2024-2025 La Nina

[bluewave]

3 hours ago, mitchnick said:

Long range Eps says no more competing MJO forces.

The EPS and GEFS continue to show a split forcing pattern and competing influences through at least the end of the more reliable 15 day ensemble range.

 

 

 

 

 

[donsutherland1]

6 minutes ago, mitchnick said:

So what's your forecast, without hedging?

I'm leaning somewhat warmer than normal for NYC, Philadelphia, Washington, DC, Chicago. The exact values will be posted on 12/31 and I can change my mind based on the latest guidance. Putting ideas for January out on December 15th ignores the stochastic changes that can occur.

My final idea will be posted in the January forecast contest. My December thinking is below (temperatures in the first set of numbers and seasonal snowfall for the second set of numbers):

[mitchnick]

7 minutes ago, bluewave said:

The EPS and GEFS continue to show a split forcing pattern and competing influences through at least the end of the more reliable 15 day ensemble range.

 

 

 

 

 

I used the 360 hr forecast and not 6 day you used. You could at least use the same forecast period. Lol

[bluewave]

8 minutes ago, mitchnick said:

He was talking temps, not snow. Why change the subject to snow or model forecasts? Unless you can show a model that showed colder than what has occurred, flawed modeling has literally nothing to do with it.

Several of the temperature forecasts have been too cold in the Northeast. Parts of the West have also been verifying warmer. The Southeast may be of the few regions to verify as cold or colder than originally forecast.

[mitchnick]

2 hours ago, MJO812 said:

But this December will most likely end up colder than normal.  Alot of people forecasted a warm December which will most likely fail.

 

5 minutes ago, bluewave said:

Several of the temperature forecasts have been too cold in the Northeast. Parts of the West have also been verifying warmer. The Southeast may be of the few regions to verify as cold or colder than originally forecast.

Nope. He was obviously referring to monthly forecasts made before the month. You're talking about medium range forecasts that you claim are wrong. 2 different things completely. 

[GaWx]

1 hour ago, michsnowfreak said:

Been waiting for your annual copy and paste rant that Chicago doesnt annual get a repeat of their most severe 1970s winters on record. At no point in Chicago's climate history has the avg low on 12/31 ever been 13°. In fact, the 1951-80 avg winter temp is just 0.9° colder than 1991-2020, not 8° lmao.

1991-2020: 27.1
1981-2010: 26.3
1971-2000: 25.9
1961-1990: 25.1
1951-1980: 26.0
1941-1970: 26.8
1931-1960: 28.0
1921-1950: 28.1
1911-1940: 27.9
1901-1930: 26.8

Avg low on 12/31 in chicago

1991-2020: 21
1981-2010: 21
1971-2000: 19
1961-1990: 17
1951-1980: 19
1941-1970: 19
1931-1960: 23
1921-1950: 22
1911-1940: 22
1901-1930: 21

Good info! To supplement your data, check this out:

LOT avg low D/J/F 10 year periods; avg of DJF

1951-60: 23.2/18.4/22.3; DJF 21.3

1961-70: 21.4/14.6/19.2; DJF 18.4

1971-80: 21.5/12.8/18.1; DJF 17.5

1981-90: 18.3/14.6/18.6; DJF 17.2

1991-00: 22.0/16.4/22.4; DJF 20.3

2001-10: 21.3/17.9/19.1; DJF 19.4

2011-20: 25.3/17.4/19.1; DJF 20.6

 
 So, imagine growing up there in the 1950s. It got significantly colder during the 1960s-80s before warming back significantly 1990s-2010s. But the warmest decade of these is still the 1950s. So, compared to their childhood, the 2010s were about the same. The 1960s-1980s were cold. Someone growing up in the 1980s could have been spoiled by how cold it was being that it was unusually cold that decade.

https://www.weather.gov/wrh/Climate?wfo=lot

[bluewave]

19 minutes ago, mitchnick said:

I used the 360 hr forecast and not 6 day you used. You could at least use the same forecast period. Lol

Those charts aren’t meant to be used for daily forcing much beyond the 10 day mark. That’s why the 7 day averages are used for the normal daily spread from run to run. You can see on the Hovmoller diagrams the forcing in the days before and after the snapshot you posted has a split look between the EPAC and WPAC. Plus you have to take into account that the models tend to underestimate the signal the further out in time we get. So this gives the appearance of correcting stronger with the convection the closer time we get.

