2024-2025 La Nina

[so_whats_happening]

3 hours ago, snowman19 said:

IMO it doesn’t get warm in the east until after mid-January. Come late month, I think it’s canonical La Niña time…..-PNA/RNA and the SE ridge pops

This is a big thing in question right now the only thing that could truly disrupt that potential is a Major SSW event which interestingly enough is starting to show some signs at hour 240 (about first week of January onward) of something trying to develop. Now I would like to see a few more runs as we get into the new year and continue showing this.

As for the pattern this has been the strongest 850mb wind response so far this event from mid November to mid December. The last was back at the end of summer (end of August/early September) with the enhanced trades. This was when we saw our first Nina like response show up where we went from warm neutral into cool neutral. This should start to level off and create another small rise in 3.4 SST coming up over the next 2-3 weeks before things potentially restart with stronger trades around mid January?

A trimonthly of below -.5 may be hard to come by again depending on how things evolve the next month. This monthly should come in around -.7 ish maybe -.8. If we get January to cooperate in the same manner we can hit that -.5 threshold for a trimonthly just barely pushing the Nina status (not officially since we won't have 5 months most likely) but the effects of this should be enough to allow the atmosphere to respond.

If we continue to cool into January and February we definitely start to run the risk of it being officially being labeled La Nina via CPC standards I'm not sure of this yet. We could potentially be setting ourselves up for another string of Ninas as several years have had Nina-like conditions before a Nino spike and going back to Nina the following years. It is fairly odd to get this type of push this late in the typical ENSO timeframe but seemingly not too unheard of as several seasons did have a late peak of NDJ and even DJF.

This season has definitely thrown some curveballs so far and I'm not sure we are done with those surprises.

[snowman19]

19 minutes ago, so_whats_happening said:

This is a big thing in question right now the only thing that could truly disrupt that potential is a Major SSW event which interestingly enough is starting to show some signs at hour 240 (about first week of January onward) of something trying to develop. Now I would like to see a few more runs as we get into the new year and continue showing this.

As for the pattern this has been the strongest 850mb wind response so far this event from mid November to mid December. The last was back at the end of summer (end of August/early September) with the enhanced trades. This was when we saw our first Nina like response show up where we went from warm neutral into cool neutral. This should start to level off and create another small rise in 3.4 SST coming up over the next 2-3 weeks before things potentially restart with stronger trades around mid January?

A trimonthly of below -.5 may be hard to come by again depending on how things evolve the next month. This monthly should come in around -.7 ish maybe -.8. If we get January to cooperate in the same manner we can hit that -.5 threshold for a trimonthly just barely pushing the Nina status (not officially since we won't have 5 months most likely) but the effects of this should be enough to allow the atmosphere to respond.

If we continue to cool into January and February we definitely start to run the risk of it being officially being labeled La Nina via CPC standards I'm not sure of this yet. We could potentially be setting ourselves up for another string of Ninas as several years have had Nina-like conditions before a Nino spike and going back to Nina the following years. It is fairly odd to get this type of push this late in the typical ENSO timeframe but seemingly not too unheard of as several seasons did have a late peak of NDJ and even DJF.

This season has definitely thrown some curveballs so far and I'm not sure we are done with those surprises.

Even if we were to see a SSW, I’m not sure that would stop a canonical La Niña response (-PNA/trough in the west) in the NPAC. It may modulate the AO/NAO states, but I can’t see it stopping a -PNA from forming or altering the Niña progression or tropical PAC convection/MJO 

[Daniel Boone]

3 minutes ago, snowman19 said:

Even if we were to see a SSW, I’m not sure that would stop a canonical La Niña response (-PNA/trough in the west) in the NPAC. It may modulate the AO/NAO states, but I can’t see it stopping a -PNA from forming or altering the Niña progression or tropical PAC convection/MJO 

Dec and January 10-11 come to mind. Moderate to strong Nina then. There's other instances as well. Enough blocking, backed flow can alter the typical response as most know. Particularly a weak Nina . 

