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Pattern January Joke

@GaWx - have we ever historically had a PNA+ and NAO- pairing for any substantial length of time and not had snow in the SE? I’m new to this game, people seem to be extremely optimistic at the possibility across the boards. Definitely sounds like a best case scenario, but nothing is guaranteed, it is indeed the weather. I figured you have some way you research/statistics compilation program where you could search with those stipulations and see prior outcomes. Appreciate all the great posts from everyone here.
 
256wx said:
@GaWx - have we ever historically had a PNA+ and NAO- pairing for any substantial length of time and not had snow in the SE? I’m new to this game, people seem to be extremely optimistic at the possibility across the boards. Definitely sounds like a best case scenario, but nothing is guaranteed, it is indeed the weather. I figured you have some way you research/statistics compilation program where you could search with those stipulations and see prior outcomes. Appreciate all the great posts from everyone here.
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Great question! Snow in the SE can be tough to get in cold/dry patterns or it could be hit and miss/localized instead of widespread even when it’s cold.

And then a question is what counts in your mind? What if much of the SE gets just flurries outside of significant upslope mtn snow? Does that count? Or what if only a small part of the non-mountain SE gets accumulating snow and the rest gets little or nothing. Does that count?

And then I’m pretty sure one can have a +PNA and -NAO and not be cold enough for snow. Or it warms up and then rains.

So, without giving specifics, I’d say the answer is an easy yes unless you’d count flurries in just a part of the SE, which I suspect is not what you mean. But even then, I’d say yes because of its likely there have been some mild +PNA/-NAO periods with no flurries anywhere.
 
That’s a good response- I should have been more specific. In general, I would not count flurries. So accumulating snow greater than. .5” is the metric I would use. And when people say SE, most probably have their own locale in mind. Eastern TN, NC, even VA or WV is considered Southeastern to some. I’ll rephrase my question to Deep South. Northern/Central areas of Gulf states. I’m in the Huntsville AL area and have been fortunate in the 3 years I’ve been here to have seen something every winter thus far. I’m a Florida transplant up here and actually having 4 seasons now is what piqued my interest in weather patterns and snow possibilities after living somewhere with boring weather for so long.

I definitely think I understand the blocking patterns and the logistics of how they should help us score snow. Maybe I’m a bit more uncertain as to how often the PNA+ and -NAO occur simultaneously and the implications for this area. It just seems from a cursory reading of the forums like it’s a holy grail/best possible setup which leads me to believe it may be very rare, but that may not be the case. Thanks for all the input!
 
GaWx said:
Great question! Snow in the SE can be tough to get in cold/dry patterns or it could be hit and miss/localized instead of widespread even when it’s cold.

And then a question is what counts in your mind? What if much of the SE gets just flurries outside of significant upslope mtn snow? Does that count? Or what if only a small part of the non-mountain SE gets accumulating snow and the rest gets little or nothing. Does that count?

And then I’m pretty sure one can have a +PNA and -NAO and not be cold enough for snow. Or it warms up and then rains.

So, without giving specifics, I’d say the answer is an easy yes unless you’d count flurries in just a part of the SE, which I suspect is not what you mean. But even then, I’d say yes because of its likely there have been some mild +PNA/-NAO periods with no flurries anywhere.
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Typically the +PNA/-NAO events that flunk is one where it’s coupled to a AK vortex/+EPO, which causes a weak cold air source and a ineffective western ridge for digging shortwaves. The best +PNA setups (2014/2015/2018/2022/2025) are ones with a -EPO/+PNA (where the ridge is lined up from the west coast through B.C and Alaska)
I’ll do a ex for NC
2014 (significant winter storm in the SE), it wasn’t long lasting, but a ridge bridge out west.

IMG_1136.gif
IMG_1143.gifIMG_1144.gif


Feb 2015 (big +PNA/-EPO) IMG_1135.gif
Events during the pattern IMG_1140.pngIMG_1141.gifIMG_1142.png

Jan 2018 (+PNA/-EPO) IMG_1137.gifIMG_1145.pngIMG_9145.png

I can’t add anymore attachments, but it seems in the last decade, our best winter storms occur when we have a -EPO/+PNA, and the Atlantic side not being the big driver at all. Not saying it isn’t a big driver, and it can definitely result in events, but the -EPO/+PNA pathway is the way to go recently. That’s always why I get excited when I see a WC/AK ridge bridge. Seems like that’s the best way to score recently. We all remember 2022, multiple events in that -EPO/+PNA regime, and 2025 as well even if they weren’t exactly great events for some.
 
NBAcentel said:
Typically the +PNA/-NAO events that flunk is one where it’s coupled to a AK vortex/+EPO, which causes a weak cold air source and a ineffective western ridge for digging shortwaves. The best +PNA setups (2014/2015/2018/2022/2025) are ones with a -EPO/+PNA (where the ridge is lined up from the west coast through B.C and Alaska)
I’ll do a ex for NC
2014 (significant winter storm in the SE), it wasn’t long lasting, but a ridge bridge out west.

View attachment 179893
View attachment 179898View attachment 179899


Feb 2015 (big +PNA/-EPO) View attachment 179894
Events during the pattern View attachment 179895View attachment 179896View attachment 179897

Jan 2018 (+PNA/-EPO) View attachment 179900View attachment 179901View attachment 179902

I can’t add anymore attachments, but it seems in the last decade, our best winter storms occur when we have a -EPO/+PNA, and the Atlantic side not being the big driver at all. Not saying it isn’t a big driver, and it can definitely result in events, but the -EPO/+PNA pathway is the way to go recently. That’s always why I get excited when I see a WC/AK ridge bridge. Seems like that’s the best way to score recently. We all remember 2022, multiple events in that -EPO/+PNA regime, and 2025 as well even if they weren’t exactly great events for some.
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That’s extremely helpful, I love learning about this stuff. Makes perfect sense. I really appreciate you guys taking the time to educate!
 
