2024-2025 La Nina

[GaWx]

Looking at cold ENSO analogs:

-Cold 1st 1/2 Dec in NE/SE but not cold 2nd half: 2007, 2005, 1954, 1949, 1934, 1915, 1898, 1893, and 1875. Zero out of these 9 cases (0%) were cold dominated in 1st half of Jan in either NE or SE. Of these in the SE: 2008, 2006, 1955, 1950, 1916, 1894, and 1876 were mild. Only 1935 and 1899 weren’t mild (close to normal) in the SE. In the NE 2008, 2006, 1950, and 1894 were mild.

-Cold BOTH halves of Dec in NE/SE: 2010, 2000, 1995, 1962, 1955, 1944, 1917, 1910, and 1903. 6 out of these 9 cases (67%) were cold dominated in 1st half of Jan in both the NE and SE: 2011, 2001, 1996, 1945, 1918, and 1904. Of these 9, only 1911 (11%) averaged mild in 1st half of Jan. in either NE or SE.

- Thus per cold ENSO cold dominated 1st half of Dec analogs: whether or not it is also cold dominated in the 2nd half of Dec appears to have significant implications on the chance for cold (much higher if cold late Dec) as well as mild domination (significantly higher if not cold late Dec) in 1st half of Jan.

- Since 2024 will verify as cold ENSO and cold dominated in 1st 1/2 of Dec, whether or not it is cold dominated 12/16-31 will be quite informative as regards the chance for a cold vs mild dominated 1/1-15/2025.

[bluewave]

1 hour ago, jbenedet said:

NAO Index is following very similar behavior to last year.

I would like to better understand why we see -NAO tendency dominate fall, flip to +NAO tendency around the beginning of winter (end of December/mid January), and predominate through mid March...

As we know from an ENSO state, this year vs last is apples to oranges and yet, the NAO index is following very closely...

Something bigger may be going on here...

I know on the climate change side there has been a semi-permanent "cold pool" observed to be centered in the region of iceland, which is theorized to be driven by the slowing down of the gulf stream component of the AMOC. Perhaps the development and peaking of this "cold pool" coincides with the the near solar minimum, which in turn drives the NAO Index to positive tendency. The cold pool is relatively less by mid March as SST's in the North Atlantic achieve minimum, and ISR is more influencial to +temp anoms in this part of the world...

It could just be something as simple as the much warmer Gulf Stream east of the Carolinas leading to a stronger Western Atlantic Ridge. The big Western Atlantic Ridge amplification last few days with 60s into the Northeast is preceding the NAO rise going forward. Higher heights near the East Coast usually leads to a trough formation several days later near Icekand.When we had the trough near the East Coast in early December heights were higher near Western Europe and Iceland.

[BuffaloWeather]

Picked up 30" in the last 12 hrs, you guys all need to move to lake effect country with the warming climate.

[jbenedet]

34 minutes ago, bluewave said:

It could just be something as simple as the much warmer Gulf Stream east of the Carolinas leading to a stronger Western Atlantic Ridge. The big Western Atlantic Ridge amplification last few days with 60s into the Northeast is preceding the NAO rise going forward. Higher heights near the East Coast usually leads to a trough formation several days later near or to the East of Iceland. When we had the trough near the East Coast in early December heights were higher near Western Europe and Iceland.

Yes but what about the seasonal pattern to this?

I think it has to do with the climatalogical peak and min of SST's In the North Atlantic. 

For example - Iceland's temperature isn't as negatively affected by the shutting off of the AMOC in late spring and summer (atmospheric temp > water temp), but it is severely reduced in winter (water temp >> atmospheric temp)... Hence the cold pool phenomomen peaks in early winter...and the peaking of the cold pool coincides with a flip to +NAO tendency.

This is the critical aspect to my hypothesis...

 

 

 

[jbenedet]

48 minutes ago, bluewave said:

It could just be something as simple as the much warmer Gulf Stream east of the Carolinas leading to a stronger Western Atlantic Ridge. The big Western Atlantic Ridge amplification last few days with 60s into the Northeast is preceding the NAO rise going forward. Higher heights near the East Coast usually leads to a trough formation several days later near Icekand.When we had the trough near the East Coast in early December heights were higher near Western Europe and Iceland.

Also, I don't know if that's the right take on this.

I think the better read is that -NAO was still in the background state but not felt in sensible weather until much further north. My belief is the cold influence of -NAO's has also weakened (at our latitude) with time due to the warmer SST's in eastern Canada and the Gulf of Maine. The mid level confluence response that we are so used to seeing in our region in a -NAO regime is now displaced further north/east, generally...

[bluewave]

1 minute ago, jbenedet said:

Also, I don't know if that's the right take on this.

I think the better read is that -NAO was still in the background state but not felt in sensible weather until much further north. My beliefe is the cold influence of -NAO's has also weakened (at our latitude) with time due to the warmer SST's in eastern Canada and the Gulf of Maine. The mid level confluence response that we are so used to seeing in our region is now displaced further north/east, generally...

I just said it that way since the wave break which is initiating the NAO shift is originating near the East Coast.

