wildly incorrect, I'm not sure how his interpretation can go awry. 

 

Which leads me back to where my musing on all this started. Given that Glaam remains high - how can we have another interaction of torques and another predicted rise in tendency? Given that we are still above +2SD in total momentum it seems bizarre to me that we have not experienced a fall in momentum, but have instead witnessed a best fit line that has projected upwards consistently. This in the context of a Nino that is not huge. But as Zac says - it may not be intense but it is a widespread phenomenon that reaches north as well as a long way west. And the Siberian High Aleutian Low combo is allowing all that energy to be channelled onto a destructive path for the winter vortex.

 

It's a fascinating season beginning to unravel. The timing of Nino's arrival in early autumn on the back of a Nina that had maintained broad control for around 2 years and a transitioning E to W QBO last month, may prove in the end to be of critical significance in how this season progresses. The timeline context of every event is surely as important as the snapshot blueprint of that event itself.

Yeah sorry I got muddled. MTs should go up in about 5-7 days. Basically going up around the 12th. I was meaning CONUS effects of a rise should be expected around Xmas, and a +PNA should be expected just before Xmas. But the AAM will definitely fall very soon, so there will be a time of less westerly momentum, which was not the tone I was getting from Maisello. From what I saw of his further tweets, the westerly momentum continues through this period. It will take 10 days for the MT generated westerly momentum to show on the AAM, so we shouldn't see impacts on CONUS until just before Xmas. 

 

My forecast of a lull around 12th to 24th, still is supported within both the framework I have set, and the GEFS forecast (and therefore Maisello's opinion), but I think he is still a bit early in terms of favouring in the PNA region.

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DthSu1ZXcAMDBqH.jpg

 

 

Big time warming up there - from tweeter PV Forecast

 

DthTiLyXQAAxfy2.jpg

 

 

From Ventrice

DthMqMBWsAcivoF.jpg

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6 hours ago, Bring Back 1962-63 said:

 

Summary:

I'll try to summarise what I said above with the low and high points for what we've seen recently and the expected changes for this month, assuming that RGTA rises strongly from now on and for a week or so. Please note that the time lagged responses are usually around 10 to 14 days and the predicted dates (shown in italics) may vary by 1 or 2 days earlier or later..

 

                                         RGTA                                       FT                                   GLMT

Low Point                Nov 14th/15th                    Nov 24th/25th                   Dec 5th-9th

High Point                    Nov 20th                          Dec 1st-2nd                     Dec 12th -15th

Low Point              Nov 30th/Dec 1st                 Dec 12th-15th                  Dec 22nd-25th  

High Point            circa Dec 8th-12th              circa Dec 18th-22nd     circa Dec 28th-Jan 1st

 

I am really sticking my neck out here but this should give an idea of what we might expect if everything falls into place. What we really need to look out for is how strong the changes and responses will be during this month's cycle.  Remember it's not just the low and high points but the trends in the rises and falls. This is also highly simplified and the MJO, ENSO and other factors all come into play too.  David :) 

 

That looks about right to me. MT peak in around 10 days time will be interesting to gauge - in the context of global pressure patterns a strong spike could potentially be the beginning of a multicausal process that witnesses vortex destruction in early to mid January. Timing this year could not be better.

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Latest GSDM outputs at the moment. While GLAAM remains high, the tendency has almost 'gone through the floor'...

 

image.png.79b9910a4edf9bc2c541b02d7db94502.png

 

Equally, of significance seems to the development of a negative frictional torque along with a response in terms of MT as well. With the exception of S America, the others have trended sharply negative, particularly the global one in particular.

 

image.png.8b0091626aaa24de660110a2fc00cc58.png

 

The main question is this going to drive the GWO down into a lower phase moving forward, or is there other factors at play that meanwhile it may well transit into phase 8 a potential recovery back round to phase 4 or 5 could well develop?

 

image.png.616a40ecb43ad9b2b9b43764e81a849f.png

 

The compo anom for GWO 5 through Dec (Momentum Transport Across 35N) is certainly tallying nicely at the moment with the overall predicted N Hem pattern looking forward, especially regarding this signal for another Scandinavian blocking high which is likely to influence the weather here in the UK. I'm not entirely sure on the lag of these, but perhaps one could also argue that the phase 5 transit occurred during Nov and not Dec.

 

image.png.6127fb7d91d0d9cf049a67f241a29f01.png

 

Given the latest MJO signal could that be enough to kick it back up towards phase 5 again looking forward?

 

image.png.e872bcf8ec1a7074ba73faa863f76612.png

 

Without question, it certainly looks as though it has aided the development of this Scandy block, but I'd be interesting to know where others thing the GWO will progress looking ahead...

 

Cheers, Matt.

