2024-2025 La Nina

[GaWx]

AAM looks solidly Ninoish starting in ~1 week as of this CFS run of 2 days ago fwiw. Will this verify? Warning: these graphs are from the very unreliable 4 member CFS ensemble (you know, the model with the very unrealistic record obliterating  plunge in Nino 3.4 by next month) and they are very jumpy/fickle! Look how much they changed from just 4 days prior (2nd image). So, be careful not to read too much into this:

Prior run wasn’t as solidly Ninoish:

[Stormchaserchuck1]

50 minutes ago, GaWx said:

AAM looks solidly Ninoish starting in ~1 week as of this CFS run of 2 days ago fwiw. Will this verify? Warning: these graphs are from the very unreliable 4 member CFS ensemble (you know, the model with the very unrealistic record obliterating  plunge in Nino 3.4 by next month) and they are very jumpy/fickle! Look how much they changed from just 4 days prior (2nd image). So, be careful not to read too much into this:

Prior run wasn’t as solidly Ninoish:

The GEFS has consistently showed a non-Nina like pattern in the long range for the last 2 days. 

I've said before that ENSO subsurface correlates strongly with the N. Pacific pattern. Since it went Neutral 2 months ago, we haven't seen as much -PNA. 

It actually shows a healthy -WPO in the medium range

and in the long range it's been trending toward a more block pattern, albeit a weak signal right now

Not the super warm pattern I expected for early Dec

[GaWx]

 Looking at TT EPS at H5 and 2M: one can see the huge difference between the 0Z 11/14 run and the 12Z 11/17 run on 11/26:

1) a) 0Z 11/14 EPS for 11/26 at H5: conducive H5 flow allowing CDN air to dominate E US

 

1) b) 0Z 11/14 EPS for 11/26 at 2m: BN dominates east resulting in 18 US HDD

 

Now compare those to the 11/17 12Z EPS

2) a) 12Z 11/17 EPS for 11/26 @H5: sig. SE ridge, which has often been underplayed late in week 2 and beyond for 7-8 years and then appears as get closer in:

2) b) 12Z 11/17 EPS for 11/26 @2m: AN instead of BN dominates east resulting in a mere 12 instead of 18 HDD with that near the normal for way back on 11/10:

 

[mitchnick]

3 hours ago, GaWx said:

 Looking at TT EPS at H5 and 2M: one can see the huge difference between the 0Z 11/14 run and the 12Z 11/17 run on 11/26:

1) a) 0Z 11/14 EPS for 11/26 at H5: conducive H5 flow allowing CDN air to dominate E US

 

1) b) 0Z 11/14 EPS for 11/26 at 2m: BN dominates east resulting in 18 US HDD

 

Now compare those to the 11/17 12Z EPS

2) a) 12Z 11/17 EPS for 11/26 @H5: sig. SE ridge, which has often been underplayed late in week 2 and beyond for 7-8 years and then appears as get closer in:

2) b) 12Z 11/17 EPS for 11/26 @2m: AN instead of BN dominates east resulting in a mere 12 instead of 18 HDD with that near the normal for way back on 11/10:

 

1 thing I  didn't consider yesterday is the delay of the MJO effects. As I think about it, that may explain what we're seeing there should it hold. But models are famous for screwing up timing, so we shall see.

[mitchnick]

11 minutes ago, mitchnick said:

1 thing I  didn't consider yesterday is the delay of the MJO effects. As I think about it, that may explain what we're seeing there should it hold. But models are famous for screwing up timing, so we shall see.

That's not to say Eps doesn't still bring in the cold.

[bluewave]

6 hours ago, GaWx said:

AAM looks solidly Ninoish starting in ~1 week as of this CFS run of 2 days ago fwiw. Will this verify? Warning: these graphs are from the very unreliable 4 member CFS ensemble (you know, the model with the very unrealistic record obliterating  plunge in Nino 3.4 by next month) and they are very jumpy/fickle! Look how much they changed from just 4 days prior (2nd image). So, be careful not to read too much into this:

My guess is that the more Nino-like look to the 500 mb pattern this week is a result of the unusual EPAC WWB we just experienced. The million dollar question is how long this pattern lasts? We need it to continue for more than just a few weeks.

 

 

 

Ridge axis shift from 30N to 60N

 

 

[GaWx]

1 hour ago, mitchnick said:

That's not to say Eps doesn't still bring in the cold.

 This is illustrative of how I like to describe the tendency of model/ensemble means to often (though of course not nearly always as I keep emphasizing as these are general tendencies (cold bias) rather than absolutes) show cold being delayed: it’s often like a mirage. Instead of fake water, it is fake blue/cold. When this occurs it will look cold at two weeks out and as that period gets closer the cold often wanes and may never materialize for that same period/could even turn warm/red like Nov 26th has dramatically already done. In this case (Dec 3rd), is it the common fake blue like Nov 26th in retrospect appears to have been, will it end up real this time, or something in between? The cold bias says better chance cold wanes rather than intensifies and of course it could remain about the same.