[BuffaloWeather]

1 hour ago, so_whats_happening said:

This is a big thing in question right now the only thing that could truly disrupt that potential is a Major SSW event which interestingly enough is starting to show some signs at hour 240 (about first week of January onward) of something trying to develop. Now I would like to see a few more runs as we get into the new year and continue showing this.

As for the pattern this has been the strongest 850mb wind response so far this event from mid November to mid December. The last was back at the end of summer (end of August/early September) with the enhanced trades. This was when we saw our first Nina like response show up where we went from warm neutral into cool neutral. This should start to level off and create another small rise in 3.4 SST coming up over the next 2-3 weeks before things potentially restart with stronger trades around mid January?

A trimonthly of below -.5 may be hard to come by again depending on how things evolve the next month. This monthly should come in around -.7 ish maybe -.8. If we get January to cooperate in the same manner we can hit that -.5 threshold for a trimonthly just barely pushing the Nina status (not officially since we won't have 5 months most likely) but the effects of this should be enough to allow the atmosphere to respond.

If we continue to cool into January and February we definitely start to run the risk of it being officially being labeled La Nina via CPC standards I'm not sure of this yet. We could potentially be setting ourselves up for another string of Ninas as several years have had Nina-like conditions before a Nino spike and going back to Nina the following years. It is fairly odd to get this type of push this late in the typical ENSO timeframe but seemingly not too unheard of as several seasons did have a late peak of NDJ and even DJF.

This season has definitely thrown some curveballs so far and I'm not sure we are done with those surprises.

Buffalo NWS says we had a SSW 10-14 days ago? Their morning discussion.

Looking further ahead into the start of 2025...

A BIG change in our weather can be expected immediately after the
New Year. The relatively low amplitude Pacific based flow that will
have dominated the Lower 48 the past week or so with above normal
temperatures will be replaced by a high amplitude, coupled +PNA/
-NAO pattern that will feature our first cross polar flow in at
LEAST two years. Boiling this down, it simply means that there is
HIGH confidence that our temperatures will plunge back to well BELOW
normal, with the potential for this change to persist at least a
week.

The first signal of this dramatic change back to mid winter weather
was a fairly significant stratospheric warming event that took place
some 10 to 14 days ago. Sudden warming above 10mb usually results in
a change in the arctic jet that translates into significant changes
to the Arctic oscillation along with the corresponding North
Atlantic oscillation. Within two to three weeks, this change in the
high latitude flow will lead to an impressive surge of cold air that
will make its way across eastern Canada and the northeastern portion
of the Lower 48. Supporting this compelling change to mid winter
conditions is agreement among many of the ensembles that anomalously
strong ridging will be found along the West Coast (+PNA) while broad
ridging will also build across Greenland and the North Atlantic (-
NAO). This coupled pattern has a very high correlation to below
normal temperatures throughout the Great Lakes region.

The proverbial `icing on the cake` for this event is that many
ensembles also suggest that a cross polar flow will develop. This
will allow arctic air to settle southwards across eastern Canada
where H85 temps in the -20s C will be common. Fortunately, the
source region for the air in this event does is not especially cold
at this time, or the event could be more noteworthy.

[mitchnick]

1 hour ago, so_whats_happening said:

This is a big thing in question right now the only thing that could truly disrupt that potential is a Major SSW event which interestingly enough is starting to show some signs at hour 240 (about first week of January onward) of something trying to develop. Now I would like to see a few more runs as we get into the new year and continue showing this.

As for the pattern this has been the strongest 850mb wind response so far this event from mid November to mid December. The last was back at the end of summer (end of August/early September) with the enhanced trades. This was when we saw our first Nina like response show up where we went from warm neutral into cool neutral. This should start to level off and create another small rise in 3.4 SST coming up over the next 2-3 weeks before things potentially restart with stronger trades around mid January?

A trimonthly of below -.5 may be hard to come by again depending on how things evolve the next month. This monthly should come in around -.7 ish maybe -.8. If we get January to cooperate in the same manner we can hit that -.5 threshold for a trimonthly just barely pushing the Nina status (not officially since we won't have 5 months most likely) but the effects of this should be enough to allow the atmosphere to respond.

