2025-2026 ENSO

[40/70 Benchmark]

10 hours ago, donsutherland1 said:

Continuing the illustration showing how I'm thinking about December 1-10 and December 11-25. Here's the framework I am using.

The CPC 8-14 day forecast is a good illustration of how I think things will evolve during the December 1-10 period:

The risks of a faster turn to a warmer pattern in much of the eastern U.S. (not the Great Lakes, northern New England, eastern Canada) have increased with growing ensemble consensus for a predominantly AO+ pattern.

Composite WPO-/EPO-/AO+/PNA- 500 mb Height Anomalies:

ECMWF Weekly 500 mb Forecast for December 8-15:

Composite WPO-/EPO-/AO+/PNA- Temperature Anomalies:

ECMWF Weekly 500 mb 2m Temperature Anomaly Forecast for December 8-15:

Right now, the guidance is still in a low-skill timeframe. What's noteworthy is the change that has taken place in the past few days. For example, this was the ECMWF weekly forecast for the December 18-15 period from three days earlier:

If the guidance holds or strengthens the forecast AO+ beyond December 10, the warmer outcome could become the baseline for that period with perhaps a mid-month shift to the milder pattern. The 18z GEFS is also suggesting that the EPO could go positive. If so, that would further increase the risks for a turn toward milder conditions. 

In sum, December 1-10 still remains on track. One should see cold move into the Upper Midwest and Great Lakes and then spread eastward. The Southeast will remain warm due to the resilient SE Ridge. Uncertainty beyond December 10 has increased and the risk of a shift toward a warmer pattern has increased. The guidance will need to be watched closely to see if its turn toward an AO+ persists.

Lots of December 2007 on that composite......my snowiest month of December on record.

[40/70 Benchmark]

7 minutes ago, bluewave said:

The ensembles always show variations with week 2 forecasts. There really hasn’t been that much of a change. Still looking at a Southeast ridge or Western Atlantic ridge and a trough digging into the Baja to start December.

New day 6-10

Old day 11-15

 

 

Chris, if we are being honest with ourselves, that is a definitive trend towards a more concerted press of the PV.

[EastonSN+]

1 hour ago, michsnowfreak said:

There was talk of underestimating the SER. If trends continue it was grossly overestimated.

IMO there is way to much overestimating the SE ridge already. Also, its the RNA pumping up the SE ridge, not the other way around.

Last year the SE ridge was not a major player, since we had a +PNA.

[EastonSN+]

55 minutes ago, stadiumwave said:

 

15 day change

The western PAC continues to cool, great sign. 

[bluewave]

4 minutes ago, 40/70 Benchmark said:

Chris, if we are being honest with ourselves, that is a definitive trend towards a more concerted press of the PV.

Which is better for the Great Lakes into New England. Gradients usually end up farther north than originally forecast once we get into the short term compared to the longer range forecasts.  Models not varying the storm track pattern with a dominant Northern Stream.

[40/70 Benchmark]

2 minutes ago, bluewave said:

Which is better for the Great Lakes into New England. Gradients usually end up farther north than originally forecast once we get into the short term compared to the longer range forecasts.  Models not varying the storm track pattern with a dominant Northern Stream.

Right....all I'm saying is it's a heavier press of the PV...I've always expected it to be a N stream dominated pattern that is favorable for NE, not so much your area into the mid atl.

[jm1220]

13 minutes ago, 40/70 Benchmark said:

Lots of December 2007 on that composite......my snowiest month of December on record.

One trillion percent pass on that month and season here where we watched I-90 get buried over and over while it cold rained IMBY. Looks like a SWFE parade being favored which I’ll never be a fan of where I am despite the one or two rabbits out of the hat that can luck out. I’m sure you’re drooling though. 

[bluewave]

3 minutes ago, 40/70 Benchmark said:

Right....all I'm saying is it's a heavier press of the PV...I've always expected it to be a N stream dominated pattern that is favorable for NE, not so much your area into the mid atl.

This is also a function of the weaker PNA than last December which we were both expecting. More cold available in Canada than last December. But the same stubborn storm track. 