[mitchnick]

3 minutes ago, GaWx said:

 This is illustrative of how I like to describe the tendency of model/ensemble means to often (though of course not nearly always as I keep emphasizing as these are general

tendencies (cold bias) rather than absolutes) show cold being delayed: it’s often like a mirage. Instead of fake water, it is fake blue/cold. When this occurs it will look cold at two weeks out and as that period gets closer the cold often wanes and may never materialize for that same period/could even turn warm/red like Nov 26th has dramatically already done.

To be fair, cold advertised on the models, like that coming this week, looks pretty concrete. But there's no doubt models overdo cold and snow at mr and lr, but we'll just have to see if it's delayed or denied. I have said ever since the alleged Euro suite upgrade in 2017 that it was, in fact, a degrade. It's never been the same and is undoubtedly snow crazy in the 3-7+ day range and not a ton better in short ranges. 

[GaWx]

24 minutes ago, mitchnick said:

To be fair, cold advertised on the models, like that coming this week, looks pretty concrete. But there's no doubt models overdo cold and snow at mr and lr, but we'll just have to see if it's delayed or denied. I have said ever since the alleged Euro suite upgrade in 2017 that it was, in fact, a degrade. It's never been the same and is undoubtedly snow crazy in the 3-7+ day range and not a ton better in short ranges. 

 I agree that E US cold is still clearly coming for 11/21 through early 11/24. But late 11/24-11/27 has warmed considerably in the E US from how it looked just 4 days ago as I’ve been showing via the HDD graphs. So, the upcoming cold period is now looking to be shorter vs how it appeared 4 days ago.
 Now we look ahead to a second potential cold period in very early Dec. Will it also diminish or shorten like often occurs in the E US and did occur for 11/24-7? Or will it fully verify this time? We’ll see.

 By the way, NG has turned out somewhat lower than it was as I was guessing would occur at about this time (due to the models warming on and near 11/26) since I noted it late last night fwiw. We’ll see what occurs the rest of today.

[PhiEaglesfan712]

2 hours ago, mitchnick said:

That's not to say Eps doesn't still bring in the cold.

Looks about right to me. The cold arrives around Dec. 1 (give or take a few days). I see a potential snow event in the East on Dec. 4-5.

[40/70 Benchmark]

20 hours ago, GaWx said:

For the period Sept 1st through Nov 14th back to 1948, 2024 is tied with 2021 for the fewest -EPO (sub -50) days with just 3:

Lowest # of sub -50 EPO days 9/1-11/14 back to 1948 (7 or fewer):
2024: 3

2021: 3

2011: 4

1994: 4

1958: 4

1948: 4

1968: 5

 
I didn’t see any notable correlation to # of sub -50 days one way or the other in the subsequent respective winters, however.

 

https://downloads.psl.noaa.gov/Public/map/teleconnections/epo.reanalysis.t10trunc.1948-present.txt

Do you have a link for the monthly tabular data, Larry?

[GaWx]

13 minutes ago, 40/70 Benchmark said:

Do you have a link for the monthly tabular data, Larry?

Ray, Unfortunately I don’t have a source for monthly EPO. To get any monthly I literally have to calculate them based on these dailies. Because that’s very tedious/time consuming, I rarely have done that. More often I’ll instead roughly estimate them or better yet just count days over or under a certain level because it is quicker and still telling.

[mitchnick]

24 minutes ago, 40/70 Benchmark said:

Do you have a link for the monthly tabular data, Larry?

https://ftp.cpc.ncep.noaa.gov/wd52dg/data/indices/epnp_index.tim

[mitchnick]

2 minutes ago, mitchnick said:

https://ftp.cpc.ncep.noaa.gov/wd52dg/data/indices/epnp_index.tim

Here's a list of all "alphabet" data indices from CPC if that's not what you were looking for.

https://ftp.cpc.ncep.noaa.gov/wd52dg/data/indices/

[bluewave]

This was the strongest WWB event in the EPAC during the month of November following such a strong El Niño winter. Reminds me a bit of the unusually strong EPAC WWB activity we saw that kicked off the El Niño in the winter and spring of 2023. This isn’t something we see during El Niño to La Niña transitions.

 

[40/70 Benchmark]

15 minutes ago, mitchnick said:

https://ftp.cpc.ncep.noaa.gov/wd52dg/data/indices/epnp_index.tim

I have that....its the more modern verison of the EPO, however, the NP-EP is different from the original EPO.