If we continue to cool into January and February we definitely start to run the risk of it being officially being labeled La Nina via CPC standards I'm not sure of this yet. We could potentially be setting ourselves up for another string of Ninas as several years have had Nina-like conditions before a Nino spike and going back to Nina the following years. It is fairly odd to get this type of push this late in the typical ENSO timeframe but seemingly not too unheard of as several seasons did have a late peak of NDJ and even DJF.

This season has definitely thrown some curveballs so far and I'm not sure we are done with those surprises.

One caveat on the possible SSW. We have had an extremely anomalous PV; hat tip to Snowman banging that drum. Notwithstanding, the shape/trajectory has not precluded the cold, and possibly enhanced it, idk. But if we get that warming as progged, that may alter the trajectory but not be enough to help the threat of cold/snow in the east. I have no control over it, obviously, but I  think I'd prefer leaving 10mb alone at this point. Lol

[michsnowfreak]

23 hours ago, Snowstorms said:

I guess it depends where you're geographically located. A strong El Nino is an almost guaranteed torch especially now with climate change and we can see that radical shift after the 70's. 82-83, 91-92, 97-98, 15-16, and 23-24 all blowtorches.

El Nino's are great in offering big storm potentials. However, most moderate-strong Nina's that were preceded by El Nino's can offer a lot of storm potentials and we saw this with 2007-08, 2010-11, 2016-2018. Most weak Nino's are great at keeping a weak Aleutian low present allowing for good cross polar and blocking patterns to emerge.  

Similarly, La Nina is great if its dominating the pattern which allows for a poleward Aleutian ridge which can either morph into a -EPO pattern or allow for cross polar flow with a -AO/NAO. It may keep the centre of cold near the Plains and Midwest, but it's good for allowing strong gradient storms to develop or coastal storms when the trough displaces east. This also helps keep a longer lasting snow cover. 

I prefer mod-strong La Nina's and weak Nino's. Weak Nina's (ONI <= -0.9) or strong Nino's can go either way. Mod Nino's are okay, if we have good blocking. 

Merry Christmas 

 

Weak ninos can be ok, but strong ninos have always, always sucked here. It's not even a contest. If it's not neutral, I'll take any kind/strength of Nina over a strong Nino.

[LibertyBell]

2 hours ago, snowman19 said:

Even if we were to see a SSW, I’m not sure that would stop a canonical La Niña response (-PNA/trough in the west) in the NPAC. It may modulate the AO/NAO states, but I can’t see it stopping a -PNA from forming or altering the Niña progression or tropical PAC convection/MJO 

It might still be okay for snow in the east come March because of shortening wavelengths though.

[mitchnick]

Euro AI was a little drunk for the past day or so but sobered up at 12z.

[so_whats_happening]

2 hours ago, snowman19 said:

Even if we were to see a SSW, I’m not sure that would stop a canonical La Niña response (-PNA/trough in the west) in the NPAC. It may modulate the AO/NAO states, but I can’t see it stopping a -PNA from forming or altering the Niña progression or tropical PAC convection/MJO 

Depends on what type of SSW takes hold and what pattern should evolve from this event. If we get a solid wave 2 potential that shows up it could reshuffle the pattern in our favor a lot better than a large wave 1 response like we saw last year. Of course a wave 2 response doesn't always mean ridge west/trough east. The propensity of the atmospheric pattern to not fully revert back to the constant deep -PNA has been a nice change-up for this year even with a La Nina starting to actually build properly.

The SSW (which this one I actually consider significant) that came in the beginning of January 2024 I think just linked up in the wrong spot for us. We had a fairly strong 500mb ridge in SE Canada already in place leading into that strong wave 1 response so it locked the pattern up rather quickly and we just could not shake it we also did not see the breakdown of the SPV fully so once the warming was done it started to gather itself together again. Talk about unlucky. Now if we get significant wave 1 or wave 2 (preferably) with an atmospheric pattern of ridging into Alaska and retracted Pacific jet like we have been seeing off an on I wonder if the results would be different, I mean they should just not sure how it would translate yet.

2 hours ago, BuffaloWeather said:

Buffalo NWS says we had a SSW 10-14 days ago? Their morning discussion.

