2024-2025 La Nina

[GaWx]

 I asked my excellent Maxar contact, Brad, about his thoughts about the colder pattern shown by the EPS for 1/6-12+. Here’s his response:

“I think the model might be seeing the MJO in phases 7-8 alongside a normal strength polar vortex. The following 500mb analog map for this combination comes from: 

https://ifurtado.org/wp-content/uploads/Publications/GreenFurtado2019.pdf

 

 If the model has these forcings correct, then I think a colder Eastern Half makes sense. That said, I’m hesitant to go all in on this pattern, at least for now. There are a couple reasons for that. The first is the MJO itself. From the hovmoller plot below, you can see that the region around Indonesia stays convectively active. This is not common of the MJO in phases 7-8, so there may be some muddying up of the signal to bring lower confidence with its role on the pattern.

A second is based on model trends for the strength of the polar vortex. I would say the most recent run is still ‘normal’ for its strength during that colder window; however, there has been a strengthening trend.

 If that strengthening trend continues and the polar vortex remains on the stronger side, it could limit that cold response per the analog composite below (MJO phases 7-8 with strong polar vortex):

 

 The other consideration is related to the warm end of December. There’s unlikely to be much snow cover left at the end of the month; and even if we get a +PNA resurgence or even a -EPO, it may take some time to reestablish a colder source region.”

[roardog]

16 minutes ago, GaWx said:

 I asked my excellent Maxar contact, Brad, about his thoughts about the colder pattern shown by the EPS for 1/6-12+. Here’s his response:

“I think the model might be seeing the MJO in phases 7-8 alongside a normal strength polar vortex. The following 500mb analog map for this combination comes from: 

https://ifurtado.org/wp-content/uploads/Publications/GreenFurtado2019.pdf

 

 If the model has these forcings correct, then I think a colder Eastern Half makes sense. That said, I’m hesitant to go all in on this pattern, at least for now. There are a couple reasons for that. The first is the MJO itself. From the hovmoller plot below, you can see that the region around Indonesia stays convectively active. This is not common of the MJO in phases 7-8, so there may be some muddying up of the signal to bring lower confidence with its role on the pattern.

A second is based on model trends for the strength of the polar vortex. I would say the most recent run is still ‘normal’ for its strength during that colder window; however, there has been a strengthening trend.

 If that strengthening trend continues and the polar vortex remains on the stronger side, it could limit that cold response per the analog composite below (MJO phases 7-8 with strong polar vortex):

 

 The other consideration is related to the warm end of December. There’s unlikely to be much snow cover left at the end of the month; and even if we get a +PNA resurgence or even a -EPO, it may take some time to reestablish a colder source region.”

It won’t take long in January to get air cold enough to snow if the flow is from northern Canada regardless of how much pacific air Canada gets filled with. 

[michsnowfreak]

41 minutes ago, roardog said:

It won’t take long in January to get air cold enough to snow if the flow is from northern Canada regardless of how much pacific air Canada gets filled with. 

Not to mention most of Canada will still remain snow covered after the warm stretch.

[GaWx]

 Today’s Euro Weeklies have a slightly weaker cold signal in the E US for Jan 6-12 vs the prior 2 days though it is still a decent signal for being out at week 4. Also, the moderate cold signal for Jan 13-19 of yesterday’s run has been replaced with a neutral signal today. 

 Also, the SPV averages a bit stronger today (not what I wanted to see).

 Jan 6-12: not as strong of a cold signal

[MJO812]

7 minutes ago, GaWx said:

 Today’s Euro Weeklies have a slightly weaker cold signal in the E US for Jan 6-12 vs the prior 2 days. Also, the moderate cold signal for Jan 13-19 of yesterday’s run has been replaced with a neutral signal today. 

 Also, the SPV averages a bit stronger today (not what I wanted to see).

 Jan 6-12: not as strong of a cold signal

Still a great cold signal. We don't want it that cold.

[GaWx]

2 minutes ago, MJO812 said:

Still a great cold signal. We don't want it that cold.

I agree that it is still a decent cold signal. You don’t want it that cold but I (in the SE) would love for it to be very cold.

[mitchnick]

20 minutes ago, GaWx said:

 Today’s Euro Weeklies have a slightly weaker cold signal in the E US for Jan 6-12 vs the prior 2 days though it is still a decent signal for being out at week 4. Also, the moderate cold signal for Jan 13-19 of yesterday’s run has been replaced with a neutral signal today. 

 Also, the SPV averages a bit stronger today (not what I wanted to see).

 Jan 6-12: not as strong of a cold signal

Surface temps are cooler than 2m temps. Sometimes, it's the other way around. Snow cover? Idk

Don't mind me, I  worry about the well being of snakes in the grass. 

