2024-2025 La Nina

[FPizz]

16 hours ago, GaWx said:

Euro Weeklies means are mainly mild in the E US through the entire run (goes through Dec 9th) fwiw. Consistent with that, the mean SPV (thick blue line) (climo is thick red line) is very strong through Dec 12th. If this verifies, JB is going to have a very hard time getting the cold Dec he keeps mentioning.

Roll this back a 45 days and compare to now, how did it do? 

[40/70 Benchmark]

38 minutes ago, bluewave said:

Like we were discussing the other day, we are really going to need a mismatch this winter in order to push back against so many early warm signals. On one hand we have the divergence that we haven’t seen since 2010 with the Niña strength and early MJO. If the weaker La Niña past winter patterns win out than the main ridge axis spot has a shot a more very high temperature departures since the weaker La Ninas have been warmest since 2010. The early hints are that it will be further south than last winter. But the early MJO indicator is following the stronger path like 20-21. Due to the divergence I don’t know yet whether it will continue to work. My guess is when we get to the early December modeling timeframe one or the other scenarios should be obvious at that time. So like many times we have to wait until the first week of December to see which way the pattern moves. 

Canada def. won't be as warm as last season because that "El Nina" configuration was a perfect storm for that, so by default much of the nothern US should be a bit cooler...even NE.

[BlizzardWx]

Like some others noted, I have also seen a loose correlation between warm season patterns and the eventual winter outcome. It's never in the exact same place and the amplitudes change (etc.) but usually there are hints of what will eventually occur. Here is what we had for April to August. Obviously the pattern that developed since then has been very different but maybe this map will still have some seasonal forecasting utility. 

[bluewave]

48 minutes ago, PhiEaglesfan712 said:

Which part of Canada? Was it the West? Because I'm pretty sure it wasn't anywhere in Eastern Canada because here in the mid-Atlantic, we got one of our coolest May-June periods ever, and an overall cool summer. May/June was dominated by a blocking pattern that caused the smoky orange skies in NYC/mid-Atlantic in June 2023.

Canada had their strongest May 500mb ridge on record in 2023. Then the ridge axis shifted a bit ESE for the winter. The La Niña background combined with the El Niño allowing more ridging than we typically see in the East during El Niños. I was pointing out the potential error that the Euro seasonal forecast was showing last fall in the East. 
 

[40/70 Benchmark]

On 8/14/2024 at 10:49 PM, Stormchaserchuck1 said:

So.. we had a record N. American ridge December 2023 through August 3rd. 

I went through the entire dataset, and found 20 top analog, which matched the signal general:

Here's what they look like rolled-forward...

November:

December:

January:

February:
 

Nov-Feb Total:

The February map having +5-6F temps for 20 analogs (+ and -), 20/75 of the whole dataset is pretty strong. You can see the progression into a SE ridge historically. 

 

On 10/24/2024 at 5:09 PM, donsutherland1 said:

The latest CFSv2 forecast for November indicates that most of the CONUS will be warmer than normal.

Thus, the question becomes what kind of winter would be likely to follow such a November. With the December 2024-February 2025 Relative ENSO Region 3.4 Index (RONI) likely to average -0.500 or below, it makes some sense to examine how CONUS  winters have fared in the past with winter values of -0.500 or below following widespread November warmth in the CONUS (1951-2010 baseline) since 1949-50.

The Composite Temperature Anomalies for North America (1991-2020 baseline, as the larger period was not available) were as follows:

November:

December-February:

The most recent C3S Multi-Ensemble Forecast for December 2024-2025:

It should be noted that even warm winters have often seen periods of cold. In cases, there have been some periods of severe cold.

Overall, the forecast winter anomalies are reasonably in line with those that have followed the kind of November that is forecast when the winter RONI averaged -0.500 or below.

 

 

Some similarities with respect to winter in these analog packages.

[40/70 Benchmark]

On 8/4/2024 at 5:29 PM, Typhoon Tip said:

I know what's your getting at and don't disagree at a granular level but there are ways in which -PNA/+NAO becomes a problem from the Great Lakes to the upper mid Atlantic and New E regions.   

The simplest way to describe that model is an episodic retrograde of a NW-SE Canadian deep layer conveyor, one that sets up around a big eastern Canadian SPV, which becomes a positive NAO derivative.   But importantly, that sets stage with presage cold loading, prior to RNA sending impulses E ... Storms are flat wave over-runners.  

+EPO ... yeah, that's a tougher sell.

Kind of like Dec 2007 and 2008...

[Typhoon Tip]

I wonder if Fuji snow is correlating with the wpac warm anomaly 

“Japan’s iconic Mount Fuji has yet to see snow this season, breaking a 130-year record” -cnn

[Maestrobjwa]

1 minute ago, Typhoon Tip said:

I wonder if Fuji snow is correlating with the wpac warm anomaly 

“Japan’s iconic Mount Fuji has yet to see snow this season, breaking a 130-year record” -cnn

Hasn't there been a warm anomaly there the last few winters? Seems like I've seen "wpac warm pool" a lot...

[Typhoon Tip]

5 minutes ago, Maestrobjwa said:

Hasn't there been a warm anomaly there the last few winters? Seems like I've seen "wpac warm pool" a lot...

yeah .. kinda why i was careful to use ‘correlating’   as in ongoing. implicitly, maybe since the warm anomaly showed up there’s also a surrounding atmospheric echo 

[snowman19]

@GaWx 

Just looking at the anomalies, the QBO is clearly still strengthening. Last month’s number was +12 and I believe the strongest westerly/positive QBO on record at 30mb was over +15. Wondering if we may rival or top that?