2024-2025 La Nina

[40/70 Benchmark]

20 hours ago, snowman19 said:

I never thought this winter was going to be a full on wall to wall torch, that’s why I went with +2 - +4 for temps from Dec-Mar with below average snow. That said, I think the pattern becomes much more La Niña like mid-month and beyond given the waning AAM and EWBs/ENSO 3.4 cooling/MJO forcing/SOI developments. I also firmly believe that once that process gets going, AAM is going to drop significantly from what is being shown right now. There is going to be a lag effect. IMO the models get warmer than what is currently depicted today for mid-late month. As @bluewave pointed out in the NYC thread, the weeklies are already backing off the cooler pattern they had yesterday. Unlike Eric Webb, I see the models now going for SPV/TPV coupling and the SPV being record strong as a bad thing. Unless we see a exact replica of 13-14 (unlikely IMO), that coupling is going to lock the NAO/AO positive and trap the arctic air over the pole with no mechanism to readily bring it south

I agree for the most part, but with some caveats relative to the bolded....sure, the cold will be focused west the majority of the time, however, don't understate the importance of Bering sea ridging in making it slighly more accessible to the east than it was in 2022-2023. This is especially true if we get more +PNA intervals, which I suspect that we will in January. I agree that it won't be as severe as 2013-2014 simply because the favorable Pacific won't be as consistent, but I think we will see some variability that includes periods like that during expecially the month of January.

[40/70 Benchmark]

3 minutes ago, bluewave said:

Will be interesting to see if extended GEFS is correct and we can get the forcing east of the Dateline in January and have the warmer Maritime Continent influence begin to weaken by then.

 

I think we will.

[snowman19]

2 hours ago, bluewave said:

The +AAM influence will start to fade since it was just a brief pattern driver which emerged for a few weeks from late November into early December. Just like the models originally underestimated the event from back in mid-November when it wasn’t showing up. Now we can see they have been underestimating the return of the milder La Niña background pattern from last week. This also matches the December seasonal progression that I posted on yesterday in the NYC Metro forum. The WPAC warm pool continues to be a dominant force as we have seen since the 15-16 winter. So it’s difficult for us to get more than a week or two of cold at a time before the warmth returns. But it will be interesting to see if there will be some more +AAM intervals to at least push back against the milder La Niña pattern at times after December.

There is going to be a lag with the AAM. Once the mid-late December pattern kicks in, it’s going to drop

[snowman19]

@Bluewave

[bluewave]

37 minutes ago, snowman19 said:

@Bluewave
 

That is correct in terms of the La Niña background pattern. The pattern from mid to late December is more a reflection of the record WPAC pool forcing. Not necessarily the weak La Niña SSTs which are still neutral. 

[40/70 Benchmark]

7 minutes ago, bluewave said:

That is correct in terms of the La Niña background pattern. The pattern from mid to late December is more a reflection of the record WPAC pool forcing. Not necessarily the weak La Niña SSTs which are still neutral. 

Agree.

[bluewave]

40 minutes ago, 40/70 Benchmark said:

Agree.

The RONI seems to work better with La Ninas since the WPAC warm pool enhances the La Niña effect. But it doesn’t work the greatest with a very strong El Niños like last winter. The record Niño 4s extending west of the Dateline served to enhance the El Niño effect of the ridge in Canada which was on par with super El Niño events. The much weaker Aleutian low and Eastern Trough than past very strong El Niño events may have been a better use of RONI. But even then the numerical value wasn’t that much of a help in describing the actual pattern.

[Typhoon Tip]

how was +aam a pattern driver? 

i may also not be exposed to/understanding the discussion's roots ... just sayn'

-aam is consistent with blocking patterns - referred at times to 'meridian flow' types.  hint, -epo/-ao/-nao/+pna are meridian flow types

+aam is consistent with less blocking patterns - referred at times to 'zonal flow' types. 

so i'm not seeing how a the last two weeks of -wpo/-epo, episodic -nao, with a +pna means a +aam is driving these to occur. 

first of all, the aam doesn't drive anything.  that is scalar of the integral for angular momentum, which in it's simplest mathematical form, is provided by,

   radius   X   mass   X   velocity

when the flow is flat/zonal/longitudinal, the radius term becomes very large, and the product of the above multiplication is thus also bigger --> +aam

the forecast of the aam off model guidance is a forecast of a scalar value out in time.  i get it that the aam is technically positive as a global integral - but all that means is that in the absence of recent -epo/-wpo and nao and so forth, the positive glaam would have just been even larger.   there's a relativistic scoping that has to be considered.  