[GaWx]

1 hour ago, donsutherland1 said:

Yesterday, I noted that the 46-day ECMWF ensembles show the development of an EPO-/PNA- pattern during the first half of January. Statistically, following a PNA+ December, a PNA- January is uncommon:

December PNA: +0.5 or above: 31 cases
January PNA < 0: 29% cases
January PNA > 0: 71% cases
January PNA +0.50 or above: 48% cases
January PNA +1.00 or above: 19% cases
Lowest January PNA: -1.14, 1954
Highest January PNA: 2.02, 2016

December PNA: +1.00 or above: 13 cases
January PNA < 0: 8% cases
January PNA > 0: 92% cases
January PNA +0.50 or above: 62% cases
January PNA +1.00 or above: 31% cases
Lowest January PNA: -1.14, 1954
Highest January PNA: +1.51, 2001

If one assumes that the PNA will average > 0 during January, especially as the December PNA could average near or even slightly above +1.00, the idea of a predominant ridge in the West and trough in the East pattern with warmth in the West and cold in the East is not anything close to a slam dunk. The predominant patterns show a wide range of diversity.

Trough in the West Patterns: 42% of cases

Ridge in the West Patterns: 33% of cases

Trough across much of the CONUS: 25% of cases

The classic ridge in the West, trough in the East pattern has occurred with mean January PNA values -0.95 or below, as did the second type of trough across the CONUS cluster (most were +1.00 or above). All of the other clusters had mean January PNA values below -0.75. The first trough in the West, ridge in the East pattern actually produces a temperature anomaly pattern that is very similar to an EPO-/PNA- pattern.

Overall, even if one assumes a predominantly positive PNA for January, which would go against the 46-day ECMWF guidance, one can't automatically assume that the eastern third or half of the U.S. would wind up colder than normal. Keeping in mind the 3-month seasonal guidance, which is more skillful than the month-by-month guidance over seasonal timeframes, a milder January outcome may be somewhat more likely than a colder one for the eastern third or half of the CONUS and southeastern Canada (Ontario and Quebec). There will likely be variability, which has been an important theme through December 14th and is likely to continue throughout the month based on a consensus of the latest guidance.

 Thanks, Don.

 Along with the actuals for 12/1-15, GEFS two week forecasts continue to suggest a good chance for a record high tabular PNA for a non-Nino Dec (records back to 1950)…keep in mind that the tabular monthly values of +PNA months have averaged ~~1.8 times the amplitude based on the daily values shown in the charts that are updated every day. Thus, it looks to me as of now that Dec will likely come in ~+1.5 to +1.75. I roughly estimate 12/1-15 to be +1.60 (based on using a 1.8 conversion factor):

 

 
 The 5 highest tabular Dec +PNAs for non-Nino on record (2024 progged to have good chance to be new highest):

2020: +1.58

1960: +1.46

1985: +1.39

2005: +1.38

2000: +1.23

 Thus, a record high non-Nino Dec PNA is quite possible.

 

Subsequent Jan PNAs for these 5 non-Nino high PNA Dec:

2021 +0.19

1961 +1.41 (4th highest on record for non-Nino)

1986 +0.97 (tied for 7th highest on record for non-Nino)

2006 +0.43

2001: +1.51 (3rd highest on record for non-Nino)

Avg Jan for these 5: +0.90

 

 So, whereas the above has one case coming in just neutral for Jan (2021), it appears that the chances for a +0.75+ PNA in Jan are pretty good. The following 9 non-Nino Jans since 1950 had a +0.75+ PNA (all cold ENSO except RONI neutral 1961 and 1981):

Year/PNA/E US temps (7 of 9 Jans cold/none mild):
1961 +1.41 cold

1981 +2.42 cold

1984 +0.97 cold

1985 +1.63 cold 

1986 +0.97 normal

2001 +1.51 normal

2011 +1.29 cold

2014 +0.97 cold

2022 +1.01 cold

 

  Here’s the average of these 9 Jans using 1981-2010 normals:

 

[mitchnick]

42 minutes ago, bluewave said:

Those charts aren’t meant to be used for daily forcing much beyond the 10 day mark. That’s why the 7 day averages are used for the normal daily spread from run to run. You can see on the Hovmoller diagrams the forcing in the days before and after the snapshot you posted has a split look between the EPAC and WPAC. Plus you have to take into account that the models tend to underestimate the signal the further out in time we get. So this gives the appearance of correcting stronger with the convection the closer time we get.

