2024-2025 La Nina

[bluewave]

One thing to note for the first week of December is that the 850 mb temperature departures are forecast to be colder than the 2m since the Northern Hemisphere snow cover is still near record lows and will need some time to catch up. 
 

 

[michsnowfreak]

49 minutes ago, 40/70 Benchmark said:

Sounds about right...any semblance of winter is always eradicated before the holiday.

White christmas on the east coast/new england this year lol. There is no possible meteorological explanation why those grinch storms always hit you at Christmas other than bad luck. Its bound to change. Our general White Christmas (1"+ snowcover) climo here is 50/50 and there's been no trend away from that in recent years.

[snowman19]

35 minutes ago, snowman19 said:

I don’t think the issue comes the 1st 2 weeks of December. The thing that would support the NAO and AO/NAM going very positive is the SPV. The SPV forecast to get extremely strong and cold on the models and “couple” with the troposphere. They also have it moving directly over the pole. *IF* that happens it may be a problem going into mid-December

 

 

 

 

Just to add to this SPV disco, if the MJO (4-6) forcing does start to exert itself and we go back to a La Niña/-PDO like atmosphere with a -PNA, as @Stormchaserchuck1 mused, at the same time of a potential coupled SPV forced +NAO/+AO, then yes, the pattern could get very mild. And as I discussed yesterday, there is a possibility we go Niña in region 3.4 by the end of December with a projected EWB next month. “Commodity weather” pointed out that there have been cold-neutral ENSO Novembers that have gone La Niña by the New Year in the past. I don’t know what to think right now after this total mismatch we’re seeing to start December TBH

[bluewave]

32 minutes ago, michsnowfreak said:

meteorological explanation why those grinch storms always hit you at Christmas other than bad luck. Its bound to change

The 2nd half of December has been warming at a faster rate than the 1st half around the Northeast spots like NYC over the last 30 years. Every year since 2011 there has been a warm up between the 17th and 25th going over 55°. So it would be quite an accomplishment if we got a relaxation of this pattern for even one year. 
 

December 17 to 25 maximum temperature NYC over 55° every year since 2011

 

Time Series Summary for NY CITY CENTRAL PARK, NY
Click column heading to sort ascending, click again to sort descending.

2023-12-25	62	0
2022-12-25	58	0
2021-12-25	60	0
2020-12-25	61	0
2019-12-25	57	0
2018-12-25	61	0
2017-12-25	55	0
2016-12-25	58	0
2015-12-25	72	0
2014-12-25	62	0
2013-12-25	71	0
2012-12-25	56	0
2011-12-25	62	0
2010-12-25	40	0

 

 

[40/70 Benchmark]

35 minutes ago, snowman19 said:

Just to add to this SPV disco, if the MJO (4-6) forcing does start to exert itself and we go back to a La Niña/-PDO like atmosphere with a -PNA, as @Stormchaserchuck1 mused, at the same time of a potential coupled SPV forced +NAO/+AO, then yes, the pattern could get very mild. And as I discussed yesterday, there is a possibility we go Niña in region 3.4 by the end of December with a projected EWB next month. “Commodity weather” pointed out that there have been cold-neutral ENSO Novembers that have gone La Niña by the New Year in the past. I don’t know what to think right now after this total mismatch we’re seeing to start December TBH

2008-2009 is one prominent example.

[GaWx]

Eric Webb discovered ABNA and that the -ABNA is driving the current/upcoming cold E US pattern. Anyone here knowledgeable about ABNA? It’s actually not a new index though we had previously never heard of it. Regardless, not having a daily forecast nor a monthly history of it makes it less useful to me though the DJF mean is shown on a graph in this Eric tweet:

 

[GaWx]

12Z GEFS is about as cold run overall as any prior run through day 11. But days 12-16 remain to be seen. Also, fwiw, it has a significant increase in members with a tropical cyclone in the W Caribbean next week….interesting.

