EasternLI

9 hours ago, so_whats_happening said:

No, there is nothing to suggest it even goes above average as we move into January.

It's actually a little bit interesting, the way things are unfolding for the PV. Having previously seen the wave 1 tropospheric precursor pattern (displacement). In the weeks prior. Followed by the displacement event we've all been monitoring in the stratosphere now. Now, looking at some ensemble runs moving forward. We're resembling something pretty close to the wave 2 precursor (split). Which, if we take into consideration what looks to be a meaningful phase 7 mjo transit upcoming (known for PV disruption). Plus the associated WWB mentioned out at the dateline. That should act to give another boost to the AAM. If I'm recalling correctly, split events are typically achieved with a wave 1 attack (preconditioning) followed up by wave 2. Added all up raises an eyebrow a little bit. I'll just add, "setbacks" (or vice versa) from a European perspective doesn't necessarily equal the same to someone in the US for anyone reading.

1 hour ago, bluewave said:

There could be some MJO 7 elements in the mix for early December. But the convection lingering near the Maritime Continent may not translate into a purely 7 composite. So with more of a split forcing pattern perhaps a variation on the phase 7 theme.

I agree that the phase 8s have been a big challenge since January 2022. Even when the RMM charts indicated a phase 8 verifying, lingering phase 4-6 convection didn’t lead to the desired outcome.

The record SST warmth near the Maritime Continent had been altering the convective forcing and sensible weather patterns.

Fair enough. However, the example you were using was displaying basically the textbook la nina phase 7 response. We'll see how it goes. Another thing for consideration. The waters in that area of the globe have cooled significantly since last year. First image below is the difference between now vs 1 year ago. Enough so, that it's mostly near normal now in the equatorial band (10N-10S). With a non insignificant area having below normal temps even for a change (2nd image). A sight for sore eyes. So perhaps that factor can be muted this time.

3 minutes ago, bluewave said:

That is just a one day snapshot from a 360 hr run. A few days before that it had a different look. Convection lingering near the Maritime Continent will tend to stall the movement toward a more classic phase 8 which was mentioned in the post that I was replying to. 

Well, yeah. It would take a little time to imprint on the circulation. Perhaps it's only one run but it was the same one. I would have expected to see some differences on the model if there were interference with the signal.

Totally agree with you regarding phase 8. We'll definitely want to see the suppressed phase center itself over 120E to achieve the proper effectiveness IMO. 

1 hour ago, bluewave said:

The RMM charts are only providing part of the picture. They are following the convection to the east of the Dateline. But we still have convection lingering near the Maritime Continent into early December. So it’s more of a split forcing pattern rather than a canonical MJO driven pattern. 

 

I don't know. That doesn't look very significant. Where is the said difference? This is that same eps run as posted and these look basically like a carbon copy, to me. 

Gotta watch this. If you pop a poleward Scandinavian ridge here that suggests further damage to the PV sometime in December.

4 hours ago, kazimirkai said:

Well it's pretty normal to expect that the MJO wouldn't reach phase 8 in a la-niña situation with base easterlies, but forecasts change. Still tough to say if it'll stay there long but that seems to be the crux of the change in forecasts over the past week or so. 

Remains to be seen if we can achieve phase 8. Still a little bit too far in the future for guidance, but this year... maybe? There's been somewhat of a notable trend on the EPS over the last couple of days now with the mjo. Incrementally amplifying the phase 7 transit through several runs. With today's 12z run the most amplified thus far. I bring up the EPS since it's been the one piece of guidance that has been the most reluctant with this event throughout. Here are yesterday's 00z run followed by the latest 12z EPS 200mb velocity potential (the ones in between follow the same trend).

00z yesterday:

12z today:

Taking a global view of this now, in the 10-15 day mean. It's a fairly clear phase 7 signature being shown now on the 5 day mean. With the suppressed phase pushing into the MC and the enhanced phase pushing into South America. Again, this signal has been growing. Not fading away, much like we are all accustomed to in recent times, as verification time approaches. 

