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Pattern December Doldrums 2025 🎄 ❄️

It's even contradicting the current MJO phase. A La Nina phase 7 MJO gives us a -EPO/WPO/AO/NAO with an enhansed sub tropical jet that cuts off a low out west with a SER and a deep trough over South/southeast Canada creating a gradient pattern over the East(cold north/warm south). Me thinks models will not have a correct sulution until at least mid week.

G52OZJsXkAAVEyC.png
 
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TriplePhaser said:
It's even contradicting the current MJO phase. A La Nina phase 7 MJO gives us a -EPO/WPO/AO/NAO with anhansed sub tropical jet that cuts off a low out west with a SER and a deep trough over South/southeast Canada creating a gradient pattern over the East(cold north/warm south). Me thinks models will not have a correct sulution until at least mid week.

View attachment 177117
Click to expand...
Hopefully they will resolve soon
 
TriplePhaser said:
As Nathan said models are completely in disarray and are in contradiction of Tropical/extratropical signals all because they're unable to figure out how the SSW will influence the 500mb pattern! If the 12z is to be believed which I take with a huge grain of salt(as should anyone), then yes the SER is gone but so is the Alaskan ridge! Also we are heading into a -NAM state(as Eric said) so I don't know why there was a huge change from 0z-12z regarding that!

La Nina is weak and on life support and the Pacific jet is shifting towards the equator so this is in contradiction to what a Jet extension is supposed to look like in this senario nevermind in a +AMM.

Click to expand...


I've heard SPV splits can invoke a temporary +NAM before blocking sets up later. But I don't think a displacement does that. They affect the atmosphere sooner as far as I know.
 
Webberweather53 said:
Lol I see you all are trying to steal my western trough for like the hundredth time this fall
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Yeah, they seriously need to stop stealing the troughs, haha. I've officially been out here in SoCal since last September working at one of the WFOs & I gotta say the weather out here is vastly differently than east coast / or east of Rockies wx - have learned a lot making me pretty well rounded love it!
 
Mitch West said:
Things don’t look as bad anymore. Here’s to a good week of trends.
Click to expand...

Not sure, it's still looks pretty stanky to me, pacific air straight into the conus. Good news cold is on our side of hemisphere. Bad news it's all in Canada. This all will change anyway, but long range pacific and atlantic is not great per eps. All will be forgiven if late December and January deliver. We continue to wait, which is fine because this weekend was gorgeous weather honestly.

1763990553970.png1763990640747.png
 
SnowNiner said:
Not sure, it's still looks pretty stanky to me, pacific air straight into the conus. Good news cold is on our side of hemisphere. Bad news it's all in Canada. This all will change anyway, but long range pacific and atlantic is not great per eps. All will be forgiven if late December and January deliver. We continue to wait, which is fine because this weekend was gorgeous weather honestly.

View attachment 177129View attachment 177130
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Apples to oranges on the model comparisons but it’s understood!
 
Going into early Dec, it looks like we'll have a good reservoir of cold across Canada, so any hiccup / mishap with the ridge / trough pattern (in the good direction) could result in a bit of action...

But broadly speaking, we're likely going to have a Pac Jet problem as the jet is retracted as about as far west as we ever see it here on Dec 5 - this leads to western ridging hanging out in the Aleutians and Bering Strait

Nov 24 Euro Jet.png


All else being equal, here are some of the parameters which control the Pac Jet:

ENSO: Retracted and Poleward jet favored during La Nina. Extended and Equatorward jet favored during El Nino
MJO: Jet extends during 5-6-7-8 and retracts during 1-2-3-4. Jet is max extended during 7-8-1 / Max retracted during 3-4-5
EAMT (East Asian Mtn Torque): +EAMT (High pressure in EAsia) adds momentum to the Jet / -EAMT (Low pressure in EAsia) reduces momentum
Arctic Oscillation: If ++AO, jet is more poleward. If --AO, jet is more equatorward


Here's an animation of the MJO in each phase, with the Pac Jet in purple. Green is enhanced convection. Brown is reduced convection.

MJO Phase Loop.gif



For -EPO / +PNA type ridging, we want the goldilocks scenario where it isn't retracted to the west and it isn't overly extended to the east, bit it's in between the 2. And we want it running west to east (more equatorward / more south) and not running poleward up toward the Gulf of Alaska.


For our current situation, we've gone thru a recent period of weak +EAMT, but all signs point to that flipping to -EAMT as seen here with Low pressure in EAsia on this 5-day avg for Nov 28 - Dec 3. That favors the retracted jet shown above.