 Edit: 12Z GEFS isn’t the coldest days 12-16 but it is still cold overall thus making the total run another cold one.

 12Z Euro: 15 day run is about as cold as any yet per my eyeballs with 4 Canadian highs including current one plunging down

[bluewave]

It will be interesting to see if we can get another round of Nino 1+2 warming in early December if a follow up WWB verifies near 120W like the GFS has.

 

 

[brooklynwx99]

my initial impression of late Nov into early Dec so far is that the persistently +AAM that's being forecasted combined with +EAMT event is extending the Pacific jet more than is typical of La Nina. extensions are often favorable for us, and I believe these factors are overriding the largely unfavorable MJO passage

this general pattern favors +EAMT into early Dec, allowing for a persistently extended Pacific jet that leads to an Aleutian trough. the MJO isn't a silver bullet, and i do think we're seeing a break in the typically strong MJO correlation. never been happier to be wrong about a forecast, let me tell you

[GaWx]

The 12Z EPS is about as cold as any through day 12 (Dec 4th). The rest of the run is a bit warmer than recent runs but is still cold overall along with reinforcing cold at the end (12/7). 

[Terpeast]

49 minutes ago, brooklynwx99 said:

 

 

 

 

I don't think I've seen an MJO RMM forecast that shows it dying into COD from the warm phases in the last few years. Usually it gets even stronger as it goes through the MC. I hope this is right.

[mitchnick]

51 minutes ago, GaWx said:

The 12Z EPS is about as cold as any through day 12 (Dec 4th). The rest of the run is a bit warmer than recent runs but is still cold overall along with reinforcing cold at the end (12/7). 

Climo is getting colder, so we're still good in absolute terms 15 days out.

[bluewave]

18 minutes ago, Terpeast said:

 

I don't think I've seen an MJO RMM forecast that shows it dying into COD from the warm phases in the last few years. Usually it gets even stronger as it goes through the MC. I hope this is right.

This October into early December MJO forecast is similar to 2020 which I mentioned with the high amplitude  MJO 5 both Octobers and weaker MJO 5 in December before going into the circle.
 

[brooklynwx99]

1 hour ago, bluewave said:

This October into early December MJO forecast is similar to 2020 which I mentioned with the high amplitude  MJO 5 both Octobers and weaker MJO 5 in December before going into the circle.
 

similar progression occurred in 2010

[EasternLI]

2 hours ago, brooklynwx99 said:

my initial impression of late Nov into early Dec so far is that the persistently +AAM that's being forecasted combined with +EAMT event is extending the Pacific jet more than is typical of La Nina. extensions are often favorable for us, and I believe these factors are overriding the largely unfavorable MJO passage

this general pattern favors +EAMT into early Dec, allowing for a persistently extended Pacific jet that leads to an Aleutian trough. the MJO isn't a silver bullet, and i do think we're seeing a break in the typically strong MJO correlation. never been happier to be wrong about a forecast, let me tell you

I have an observation to share regarding the MJO/status of tropical convection. It's been quite interesting this month. I think I can provide an explanation and illustration of why it's rendered ineffective currently. I think it's actually a really good example of a time when the MJO just isn't going to mean very much to us. The image below is from the JMA. It has OLR overlayed with 200MB VP anomalies. Note how the center of action along with the bulk of the forcing this month is south of the equator. When that happens, it's just not going to effect the NH very much if at all. It seems like this is also leaving some room for the Pacific jet to be more equatorward rather than poleward. Which I've seen you make mention of in a different post. So as long as this continues, which could certainly be debatable, I don't think the MJO is going to be telling anyone much of anything. And maybe we can actually achieve some Aleutian low this year when that equatorward jet extends like guidance is currently showing. 

[snowman19]

Multi model signal for a very strong SPV next month:

[BuffaloWeather]

Cold reloads on all 3 ensembles

[Snowstorms]

13 hours ago, bluewave said:

One thing to note for the first week of December is that the 850 mb temperature departures are forecast to be colder than the 2m since the Northern Hemisphere snow cover is still near record lows and will need some time to catch up. 
 