Consistent with the slower moving mjo events, as mentioned earlier in this thread. There should be a response reflected in the 500mb pattern. Or at least more likely. So I like to check the model output against the mjo composites in times like these. Since that is most certainly not always the case. In this instance though, there do seem to be at least several similarities between the phase 7 December La Nina composite. When compared with the 12z EPS forecast at day 15. Which, to me, suggests it is indeed being effective. At least in the model.  What happens from here? I'm beginning to think it might be interesting to find out.

25 minutes ago, kazimirkai said:

Warm waters into the W pac. from this westerly wind burst are priming the ENSO for a real shift come the next big event. 

Yeah, that will be interesting to watch evolve. Extended range EPS and GEFS are advertising this WWB to push out to the dateline. Which has proven difficult to do in other recent La Niña years. So I'm curious to see how this one goes as we move into December. 

12 minutes ago, brooklynwx99 said:

the Pacific jet is going to retract and shift equatorward after its poleward extension next week, which should lead to the -EPO that we're waiting for. I have pretty high confidence in this -EPO developing; the progression makes sense. BN to much BN temps in the East would follow into early Dec

trough near Japan/HI are also old-school signs of a favorable Pacific pattern

Sharp rise in momentum starting to percolate into the circulation. Good stuff. 

I've been occasionally browsing these myself. Nice of him to provide an explanation here of how it works/what it does/what it's doing. 

Its interesting times when there's potential to see an amplified MJO in the Pacific. Then firing off an +EAMT into that. Especially given the time of year...

Eps had a bit of a nod to the Gefs ideas with the MJO at 00z.

11 hours ago, GaWx said:

  This has the ens 10 mb mean zonal wind as low as only +14 to +15 in late Nov (prior runs’ lowest were +18) and is at least tied for the highest % of members of any run so far this season with a very early season major SSW (reversal) at 25%+.

There are perhaps some clues to keep an eye on in the context of this. As whatever happens higher up in the atmosphere is strongly tied to the progression in the troposphere. Namely, keep an eye on what transpires in the north Pacific. There's a great paper on these events and why they occur in both el nino and la nina. I'll post below figure 1 from this paper along with the explanation given for the image. Also of note, some of the recent ensemble runs have been showing some similarities to the precursor 500mb later in the runs. I'll add the 00z EPS from last night after that for example. I suspect the amount of members achieving the ssw have been the ones with a deep north Pacific low in their progression in the proper location. Not saying one happens, only that there seems to be a valid reason for some of those members to be showing it. 

Why might stratospheric sudden warmings occur with similar frequency in El Niño and La Niña winters?

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2012JD017777

Quote

In this section we develop an explanation for the similar fSSW in EN and LN winters in the observational record. We will then test this explanation in Section 3.2. Figures 1a and 1b show the teleconnections associated with LN and EN, and Figure 1c shows geopotential height anomalies at 500 hPa preceding SSWs (independent of ENSO phase). Prior to SSWs, a deep subpolar low height anomaly is centered just west of the dateline (denoted by a square on Figure 1). As discussed in the introduction, anomalously deep lows in this region constructively interfere with the stationary waves and weaken the vortex [Garfinkel and Hartmann, 2008; Ineson and Scaife, 2009; Nishii et al., 2009; Garfinkel et al., 2010]. Regardless of ENSO phase, low height anomalies in the North Pacific are present throughout the period in which the vortex is weakening (not shown). The key point of Figure 1 is that the anomalies preceding SSWs are different from the LN and EN teleconnections; namely, the anomalous low that precedes SSWs (the square) is to the northwest of the region where ENSO teleconnections are strongest (the star).

