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Wintry Winter 2024-25 Discussion

The Pacific jet extension is not the true issue here late in Dec.

The poleward shift in the pacific jet has more to do with the mild spell out east late in the month than the jet extension.

Outside of big Nino winters, it’s only when a jet extension is coupled with a poleward shift that we see a big warm up over N America.

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Here’s the pacific jet phase diagram from WPC that runs this once a day on the 0z run:

North Pacific Jet Phase Diagram

Notice, the pacific jet is already extended at model initialization. Also note how it’s mostly a jet extension without much of an equatorward or poleward shift (points are orbiting well within the jet extension quadrant).

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Notice how well the first week where we are getting almost purely a jet extension (previous post), actually fits with the jet extension composite (top row). (It’s a +PNA pattern).

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It’s not really until we get close to and beyond Christmas when we start to approach the adjacent poleward shift quadrant that the warmth really overspreads North America.

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Poleward shift in the pacific jet coupled with an extension is usually how we get a big torch over N America. A jet extension on its own actually favors colder temps in the eastern US and is the kind of pattern we’ve seen most of Dec so far.

I just want to make the distinction here clear because there’s a huge difference in sensible impacts between a jet extension on its own and a poleward shift in the jet on its own. I think the jet extension (while accurate in this case) takes a little too much of the blame when these kind of patterns show up & most folks (including S2S forecasters) don’t pay enough attention to the latitude of the jet, which actually matters more in regulating the EPO. It usually takes more than a pacific jet extension by itself to get these kind of warm anomalies.

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Webberweather53 said:
The Pacific jet extension is not the true issue here late in Dec.

The poleward shift in the pacific jet has more to do with the mild spell out east late in the month than the jet extension.

Outside of big Nino winters, it’s only when a jet extension is coupled with a poleward shift that we see a big warm up over N America.

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Funny thing on the chart wording too is that the Poleward Shift has a farther east jet extension than the “Jet Extension” phase (I suppose it’s because the farther north location is caught in the stronger westerlies, carrying it farther east)
 
griteater said:
Funny thing on the chart wording too is that the Poleward Shift has a farther east jet extension than the “Jet Extension” phase (I suppose it’s because the farther north location is caught in the stronger westerlies, carrying it farther east)
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Yes.

This is because a poleward shift in the jet stream actually causes a further acceleration/extension of the jet through angular momentum conservation principles. Moving the jet stream closer to earth’s rotational axis/the North Pole forces it to accelerate (in much of the same way a figure skater pulls in her arms and spins more quickly).

You usually need a poleward shift or hybrid poleward shift/extension of the pacific jet to kick off a +EPO and really warm N America. A pacific jet extension on its own usually only regulates the PNA (& forces it to become positive).
 
Webb thanks for the post above on Jet extension and Poleward shifts. That was very easy to grasp and makes a lot of common sense to amateur like myself.
We need to be sweating the Pac Jets aiming point more than whether its a firehose or not.
 
Great video from DT last night. Looks like the teleconnections and MJO are lining up to all be more favorable starting around 1/5. Let’s see what it brings. Enjoy your holidays and then come back rested and ready to track in January.

 
CaryWx said:
I wouldn't count on February. Conditions will not be favorable. It's going to have to be January more or less
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I keep hearing this. How in the world is anyone about to predict how an entire specific month will turn out? I mean, I'm just as pessimistic as anyone when it comes to cold and snowy patterns around here, but there's no way we know whether or not something unforeseen might pop up to interfere with the hot February outlooks.

The only thing I can think of that holds water is that you can make the argument that February has been trash for years now, and that is the new normal (which i guess you could apply to modern winters as a whole). Otherwise, I submit that we don't know how it will turn out.
 
Rain Cold said:
I keep hearing this. How in the world is anyone about to predict how an entire specific month will turn out? I mean, I'm just as pessimistic as anyone when it comes to cold and snowy patterns around here, but there's no way we know whether or not something unforeseen might pop up to interfere with the hot February outlooks.