[bluewave]

1 hour ago, GaWx said:

 I asked my excellent Maxar contact, Brad, about his thoughts about the colder pattern shown by the EPS for 1/6-12+. Here’s his response:

“I think the model might be seeing the MJO in phases 7-8 alongside a normal strength polar vortex. The following 500mb analog map for this combination comes from: 

https://ifurtado.org/wp-content/uploads/Publications/GreenFurtado2019.pdf

 

 If the model has these forcings correct, then I think a colder Eastern Half makes sense. That said, I’m hesitant to go all in on this pattern, at least for now. There are a couple reasons for that. The first is the MJO itself. From the hovmoller plot below, you can see that the region around Indonesia stays convectively active. This is not common of the MJO in phases 7-8, so there may be some muddying up of the signal to bring lower confidence with its role on the pattern.

A second is based on model trends for the strength of the polar vortex. I would say the most recent run is still ‘normal’ for its strength during that colder window; however, there has been a strengthening trend.

 If that strengthening trend continues and the polar vortex remains on the stronger side, it could limit that cold response per the analog composite below (MJO phases 7-8 with strong polar vortex):

 

 The other consideration is related to the warm end of December. There’s unlikely to be much snow cover left at the end of the month; and even if we get a +PNA resurgence or even a -EPO, it may take some time to reestablish a colder source region.”

This is what I said yesterday. The actual forcing has been spread out across the entire Pacific. The hovmollers have been working better than the RMMs. So the patterns haven’t been matching the single MJO phase composites. We can see the actual forcing forecast for January starts out near South America and then shifts back to the Maritime Continent. More of a competing influence pattern rather than one specific MJO phase composite. This is why there will probably be plenty of volatility in the model forecasts next few weeks for the January pattern. We may just have to be patient and watch what actually unfolds due to the varying influences as the models could really struggle more than usual.

 

[mitchnick]

4 minutes ago, mitchnick said:

Surface temps are cooler than 2m temps. Sometimes, it's the other way around. Snow cover? Idk

Don't mind me, I  worry about the well being of snakes in the grass. 

On 2nd thought, it's probably just lag time for surface to catch up to air temp. Though, sometimes it could be snow cover too.

[Snowstorms]

5 hours ago, michsnowfreak said:

I cant believe it needs to be said every single time its discussed. I know some like to start a dataset in 1960 or 1970 when winters turned SHARPLY colder than the previous several decades. But climate data did not start in 1960 or 1970. For some wild reason, Im not a fan of holding the coldest winters in the entire period of record as the baseline for what is "normal". I like to look at local climate trends, what has changed, and what hasnt. Chicagos winters have certainly warmed since the 1960s...but in the 1960s and 1970s they noticably COOLED from previous decades.

PERIOD OF RECORD REGRESSION LINE DATA:

Detroit snow 1874-2024: 40.6” to 41.3” = +0.7” over 151 years
Chicago snow 1885-2024: 32.5” to 41.0” = +7.5” over 140 years
New York City snow 1900-2024: 32.1” to 24.4” = -7.7” over 156 years

Detroit DJF temps 1874-2024: 25.9F to 28.2F = +2.1F over 151 years
Chicago DJF temps 1873-2024: 26.7F to 27.0F = +0.3F over 152 years
New York City DJF temps 1869-2024: 31.0F to 36.6F = +5.6F over 156 years
 

I mean there's no questionable doubt that winters have warmed in the past 150 years. The more alarming trend has been the lack of any sustained winter conditions especially in the last 10 years. Our winters feel like they've been reduced to 2-3 intense weeks. And I don't think the -PDO is the driving factor for that. The PDO was primarily negative from 1998-2014 and we saw a handful of cold winter months. Every Nina December from 2000-2017 except 2011 featured sustained cold/snow for most everyone. Quite the opposite with every Nina since 2020. 

The 60's and 70's were likely cooler than other decades with the -PDO/AMO combination plus other factors. That continued into the mid 80's with the ongoing -AMO which may have muted any SE ridge. 

[GaWx]

New from BAMwx:

 

[PhiEaglesfan712]

55 minutes ago, GaWx said:

New from BAMwx:

 

Yeah, that "cold oval" isn't going to happen, lol.

[chubbs]

8 hours ago, michsnowfreak said:

I cant believe it needs to be said every single time its discussed. I know some like to start a dataset in 1960 or 1970 when winters turned SHARPLY colder than the previous several decades. But climate data did not start in 1960 or 1970. For some wild reason, Im not a fan of holding the coldest winters in the entire period of record as the baseline for what is "normal". I like to look at local climate trends, what has changed, and what hasnt. Chicagos winters have certainly warmed since the 1960s...but in the 1960s and 1970s they noticably COOLED from previous decades.