Last nights 00z EPS - note this is a 5 day mean

Curious to see how the mjo behaves this week. Eps dampens the wave as it has been throughout. Gefs is more amped. But, both of those things are known biases of each respectively as far as I know (lol). In real time thus far the Gefs has been verifying better (stronger). That doesn't necessarily mean that will continue though. Nobody knows for certain, we watch. Looking forward to the CPC update on Monday. For now here's Gefs and eps forecasts followed by the current map. There does appear to be kelvin wave like feature visible too on these charts, slicing through the overall mjo signal at faster speed. Those have been a catalyst in propagating this event thus far according to other CPC updates. How well are they modeled? 

30 minutes ago, GaWx said:

As is often the case, EPS is correcting stronger as we get closer:

10/23 EPS had weak 10/27+:

 

10/29 EPS shows that 10/23 EPS verified too weak 10/25-9, is less weak (to the right) 10/30-11/6 than 10/23 run, and then heads into moderate 11/9-12 (will likely later correct stronger 11/9-12+ as in toward today’s GEFS, which is below this):

10/29 GEFS is stronger than 10/29 EPS for 11/1-12 (I expect EPS to correct toward this later):

Yeah I agree it will likely trend that way too in this instance. Gefs guidance can overdo it sometimes too though. So I've been kinda focused on euro guidance to see if it would trend more amplified. And it has been which is good to see. Yesterday's weeklies were another good step too. Avoiding the circle completely that run with some amplified members too. 

Some good trends this morning... and an interesting thought. 

Improvement on the EPS from last night also. Which has been much weaker with this event compared to others. Still very much worth watching.

Generally not a fan of the RMM MJO charts. However, I think these euro weekly ones are beneficial. Mainly to visualize what the individual members are doing inside the mean and for trends. IMHO, not sure how anyone can call what happens with this event currently with any confidence. Still think it's too early. With that being said, lets look at the trend over the past week wrt this event. EC 46 one week ago versus today's forecast. A few things are noticeable. The verification vs the forecast from a week ago has been much higher in amplitude. With verification higher than the highest ensemble members forecast. The mean which was spiraling off into the COD is no longer doing so with a signal into the Pacific now. Also interestingly, later in the forecast period, there are many more members with renewed amplification in the Pacific now on today's run which just updated. This is still worth watching...

One week ago:

Today:

Theoretically, according to some studies, to have the best chance of a successfully propagating MJO event beyond the MC. There are 2 main factors to consider. Indian Ocean temps and the QBO. With the combination of a warm Indian Ocean combined with an EQBO offering the highest chance for success. 

Understanding the Factors Controlling MJO Prediction Skill across Events

https://journals.ametsoc.org/view/journals/clim/37/20/JCLI-D-23-0635.1.xml

The results show that the low-frequency background states of the Indian Ocean sea surface temperature and the quasi-biannual oscillation are good indicators for MJO prediction skill, for their modulatory role in the MJO propagation range.

The difference in intraseasonal fields can further be attributed to the LFBS of IO sea surface temperature (SST) and quasi-biannual oscillation (QBO), with the high-skill (low-skill) events corresponding to a warmer (colder) IO and easterly (westerly) QBO phase. The physical link is that a warm IO could increase the low-level convective instability and thus amplify MJO convection over the IO, whereas an easterly QBO phase could weaken the Maritime Continent barrier effect by weakening the static stability near the tropopause, thus favoring eastward propagation of the MJO. It is also found that the combined effects of IO SST and QBO phases are more effective in influencing MJO prediction skill than individual LFBS.

Some thoughts from the MJO desk weekly update from yesterday. 

14 minutes ago, DarkSharkWX said:

if the MJO makes it to the west pacific(which, it shouldn't have too much trouble doing so) then the IPWP will be pushed further east in addition to upwelling some of the heat in the subsurface

Intuitively, makes sense and I agree. The MC is a tricky area for convection though and can play games sometimes. We'll see what modeling trends decide to do with it over the coming days. I suspect it will make it as well, but we'll see. 