I correctly posted a map at 360 hours that showed forcing over the W Hem. Period! Lol

But even considering the map you posted, the trend is for forcing to weaken over the Maritime and end up over the W Hem. This can be seen by using the slide function to put the forecast in motion starting on day 9 (the first day of the period your map showed) and going to the end of the forecast, my 360 hr map.

By the way, when did this site employ "model police" anyway? Lol

https://www.tropicaltidbits.com/analysis/models/?model=eps&region=global&pkg=chi200&runtime=2024121500&fh=216

 

[michsnowfreak]

59 minutes ago, GaWx said:

Good info! To supplement your data, check this out:

LOT avg low D/J/F 10 year periods; avg of DJF

1951-60: 23.2/18.4/22.3; DJF 21.3

1961-70: 21.4/14.6/19.2; DJF 18.4

1971-80: 21.5/12.8/18.1; DJF 17.5

1981-90: 18.3/14.6/18.6; DJF 17.2

1991-00: 22.0/16.4/22.4; DJF 20.3

2001-10: 21.3/17.9/19.1; DJF 19.4

2011-20: 25.3/17.4/19.1; DJF 20.6

 
 So, imagine growing up there in the 1950s. It got significantly colder during the 1960s-80s before warming back significantly 1990s-2010s. But the warmest decade of these is still the 1950s. So, compared to their childhood, the 2010s were about the same. The 1960s-1980s were cold. Someone growing up in the 1980s could have been spoiled by how cold it was being that it was unusually cold that decade.

https://www.weather.gov/wrh/Climate?wfo=lot

Excellent post. The mild winters of the 1950s rarely get talked about and on the flip side the cold 1970s are often treated as what was the norm. You will always have your naysayers who will try and twist things, cherry pick data of a specific station, etc, but in reality it's very clear cut. Winters of the 1930s-1950s were very anemic in this region compared to our overall climate. It grew much colder in the 1960s but was also dry, which led to more feast or famine in snowfall. Then the 1970s were the golden child of winters (and the embellishments of these have grown since). Cold lingered in the 80s, then much milder winters hit in the 90s (similar to the 50s) before the 2000s-10s saw unusually heavy snowfall.

This is the average annual DJF temp and seasonal snowfall thru the decades at Detroit. 1930s-60s stick out like a sore thumb for snow. And for temps, the 1950s are 2nd only to 1990s for mild winters. 

1880s- 27.6°, 43.1"

1890s- 26.5°, 42.6"

1900s- 24.9°, 46.3"

1910s- 25.5°, 39.7"

1920s- 25.8°, 46.1"

1930s- 28.3°, 32.9"

1940s- 27.0°, 27.8"

1950s- 28.6°, 37.8"

1960s- 26.2°, 31.8"

1970s- 24.8°, 45.6"

1980s- 25.9°, 45.2"

1990s- 29.2°, 37.2"

2000s- 27.7°, 45.3"

2010s- 28.2°, 49.9"

[bluewave]

1 hour ago, mitchnick said:

 

Nope. He was obviously referring to monthly forecasts made before the month. You're talking about medium range forecasts that you claim are wrong. 2 different things completely. 

The Euro monthly forecast for December is released in the 5th of the month. The other modeling centers get posted around the 1st. Computer model forecasts issued in October into early November have very little skill for the December time frame. 

[GaWx]

Euro Weeklies coldest yet Jan 6-12 of the 17 runs and by a good margin!