The only thing I can think of that holds water is that you can make the argument that February has been trash for years now, and that is the new normal (which i guess you could apply to modern winters as a whole). Otherwise, I submit that we don't know how it will turn out.
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I agree. Although a pessimist might say “if it walks like a duck and quacks like a duck”.

Febs have been awful lately so I can’t disparage someone for trashing it.
 
You can have 27 torch days in Feb. But if you can just find that 1 day to win the " SE has to Time Everything out just Right Lottery", Its usually a storm for the History books. Feb and March is usually Go Big or Go Home type deals.
 
Rain Cold said:
I keep hearing this. How in the world is anyone about to predict how an entire specific month will turn out? I mean, I'm just as pessimistic as anyone when it comes to cold and snowy patterns around here, but there's no way we know whether or not something unforeseen might pop up to interfere with the hot February outlooks.

The only thing I can think of that holds water is that you can make the argument that February has been trash for years now, and that is the new normal (which i guess you could apply to modern winters as a whole). Otherwise, I submit that we don't know how it will turn out.
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I didn't speak in absolutes here. Just this year Feb is not looking favorable but Jan is as of right now. I wouldn't even argue its a "new normal" we do seem to have to hit things more 'just right' though the later in the winter we get.
 
Rain Cold said:
I keep hearing this. How in the world is anyone about to predict how an entire specific month will turn out? I mean, I'm just as pessimistic as anyone when it comes to cold and snowy patterns around here, but there's no way we know whether or not something unforeseen might pop up to interfere with the hot February outlooks.

The only thing I can think of that holds water is that you can make the argument that February has been trash for years now, and that is the new normal (which i guess you could apply to modern winters as a whole). Otherwise, I submit that we don't know how it will turn out.
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I don't think that we are to a point where you can say for certain an entire month will be terrible at an extended lead. I do think at an extended lead you can get an idea of what the general pattern progression should be. I know you know this but the fluidity of weather does lead to a likely failure as you increase lead but if 24 of 28 days in Feb are a SE ridge but we get a foot of snow in the 4 days we didn't have a SER the ridge forecast verified to me
 
I feel reasonably confident February will be milder than usual, especially early to mid month when the subseasonal forcing will be stacked against us and heavily in favor of a SE ridge (as well as crappy -ENSO climo). Maybe things could get interesting at the tail end of Feb or Mar, as the wavelengths start to rapidly shorten, but I definitely don’t feel yet the same way about then as I have with the coming favorable pattern in January.

We really need to get the stratospheric polar vortex on our side of the pond to lock in the Hudson Bay vortex (talked about this several weeks ago) and these Canadian warming events are screwing us over & may really come back to bite us unless we get a giant SSWE like say 1985 (x doubt).

I see most of, if not all of ingredients there for this to happen with little conflicting signals, in much of the same way I’ve liked early to mid January ish for the last several weeks before it appeared on the models as it is now. Crazy as it sounds, I honestly feel more confident in Feb’s overall outcome than I do with January.
 
Webberweather53 said:
I feel reasonably confident February will be milder than usual, especially early to mid month when the subseasonal forcing will be stacked against us and heavily in favor of a SE ridge (as well as crappy -ENSO climo). Maybe things could get interesting at the tail end of Feb or Mar, as the wavelengths start to rapidly shorten, but I definitely don’t feel yet the same way about then as I have with the coming favorable pattern in January.

We really need to get the stratospheric polar vortex on our side of the pond to lock in the Hudson Bay vortex (talked about this several weeks ago) and these Canadian warming events are screwing us over & may really come back to bite us unless we get a giant SSWE like say 1985 (x doubt).

I see most of, if not all of ingredients there for this to happen with little conflicting signals, in much of the same way I’ve liked early to mid January ish for the last several weeks before it appeared on the models as it is now. Crazy as it sounds, I honestly feel more confident in Feb’s overall outcome than I do with January.
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Not crazy at all IMO. Not only everything you've said, but the MJO may back in 4-5-6 by then also. Not much to suggest this time period isn't warm and a lot to suggest it will be.
 