Nov 24 Euro Asia.png


Typically, these -EAMT and +EAMT episodes run in cycles, so I wouldn't be surprised for this to flip back around to +EAMT in mid-late Dec


And this MJO wave looks as good as ever to me. Sure, we can quibble about a slow down with convection lingering in the W Pac etc., but that's common with the MJO of today...hard to get it to look much better than this. Whether it runs thru 8-1-2 in low amp or within the circle is pretty immaterial in my mind - just get it out of that area from the far E Indian Ocean thru the Maritime Continent, thru the far W Pacific (2nd half of Phase 3 to 1st half of Phase 7)

In a post back on Nov 13th, I mentioned a general progression of Dec (7-8- 1/2 way thru 1) and Jan 1-15 (1/2 of 1 and thru 2). That looks to be on track.


The GFS Ext and Euro Monthly are lock in step here:

Nov 24 MJO EPS.png

Nov 24 MJO GEFS.png


So the winning plan as we go into mid and late Dec will be to keep the core of the cold in Canada and have the MJO progression and flip to more +EAMT to extend the Pac Jet to the east, resulting in ridging being closer to the West Coast and more troughing E of the Rockies.


The SSW going reflective and not absorptive is a bit of a kick in thuh...as historically these early winter Canadian Warming SSWs have contributed to high latitude blocking patterns showing up - but what do you know, not this time it seems. This may be another feather in the cap of the "I hate SSWs" camp (which I am not a member of, lol).

Although, as seen in Judah's post yesterday, his world-famous model is showing cold for us in mid-Dec. It's probably because of the model showing SPV stretching associated with the SSW.
 
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griteater said:
Going into early Dec, it looks like we'll have a good reservoir of cold across Canada, so any hiccup / mishap with the ridge / trough pattern (in the good direction) could result in a bit of action...

But broadly speaking, we're likely going to have a Pac Jet problem as the jet is retracted as about as far west as we ever see it here on Dec 5 - this leads to western ridging hanging out in the Aleutians and Bering Strait

View attachment 177131


All else being equal, here are some of the parameters which control the Pac Jet:

ENSO: Retracted and Poleward jet favored during La Nina. Extended and Equatorward jet favored during El Nino
MJO: Jet extends during 5-6-7-8 and retracts during 1-2-3-4. Jet is max extended during 7-8-1 / Max retracted during 3-4-5
EAMT (East Asian Mtn Torque): +EAMT (High pressure in EAsia) adds momentum to the Jet / -EAMT (Low pressure in EAsia) reduces momentum
Arctic Oscillation: If ++AO, jet is more poleward. If --AO, jet is more equatorward


Here's an animation of the MJO in each phase, with the Pac Jet in purple. Green is enhanced convection. Brown is reduced convection.

View attachment 177132



For -EPO / +PNA type ridging, we want the goldilocks scenario where it isn't retracted to the west and it isn't overly extended to the east, bit it's in between the 2. And we want it running west to east (more equatorward / more south) and not running poleward up toward the Gulf of Alaska.


For our current situation, we've gone thru a recent period of weak +EAMT, but all signs point to that flipping to -EAMT as seen here with Low pressure in EAsia on this 5-day avg for Nov 28 - Dec 3. That favors the retracted jet shown above.

View attachment 177133


Typically, these -EAMT and +EAMT episodes run in cycles, so I wouldn't be surprised for this to flip back around to +EAMT in mid-late Dec


And this MJO wave looks as good as ever to me. Sure, we can quibble about a slow down with convection lingering in the W Pac etc., but that's common with the MJO of today...hard to get it to look much better than this. Whether it runs thru 8-1-2 in low amp or within the circle is pretty immaterial in my mind - just get it out of that area from the far E Indian Ocean thru the Maritime Continent, thru the far W Pacific (2nd half of Phase 3 to 1st half of Phase 7)

In a post back on Nov 13th, I mentioned a general progression of Dec (7-8- 1/2 way thru 1) and Jan 1-15 (1/2 of 1 and thru 2). That looks to be on track.


The GFS Ext and Euro Monthly are lock in step here:

View attachment 177134

View attachment 177135


So the winning plan as we go into mid and late Dec will be to keep the core of the cold in Canada and have the MJO progression and flip to more +EAMT to extend the Pac Jet to the east, resulting in ridging being closer to the West Coast and more troughing E of the Rockies.


The SSW going reflective and not absorptive is a bit of a kick in thuh...as historically these early winter Canadian Warming SSWs have contributed to high latitude blocking patterns showing up - but what do you know, not this time it seems. This may be another feather in the cap of the "I hate SSWs" camp (which I am not a member of, lol).