 

Snow cover is building pretty fast across Western Canada with a few storms that have passed through the region this week and again into next week. After a record breaking warm start to November, things flipped pretty quickly out west. Currently 12 in Calgary. Only thing concerning is the lack of ice around Hudson Bay. 

[bluewave]

6 hours ago, Snowstorms said:

Snow cover is building pretty fast across Western Canada with a few storms that have passed through the region this week and again into next week. After a record breaking warm start to November, things flipped pretty quickly out west. Currently 12 in Calgary. Only thing concerning is the lack of ice around Hudson Bay. 

Thats OK for areas further north in the Upper Midwest into Canada closer to where the Arctic highs are generated. But those air masses moderate quickly in early December coming south with the lower snow cover.The Great Lakes are also near record warm after the warmest fall on record for many areas. So while we will see a colder start to December , the air masses will moderate coming east of the Great Lakes.

Cold air moderating coming east of the Lakes with coldest departures going to the south 

 

 

[snowman19]

23 minutes ago, bluewave said:

Thats OK for areas further north in the Upper Midwest into Canada closer to where the Arctic highs are generated. But those air masses moderate quickly in early December coming south with the lower snow cover.The Great Lakes are also near record warm after the warmest fall on record for many areas. So while we will see a colder start to December , the air masses will moderate coming east of the Great Lakes.

Cold air moderating coming east of the Lakes with coldest departures going to the south 

 

 

Besides low snowcover and the warm lakes, Hudson Bay is still ice free. That is also going to modify the arctic airmasses

[bluewave]

5 minutes ago, snowman19 said:

Besides snowcover and the warm lakes, Hudson Bay is still ice free. That is also going to modify the arctic airmasses

My guess is that the December forecast will be determined by jet extension and retraction dynamics. Sometimes these big WPAC jet extensions can sustain an existing pattern like we are seeing in the forecast for the first week of December. So it would cause the pattern to reload for the 2nd week. But the wild card with all these jet extensions is that they can also reverse a pattern. So the thing  to watch in later runs is whether one of the jet extensions can cause the ridge out West to drift into the East by mid-December. 

[mitchnick]

9 minutes ago, bluewave said:

My guess is that the December forecast will be determined by jet extension and retraction dynamics. Sometimes these big WPAC jet extensions can sustain an existing pattern like we are seeing in the forecast for the first week of December. So it would cause the pattern to reload for the 2nd week. But the wild card with all these jet extensions is that they can also reverse a pattern. So the ring to watch in later runs is whether one of the jet extensions can cause the ridge out West to drift into the East by mid-December. 

You can already see the ridge wanting to drift east at the end of the ensembles. Time will tell if and when it does because I  would say it's inevitable any pattern breaks down. For that matter, both Euro and Cfs2 weeklies have the ridge moving east by the 15th.  The only caveat is that the weeklies and seasonal models completely missed this cold period, so it's not out of question they screw it up again. 

[PhiEaglesfan712]

I think we're more likely to get a 2020-21 type season, rather than a 2010-11 or 2017-18 (both of which were cold through most of December and January). I think the 2nd half of December and most of January is going to be warm. The big question is if, like in 2021, it turns back to a colder than average pattern in late January or early February.

[bluewave]

16 minutes ago, mitchnick said:

You can already see the ridge wanting to drift east at the end of the ensembles. Time will tell if and when it does because I  would say it's inevitable any pattern breaks down. For that matter, both Euro and Cfs2 weeklies have the ridge moving east by the 15th.  The only caveat is that the weeklies and seasonal models completely missed this cold period, so it's not out of question they screw it up again. 