[GaWx]

21 minutes ago, mitchnick said:

https://ftp.cpc.ncep.noaa.gov/wd52dg/data/indices/epnp_index.tim

 What exactly is that? It isn’t EPO, itself, as one can see just looking at Sept and Oct of 2024. This monthly table has a near record strong negative for Sep of -2.75 (2nd lowest to April of 1968’s -2.88) even though the dailies show that they were solidly positive. Also, this has Aug of 2024 way down at -2.62 despite the dailies averaging neutral.

[mitchnick]

18 minutes ago, GaWx said:

 What exactly is that? It isn’t EPO, itself, as one can see just looking at Sept and Oct of 2024. This monthly table has a near record strong negative for Sep of -2.75 (2nd lowest to April of 1968’s -2.88) even though the dailies show that they were solidly positive. Also, this has Aug of 2024 way down at -2.62 despite the dailies averaging neutral.

See 40/70 post above.

[GaWx]

12 minutes ago, mitchnick said:

See 40/70 post above.

So that means these aren’t at all the monthlies for the original EPO. Actually, these monthlies usually have the opposite sign the dailies calculate to. So, a strong negative monthly on your link’s table actually correlates rather well to +EPO (I mean the original and only version I have ever followed). But even that negative correlation is far from 100% as Aug of 2024 shows. Your link’s table has a strong negative for Aug of 2024 vs a very slight negative (essentially neutral) based on the avg of the dailies of the original EPO.

[40/70 Benchmark]

34 minutes ago, GaWx said:

 What exactly is that? It isn’t EPO, itself, as one can see just looking at Sept and Oct of 2024. This monthly table has a near record strong negative for Sep of -2.75 (2nd lowest to April of 1968’s -2.88) even though the dailies show that they were solidly positive. Also, this has Aug of 2024 way down at -2.62 despite the dailies averaging neutral.

The NP/EP has a comparable domain space to that of the EPO, however, it has the opposite correlations....ie +NP-EP is more favorable for east coast cold/snow. What I do for purposes of verification is flip the NP-EP and use it as EPO.

[GaWx]

18 minutes ago, 40/70 Benchmark said:

The NP/EP has a comparable domain space to that of the EPO, however, it has the opposite correlations....ie +NP-EP is more favorable for east coast cold/snow. What I do for purposes of verification is flip the NP-EP and use it as EPO.

Yes, I agree that taking those NP-EP monthlies and flipping the sign seems to give a good (though not perfect by any means as Aug of 24 shows, for example) indication of what the classical/original EPO would calculate to be based on the dailies. Is the EP portion of that the actual classical EPO? If so, that would explain why it isn’t a perfect negative correlation since “NP” is also in the calc.

 Why are we having so much trouble finding a monthly EPO table based on the pure original calc? I’m going to continue looking at the daily EPO table as my go to for EPO back to 1948.

[mitchnick]

14 minutes ago, GaWx said:

Yes, I agree that taking those NP-EP monthlies and flipping the sign seems to give a good (though not perfect by any means as Aug of 24 shows, for example) indication of what the classical/original EPO would calculate to be based on the dailies. Is the EP portion of that the actual classical EPO? If so, that would explain why it isn’t a perfect negative correlation since “NP” is also in the calc.

 Why are we having so much trouble finding a monthly EPO table based on the pure original calc? I’m going to continue looking at the daily EPO table as my go to.

Look at this link Larry. Red ink print under EP/NP.

https://psl.noaa.gov/data/climateindices/list/#EPO

[GaWx]

23 minutes ago, mitchnick said:

Look at this link Larry. Red ink print under EP/NP.

https://psl.noaa.gov/data/climateindices/list/#EPO

Thanks, Mitch. From that: “This index replaces the old EP index which is no longer maintained by CPC.”

I don’t understand why that is the case when it is still maintained on a daily basis here:

https://downloads.psl.noaa.gov/Public/map/teleconnections/epo.reanalysis.t10trunc.1948-present.txt

 Meanwhile, a whopping 46 of the last 55 days have had a +50+ EPO. But the correlation of autumn EPO and winter EPO has been only weakly positive from what I can tell looking at actual winter vs autumn.

[Daniel Boone]

11 hours ago, GaWx said:

 Here’s a better illustration of a main reason why NG has been up this evening, which is interesting: it is because the 12Z 11/17 EPS (purple) is coldest at the end, Dec 1st, with 20.4 HDD and rising. However, keep in mind that 11/23-7 total HDD are down to only 71 vs 89.5 on the Thu 11/14 0Z run, when NG was about where it has been this evening. Check out 11/26: it’s only at 12 on the 11/17 12Z, which is a whopping 6 BN and the normal for 11/10, 16 days earlier. On the 11/14 0Z, it was way up at 18.1 or near normal!