 

[40/70 Benchmark]

13 minutes ago, bluewave said:

The RONI seems to work better with La Ninas since the WPAC warm pool enhances the La Niña effect. But it doesn’t work the greatest with a very strong El Niños like last winter. The record Niño 4s extending west of the Dateline served to enhance the El Niño effect of the ridge in Canada which was on par with super El Niño events. The much weaker Aleutian low and Eastern Trough than past very strong El Niño events may have been a better use of RONI. But even then the numerical value wasn’t that much of a help in describing the actual pattern.

Yea, I learned that the hard way....the lower RONI being more reflective of competing sources, rather than simply a weaker El Nino was great way to conceptuialize it. I think it work better for an El Nino like 2002 or 1957...in which the lower RONI was reflecvtive of a more Modoki look.

[snowman19]

2 hours ago, 40/70 Benchmark said:

Agree.

It’s the op GFS so it’s probably not right but Jesus Christ is that ugly on the PAC side after 12/16

https://www.pivotalweather.com/model.php?m=gfs&p=500h_anom&rh=2024120212&fh=372&r=na&dpdt=&mc=&pwplus=1

@MJO812 Yea a ++EPO looks lovely. Better hope the op has no clue (likely) and the GEFS doesn’t show the same thing

[MJO812]

6 minutes ago, snowman19 said:

It’s the op GFS so it’s probably not right but Jesus Christ is that ugly on the PAC side after 12/16

https://www.pivotalweather.com/model.php?m=gfs&p=500h_anom&rh=2024120212&fh=372&r=na&dpdt=&mc=&pwplus=1

Cold air lurks nearby.  Not a bad pattern .

[brooklynwx99]

why are we discussing the 16 day OP GFS in this thread at all? good or bad

[George001]

It’s a bit concerning that the cold period before the relaxation appears to only be a 10 day window, I was hoping it would last another week. However, like I said before we won’t have a great idea of how things will play out until we get to the other side of the relaxation period. Are we looking at 10 days of cold/5 days of warm then back to cold? Or 10 days of cold followed by 2+ weeks of warm before a flip to cold? 

[Maestrobjwa]

44 minutes ago, brooklynwx99 said:

why are we discussing the 16 day OP GFS in this thread at all? good or bad

This is when I wish OPs didn't go out that far, lol

[GaWx]

Latest CFS ensemble AAM is still positive late Dec/early Jan (avg +1 to +2) though not quite as positive early Jan as that of prior (+2 to +3):

Latest: 

Prior:

[bluewave]

18 hours ago, George001 said:

It’s a bit concerning that the cold period before the relaxation appears to only be a 10 day window, I was hoping it would last another week. However, like I said before we won’t have a great idea of how things will play out until we get to the other side of the relaxation period. Are we looking at 10 days of cold/5 days of warm then back to cold? Or 10 days of cold followed by 2+ weeks of warm before a flip to cold? 

These brief windows in recent years have favored the Great Lakes with the record lake warmth and the dominant northern branch of the Pacific Jet. 
 

 

[40/70 Benchmark]

5 minutes ago, bluewave said:

These brief windows in recent years have favored the Great Lakes with the record lake warmth and the dominant northern branch of the Pacific Jet. 
 

 

My area did just fine in early Feb 2021, January 2022 and even March 2023 across the interior.

[bluewave]

12 minutes ago, 40/70 Benchmark said:

My area did just fine in early Feb 2021, January 2022 and even March 2023 across the interior.

January 2022 was the last time my area had a real winter month with the average temperature below freezing and heavy snows.

[40/70 Benchmark]

1 minute ago, bluewave said:

January 2022 was the last time my area had a real winter month with the average temperature below freezing and heavy snows.

I expect a similar, but modified outcome next month...perhaps without the blizzard and still slightly above normal.

[bluewave]

5 minutes ago, 40/70 Benchmark said:

I expect a similar, but modified outcome next month...perhaps without the blizzard and still slightly above normal.

My guess is that will need a solid MJO 8 in January  like in 2022 to see more than a brief 10 day window of cold.

[40/70 Benchmark]

2 minutes ago, bluewave said:

My guess is that will need a solid MJO 8 in January  like in 2022 to see more than a brief 10 day window of cold.