H5: now has even lower hts in Aleutian low position and the mean ridge is slightly further E  allowing for even stronger +PNA along with some -EPO; note how E N.A. sticks out like a blue thumb on global view: for week 4 this is quite a strong signal for cold:

 

2 meter temps show easily the coldest yet of 17 runs for the E US:

 

Global view of 2m:

 

IF this is a real threat for cold that week as opposed to a head fake, the anomalies would likely grow substantially as we get closer as that’s how ensemble means usually work. At 4 weeks out, it is rare to get substantially sized areas colder than the 2nd level. This map for week 4 has a substantially sized 2nd level of cold.

[bluewave]

1 hour ago, GaWx said:

The 5 highest tabular Dec +PNAs for non-Nino on record (2024 progged to have good chance to be new highest):

2020: +1.58

1960: +1.46

1985: +1.39

2005: +1.38

2000: +1.23

Much different pattern outside the raw PNA values from most of those Decembers which were very snowy around NYC compared to this year. Several of those Decembers were also much colder than this year. So the following Januaries may also not have that much in common.

NYC December snowfall

2024 so far….T

2020………….10.5”

1960…………..18.6”

1985…………….0.9”

2005…………..9.7”

2000………….13.4”

[PhiEaglesfan712]

1 hour ago, bluewave said:

Much different pattern outside the raw PNA values from most of those Decembers which were very snowy around NYC compared to this year. Several of those Decembers were also much colder than this year. So the following Januaries may also not have that much in common.

NYC December snowfall

2024 so far….T

2020………….10.5”

1960…………..18.6”

1985…………….0.9”

2005…………..9.7”

2000………….13.4”

I've been saying 2005 is the best fit. 2020 and 1985 might also be good analog years. All had a warm November before turning cold in December.

[bluewave]

2 hours ago, mitchnick said:

I correctly posted a map at 360 hours that showed forcing over the W Hem. Period! Lol

But even considering the map you posted, the trend is for forcing to weaken over the Maritime and end up over the W Hem. This can be seen by using the slide function to put the forecast in motion starting on day 9 (the first day of the period your map showed) and going to the end of the forecast, my 360 hr map.

By the way, when did this site employ "model police" anyway? Lol

https://www.tropicaltidbits.com/analysis/models/?model=eps&region=global&pkg=chi200&runtime=2024121500&fh=216

 

The hovmoller charts are showing something different. That being said, it’s beyond the more reliable 15 day range. But it still has forcing over the Maritime Continent in early January. 

 

[PhiEaglesfan712]

Warm November/+PNAs for non-Nino cool December composite:

[mitchnick]

3 hours ago, bluewave said:

The hovmoller charts are showing something different. That being said, it’s beyond the more reliable 15 day range. But it still has forcing over the Maritime Continent in early January. 

 

That's between 15N and 15S, so of course it will be different from the entire world view shown on the TT map I posted. 

But if the TT maps are no good, misleading, or shouldn't be posted, why do you post them? 

Bottom line, they show what they show even if you apparently don't like or agree with them. I'm just a humble messenger. 

[snowman19]

10 hours ago, donsutherland1 said:

Yesterday, I noted that the 46-day ECMWF ensembles show the development of an EPO-/PNA- pattern during the first half of January. Statistically, following a PNA+ December, a PNA- January is uncommon:

December PNA: +0.5 or above: 31 cases
January PNA < 0: 29% cases
January PNA > 0: 71% cases
January PNA +0.50 or above: 48% cases
January PNA +1.00 or above: 19% cases
Lowest January PNA: -1.14, 1954
Highest January PNA: 2.02, 2016

December PNA: +1.00 or above: 13 cases
January PNA < 0: 8% cases
January PNA > 0: 92% cases
January PNA +0.50 or above: 62% cases
January PNA +1.00 or above: 31% cases
Lowest January PNA: -1.14, 1954
Highest January PNA: +1.51, 2001

If one assumes that the PNA will average > 0 during January, especially as the December PNA could average near or even slightly above +1.00, the idea of a predominant ridge in the West and trough in the East pattern with warmth in the West and cold in the East is not anything close to a slam dunk. The predominant patterns show a wide range of diversity.