[brooklynwx99]

this is a pretty obvious colder shift. SE ridge is squashed, potentially opening up a risk for accumulating snow for the Northeast mid-week. can thank the more robust -EPO for that

[40/70 Benchmark]

4 minutes ago, jm1220 said:

One trillion percent pass on that month and season here where we watched I-90 get buried over and over while it cold rained IMBY. Looks like a SWFE parade being favored which I’ll never be a fan of where I am despite the one or two rabbits out of the hat that can luck out. I’m sure you’re drooling though. 

Yes, I def. wouldn't love this in your area.

3 minutes ago, bluewave said:

This is also a function of the weaker PNA than last December which we were both expecting. More cold available in Canada than last December. But the same stubborn storm track. 

Yea, difference should be enough to get me in the game, at least. 

[binbisso]

7 minutes ago, bluewave said:

Which is better for the Great Lakes into New England. Gradients usually end up farther north than originally forecast once we get into the short term compared to the longer range forecasts.  Models not varying the storm track pattern with a dominant Northern Stream.

Hopefully you are right with guidance showing this at day 7

 

[Terpeast]

Just now, brooklynwx99 said:

this is a pretty obvious colder shift. SE ridge is squashed, potentially opening up a risk for accumulating snow for the Northeast mid-week. can thank the more robust -EPO for that

It looks like this is our first window (I'm on the very very southern edge of it so not expecting much). After this first window, the PNA looks to go pretty deeply negative then rise back to neutral-ish by mid-month. Then we should get another window sometime after that.

[brooklynwx99]

Just now, Terpeast said:

It looks like this is our first window (I'm on the very very southern edge of it so not expecting much). After this first window, the PNA looks to go pretty deeply negative then rise back to neutral-ish by mid-month. Then we should get another window sometime after that.

yeah, the poleward extension should make things rougher for a week or so, then it should become more favorable again after the 15th as the MJO orbits

even then, the TPV being nearby and a cold source region won't make it impossible to get lucky

[MJO812]

12 minutes ago, bluewave said:

Which is better for the Great Lakes into New England. Gradients usually end up farther north than originally forecast once we get into the short term compared to the longer range forecasts.  Models not varying the storm track pattern with a dominant Northern Stream.

Typically yes but we will not know how much press there will be for days .

There has been a trend on the models with the PV getting further south thanks to the negative epo.

[michsnowfreak]

1 hour ago, donsutherland1 said:

Here you go:

Thank you Don. I knew todays run was colder, which is why I said that to spartman. You don't ever look at the cfs weeklies (or any weeklies) and speak in absolutes. They change all the time.

 

[GaWx]

Euro Weeklies 2m temps for 11/24-30 and this is before the very recent cooldown for early Dec:

11/17 run:

 

11/24 run:

[donsutherland1]

39 minutes ago, GaWx said:

The colder trend for early Dec is happening on all ensembles including GEFS: these are all for a week from today at 7PM: watch the SER disappear:
 

 

@donsutherland1@bluewave

This is pretty much the consensus idea for the first 10 days of December. The cold will spread through the Upper Midwest, the Great Lakes and then eastward. Some pieces could reach the Southeast as the ridge is flattened for a time. Unfortunately, if the latest guidance is right, like a champion fighter, the SE Ridge will pick itself up and keep coming back. Then, if some of the more recent guidance is right, namely the development of an AO+ pattern, the ridge could rebuild. The Great Lakes Area (Chicago, Detroit, Milwaukee, Toronto) and northern New England/eastern Canada should see a continuation of the cold past mid-December and perhaps onward. 

I suspect that snow will develop in the Chicago area late Saturday or Saturday night and then spread into Detroit and Toronto afterward. A moderate snowfall appears likely.

[SnowGoose69]

1 hour ago, snowman19 said:

The ensembles (GEFS, GEPS, EPS) want to retrograde the Alaskan ridge (-EPO) to an Aleutian ridge (-WPO) by the beginning of the 2nd week of December. So you end up with a -WPO/+EPO/-PNA setup. It’s been a consistent theme for several cycles now 

It looks transient and more like a reshuffle though on the GEPS/EPS, you can see D15-16 already it seems a ridge is trying to begin popping again in W Canada or along the coast.  I'd be surprised if we have that rabid of an MJO wave going into 8 that we see a pattern like that, though once in a great while we've seen a raging -PNA/+AO/NAO with a phase 8 MJO, I think maybe January of 1990 we did, but I'm not sure if its ever been with a wave potentially that strong.