[GaWx]

12Z GEFS coldest run yet for E US 12/20-3+ with stronger mean Arctic high! 12Z GFS was also very cold then.

 Edit: 12Z GEFS: has mean Aleutian Low 12/16-25+!

[Maxim]

On 7/31/2024 at 11:08 PM, Stormchaserchuck1 said:

It's interesting that the roll-forwards for warm CONUS Dec - June, and Dec - July, had August as a break month along with December.. This beats even CPC, who was very bullish on much above average temperatures a short time ago. Something to consider.. the roll forwards were very warm every month through March 2025, with Dec and August being only neutral. August looks like it will fit that pattern with a -EPO developing for some of the time. Doesn't mean Sept-Oct will be cool. 

Absolutely astounding to see how well the roll-forwards have progressed thus far, with Dec indeed looking to be a "break month" from the unrelenting warmth of Sept-Nov. Will be very interesting to see if Jan-Mar goes back to torching.

[Stormchaserchuck1]

35 minutes ago, Maxim said:

Absolutely astounding to see how well the roll-forwards have progressed thus far, with Dec indeed looking to be a "break month" from the unrelenting warmth of Sept-Nov. Will be very interesting to see if Jan-Mar goes back to torching.

I was impressed by how strong of a signal it was giving, as 40% of the dataset was being used (30/75 years) and it was giving +4-5 mean anomalies for a 5-month period. In Jan-Feb, the max went up to +6F. Something like 85% of the years followed the above average pattern for Jan-Feb.  It has hit every month so far, I'd guess it favors a +NAO or +EPO/-PNA for Jan-Feb. 

[PhiEaglesfan712]

51 minutes ago, Maxim said:

Absolutely astounding to see how well the roll-forwards have progressed thus far, with Dec indeed looking to be a "break month" from the unrelenting warmth of Sept-Nov. Will be very interesting to see if Jan-Mar goes back to torching.

September was still cool where I lived, so the unrelenting warmth was really only October and November. The most recent fall with that temperature profile was 2020. There really wasn't a torch that winter, but we did have a notable snow shut-off the 2nd half of December and almost all of January. February was the cold and snowy month that winter.

[snowman19]

I was impressed by how strong of a signal it was giving, as 40% of the dataset was being used (30/75 years) and it was giving +4-5 mean anomalies for a 5-month period. In Jan-Feb, the max went up to +6F. Something like 85% of the years followed the above average pattern for Jan-Feb.  It has hit every month so far, I'd guess it favors a +NAO or +EPO/-PNA for Jan-Feb. 

Very impressive forecast from back in August. I’m pretty shocked with how well it worked out. I’m still definitely not buying that the MJO is just going to plow right into 7-8-1-2. Not buying it having absolutely no resistance to the Niña standing wave/EWBs/subsidence and cooler SSTs. Neither is Earthlight, who everyone well knows is far, far away from being a warmista. If I end up being wrong, I’ll gladly admit it and you guys can rip me apart

[snowman19]

And as far as this ridiculous SSWE hype on twitter, it is complete and total BS. A blatant wishcast if I ever saw one

[BuffaloWeather]

Got this in 12 hours. Got a spare bedroom for fellow winter weather weenies.

[PhiEaglesfan712]

High probability of an ENSO neutral year in 2025-26: 

[snowman19]

Very impressive forecast from back in August. I’m pretty shocked with how well it worked out. I’m still definitely not buying that the MJO is just going to plow right into 7-8-1-2. Not buying it having absolutely no resistance to the Niña standing wave/EWBs/subsidence and cooler SSTs. Neither is Earthlight, who everyone well knows is far, far away from being a warmista. If I end up being wrong, I’ll gladly admit it and you guys can rip me apart

[/url]

I absolutely believe that the Christmas week period is not going to end up an arctic tundra like twitter would have us believe right now. I completely agree with Earthlight. Again, if I end up being wrong, so be it, you guys can roast me lol New EPS:

[GaWx]

47 minutes ago, snowman19 said:

I absolutely believe that the Christmas week period is not going to end up an arctic tundra like twitter would have us believe right now. I completely agree with Earthlight. Again, if I end up being wrong, so be it, you guys can roast me lol New EPS:

 

 

 

 

 
 Per latest model consensus trends, a good portion of the first half of Christmas week (12/22-25) as well as late in the prior week (12/20-1) is increasingly likely looking to be quite cold in the E US, especially MidAtlantic south. Are you aware of this?

12Z GEFS:

[MJO812]

1 minute ago, GaWx said:

 
 Per latest model consensus trends, a good portion of the first half of Christmas week (12/22-25) as well as late in the prior week (12/20-1) is increasingly likely looking to be quite cold in the E US, especially MidAtlantic south. Are you aware of this?

A big cold outbreak on the models with storm chances because of the huge ridge out west.

[snowman19]

6 minutes ago, GaWx said:

 
 Per latest model consensus trends, a good portion of the first half of Christmas week (12/22-25) as well as late in the prior week (12/20-1) is increasingly likely looking to be quite cold in the E US, especially MidAtlantic south. Are you aware of this?