Trough in the West Patterns: 42% of cases

Ridge in the West Patterns: 33% of cases

Trough across much of the CONUS: 25% of cases

The classic ridge in the West, trough in the East pattern has occurred with mean January PNA values -0.95 or below, as did the second type of trough across the CONUS cluster (most were +1.00 or above). All of the other clusters had mean January PNA values below -0.75. The first trough in the West, ridge in the East pattern actually produces a temperature anomaly pattern that is very similar to an EPO-/PNA- pattern.

Overall, even if one assumes a predominantly positive PNA for January, which would go against the 46-day ECMWF guidance, one can't automatically assume that the eastern third or half of the U.S. would wind up colder than normal. Keeping in mind the 3-month seasonal guidance, which is more skillful than the month-by-month guidance over seasonal timeframes, a milder January outcome may be somewhat more likely than a colder one for the eastern third or half of the CONUS and southeastern Canada (Ontario and Quebec). There will likely be variability, which has been an important theme through December 14th and is likely to continue throughout the month based on a consensus of the latest guidance.

Good discussion Don. I think we see a -PNA develop by the 2nd week of January. It’s pretty clear that the big “Nino like” NPAC trough is going to retro and I believe we see a -PNA take shape right around that time frame. The tropical PAC is very clearly in full Niña mode and it’s not going to be denied IMO

[snowman19]

6 hours ago, bluewave said:

The hovmoller charts are showing something different. That being said, it’s beyond the more reliable 15 day range. But it still has forcing over the Maritime Continent in early January. 

 

That’s the Niña standing wave and the reason why I think we go -PNA mode around the 2nd week of January as the entire “Nino like” NPAC pattern retros

[LakePaste25]

January looks on track to start cold, at least shortly after the New Year due to a pacific jet retraction to a more favorable wave breaking/exit position. The question then becomes, how long does this last? Some guidance retracts the jet further to the more traditional -PNA/SE ridge by mid-January, while others hold off until the end of the month. I am going with a blend, with the cold lasting until the 4th week of january. By early February the latest, we will see a return to the full SE ridge Nina pattern.

[bluewave]

The latest JMA splits the difference between the Niña-like WPAC forcing  and EPAC Nino-like forcing in its latest run placing the mean trough axis in the Plains during January.

[MJO812]

5 minutes ago, bluewave said:

The latest JMA splits the difference between the Niña-like WPAC forcing  and EPAC Nino-like forcing in its latest run placing the mean trough axis in the Plains during January.

This looks good

We might have a chance of wintry weather in January.

[mitchnick]

14 minutes ago, bluewave said:

The latest JMA splits the difference between the Niña-like WPAC forcing  and EPAC Nino-like forcing in its latest run placing the mean trough axis in the Plains during January.

Hmm, just about to respond to your last post, but it's been deleted. But I know what you said and in light of the JMA, why it was deleted. 

Anyway, Euro using your, I'll call it, "preferred" method from last night's run (7 day average), has diminished almost all forcing from W-Pac. Attached are last night's 0z (top) and Saturday night's (middle).  While using the 360 hrs panel (bottom) alone (there being no reason not to), continues to show all forcing in the E-Pac.

 

[LakePaste25]

 

29 minutes ago, bluewave said:

The latest JMA splits the difference between the Niña-like WPAC forcing  and EPAC Nino-like forcing in its latest run placing the mean trough axis in the Plains during January.

A trough axis centered more west isn’t terrible for I-95 snow threats. The late november to early december pattern of clippers dropping into Michigan and the ridge axis over BC produced plenty of lake snow here, but it was too far east to produce anything appreciable for the I-95 corridor.

[bluewave]

29 minutes ago, mitchnick said:

Hmm, just about to respond to your last post, but it's been deleted. But I know what you said and in light of the JMA, why it was deleted. 

Anyway, Euro using your, I'll call it, "preferred" method from last night's run (7 day average), has diminished almost all forcing from W-Pac. Attached are last night's 0z (top) and Saturday night's (middle).  While using the 360 hrs panel (bottom) alone (there being no reason not to), continues to show all forcing in the E-Pac.