Looks like a nice stretch of cold weather here starting rhe 30th with highs in the 40s for a week at least. Wouldn't be surprised if we get an ice storm chance during that stretch.
 
256wx said:
That’s extremely helpful, I love learning about this stuff. Makes perfect sense. I really appreciate you guys taking the time to educate!
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I forgot to mention that even if all of the indices are lined up favorably like 7s on a slot machine, there’s a strong enough cold air connection, there’s plentiful moisture, and there’s an energetic storm, the exact track of the storm’s surface low still often trumps just about everything else for one’s specific area. That could be the difference in you being in one of the lucky sweet spots and getting a major snow, it being further NW and you getting a quick change to rain, it being even further NW and you getting no snow and instead just rain, or it being too far SE and you getting only light snow or even no precip.

Predicting the exact track is difficult too far in advance.

But you probably already realize all of this.
 
256wx said:
@GaWx - have we ever historically had a PNA+ and NAO- pairing for any substantial length of time and not had snow in the SE? I’m new to this game, people seem to be extremely optimistic at the possibility across the boards. Definitely sounds like a best case scenario, but nothing is guaranteed, it is indeed the weather. I figured you have some way you research/statistics compilation program where you could search with those stipulations and see prior outcomes. Appreciate all the great posts from everyone here.
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You love to see people asking great questions and trying to learn 👏👏👏👏👏
 
CNCsnwfan1210 said:
That’s one firecracker of a -NAO. Seems like its bullying that TPV


Sent from my iPhone using Tapatalk
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Another reason I like the pattern in the medium range getting colder is because now the AIGFS shows something wintry with the system looming just under D10 for the first time, it’s not great but it’s a start. The overall synoptic scale pattern doesn’t look great for snow, but if the pattern keeps slowing/gets colder, we can wiggle ourselves into a messy setup IMG_1152.gifIMG_1153.gifIMG_1154.pngIMG_1156.gif
 
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The end of the UKMET looks intriguing. It drops an expansive Arctic high with cold air draped from the Rockies to the coast, with energy lurking in the SW that looks poised to move eastward as the main trough lifts out. Seeing that second push of cold air following the end of the month cold front is nice.
ukmo_global-sfct_b-imp-conus-2025122600-168.pngukmo_global-500hv-conus-2025122600-168.png
 
Wild Weather Monger said:
The end of the UKMET looks intriguing. It drops an expansive Arctic high with cold air draped from the Rockies to the coast, with energy lurking in the SW that looks poised to move eastward as the main trough lifts out. Seeing that second push of cold air following the end of the month cold front is nice.
View attachment 179914View attachment 179915
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We need to make sure we don’t get too much of the suppressive cold front like vorticity feature. Seen a lot of runs recently with multiple periods of that long ribbon of vorticity appearance and it will kill anything that gets close to it
 
As others have mentioned, clearly things should try to get a bit more interesting as we move toward mid-January with Asia finally waking up (+EAMT), the Pac Jet extending, and wave breaking occurring in the E Pacific (-EPO / +PNA) rather than in the W Pacific (-WPO / -PNA) at the jet exit region.

+EAMT and the associated Pac Jet changes look to be driving the bus with the pattern ahead.

Other than the MJO not being camped out in the Maritime Continent, I'm viewing it as a non-factor thus far this winter (not what I expected back in Oct/Nov). You can see on the VP hovmoller (last image) how the enhanced convective signal in the tropics is cycling every 10-20 days going back to mid-Nov (and before that really) - that's not a typical MJO which cycles every 30-60 days....so, I don't think we are getting the typical MJO response here.

Dec 26 GFS Jet Loop.gif

Dec 26 AI Jet Loop.gif


Dec 26 VP.png
 
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The models have been showing something off and on for around Jan 5 and 6. I think the Euro had a big storm around then a while back before dropping it. Sometimes we get that with a model where it shows a big one and then it goes poof only for the models to bring something back down the road for the same time frame.
 
griteater said:
As others have mentioned, clearly things should try to get a bit more interesting as we move toward mid-January with Asia finally waking up (+EAMT), the Pac Jet extending, and wave breaking occurring in the E Pacific (-EPO / +PNA) rather than in the W Pacific (-WPO / -PNA) at the jet exit region.

+EAMT and the associated Pac Jet changes look to be driving the bus with the pattern ahead.

Other than the MJO not being camped out in the Maritime Continent, I'm viewing it as a non-factor thus far this winter (not what I expected back in Oct/Nov). You can see on the VP hovmoller (last image) how the enhanced convective signal in the tropics is cycling every 10-20 days going back to mid-Nov (and before that really) - that's not a typical MJO which cycles every 30-60 days....so, I don't think we are getting the typical MJO response here.

View attachment 179921

View attachment 179922


View attachment 179920
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Yeah a lot of this is internally driven multi-week mid-latitude variability’s

Honestly, the biggest impacts the MJO is having on our weather going forward are just very slow lagged responses to the previous big event in late November.

Namely, the weakening of the polar vortex with those circulation anomalies finally propagating into the troposphere and the strong +u anomalies that have propagated poleward into the subtropics now (in typical GWO fashion)

IMG_7025.jpeg
 
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