Although, as seen in Judah's post yesterday, his world-famous model is showing cold for us in mid-Dec. It's probably because of the model showing SPV stretching associated with the SSW.
Click to expand...

Thank you Grit for that excellent summary of where we are at the moment. A few elements have fizzled out the last week but the most important element (IMO), the pacific jet and the mjo convection, is still set up for potential success later in the month. đź’Ş
 
griteater said:
Going into early Dec, it looks like we'll have a good reservoir of cold across Canada, so any hiccup / mishap with the ridge / trough pattern (in the good direction) could result in a bit of action...

But broadly speaking, we're likely going to have a Pac Jet problem as the jet is retracted as about as far west as we ever see it here on Dec 5 - this leads to western ridging hanging out in the Aleutians and Bering Strait

View attachment 177131


All else being equal, here are some of the parameters which control the Pac Jet:

ENSO: Retracted and Poleward jet favored during La Nina. Extended and Equatorward jet favored during El Nino
MJO: Jet extends during 5-6-7-8 and retracts during 1-2-3-4. Jet is max extended during 7-8-1 / Max retracted during 3-4-5
EAMT (East Asian Mtn Torque): +EAMT (High pressure in EAsia) adds momentum to the Jet / -EAMT (Low pressure in EAsia) reduces momentum
Arctic Oscillation: If ++AO, jet is more poleward. If --AO, jet is more equatorward


Here's an animation of the MJO in each phase, with the Pac Jet in purple. Green is enhanced convection. Brown is reduced convection.

View attachment 177132



For -EPO / +PNA type ridging, we want the goldilocks scenario where it isn't retracted to the west and it isn't overly extended to the east, bit it's in between the 2. And we want it running west to east (more equatorward / more south) and not running poleward up toward the Gulf of Alaska.


For our current situation, we've gone thru a recent period of weak +EAMT, but all signs point to that flipping to -EAMT as seen here with Low pressure in EAsia on this 5-day avg for Nov 28 - Dec 3. That favors the retracted jet shown above.

View attachment 177133


Typically, these -EAMT and +EAMT episodes run in cycles, so I wouldn't be surprised for this to flip back around to +EAMT in mid-late Dec


And this MJO wave looks as good as ever to me. Sure, we can quibble about a slow down with convection lingering in the W Pac etc., but that's common with the MJO of today...hard to get it to look much better than this. Whether it runs thru 8-1-2 in low amp or within the circle is pretty immaterial in my mind - just get it out of that area from the far E Indian Ocean thru the Maritime Continent, thru the far W Pacific (2nd half of Phase 3 to 1st half of Phase 7)

In a post back on Nov 13th, I mentioned a general progression of Dec (7-8- 1/2 way thru 1) and Jan 1-15 (1/2 of 1 and thru 2). That looks to be on track.


The GFS Ext and Euro Monthly are lock in step here:

View attachment 177134

View attachment 177135


So the winning plan as we go into mid and late Dec will be to keep the core of the cold in Canada and have the MJO progression and flip to more +EAMT to extend the Pac Jet to the east, resulting in ridging being closer to the West Coast and more troughing E of the Rockies.


The SSW going reflective and not absorptive is a bit of a kick in thuh...as historically these early winter Canadian Warming SSWs have contributed to high latitude blocking patterns showing up - but what do you know, not this time it seems. This may be another feather in the cap of the "I hate SSWs" camp (which I am not a member of, lol).

Although, as seen in Judah's post yesterday, his world-famous model is showing cold for us in mid-Dec. It's probably because of the model showing SPV stretching associated with the SSW.
Click to expand...
Is there any particular reason why it always flies through phase 8?
 
griteater said:
Going into early Dec, it looks like we'll have a good reservoir of cold across Canada, so any hiccup / mishap with the ridge / trough pattern (in the good direction) could result in a bit of action...

But broadly speaking, we're likely going to have a Pac Jet problem as the jet is retracted as about as far west as we ever see it here on Dec 5 - this leads to western ridging hanging out in the Aleutians and Bering Strait

View attachment 177131


All else being equal, here are some of the parameters which control the Pac Jet:

ENSO: Retracted and Poleward jet favored during La Nina. Extended and Equatorward jet favored during El Nino
MJO: Jet extends during 5-6-7-8 and retracts during 1-2-3-4. Jet is max extended during 7-8-1 / Max retracted during 3-4-5
EAMT (East Asian Mtn Torque): +EAMT (High pressure in EAsia) adds momentum to the Jet / -EAMT (Low pressure in EAsia) reduces momentum
Arctic Oscillation: If ++AO, jet is more poleward. If --AO, jet is more equatorward


Here's an animation of the MJO in each phase, with the Pac Jet in purple. Green is enhanced convection. Brown is reduced convection.