 

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Gents,

 

Find below two graphics, just quickly put together. As I've mentioned I'm trying to piece more and more information together to get an understanding of the connection and relationships and, from the two earlier posts I've tried to use an example to see if I'm either barking up the wrong tree or at least on the right lines. One example I thought of was the major Scandinavian blocking pattern in mid-November. I've tried to annotate the graphic as I see it and how the graphics and the AAM information would 'tell the story' and help support that previous blocking regime.

 

Can 'Catacol' or anyone please either shoot me down in flames with reasoning please or confirm what I've put in the graphics holds some weight and I'm thinking along the right lines.  PS: Apols if any grammar/text errors, quick Paint job after a long forecasting shift!

 

Many thanks once again...

 

image.png.1f932b6c14c8d9bfb268f03a89392a88.png

image.png.24bdbddb0d20d30887834970c24decc9.png

 

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9 hours ago, Snowy Hibbo said:

 

Looking towards the next period of cold, there are a number of questions.

  1. When will the cold period start?
  2. How long will it be?
  3. How strong will it be?

So I am going to look at it from as many angles as I can.

 

I forecast in a few days the AAM will be at a neutral phase, and the GWO will be in Phase 1. I expect the next week to feature this decrease from GWO Phases 7/8/1. Week 2 features a movement from Phase 1 to 4, via the COD, or via low amplitude Phase 2 & 3. The main point of this, is to state that there will be a neutralisation and/or a slightly negative anomaly in the global momentum budgets around the 15th of Dec. This would be the low point of the AAM. Momentum would be slowed, and the pattern would be in line with a cool neutral ENSO. This in in line with global anomalies acknowledging that current negative torques have respective lags against changes to the AAM in line with the GSDM framework (+FT > +MT > +AAM).

 

Then Week 3 shows the beginning of the strong torques coming into play, and with a 3-5 day lag, the AAM goes positive falling back into the atmospheric state it has set for itself. Late Week 1 (~10th) should feature a +FT, Early Week 2 (~14-15th) should feature +MT in both the North American and East Asia domains. Week 3 (20-27 Dec) should see the realtime effects of the increase in AAM, and after the 7-10 day NP jet extension lag, we should see +PNA effects come into play around the 23rd, give or take a few days. It's going to take the AAM a week to respond to the torques and get itself through the GWO P1 > 4 stage, and into Phase 5. Phase 5 isn't the greatest place to be in either (remember these correlate somewhat to the tropical momentum patterns, also known as the MJO), so a Maritime Continent pass, while invigorating a +FT it will do, it doesn't mean great immediate effects for the Eastern US. It in fact assists the strengthening and extending of the NP Jet, and is why Phase 5 (Phase 3 & 4 probably more, so P5 to a lesser extent, but still relevant) works well for the start of a California Atmospheric River event. 

 

Week 4 sees the peak of the +AAM. I expect a P6-7 GWO for roughly 2 weeks, given the Nino base state and the recent climatology, as well as the feedback loop with the stratosphere (more on that in a second). So we should see positive leaning PNA effects for the first half of January, and any downstream stratosphere influences only serve to perpetuate these influences.  

 

We have a +EAMT in the 10 day forecast (so by the 18th). The forecasts shown by the EPS in the Aleutian Domain, look like they are in the process of creating +EAMT with the pushing down of Ural Highs, by the TPV moving into Siberia in the 8-12 day period. The Aleutian Low gears up the +EAMT for it's jet extension, and once the part of the TPV turns into a Okhotsk Low, we will see increased heights into the Barents-Kara Sea, and perfect conditions for a SPV attack. We also have a strong Brewer-Dobson Circulation, as noted by @Tamara and @Isotherm several times previously (increased ozone transport > weakening of strat effects). This all gives us conditions for a SSW in the 18-23 Dec period, with the tropospheric impacts around Xmas. The actual reversal (which I do forecast has a 60-70% chance of happening in this period, despite my own, and various other expert's seasonal forecasts) would take place around Xmas itself, with the greatest effects around New Years, and resulting in a -AO at the troposphere level for a good two weeks into January at least.

 

ens_nh-stratwinds_010hPa_20181205.png

Most of the models go for a drop, but don't reverse. Just to be clear, this will be plenty enough to impact the troposphere and assist the AAM to deliver cold risks to the Eastern US. But it also doesn't show the Xmas period or directly after, which is where a reversal occur if it were to happen.

 

Below is another one of @zdlawrence's plots showing the AO at all levels. You can see the lack of coupling over the past few months, and the potential for a relatively coupled vortex around the 20th, with negative anomalies across the stratosphere and the troposphere. 

gfs_nh-namindex_20181205.png

This will continue to be fluid and change in terms of the preconditions of the SSW.

@MattHugo

The above post from the winter thread may be of interest.

 

The B circle showing the easterly momentum around the Arctic, is probably more a result of the -AO in the latter half of November.

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