1300m said:
Not crazy at all IMO. Not only everything you've said, but the MJO may back in 4-5-6 by then also. Not much to suggest this time period isn't warm and a lot to suggest it will be.
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If we had more of a 2013-14 type situation where we had a stronger stratospheric polar vortex sitting over our heads, I’d feel a lot differently and that we could go off script more. These kind of -ENSO winters with North Pacific blocking tend to break very hard one way or the other in Feb, and the majority of the time they do go warm, with cold centered out west and into the plains. Seems like where this year wants to head, although I guess there’s enough room for something to happen closer to March.

A lot of (but certainly not all) of the ENSO modulation of sensible weather evolution in North America during the winter just has to do with how each phase interacts with seasonal changes in the jet wavelengths.

The same El Niño-like pacific jet extension in February will have different impacts than December-January, simply because the wavelengths are shorter in Feb than Dec-Jan. The shorter late winter/Feb wavelengths cause the downstream wave pattern from a jet extension to shift westward against the mean flow compared to Dec-Jan. The ridge that was over central-eastern Canada in Dec-Jan now instead moves towards the west coast and turns into a +PNA. The opposite tends to happen in Nina/-ENSO winters and the inflection/break point most of the time seems to be around January 25th or so

I made this plot last winter for major mid Atlantic snowstorm relative frequencies between different enso phases since the late 1800s and it makes total sense.

This year for the most part is following the script, with the biggest Nina favored gains in early-mid January or so, then tailing off late January & flipping in favor of Ninos by early-mid Feb. By late Feb & early Mar, we’re closer to a wash.

IMG_3683.jpeg
 
Webberweather53 said:
If we had more of a 2013-14 type situation where we had a stronger stratospheric polar vortex sitting over our heads, I’d feel a lot differently and that we could go off script more. These kind of -ENSO winters with North Pacific blocking tend to break very hard one way or the other in Feb, and the majority of the time they do go warm, with cold centered out west and into the plains. Seems like where this year wants to head, although I guess there’s enough room for something to happen closer to March.

A lot of (but certainly not all) of the ENSO modulation of sensible weather evolution in North America during the winter just has to do with how each phase interacts with seasonal changes in the jet wavelengths.

The same El Niño-like pacific jet extension in February will have different impacts than December-January, simply because the wavelengths are shorter in Feb than Dec-Jan. The shorter late winter/Feb wavelengths cause the downstream wave pattern from a jet extension to shift westward against the mean flow compared to Dec-Jan. The ridge that was over central-eastern Canada in Dec-Jan now instead moves towards the west coast and turns into a +PNA. The opposite tends to happen in Nina/-ENSO winters and the inflection/break point most of the time seems to be around January 25th or so

I made this plot last winter for major mid Atlantic snowstorm relative frequencies between different enso phases since the late 1800s and it makes total sense.

This year for the most part is following the script, with the biggest Nina favored gains in early-mid January or so, then tailing off late January & flipping in favor of Ninos by early-mid Feb. By late Feb & early Mar, we’re closer to a wash.

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That’s a great plot. Definitely interesting to see that increase in -ENSO winters in early to mid January.
 
Rain Cold said:
I keep hearing this. How in the world is anyone about to predict how an entire specific month will turn out? I mean, I'm just as pessimistic as anyone when it comes to cold and snowy patterns around here, but there's no way we know whether or not something unforeseen might pop up to interfere with the hot February outlooks.

The only thing I can think of that holds water is that you can make the argument that February has been trash for years now, and that is the new normal (which i guess you could apply to modern winters as a whole). Otherwise, I submit that we don't know how it will turn out.
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I would agree that anything can happen in winter, and you just never know. But it just seems February has gotten warmer and warmer the last several years to me. And last year was the pinnacle of a "meteorological" slam dunk for late February and March to supposedly turn cold, and the weeklies, ensembles, mjo, jet, everything was right for cold. And it went straight warm like many of us feared. That really was the straw that broke me for February. If any February was supposed to be different it was that one (late), and it wasn't. It leads me to believe there's a silver bullet issue(s) that's unresolved and unknown that's making Februarys a new spring month for our back yard. Anything can happen, like the early December cold shot....but persistence and repetition eventually mean something in my mind.
 