View attachment 177132



For -EPO / +PNA type ridging, we want the goldilocks scenario where it isn't retracted to the west and it isn't overly extended to the east, bit it's in between the 2. And we want it running west to east (more equatorward / more south) and not running poleward up toward the Gulf of Alaska.


For our current situation, we've gone thru a recent period of weak +EAMT, but all signs point to that flipping to -EAMT as seen here with Low pressure in EAsia on this 5-day avg for Nov 28 - Dec 3. That favors the retracted jet shown above.

View attachment 177133


Typically, these -EAMT and +EAMT episodes run in cycles, so I wouldn't be surprised for this to flip back around to +EAMT in mid-late Dec


And this MJO wave looks as good as ever to me. Sure, we can quibble about a slow down with convection lingering in the W Pac etc., but that's common with the MJO of today...hard to get it to look much better than this. Whether it runs thru 8-1-2 in low amp or within the circle is pretty immaterial in my mind - just get it out of that area from the far E Indian Ocean thru the Maritime Continent, thru the far W Pacific (2nd half of Phase 3 to 1st half of Phase 7)

In a post back on Nov 13th, I mentioned a general progression of Dec (7-8- 1/2 way thru 1) and Jan 1-15 (1/2 of 1 and thru 2). That looks to be on track.


The GFS Ext and Euro Monthly are lock in step here:

View attachment 177134

View attachment 177135


So the winning plan as we go into mid and late Dec will be to keep the core of the cold in Canada and have the MJO progression and flip to more +EAMT to extend the Pac Jet to the east, resulting in ridging being closer to the West Coast and more troughing E of the Rockies.


The SSW going reflective and not absorptive is a bit of a kick in thuh...as historically these early winter Canadian Warming SSWs have contributed to high latitude blocking patterns showing up - but what do you know, not this time it seems. This may be another feather in the cap of the "I hate SSWs" camp (which I am not a member of, lol).

Although, as seen in Judah's post yesterday, his world-famous model is showing cold for us in mid-Dec. It's probably because of the model showing SPV stretching associated with the SSW.
Click to expand...
Yeah after a brief stout of -EAMT around Dec. 1st retracting the jet early Dec(which current models I believe could be overreacting to) the next +EAMT towards the 5th + should give us a stout Equater-shifted Jet extension mid-month that would give us a good -EPO/+PNA! Couple that with an eventual -AO/NAO(delayed but not denied) and we got a solid Dec 15th-Jan 15th period on our hands!
 
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Bigedd09 said:
Is there any particular reason why it always flies through phase 8?
Click to expand...
I would answer that in an opposite way...the area of the tropics where the most convection / thunderstorms occur is in the Indo-Pacific (E Indian Ocean thru the Maritime Continent to the W Pacific). This is especially the case during La Ninas. So as the MJO moves west to east across the equator, it tends to get bogged down in that region (constructive interference) and runs slower thru there (Phases 3-6)

This map is for the last 6 months showing the enhanced signal for tropical convection in that region (-VP is upper-level divergence promoting rising motion and thunderstorms).

See this link as well: Blog Post: What is the MJO, and why do we care?

Nov 24 VP.png
 
Models are going to bounce around. A lot. The consistent things is the cold steadily showing up in Canada. I mean, I get the frustration about the arctic motherload not continually dropping on our heads. But with a few, not-so-out-of-reach tweaks, it can go from Spring to Winter in 48 hours.

At least it doesn't look like we're going to have to wait weeks to set up the opportunity for a pattern to set up the potential for cold air to return to our side of the globe to set up the potential for a pattern that delivers the cold air into the US to set up a potential for a winter storm to set up....
 
Rain Cold said:
Models are going to bounce around. A lot. The consistent things is the cold steadily showing up in Canada. I mean, I get the frustration about the arctic motherload not continually dropping on our heads. But with a few, not-so-out-of-reach tweaks, it can go from Spring to Winter in 48 hours.

At least it doesn't look like we're going to have to wait weeks to set up the opportunity for a pattern to set up the potential for cold air to return to our side of the globe to set up the potential for a pattern that delivers the cold air into the US to set up a potential for a winter storm to set up....
Click to expand...
Yeh I am actually surprised by the lack of talk in here. But I get it.. But like you said.. Cold is right there.
 
jackendrickwx said:
sunday sunday sunday

View attachment 177143
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This is a perfect example of another reason I prefer the Upstate over other regions of SC. Even if it doesn't snow here, I always love these wedge days where we are 20-30 degrees colder. I would be completely bummed on these days living in CAE or CHS.
 
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