 

 

 

The Euro hovmollers continue the split forcing into early January along with the GEFS. So the hope is that the EPAC forcing becomes more dominant and we get more of an El Niño influence. If we still have even a small amount of forcing in the WPAC ,then it could continue the competing influences with La Niña  and a stronger northern branch like we have seen in December. I hear the disappointment with the pattern this month in your tone. But I think you are probably better than the gottcha persona you are trying to portray online.
 

 

[mitchnick]

21 minutes ago, bluewave said:

The Euro hovmollers continue the split forcing into early January along with the GEFS. So the hope is that the EPAC forcing becomes more dominant and we get more of an El Niño influence. If we still have even a small amount of forcing in the WPAC ,then it could continue the competing influences with La Niña  and a stronger northern branch like we have seen in December. I hear the disappointment with the pattern this month in your tone. But I think you are probably better than the gottcha persona you are trying to portray online.
 

 

Now it's time for the "I'm better than you" cheap shots. Lol You are way too transparent with your glib posts.

It's obvious you are having a problem with forcing moving into the E-Pac. I guess it goes againt your forecast or agenda, idk. It is odd though. Modeling shows it happening, whether you look at individual hourly forecast panels or 7 day. Enjoy it.

[bluewave]

8 minutes ago, mitchnick said:

Now it's time for the "I'm better than you" cheap shots. Lol You are way too transparent with your glib posts.

It's obvious you are having a problem with forcing moving into the E-Pac. I guess it goes againt your forecast or agenda, idk. It is odd though. Modeling shows it happening, whether you look at individual hourly forecast panels or 7 day. Enjoy it.

 

 

 

seemingly unwilling to

 

You are one of the only posters in this thread that has seemed more concerned about getting jabs in against perceived imaginary threats. Your history in this thread speaks for itself. Did you ever think that maybe there are a number of posters which left this forum due to posters like you? The only agenda that matters is getting the pattern correct.

[Terpeast]

1 hour ago, bluewave said:

The latest JMA splits the difference between the Niña-like WPAC forcing  and EPAC Nino-like forcing in its latest run placing the mean trough axis in the Plains during January.

It's looking like after the late month warm up, we're looking at a flip to a colder pattern in January once the EPO goes back negative and PNA ridging returns. But I'm still unsure as to the orientation of the ridge out west that may influence the cold trough east. If we get a mixed bag of competing influences, we may either see that trough dump out into the Atlantic and/or pressed NWard by a SE ridge. I'm actually hoping for the latter because it would bring that storm track closer to us instead of shortwaves sliding way out to sea like the one on 12/21-22.

[michsnowfreak]

18 minutes ago, bluewave said:

You are one of the only posters in this thread that has seemed more concerned about getting jabs in against perceived imaginary threats. Your history in this thread speaks for itself. Did you ever think that maybe there are a number of posters which left this forum due to posters like you? The only agenda that matters is getting the pattern correct.

I doubt mitch is who drove some away. There are clearly some in this thread who try anything and everything to go against cold and look for warmth. After a warm year the unexpected cold weather in December has not only greatly dissatisfied them, but it's also showed true colors. For a select few, there isn't a pattern possible where they would go cold other than if it is happening right at that moment. And even then they will immediately look for the next sign of warmth, why the cold won't last, why models showing a colder look will be wrong, etc. 

[bluewave]

15 minutes ago, Terpeast said:

It's looking like after the late month warm up, we're looking at a flip to a colder pattern in January once the EPO goes back negative and PNA ridging returns. But I'm still unsure as to the orientation of the ridge out west that may influence the cold trough east. If we get a mixed bag of competing influences, we may either see that trough dump out into the Atlantic and/or pressed NWard by a SE ridge. I'm actually hoping for the latter because it would bring that storm track closer to us instead of shortwaves sliding way out to sea like the one on 12/21-22.

This season so far has been a study in competing influences which we usually don’t see running at the same time. Past Decembers with such strong ridges out West were able to anchor the ridge axis closer to the West Coast. This December the stronger Pacific Jet has resulted in the ridge shifting further east. It may be that the combination of WPAC forcing and the strong -PDO gradient is leading to a stronger Pacific Jet influence. So we would want to see this jet influence shift in early January otherwise any ridge pullback to the west could be short lived again.