SnowNiner said:
I would agree that anything can happen in winter, and you just never know. But it just seems February has gotten warmer and warmer the last several years to me. And last year was the pinnacle of a "meteorological" slam dunk for late February and March to supposedly turn cold, and the weeklies, ensembles, mjo, jet, everything was right for cold. And it went straight warm like many of us feared. That really was the straw that broke me for February. If any February was supposed to be different it was that one (late), and it wasn't. It leads me to believe there's a silver bullet issue(s) that's unresolved and unknown that's making Februarys a new spring month for our back yard. Anything can happen, like the early December cold shot....but persistence and repetition eventually mean something in my mind.
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Last year fooled me too. Last winter’s El Niño was truly the closest thing we’ve seen to 1997-98 since. Even the way last winter evolved was similar to 1997-98 (actually got warmer in Feb).
 
Webberweather53 said:
I feel reasonably confident February will be milder than usual, especially early to mid month when the subseasonal forcing will be stacked against us and heavily in favor of a SE ridge (as well as crappy -ENSO climo). Maybe things could get interesting at the tail end of Feb or Mar, as the wavelengths start to rapidly shorten, but I definitely don’t feel yet the same way about then as I have with the coming favorable pattern in January.

We really need to get the stratospheric polar vortex on our side of the pond to lock in the Hudson Bay vortex (talked about this several weeks ago) and these Canadian warming events are screwing us over & may really come back to bite us unless we get a giant SSWE like say 1985 (x doubt).

I see most of, if not all of ingredients there for this to happen with little conflicting signals, in much of the same way I’ve liked early to mid January ish for the last several weeks before it appeared on the models as it is now. Crazy as it sounds, I honestly feel more confident in Feb’s overall outcome than I do with January.
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I'm not confident of anything 2 months out 🤣🤣
 
SnowNiner said:
I would agree that anything can happen in winter, and you just never know. But it just seems February has gotten warmer and warmer the last several years to me. And last year was the pinnacle of a "meteorological" slam dunk for late February and March to supposedly turn cold, and the weeklies, ensembles, mjo, jet, everything was right for cold. And it went straight warm like many of us feared. That really was the straw that broke me for February. If any February was supposed to be different it was that one (late), and it wasn't. It leads me to believe there's a silver bullet issue(s) that's unresolved and unknown that's making Februarys a new spring month for our back yard. Anything can happen, like the early December cold shot....but persistence and repetition eventually mean something in my mind.
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9 of the last 14 Febs have been cold enso so it's not super shocking to me that we've largely lost February but had winters revenge too late to matter. That said last Feb was one of the most disappointing things weather wise in ages. I'll always wonder how well we would have done of the -nao materialized and the mjo didn't stop in p7/cod then refire in he IO
 
SD said:
9 of the last 14 Febs have been cold enso so it's not super shocking to me that we've largely lost February but had winters revenge too late to matter. That said last Feb was one of the most disappointing things weather wise in ages. I'll always wonder how well we would have done of the -nao materialized and the mjo didn't stop in p7/cod then refire in he IO
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It really was the monthly version of losing a storm in the short term
 
deltadog03 said:
Can I get a little snow at the end of Jan/early Feb in Tahoe please? I’m 0/2 the last 2 visits. lol
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I'm still amazed it snowed in Breckenridge but what really has surprised me and is the realization today that Tulsa will go through December without even a flake of snow. Even last year's catastrophe had that

I don't know but I'm gonna have super high expectations for January at this point because like we're better than this
 
Brent said:
I'm still amazed it snowed in Breckenridge but what really has surprised me and is the realization today that Tulsa will go through December without even a flake of snow. Even last year's catastrophe had that

I don't know but I'm gonna have super high expectations for January at this point because like we're better than this
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Why were you surprised about it snowing in Breckenridge?
 
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