Winter 2024-2025 DISC

[Typhoon Tip]

That looks like the new climate footprint:     speed  

..which is a crapse shoot that actually tends to roll pieces of shit more than not

[Torch Tiger]

Dec. 03 wasn't amazing but the  anomaly was a very nice snowstorm, underrated one

[Torch Tiger]

that and '05 were my favorite Decembers, both had absolute whoppers but otherwise fairly tame

[40/70 Benchmark]

@weatherwizHave you noticed the site to use the 1951-2010 and other climo periods isn't working?

https://psl.noaa.gov/data/atmoswrit/map/index.html

[40/70 Benchmark]

Preliminary Assessment of the Extra Tropical Pacific for Winter 2024-2025

Mutually Reenforcing Cool ENSO & Pacific Cold Phase

ENSO & North Pacific are In Sync

One of the worst kept secrets in meteorology is the link between La Nina and the Pacific Decadal Oscillation, also referred to as the Pacific cold phase. There have been a total of 25 seasons that have met the official criteria for La Nina as designated by the Climate Prediction Center since 1950 and of those 23 La Nina events, 19 (75%) have co-occurred with the negative phase of the PDO. This year will not deviate from that trend.

The latest update from the International Research Institute (IRI) as of August 19th is still reflective of a  consensus for a weak La Niña NDJ peak per ONI, albeit the trend for an even weaker event has continued with a dynamical model average now at -.62 as opposed to -.7 in July.

 

 

 

In fact, the statistical guidance continues to suggest an ENSO neutral season with a forecast peak DJF peak of -.29  DJF. This is likely to a large degree a reflection of the of the fact that the current 0.2 MJJ ONI value would mark the second greatest of any developing La Nina on record. Only the 1983 La Nina was preceded by a greater MJJ ONI value of 0.7 and that particular La Nina event peaked at -1.0. While this renders a peak ONI value of anything lower than approximately -1.0 exceedingly unlikely given that such an occurrence following a MJJ ONI this high is unprecedented, a weak event is still very feasible. In fact, given the state of the Pacific basin, La Niña is still expected to materialize and couple with the atmosphere to a degree commensurate with a moderate event. This is evinced by a JJ MEI value that is already nearing moderate La Nina intensity at -.07 and is comparable to other moderate to strong La Nina events at this time of the year, such as 1999, 2011 and 2022. 

 

Note that the aforementioned seasons reached peak MEI values of -1.4, -1.3 and -1.7 respectively and are reasonable analogs with regard to the ultimate peak MEI value of this particular La Niña event. The peak Relative Ocean Nino Index (RONI) of the three seasons was comparable, having reached -1.67 in 1999, 1.05 in 2011 and -1.08 in 2022. Thus the 2008 analog represents a viable floor for the peak intensity of this particular La Niña episode in that it remained weak per ONI (-0.8) and near the threshold of weak-moderate in terms of its imprint on the hemisphere, as depicted by the -1.1 peak MEI value and -.90 RONI. The year 1996 and its -0.8 JJ MEI value from the above analog graphic is a sound illustration of the scenario favored by statistical guidance in that it remained a cool ENSO neutral season as opposed to a full-fledged La Niña event. However, this is not considered to be viable a possibility because it occurred during a time when the extra tropical Pacific was incongruent with the tropical Pacific and this is something that statistical guidance does not consider. The contrast is evident with even a cursory analysis of the subsurface plots.

Here is a plot from August 1996, which featured roughly -1C anomalies beneath the surface:

 

 

Versus anomalies of around -3C and -2C in August 2022 and 2008:

 

 

The current subsurface plot represents a compromise between the more robust 2022 La Niña and the more modest 2008 event:

 

 

 

 

 Having the ENSO regions in conflict with the north Pacific acts to impede the ability of ENSO to impress on the hemisphere, whereas this year the opposite is the case.