I think this deviations should grow easier to come by over the next few years as the Pacific cold phase relinquishes its grip. Caveat being I think polar blockking may be scarcer as we enter the descending phase of the solar cycle.

[bluewave]

12 minutes ago, 40/70 Benchmark said:

I think this deviations should grow easier to come by over the next few years as the Pacific cold phase relinquishes its grip. Caveat being I think polar blockking may be scarcer as we enter the descending phase of the solar cycle.

We will probably need to see more Nino 1+2 warming in order to try and shift the Pacific cold phase. But even if we do a potential warm phase will still have to compete with the WPAC warm pool near the equator. In the age of marine heatwaves any cold pool east of Japan would pale in comparison to the marine heatwaves across other parts of the Pacific which would be different from our last +PDO era. Another wild card could be that we could actually see an east based El Niño like 97-98 should 1+2 really take off. But the actual 500 mb pattern could be different due to a stronger WPAC warm pool. 

[40/70 Benchmark]

2 minutes ago, bluewave said:

We will probably need to see more Nino 1+2 warming in order to try and shift the Pacific cold phase. But even if we do a potential warm phase will still have to deal withe the WPAC warm pool near the equator. In the age of marine heatwaves any cold pool east of Japan would pale in comparison to the marine heatwaves across other parts of the Pacific which would be different from our last +PDO era. Another wild card could be that we could actually see an east based El Niño like 97-98 should 1+2 really take off. But the actual 500 mb pattern could be different due to a stronger WPAC warm pool. 

Yea, I understand there are caveats abound. We are due for a 1997 type of El Nino, but hopefully after the turn of the decade, which is when I think we could have a very favorable period, otherwise.

[40/70 Benchmark]

Maybe hold the 1997 redux off until about 2033 or so...

[bluewave]

25 minutes ago, 40/70 Benchmark said:

Yea, I understand there are caveats abound. We are due for a 1997 type of El Nino, but hopefully after the turn of the decade, which is when I think we could have a very favorable period, otherwise.

A recent paper is trying to figure out why the EPAC hasn’t warmed like the rest of the Pacific and whether it will continue. It will be interesting to see if the record EPAC WWB and warming in the spring of 2023 was the beginning of a shift. Plus we just had the near record EPAC WWB back in November with the +AAM. It’s also possible that the big jump in global temperatures which wasn’t forecast last few years is somehow related. 

 

 

[PhiEaglesfan712]

52 minutes ago, 40/70 Benchmark said:

I expect a similar, but modified outcome next month...perhaps without the blizzard and still slightly above normal.

I feel like this month is the November 2021, rather than January 2022. It seems like a cool, but dry month. I feel like we're going to get a torch next month, and February will be another cool, but this time snowier, month. 2021-22, if shifted by a month, looks like a fairly good analog to me:

November 2024 = October 2021

December 2024 = November 2021

January 2025 = December 2021

February 2025 = January 2022

This winter will end up having a similar temperature profile as 2005-06.

[snowman19]

2 hours ago, GaWx said:

Latest CFS ensemble AAM is still positive late Dec/early Jan (avg +1 to +2) though not quite as positive early Jan as that of prior (+2 to +3):

Latest: 

Prior:

That’s the beginning of the drop I’ve been suspecting. There’s going to be a lag with the changes taking place in the PAC before the AAM catches up and really reflects it

[PhiEaglesfan712]

1 hour ago, 40/70 Benchmark said:

Yea, I understand there are caveats abound. We are due for a 1997 type of El Nino, but hopefully after the turn of the decade, which is when I think we could have a very favorable period, otherwise.

Didn't we get one in 2015?

[bluewave]

12 minutes ago, PhiEaglesfan712 said:

Didn't we get one in 2015?

Our last +4 east based El Niño during the winter was 97-98.

https://www.cpc.ncep.noaa.gov/data/indices/ersst5.nino.mth.91-20.ascii
 

 

 

 

[GaWx]

1 hour ago, snowman19 said:

That’s the beginning of the drop I’ve been suspecting. There’s going to be a lag with the changes taking place in the PAC before the AAM catches up and really reflects it

NG is down another 3%, which is very likely indicative of an overall warmer E US mid-Dec forecast. Also, yesterday’s longer term Euro Weeklies run for late Dec/early Jan was warmer than Sunday’s run overall fwiw.