 This is the nature of these cold biases. They’ll often be too cold late in week 2 and then get back to reality and warm up as those days get closer. Back on 11/14, 11/23-27 were out 9-13 days. Now that these days are only out 6-10, they’ve warmed substantially. They don’t always do that, of course. But they tend to do that more than the opposite (nature of cold bias).

 If I were a betting man, I’d bet based on the cold bias that Dec 1st will end up verifying lower than 20 HDD. Of course it may not but the odds favor that. Also, even though I’m not trading commodities, I’m guessing that NG will be lower than it is now by morning. That’s partially because 11/23-7 are so much warmer than they were as of 3 days ago. But that’s just a guess. If the overnight GEFS/EPS runs turn out cold enough especially late, NG probably wouldn’t turn down in the morning and may even rise further.

 

Thanks Larry. Great explanation per usual from you. Interesting.

[GaWx]

 Despite the dominance of +EPO so far this autumn, the rest of Nov is favored to have -EPO on most days. That would likely mean Nov ends up pretty neutral. So, we have solid +EPO Sep and Oct followed likely by (pretty) neutral Nov. 
  
 Regarding NP-EP, what other autumns since 1948 had similar assuming Nov ends up pretty neutral (a big if, of course)?

-2021 excellent analog and also Nina

-2007 good analog and also Niña

-2005 excellent analog and also Nina

-2004 good analog though was Nino

-No other good analogs back to 1948!

 So, these are the only four potentially good to excellent autumn NP-EP (keeping in mind Nov still TBD). And with 2004 being Nino, it should probably be thrown out. So, I’ll focus on especially 2021 and 2005 and secondarily on 2007. Unfortunately it is a very small sample. So, fwiw, how did EPO (based on dailies) end up in winter for these three?

 

-2021-2 averaged neutral EPO: -10

Dec mixed/neutral: -20

Jan mixed/neutral: 0

Feb mixed/neutral: -10

 

-2005-6 averaged neutral EPO: +20

Dec mixed but more -EPO: -50

Jan strong +EPO: +140

Feb mixed but more -EPO: -30

 

-2007-8 averaged moderate +EPO: +60

Dec mixed but more +EPO: +40

Jan mixed but more +EPO: +50

Feb +EPO: +90

[brooklynwx99]

this is a really impressive trend. wouldn't be surprised to see waters near Japan cool and waters in the GoAK warm given the upcoming pattern

[bluewave]

6 hours ago, GaWx said:

 This is illustrative of how I like to describe the tendency of model/ensemble means to often (though of course not nearly always as I keep emphasizing as these are general tendencies (cold bias) rather than absolutes) show cold being delayed: it’s often like a mirage. Instead of fake water, it is fake blue/cold. When this occurs it will look cold at two weeks out and as that period gets closer the cold often wanes and may never materialize for that same period/could even turn warm/red like Nov 26th has dramatically already done. In this case (Dec 3rd), is it the common fake blue like Nov 26th in retrospect appears to have been, will it end up real this time, or something in between? The cold bias says better chance cold wanes rather than intensifies and of course it could remain about the same.

It’s tough to get any colder temperatures lasting for more than 3-4 days at a time with such an overpowering Pacific Jet.

 

 

[snowman19]

23 hours ago, bluewave said:

My guess is that the more Nino-like look to the 500 mb pattern this week is a result of the unusual EPAC WWB we just experienced. The million dollar question is how long this pattern lasts? We need it to continue for more than just a few weeks.

 

 

 

Ridge axis shift from 30N to 60N

 

 

If this is indeed a temporary, transient flux from the WWB then we should see the long range models start changing the PAC within the next week or so 
 

Edit:

@bluewave @GaWx  You can see the new ensembles starting to trend stronger with the SE ridge/WAR as we get closer in time. Alan Huffman’s analysis appears to be correct

[bluewave]

7 minutes ago, snowman19 said:

If this is indeed a temporary, transient flux from the WWB then we should see the long range models start changing the PAC within the next week or so 

The forecast issue going forward may be that the La Niña is so weak that we get a mix of Nino-like and Nina-like intervals. Kind of like a windshield wiper effect. So would be a challenge getting any sustained cold with since a strong Pacific Jet.

[snowman19]

2 minutes ago, bluewave said:

The forecast issue going forward may be that the La Niña is so weak that we get a mix of Nino-like and Nina-like intervals. Kind of like a windshield wiper effect. So would be a challenge getting any sustained cold with since a strong Pacific Jet.

DT also presented some good evidence a few years ago that very strong +QBO’s (which we have) lead to a raging PAC jet