Looking further ahead into the start of 2025...

A BIG change in our weather can be expected immediately after the
New Year. The relatively low amplitude Pacific based flow that will
have dominated the Lower 48 the past week or so with above normal
temperatures will be replaced by a high amplitude, coupled +PNA/
-NAO pattern that will feature our first cross polar flow in at
LEAST two years. Boiling this down, it simply means that there is
HIGH confidence that our temperatures will plunge back to well BELOW
normal, with the potential for this change to persist at least a
week.

The first signal of this dramatic change back to mid winter weather
was a fairly significant stratospheric warming event that took place
some 10 to 14 days ago. Sudden warming above 10mb usually results in
a change in the arctic jet that translates into significant changes
to the Arctic oscillation along with the corresponding North
Atlantic oscillation. Within two to three weeks, this change in the
high latitude flow will lead to an impressive surge of cold air that
will make its way across eastern Canada and the northeastern portion
of the Lower 48. Supporting this compelling change to mid winter
conditions is agreement among many of the ensembles that anomalously
strong ridging will be found along the West Coast (+PNA) while broad
ridging will also build across Greenland and the North Atlantic (-
NAO). This coupled pattern has a very high correlation to below
normal temperatures throughout the Great Lakes region.

The proverbial `icing on the cake` for this event is that many
ensembles also suggest that a cross polar flow will develop. This
will allow arctic air to settle southwards across eastern Canada
where H85 temps in the -20s C will be common. Fortunately, the
source region for the air in this event does is not especially cold
at this time, or the event could be more noteworthy.

https://acd-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/merra2/flux/vtn_10_2024_merra2.pdf

https://acd-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/merra2/temp/t60_90n_10_2024_merra2.pdf

We had a heat flux but not a significant stratospheric warming event that took place. It was at best a displacement event that happened to work a little bit in our favor instead of roasting us like what typically happens in a Wave 1 response. I don't want to discredit that it was a stratospheric warming event but it was nothing noteworthy. Maybe it was because the SPV was already well established and strong that we didn't see a significant rise in temperature other than to near average? 

1 hour ago, mitchnick said:

One caveat on the possible SSW. We have had an extremely anomalous PV; hat tip to Snowman banging that drum. Notwithstanding, the shape/trajectory has not precluded the cold, and possibly enhanced it, idk. But if we get that warming as progged, that may alter the trajectory but not be enough to help the threat of cold/snow in the east. I have no control over it, obviously, but I  think I'd prefer leaving 10mb alone at this point. Lol

This warming event we just had helped relax the SPV and bring it back to what is typically average for this time of year so any further attacks will start to impede in the strength much more, if we do see these attacks come to fruition. As for the snow/cold possibilities that come along with it I think the important thing would be to have much more wave 2 response, this means help not only from the Alaska region (which is the typical location of the 10mb ridge) but also over northern Europe. We need poleward flux/ wavebreak events (negative tilted troughing leading to large blocking highs) to happen and that seems to only be on the Pacific side right now, the Atlantic has been having more equatorward wavebreak events which still helps to keep the SPV intact. We had a very strong wave 1 response last year that gave us a blip of winter weather hopefully it is not a wash rinse repeat scenario.

This was last years wave 1 response compared to this years (seen above). Of course the SPV was a bit weaker last year so it helped to rock the boat a bit more compared to this year. Angle of attack is also extremely important as to the proper effects into the mid latitude maybe because the Pacific jet was a bit stronger due to a deep -PDO state that was not changing caused it to have a different location for the atmospheric ridging location? May be something worth looking into down the road.

[so_whats_happening]

Just now, so_whats_happening said:

Depends on what type of SSW takes hold and what pattern should evolve from this event. If we get a solid wave 2 potential that shows up it could reshuffle the pattern in our favor a lot better than a large wave 1 response like we saw last year. Of course a wave 2 response doesn't always mean ridge west/trough east. The propensity of the atmospheric pattern to not fully revert back to the constant deep -PNA has been a nice change-up for this year even with a La Nina starting to actually build properly.