[MJO812]

MJO moving along

Great sign

[40/70 Benchmark]

10 minutes ago, SnowGoose69 said:

It looks transient and more like a reshuffle though on the GEPS/EPS, you can see D15-16 already it seems a ridge is trying to begin popping again in W Canada or along the coast.  I'd be surprised if we have that rabid of an MJO wave going into 8 that we see a pattern like that, though once in a great while we've seen a raging -PNA/+AO/NAO with a phase 8 MJO, I think maybe January of 1990 we did, but I'm not sure if its ever been with a wave potentially that strong.

We didn't have MJO phase 8 in January of 1990. it was December 1989.

https://www.bom.gov.au/clim_data/IDCKGEM000/rmm.74toRealtime.txt

[MJO812]

[40/70 Benchmark]

1 minute ago, MJO812 said:

MJO moving along

Great sign

BC version has it entering the COD on Xmas eve.

[FPizz]

31 minutes ago, GaWx said:

Euro Weeklies 2m temps for 11/24-30 and this is before the very recent cooldown for early Dec:

11/17 run:

 

11/24 run:

I think it is safe to say these haven't been good past week 1.  Also, saying anything is consistent day 14/15 is just silly

[SnowGoose69]

I think a big part of the reason we lost the SER in early Dec is the storm system D5-6 ended up much less amped and not like a bomb models shows 3-4-5 days ago.  Now of course they try to do the same thing with the ensuing storm, once again I am inclined to lean flatter as that has been the trend seemingly forever.  If we don't get a monster cutter into the Lakes or MW the SER will keep verifying weaker in the medium range.  The question is if the LR is going too weak on it.  If we do blast hard into phase 8, that will certainly help

[brooklynwx99]

2 minutes ago, 40/70 Benchmark said:

BC version has it entering the COD on Xmas eve.

if looking at RMM, the left of the COD is usually a cold signal as well

[GaWx]

Yesterday’s Euro: phase 8 starts 12/14:

 

Today’s Euro: phase 8 starts 10 days earlier, 12/4, (with a 6+day long phase 8 implied) although I’d want to make sure it isn’t curling back into 7 and staying there:

last time Dec had a 6+ day long phase 8 was way back in 1995 (12/20-5):

[donsutherland1]

16 minutes ago, SnowGoose69 said:

It looks transient and more like a reshuffle though on the GEPS/EPS, you can see D15-16 already it seems a ridge is trying to begin popping again in W Canada or along the coast.  I'd be surprised if we have that rabid of an MJO wave going into 8 that we see a pattern like that, though once in a great while we've seen a raging -PNA/+AO/NAO with a phase 8 MJO, I think maybe January of 1990 we did, but I'm not sure if its ever been with a wave potentially that strong.

Those are rare outcomes. For December, there have been just 5 dates that saw such criteria (1980-2024).

[SnowGoose69]

1 minute ago, donsutherland1 said:

Those are rare outcomes. For December, there have been just 5 dates that saw such criteria (1980-2024).

Not surprised to see it was during a Nino too where Dec tends to lean milder anyway.  I think we had a small snow event in SNE a few days prior to that too.  

[40/70 Benchmark]

4 minutes ago, brooklynwx99 said:

if looking at RMM, the left of the COD is usually a cold signal as well

If all else is equal, but it allows for other factors to overwhelm...just as weaker ENSO does. That shouldn't be prohibitive to an intensifying PV and the development of a PT.

[brooklynwx99]

6 minutes ago, 40/70 Benchmark said:

If all else is equal, but it allows for other factors to overwhelm...just as weaker ENSO does. That shouldn't be prohibitive to an intensifying PV and the development of a PT.

true. I think that Pacific trough is transient as the momentum from the poleward jet extension pushes into AK. then, as the MJO continues progressing, it wouldn't be surprising to see another equatorward extension... that period will become clearer over the next week or so

I think we warm up for a week from like the 10-17th... what happens afterwards is more dubious