PERIOD OF RECORD REGRESSION LINE DATA:

Detroit snow 1874-2024: 40.6” to 41.3” = +0.7” over 151 years
Chicago snow 1885-2024: 32.5” to 41.0” = +7.5” over 140 years
New York City snow 1900-2024: 32.1” to 24.4” = -7.7” over 156 years

Detroit DJF temps 1874-2024: 25.9F to 28.2F = +2.1F over 151 years
Chicago DJF temps 1873-2024: 26.7F to 27.0F = +0.3F over 152 years
New York City DJF temps 1869-2024: 31.0F to 36.6F = +5.6F over 156 years
 

You have to be careful using raw data from multiple station sites with different baseline temperatures; airport vs downtown for instance.  Per NOAA, who corrects for site differences, the past 10 winters in Cook county (2015-2024) were 4.6F warmer than 1895-1930 and the last 5 years (2020-2024) 5.8F warmer.

Independently, Madison,Wisconsin Lake freeze data going back to 1852 shows much shorter duration of ice cover now vs the 19'th century and the 1960s and 1970s don't stand out as cold decades. (Mendota and Monona Lakes below.)

https://climatology.nelson.wisc.edu/first-order-station-climate-data/madison-climate/lake-ice/history-of-ice-freezing-and-thawing-on-lake-monona/

[PhiEaglesfan712]

More realistic forecast (no cold oval): 

[GaWx]

1 hour ago, PhiEaglesfan712 said:

More realistic forecast (no cold oval): 

I agree this is realistic. This will include two days, Dec 26 and 27, that may flirt with record warmth for the country as a whole. But wait til just after Jan gets here though! Things could change drastically. 
 

I know. Where have we heard this before? But wx history doesn’t have to repeat itself. Don’t place any big bets one way or the other. Even my pro met contact at Maxar admitted that Jan is a tough call. I’m expecting very robust discussions and debates in here over the next few weeks. Should be fun, regardless!

[MJO812]

4 hours ago, PhiEaglesfan712 said:

Yeah, that "cold oval" isn't going to happen, lol.

He is talking about January.  Pattern supports a shift to cold.

[PhiEaglesfan712]

6 minutes ago, MJO812 said:

He is talking about January.  Pattern supports a shift to cold.

If the pattern supports a shift to cold, shouldn't it look something like this, and not a cold oval over the heart of I-95?

 

 

[snowman19]

This is what I said yesterday. The actual forcing has been spread out across the entire Pacific. The hovmollers have been working better than the RMMs. So the patterns haven’t been matching the single MJO phase composites. We can see the actual forcing forecast for January starts out near South America and then shifts back to the Maritime Continent. More of a competing influence pattern rather than one specific MJO phase composite. This is why there will probably be plenty of volatility in the model forecasts next few weeks for the January pattern. We may just have to be patient and watch what actually unfolds due to the varying influences as the models could really struggle more than usual.
 

Agreed. There is very clearly a La Niña standing wave there. Some people have no idea what they’re talking about. You don’t have Maritime Continent convection firing while in a true MJO phase 8. And the new GEPS is already showing a -PNA at the beginning of January 

[mitchnick]

4 hours ago, snowman19 said:

Agreed. There is very clearly a La Niña standing wave there. Some people have no idea what they’re talking about. You don’t have Maritime Continent convection firing while in a true MJO phase 8. And the new GEPS is already showing a -PNA at the beginning of January 

 

 

 

 

Snowman, that Geps map is not 500mb anomalies.  It's run-to-run changes. This is the 336 hr Geps 500mb anomalies off 0z. 

As for the Maritime Niña standing wave, the 7-DAY EPS 200mb from 0z says it will be taking a seat by the end of the run. In fact, the hourly map says it's gone at 216 hrs.

[bluewave]

5 hours ago, snowman19 said:

Agreed. There is very clearly a La Niña standing wave there. Some people have no idea what they’re talking about. You don’t have Maritime Continent convection firing while in a true MJO phase 8. And the new GEPS is already showing a -PNA at the beginning of January 

 

 

 

 

You can see the long range models struggling with the Pacific pattern again as they are showing lower heights over the EPAC and the Western North America to start January than previous runs. This has been the long range bias since the start of December. 500 mb Heights over the EPAC and WNA have been verifying lower than forecast beyond 168-240 hrs.

New run

Old run

 

[snowman19]

31 minutes ago, mitchnick said:

Snowman, that Geps map is not 500mb anomalies.  It's run-to-run changes. This is the 336 hr Geps 500mb anomalies off 0z. 

As for the Maritime Niña standing wave, the 7-DAY EPS 200mb from 0z says it will be taking a seat by the end of the run. In fact, the hourly map says it's gone at 216 hrs.