It will be an interesting test of what occurs during the 2nd week of December. On one hand the EPS weeklies  back in 13-14 and 14-15 were continuously trying to break the ABNA pattern down beyond 15 days. The models kept pushing the pattern moderation back in time the closer in we got. But the Pacific Jet from Japan to the east was much weaker those winters. The model forecasts have some pretty impressive jet extensions forecast in early December near Japan. So it will be interesting to see if they can sustain the pattern or cause it to relax.

 

 

[snowman19]

It will be an interesting test of what occurs during the 2nd week of December. On one hand the EPS weeklies  back in 13-14 and 14-15 were continuously trying to break the ABNA pattern down beyond 15 days. The models kept pushing the pattern moderation back in time the closer in we got. But the Pacific Jet from Japan to the east was much weaker those winters. The model forecasts have some pretty impressive jet extensions forecast in early December near Japan. So it will be interesting to see if they can sustain the pattern or cause it to relax.
 

 

That’s a good question….this is going to be a test to see what happens once this WWB/+AAM/Rossby wave flux wears off….does it just rebuild itself again or do we go back into the same old PAC pattern that we’ve had for years now?

[michsnowfreak]

1 hour ago, bluewave said:

Thats OK for areas further north in the Upper Midwest into Canada closer to where the Arctic highs are generated. But those air masses moderate quickly in early December coming south with the lower snow cover.The Great Lakes are also near record warm after the warmest fall on record for many areas. So while we will see a colder start to December , the air masses will moderate coming east of the Great Lakes.

Cold air moderating coming east of the Lakes with coldest departures going to the south 

 

 

While that's true, another thing to note is that the colder departures going south could be in part due to socking Michigan, northern IN/OH, and upstate NY in overcast while other areas are more clear. 

[Allsnow]

20 minutes ago, bluewave said:

It will be an interesting test of what occurs during the 2nd week of December. On one hand the EPS weeklies  back in 13-14 and 14-15 were continuously trying to break the ABNA pattern down beyond 15 days. The models kept pushing the pattern moderation back in time the closer in we got. But the Pacific Jet from Japan to the east was much weaker those winters. The model forecasts have some pretty impressive jet extensions forecast in early December near Japan. So it will be interesting to see if they can sustain the pattern or cause it to relax.

 

 

I remember the pattern breaking down briefly between Christmas and NYE in December 2013. I think we had a huge cutter around that time to spike temperatures into the 60’s 

[jbenedet]

Admittedly from just an observational standpoint here but a lot of what I’m seeing looks like previous years, with best wintry patterns in place in late fall…

Relative to last early December, there was even a similar significant cold shot—as advertised for day 10ish—that originated in the mountain west and covered most of the CONUS for ~5 days.

I’m also noticing significant -NAO’s/-AO’s with regularity; our problem —snowfall wise— is this has flipped in late December to February time frame to predominately +NAO/+AO. The lack of snowpack in New England and eastern Canada also tracking similarly….

We’ll see if past is prologue…

 

[mitchnick]

All modeling really starting to kill the MJO wave vs prior forecasting. 

https://www.stormsurf.com/page2/links/mjo_phase.html

[snowman19]

21 minutes ago, jbenedet said:

Admittedly from just an observational standpoint here but a lot of what I’m seeing looks like previous years, with best wintry patterns in place in late fall…

Relative to last early December, there was even a similar significant cold shot—as advertised for day 10ish—that originated in the mountain west and covered most of the CONUS for ~5 days.

I’m also noticing significant -NAO’s/-AO’s with regularity; our problem —snowfall wise— is this has flipped in late December to February time frame to predominately +NAO/+AO. The lack of snowpack in New England and eastern Canada also tracking similarly….

We’ll see if past is prologue…

 

The risk with the upcoming cold wave is cold and dry. Unlike last year where we had the El Niño juiced STJ screaming along with a bunch of moisture and shortwaves….opposite this year and the strengthening -PMM supports a continuation of a weak STJ. We will be relying on vorts in the fast, progressive northern branch flow to “do something”. While that may work for New England maybe, south of there remains questionable, which is why the models aren’t showing a big coastal signal to go along with the cold in early December