The AAM is set for a rapid rise towards neutral. After having fallen to strongly negative values. The cause of this will be the addition of momentum from the upcoming pacific jet extention in conjunction with the MJO event. How this plays out should have an effect further down the road. The MJO is modeled differently on different systems currently. The EPS AI ensembles have been pretty robust with it. Ideally, we'd like to see the negative AAM anomalies propagate poleward to 60N over time. If so, there could be some actual potential for early winter northern blocking. Towards December perhaps. I'll be interested to see how this plays out..

By which metric is the Pacific warm pool warmer than last year at this time?

NOAA keeps a dataset on that area here :

https://psl.noaa.gov/data/correlation/pacwarm.data

2024     0.592     0.659     0.500     0.591     0.604     0.605     0.655     0.635     0.640     0.654     0.658     0.492
2025     0.536     0.459     0.448     0.433     0.473     0.382     0.472     0.483     0.458

That data doesn't agree with the assertion...

As per their defined area, here are last year versus this year for visual comparison.

Last year:

This year:

The negative IOD certainly front and center in this part of the world, as has been discussed in this thread. No issue with that whatsoever. However, the tropical western pacific is actually not as warm as it was at this time last year. Neither are the waters in the vicinity of Indonesia. NOAA data reflects this year being less impressive as well.

So by which metrics is this years west pacific much warmer than last year? I'm not seeing it and I disagree. 

2 hours ago, DarkSharkWX said:

this is really interesting b/c if im not mistaken IOD/IO forcing has the highest correlation to +WPO, so you wouldn't think that it would exactly be favorable for NAO

maybe through stratospheric reflection events?

This year is seemingly lining up to be an interesting case to watch regarding all of this. The paper did mention the addition of enso forcing alters things. Sometimes drastically. However over the course of the last 30 days, it does appear to be a stand out feature on the VP200 charts and OLR charts. I didn't notice any recent years, when looking back through that data, looking quite like this. So certainly a very valid feature to monitor. 

14 minutes ago, snowman19 said:

16-17 was strong -IOD and a +NAO winter

Yeah, like I said, barring some other overpowering influences.

The negative IOD is kind of interesting. This is a good article about the IOD and it's effects. The relationship is modeled to weaken over time in the future with some changes to the sst gradients. However, for now and when you eliminate other factors. -IOD seemingly favors -NAO in and of itself if it were the dominating feature. 

Climate change alters the Indian Ocean Dipole and weakens its North Atlantic teleconnection

https://www.nature.com/articles/s43247-025-02131-5

Quote

In the HIST period, the northern hemisphere MSLP response to the IOD (with ENSO neutral) resembles the positive Arctic Oscillation with a significant band of low pressure at high latitudes (Fig. 5a); there is also a positive NAO in the Atlantic sector. The pIOD/nIOD favours the positive/negative NAO phase. In the meridional wind field (Fig. 5b), a Rossby wave train of alternating positive and negative nodes extends across the North Pacific into the North Atlantic/European sector, representing a tropospheric teleconnection pathway. This CMIP6 IOD-NAO teleconnection pattern strikingly resembles that seen in 2019/2020 (their Fig. 3), suggesting that the 2019/2020 pattern represents the standard response to the IOD and that such events could therefore recur in the present climate.

 

Consistent with the 2019/2020 study, we also find a stratospheric teleconnection pathway; the IOD affects the strength of the stratospheric polar vortex (SPV) in HIST, which in turn influences the NAO. For pIOD minus nIOD in ENSO-neutral years, the SPV and NAO significantly increase (p = 0.01) for both December (3.9 m/s; 2.1 hPa) and DJF (2.4 m/s; 1.8hPa). The IOD, therefore, appears to partly drive the NAO via the polar vortex, similar to the stratospheric teleconnection pathway driven by ENSO. The DJF shifts for SPV and NAO are roughly double what would occur if the teleconnection were active in December alone, suggesting that the stratospheric pathway prolongs the teleconnection beyond early winter as the IOD decays.