Remember how bad the EPS was last winter when it kept incorrectly killing off the Maritime Continent convection?

[mitchnick]

11 minutes ago, snowman19 said:

Remember how bad the EPS was last winter when it kept incorrectly killing off the Maritime Continent convection?

1. No I don't. 

2. Past performance is no guarantee. 

3. Eps just had a major upgrade, so assuming it will have same biases/errors is probably not something one would want to expect.

4. Eps still has better performance numbers, though I  admit I'm not in love with that method.

5. It shows exactly what I want to happen just as the Gefs shows exactly what you want to happen! Lol

[Terpeast]

1 hour ago, bluewave said:

You can see the long range models struggling with the Pacific pattern again as they are showing lower heights over the EPAC and the Western North America to start January than previous runs. This has been the long range bias since the start of December. 500 mb Heights over the EPAC and WNA have been verifying lower than forecast beyond 168-240 hrs.

New run

Old run

 

Did EPS show the same thing? It’s been doing better than GEFS with verification.  Either way both models show AR building back and just about to reconnect the cold source. Timing is TBD, but they’ve been consistent. 

[bluewave]

8 minutes ago, Terpeast said:

Did EPS show the same thing? It’s been doing better than GEFS with verification.  Either way both models show AR building back and just about to reconnect the cold source. Timing is TBD, but they’ve been consistent. 

Yeah, the EPS runs at the start of December had much higher heights over the EPAC and WNA than are currently being forecast in late December. So I like to look at the GEFS for some counterpoint against whatever the EPS is showing beyond 10 days. Thats why I am glad they added the GEFS weeklies so we don’t just get stuck with one piece of guidance longer range. Since the CFS is just too erratic a model to be of much use most of the time. 

New run 12-23 to 12-30 much lower EPAC and WNA heights than forecast 

Old run

 

[Terpeast]

2 minutes ago, bluewave said:

Yeah, the EPS runs at the start of December had much higher heights over the EPAC and WNA than are currently being forecast in late December. So I like to look at the GEFS for some counterpoint against whatever the EPS is showing beyond 10 days. Thats why I am glad they added the GEFS weeklies so we don’t just get stuck with one piece of guidance longer range. Since the CFS is just too erratic a model to be of much use most of the time. 

New run 12-23 to 12-30 much lower EPAC and WNA heights than forecast 

Old run

 

Yeah, for 12/23-30 MC convection slowed down and increased in strength so naturally it would have corrected warmer for NA. I think that once MC convection dies down (and it will) cold will come back sometime in the first week of January. Just not sure how durable that will be, though. IOW, how long can we hold off MC reloading in mjo 4, for example. If at least 2 weeks, we’ll have some chances during prime climo. 

[bluewave]

6 minutes ago, Terpeast said:

Yeah, for 12/23-30 MC convection slowed down and increased in strength so naturally it would have corrected warmer for NA. I think that once MC convection dies down (and it will) cold will come back sometime in the first week of January. Just not sure how durable that will be, though. IOW, how long can we hold off MC reloading in mjo 4, for example. If at least 2 weeks, we’ll have some chances during prime climo. 

These quick forcing shifts from the EPAC at the start of January back to the IO and MC after that don’t inspire a lot of confidence in the individual 500 mb forecasts especially longer range.

 

[Terpeast]

Just now, bluewave said:

These quick forcing shifts from the EPAC at the start of January back to the IO and MC after that didn’t inspire a lot of confidence in the individual forecasts especially longer range.

 

Honestly I’m skeptical of this panning out as depicted, but we will see. 

[bluewave]

1 minute ago, Terpeast said:

Honestly I’m skeptical of this panning out as depicted, but we will see. 

Is anyone working on an AI bias correction to the EPS weeklies numerical forecasts? It seems like this is the way to go. Since the AI forecasts on their own I have seen haven’t been the greatest. But maybe if they join forces with NWP they could make some real progress in modeling beyond 10 days.

[Terpeast]

3 minutes ago, bluewave said:

Is anyone working on an AI bias correction to the EPS weeklies numerical forecasts? It seems like this is the way to go. Since the AI forecasts on their own I have seen haven’t been the greatest. But maybe if they join forces with NWP they could make some real progress in modeling beyond 10 days.

Yes, I've been seeing efforts to create hybrid models where AI helps with data assimilation for initial conditions, and then the NWP physical models run them out forward. None of that is is public yet, but so far it seems promising and I'm sure we will see a lot of new stuff coming down the pike in 2025.

[GaWx]

The often highly changeable CFS ens based AAM forecast (last one from 12Z on Mon) dropped significantly vs 9 days earlier fwiw:

12/16 12Z: neutral mean by Jan 9

 

12/7 0Z: strong +AAM on Jan 9