Well aware, and I’m not buying an arctic outbreak/extreme cold. Sorry we disagree but not believing the BAMWX, etc. GEFS model hype on twitter. Again, if I’m wrong I’ll own it

 

 

 

 

[GaWx]

6 minutes ago, MJO812 said:

A big cold outbreak on the models with storm chances because of the huge ridge out west.

 This isn’t hype, folks. The cold is really on the models and is intensifying on the GEFS/EPS as we get closer.

 I don’t hype. I hate hype with a passion!

Edit: I also hate downplaying just for the sake of downplaying.

[brooklynwx99]

3 minutes ago, GaWx said:

 This isn’t hype, folks. The cold is really on the models and is intensifying on the GEFS/EPS as we get closer.

 I don’t hype. I hate hype with a passion!

pretty major change

[mitchnick]

11 minutes ago, snowman19 said:

Well aware, and I’m not buying an arctic outbreak/extreme cold. Sorry we disagree but not believing the BAMWX, etc. GEFS model hype on twitter. Again, if I’m wrong I’ll own it

 

 

 

 

The way winters have hone recently, you just may be rushing the warmth. It's been hard to fight it.

[snowman19]

43 minutes ago, brooklynwx99 said:

pretty major change

I’m not denying that at 12z today there has been a major change on the models. And I’m not downplaying. However, given the PAC jet extension and the tropical forcing, I believe that model change to be totally wrong. Once again, just my opinion given the totality of the synoptic pattern. The great part of this forum is that we can have differing opinions and disagree and I’m not changing my opinion based on one or two ensemble runs. I’m sticking by it. Maybe I’m wrong and that’s fine

@MJO812 Christmas week hasn’t happened yet. Something that hasn’t happened yet isn’t “in trouble”

[GaWx]

Looking out further on the Euro Weeklies:

-Still no sign of a major SSW before mid-Jan

-Jan 6-19 continues the last 7 days of runs showing the lack of either a warm or cold signal.

-Jan 20-26: a new week and it also has no strong signal

-Although the period 1/6-26 lacks a cold signal at 2 meters, H5 maintains BN hts upper Midwest to NE US as well as in SE to SC Canada that expands westward Jan 20-6. These cold H5 anomalies are the most negative anomalies in the entire N Hem and that has been the case over the last week of runs. I wonder if that’s signaling that the risk to turning colder in later runs during some or much of 1/6-26 is higher than the risk to turning warmer. Over the last 8 or so years and although there are always a good number of exceptions, extended model periods have tended to verify warmer rather than colder (cold bias). But perhaps this winter will be different based on Dec so far and relevant analogs.

[MJO812]

44 minutes ago, snowman19 said:

Well aware, and I’m not buying an arctic outbreak/extreme cold. Sorry we disagree but not believing the BAMWX, etc. GEFS model hype on twitter. Again, if I’m wrong I’ll own it

 

 

 

 

It's not 1 ensemble run .The warmth for Christmas week was erased 3 days ago on the models.

Once the EPO was forecasted negative, the warm calls were in trouble .

[mitchnick]

4 minutes ago, MJO812 said:

It's not 1 ensemble run .The warmth for Christmas week was erased 3 days ago on the models.

Once the EPO was forecasted negative, the warm calls were in trouble .

Warmth is on the weeklies with the week starting 12/23, so there seems to be a bit of a conflict with the Eps. 

 

[MJO812]

17 minutes ago, mitchnick said:

Warmth is on the weeklies with the week starting 12/23, so there seems to be a bit of a conflict with the Eps. 

 

 Alot of conflicting forecasts. 

[GaWx]

34 minutes ago, mitchnick said:

Warmth is on the weeklies with the week starting 12/23, so there seems to be a bit of a conflict with the Eps. 

 

Here’s why (combo of things):

-Don’t forget that the Weeklies are run at 0Z rather than 12Z

-12Z EPS was significantly colder than 0Z 12/22-5 in the E US

-The top map’s week (12/23-29) had only 2 of 7 days cold (12/23-4) at 0Z in the far E US and only 1 cold day back to the E Midwest. West of there all 7 days were mainly mild. And even in the E US most of 12/25-9 were mild. Chicago westward was mainly mild the entire 12/23-9.

-Also, the E US cold of the 12Z also includes 12/20-2 with 12/22 colder vs 0Z. So, the cold is split up between two weeks and is muted in each full week by surrounding warmth.

[mitchnick]

Whatever happens before Christmas thru the NY, weeklies are and have been (as Larry posted earlier), adamant with parking a trough over or near the GL  insuring at least average temps for the bulk of January in the central and eastern Conus. And that WILL feel cold after the past few years.

[LakePaste25]

The models have certainly trended towards a pre-christmas cold shot, on average lasting about 5 days. The only thing I will point out is that we shouldn’t verify a forecast with a forecast. Before jumping the gun on calling certain outlooks wrong, we should wait and see how this actually plays out. 

[bluewave]

All we are seeing on the guidance is the ridge axis shifting east and pulling back west every 3-4 days or so. So we warm up ahead of the storm systems and then we cool down after they go past. It’s tough for the models to see the individual shortwaves in the longer range moving through the fast flow. So the timing of the ridges and troughs will probably be off the further out in time you go.