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Pattern December Doldrums 2025 🎄 ❄️

With the unfavorable changes in the MJO and AO/NAO, today’s 0Z GEFS is not surprisingly significantly warmer than yesterday’s run for the 2nd week in Dec. However, today’s 0Z EPS, which maintained its very long phase 8, is much colder than yesterday as well as the GEFS

Yesterday’s 0Z EPS for 12/5-11:
IMG_5719.png


Today’s 0Z EPS for 12/5-11: it’s pretty rare for a 7 day period of the EPS to have that much of a change within just 24 hours:
IMG_5720.png

As a result, the aggregate of today’s Euro Weeklies 12/1-7 and 12/8-14 2m temp anomaly maps will very likely be notably colder than yesterday’s.
 
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Webberweather53 said:
Despite all the back-and-forth on the models on the pattern, MJO, the stratosphere, etc. this is what the MJO + ER + low frequency analog had nearly a month ago for early December.

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This is the latest forecast, which is largely unchanged over N America.
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And if you keep it rolling the trough just stays over the East through at least mid January
 
Mitch West said:
I really think we are just going to keep doing this.

And honestly it all makes perfect sense with MJO progression.
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Better looking H5 further out in time, I’ll take it…EPS just keeps moving toward a favorable pattern is very encouraging to me.


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CNCsnwfan1210 said:
Better looking H5 further out in time, I’ll take it…EPS just keeps moving toward a favorable pattern is very encouraging to me.


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Been waiting on the H5 pattern to respond to the MJO progression in the longer ranges in the modeling. It's finally starting to happen. As Webber said, a threat or two will emerge.

Then, we probably get another assault on the SPV in December. I think the Southeast is in for a good winter, and all those straight Nina climo winter outlooks are on the verge of some serious trouble.

Always nice to see the biggest - departures on our side of the globe. Strap in and remember to keep your hands and feet inside the ride at all times!

ecmwf-ensemble-avg-nhemi-t850_anom_stream-5087200.png
 
Like or don’t like J Cohen and his work, but he’s not a cold hype-ster. He’ll call it warm when appropriate.

As a supplement to a tweet from Nov 23, here is what he stated yesterday in a USA Today article…

"My thinking is that the cold the first week of December is the appetizer and the main course will be in mid-December," said climatologist Judah Cohen, a research scientist at MIT, in an email to USA TODAY.

Indeed, according to Cohen's computer model, "which I can credibly claim as the world's best – is predicting that the most expansive region of most likely extreme cold on Earth stretches from the Canadian Plains to the U.S. East Coast in the 3rd week of December."

Note: him saying the model is the world’s best is “hypey” I’d say though

But he’s seeing a textbook reflection of wave energy with troposphere / stratosphere interactions

IMG_4403.jpeg


This is associated with a stretched SPV in the configuration in “P3” in this diagram

Source: https://www.science.org/doi/10.1126/sciadv.adq9557

See “C” within “P3”. H10 here is 10 hPa (10mb) in the stratosphere.

IMG_4406.jpeg


“C” in the diagram matches well with what the Euro is currently showing for Dec 13th. Long way off but hopefully that holds

IMG_4407.png


But high values of the Reflectivity Index and this type of SPV configuration are associated with P3-H (500mb) and P3-M (Surface Temperatures)…i.e. AK ridge and weak Greenland ridge with trough and cold temperatures east of the Rockies

IMG_4408.jpeg
 
The good news is that for mid-Dec and beyond we are trying to marry the benefits of a favorable MJO, with benefits of positive troposphere - stratosphere interactions, with what appears to seemingly be a base state that doesn’t want to send troughs deep into the southwest states…a potential triple threat for cold east of the Rockies
 
griteater said:
Like or don’t like J Cohen and his work, but he’s not a cold hype-ster. He’ll call it warm when appropriate.

As a supplement to a tweet from Nov 23, here is what he stated yesterday in a USA Today article…

"My thinking is that the cold the first week of December is the appetizer and the main course will be in mid-December," said climatologist Judah Cohen, a research scientist at MIT, in an email to USA TODAY.

Indeed, according to Cohen's computer model, "which I can credibly claim as the world's best – is predicting that the most expansive region of most likely extreme cold on Earth stretches from the Canadian Plains to the U.S. East Coast in the 3rd week of December."

Note: him saying the model is the world’s best is “hypey” I’d say though

But he’s seeing a textbook reflection of wave energy with troposphere / stratosphere interactions

View attachment 177428


This is associated with a stretched SPV in the configuration in “P3” in this diagram

Source: https://www.science.org/doi/10.1126/sciadv.adq9557

See “C” within “P3”. H10 here is 10 hPa (10mb) in the stratosphere.

View attachment 177429


“C” in the diagram matches well with what the Euro is currently showing for Dec 13th. Long way off but hopefully that holds

View attachment 177430


But high values of the Reflectivity Index and this type of SPV configuration are associated with P3-H (500mb) and P3-M (Surface Temperatures)…i.e. AK ridge and weak Greenland ridge with trough and cold temperatures east of the Rockies

View attachment 177431
Click to expand...

Good stuff Grit, I’ve been following Judah for quite awhile and he has put some extensive research into the SPV behavior and the associated wx patterns that follow. If all that holds true, P3 H/M on the last diagram is about as good as it gets for December from what I can tell.


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griteater said:
The good news is that for mid-Dec and beyond we are trying to marry the benefits of a favorable MJO, with benefits of positive troposphere - stratosphere interactions, with what appears to seemingly be a base state that doesn’t want to send troughs deep into the southwest states…a potential triple threat for cold east of the Rockies
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This is such a delightful paragraph
 

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EPS vs euro at D8.5-9, anything could show up with the pattern coming up, something to watch for now, but these slow moving/stuck Baja lows have produced in the past. Just not easy to time them, need a strong trough that’s just moving out with the southern stream low trailing right behind it. But imo, the pattern is there and something could show up IMG_0130.pngIMG_0129.png
 
Cad Wedge NC said:
Somebody needs to wake up @Mitch and @Rain Cold/ They are going to love this. Too bad it's 10 days out. Just goes to show you what a good pattern we are heading into. You got to love snow in December.
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I'm fired up buddy! Hopefully us in the foothills get some love this year along with with everyone else. Looks like a great pattern setting up down the line. Hopefully it holds for future runs.
 
Cad Wedge NC said:
Somebody needs to wake up @Mitch and @Rain Cold/ They are going to love this. Too bad it's 10 days out. Just goes to show you what a good pattern we are heading into. You got to love snow in December.
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Oh I'm awake. It's going to be Epic! 😁 Has another one brewing in the Gulf around D15 also.

ecmwf_mslp_pcpn_frzn_us_84.png
 
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