The SSW (which this one I actually consider significant) that came in the beginning of January 2024 I think just linked up in the wrong spot for us. We had a fairly strong 500mb ridge in SE Canada already in place leading into that strong wave 1 response so it locked the pattern up rather quickly and we just could not shake it we also did not see the breakdown of the SPV fully so once the warming was done it started to gather itself together again. Talk about unlucky. Now if we get significant wave 1 or wave 2 (preferably) with an atmospheric pattern of ridging into Alaska and retracted Pacific jet like we have been seeing off an on I wonder if the results would be different, I mean they should just not sure how it would translate yet.

https://acd-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/merra2/flux/vtn_10_2024_merra2.pdf

https://acd-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/merra2/temp/t60_90n_10_2024_merra2.pdf

We had a heat flux but not a significant stratospheric warming event that took place. It was at best a displacement event that happened to work a little bit in our favor instead of roasting us like what typically happens in a Wave 1 response. I don't want to discredit that it was a stratospheric warming event but it was nothing noteworthy. Maybe it was because the SPV was already well established and strong that we didn't see a significant rise in temperature other than to near average? 

This warming event we just had helped relax the SPV and bring it back to what is typically average for this time of year so any further attacks will start to impede in the strength much more, if we do see these attacks come to fruition. As for the snow/cold possibilities that come along with it I think the important thing would be to have much more wave 2 response, this means help not only from the Alaska region (which is the typical location of the 10mb ridge) but also over northern Europe. We need poleward flux/ wavebreak events (negative tilted troughing leading to large blocking highs) to happen and that seems to only be on the Pacific side right now, the Atlantic has been having more equatorward wavebreak events which still helps to keep the SPV intact. We had a very strong wave 1 response last year that gave us a blip of winter weather hopefully it is not a wash rinse repeat scenario.

This was last years wave 1 response compared to this years (seen above). Of course the SPV was a bit weaker last year so it helped to rock the boat a bit more compared to this year. Angle of attack is also extremely important as to the proper effects into the mid latitude maybe because the Pacific jet was a bit stronger due to a deep -PDO state that was not changing caused it to have a different location for the atmospheric ridging location? May be something worth looking into down the road.

Mind you scale is different between the two years but here was the temperature anomaly that occurred between the two events. Similar placement as far as warming goes (again fairly typical location) this years was a bit weaker than last years that took place in the beginning of December. Now will be the interesting part of what comes of it. We saw another attack that occurred, a much more significant one, about a month later so if timing is similar we should see a significant warming event after the first week of January. We should start to see it on models by the end of the month as the first 10 days will be within view for January, 10th day being about the month mark after the first strike took place.

Reminder the atmospheric pattern is much different this year so far leading into the potential second strike onto the SPV than what we had last year. Just something to keep in mind. I say potential because nothing is set in stone this far out but it is nice to see the models are trying to pick up on something.

[LakePaste25]

3 hours ago, BuffaloWeather said:

Buffalo NWS says we had a SSW 10-14 days ago? Their morning discussion.

Looking further ahead into the start of 2025...

A BIG change in our weather can be expected immediately after the
New Year. The relatively low amplitude Pacific based flow that will
have dominated the Lower 48 the past week or so with above normal
temperatures will be replaced by a high amplitude, coupled +PNA/
-NAO pattern that will feature our first cross polar flow in at
LEAST two years. Boiling this down, it simply means that there is
HIGH confidence that our temperatures will plunge back to well BELOW
normal, with the potential for this change to persist at least a
week.

The first signal of this dramatic change back to mid winter weather
was a fairly significant stratospheric warming event that took place
some 10 to 14 days ago. Sudden warming above 10mb usually results in
a change in the arctic jet that translates into significant changes
to the Arctic oscillation along with the corresponding North
Atlantic oscillation. Within two to three weeks, this change in the
high latitude flow will lead to an impressive surge of cold air that
will make its way across eastern Canada and the northeastern portion
of the Lower 48. Supporting this compelling change to mid winter
conditions is agreement among many of the ensembles that anomalously
strong ridging will be found along the West Coast (+PNA) while broad
ridging will also build across Greenland and the North Atlantic (-
NAO). This coupled pattern has a very high correlation to below
normal temperatures throughout the Great Lakes region.

The proverbial `icing on the cake` for this event is that many
ensembles also suggest that a cross polar flow will develop. This
will allow arctic air to settle southwards across eastern Canada
where H85 temps in the -20s C will be common. Fortunately, the
source region for the air in this event does is not especially cold
at this time, or the event could be more noteworthy.

They might just be referring to a sudden weakening of the PV. For an official SSW, these winds need to drop below 0 m/s which only has a few ensemble members doing so near the end of January into February.

[so_whats_happening]

28 minutes ago, LakePaste25 said:

They might just be referring to a sudden weakening of the PV. For an official SSW, these winds need to drop below 0 m/s which only has a few ensemble members doing so near the end of January into February.

Major SSW cause a reversal or winds dropping below 0m/s as well as warming. Minor SSW weaken the SPV and typically these are induced by a Wave 1 response.

Here is a good read for those interested in the MJO response to the SPV and potential SSW events that take place.

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2012GL053144

[EasternLI]

7 hours ago, so_whats_happening said:

Depends on what type of SSW takes hold and what pattern should evolve from this event. If we get a solid wave 2 potential that shows up it could reshuffle the pattern in our favor a lot better than a large wave 1 response like we saw last year. Of course a wave 2 response doesn't always mean ridge west/trough east. The propensity of the atmospheric pattern to not fully revert back to the constant deep -PNA has been a nice change-up for this year even with a La Nina starting to actually build properly.

The SSW (which this one I actually consider significant) that came in the beginning of January 2024 I think just linked up in the wrong spot for us. We had a fairly strong 500mb ridge in SE Canada already in place leading into that strong wave 1 response so it locked the pattern up rather quickly and we just could not shake it we also did not see the breakdown of the SPV fully so once the warming was done it started to gather itself together again. Talk about unlucky. Now if we get significant wave 1 or wave 2 (preferably) with an atmospheric pattern of ridging into Alaska and retracted Pacific jet like we have been seeing off an on I wonder if the results would be different, I mean they should just not sure how it would translate yet.

https://acd-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/merra2/flux/vtn_10_2024_merra2.pdf

https://acd-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/merra2/temp/t60_90n_10_2024_merra2.pdf

We had a heat flux but not a significant stratospheric warming event that took place. It was at best a displacement event that happened to work a little bit in our favor instead of roasting us like what typically happens in a Wave 1 response. I don't want to discredit that it was a stratospheric warming event but it was nothing noteworthy. Maybe it was because the SPV was already well established and strong that we didn't see a significant rise in temperature other than to near average? 

This warming event we just had helped relax the SPV and bring it back to what is typically average for this time of year so any further attacks will start to impede in the strength much more, if we do see these attacks come to fruition. As for the snow/cold possibilities that come along with it I think the important thing would be to have much more wave 2 response, this means help not only from the Alaska region (which is the typical location of the 10mb ridge) but also over northern Europe. We need poleward flux/ wavebreak events (negative tilted troughing leading to large blocking highs) to happen and that seems to only be on the Pacific side right now, the Atlantic has been having more equatorward wavebreak events which still helps to keep the SPV intact. We had a very strong wave 1 response last year that gave us a blip of winter weather hopefully it is not a wash rinse repeat scenario.

This was last years wave 1 response compared to this years (seen above). Of course the SPV was a bit weaker last year so it helped to rock the boat a bit more compared to this year. Angle of attack is also extremely important as to the proper effects into the mid latitude maybe because the Pacific jet was a bit stronger due to a deep -PDO state that was not changing caused it to have a different location for the atmospheric ridging location? May be something worth looking into down the road.

Great post. I've done a fair amount of reading on this topic over the last several years. I think your thoughts are right on the mark as far as lining up with said reading. One thing I remember seeing, and I don't remember where, is that if one is looking for an ssw to deliver a colder pattern. There's a higher probability of that occurring from one that initiated during an already colder pattern. Which sounds like it lines up with your thinking on the phenomenon and kinda makes sense to me.