 

Extra Tropical Pacific will Enhance La Niña During 2024-2025

The behavior of the extra tropical pacific is usually relatively predictable during a well coupled cool ENSO event such as the present one and vice versa. Intense negative PDO episodes are usually accompanied by La Nina because the two share a symbiotic, mutually reenforcing and sustaining relationship. La Nina represents the cold phase of ENSO and cooler waters present during episodes of La Nina such as the one observed this season tend to be generally supportive of a negative phase of the Pacific Decadal Oscillation (PDO), which are marked by cooler waters along the west coast of the US.This is because la Nina favors Aleutian ridging, as identified in the la Nina composite below:

 

This season will be no different in that respect, as the PDO value for the month of July was -2.97 and it will once again average decidedly negative for the DM period. In fact, July 1894 (-2.98) is the only year in recorded history with a lower PDO value for the month of July. This immensely intense cold phase of the extra tropical Pacific will accentuate the relatively modest developing cold phase ENSO, as they are harmonious.This is very evident when considering the resultant 500mb pattern this past summer. The ONI has been reflective of ENSO neutral conditions, yet the pattern was reminiscent of a robust la Nina season with powerful ridges near Japan, south of the Aleutians and east of New England.

 

 

This is a very stable pattern that is likely to persist into and through much of the winter season given the ongoing near record intense cold phase of the extra tropical Pacific.

Potential Implications for the Extra Tropical Pacific in Winter 2024-2025

 

Below is a generic plot of the potent La Nina 500mb pattern that has been prevalent throughout this summer season extrapolated into the cold season.

 

There exists striking similarities to the aforementioned MEI analog composite.

This is further proof of the notion that the unremarkable MJJ ONI value belies the magnitude of the formidable cool ENSO regime that has and will continue to be well entrenched throughout the northern hemisphere as we progress through the fall and into boreal winter 2024-2025. The flat nature of the Aleutian ridge is very evident in this composite, which is unsurprising given that 3/4 four seasons in the composite are characterized as Modoki La Nina events (right). 

 

Some Tendency for Poleward Aleutian Ridging and High Latitude Blocking in Basin-Wide Composite (center)

 

The flatter ridge in these type of La Niña episodes have a reduced ability to deliver cold south and eastward, which results in a more composite across the southern and eastern US (left) relative to the more eastern composites.

 

 

East-Based, Basin-Wide, Modoki La Niña

However, the developing La Niña event is currently central-based, or basin-wide (middle) and is forecast to continue to remain as such.

 

 

 

 

Thus if is fair to conclude that while the overall DM period should undoubtedly be rather mild throughout at least the eastern third of the US and most especially the southeast, there may very well be significant period(s) of poleward Aleutian ridging and/or high latitude blocking. This is a concept that is also bolstered by a north Atlantic Accumulated Cyclone Energy that is currently well above average, which will be discussed at greater length this fall. It should be more of an either/or proposition in terms of amplified Aleutian ridging versus NAO blocking, as they are unlikely to occur simultaneously using recent history as a guide, which would render the northeast far more favorable to intervals of wintry weather versus the mid Atlantic and southeast. December 2008 is one such example, whereas poleward Aleutian ridging was present in the absence of AO/NAO style blocking.

 

 

 

 

 

December 2022 and March 2023 are illustrations of the other likely scenario in which a pronounced RNA pattern coincides with NAO blocking.

 

 

December 2022

 

 

 

March 2023

 

 

The type of patten being envisioned clearly fits one of three prominent types of extra-tropical Pacific regimes during cool ENSO winter seasons, which of course all exert themselves upon the weather pattern over N America in various ways.

 

RNA Style Winter Likely

The first pattern is associated with a distinct -EPO appeal in which high latitude ridging is concentrated in the general vicinity of Alaska and the Gulf of Alaska.

 

Here is the DM 500mb composite of these la Nina seasons:

 

 

Note that the giant EPO style ridging delivers cold...this composite contains the 2008-2009 analog and
31% of these seasons averaged a negative NAO for the DM period, which is a bit less than the next dataset due to the fact that lower heights are displaced to the east due to the large EPO ridge in the vicinity of Alaska.

DM temp anomaly composite:

 

 

Said EPO block also inhibits Pacific moisture inflow in the absence of a split flow, which limits precipitation across most of the nation
DM Precip anomaly composite:

 

 

The most likely extra tropical Pacific pattern for winter 2024-2025, as alluded to, will feature a -PNA as the most prominent characteristic.:

40% of these seasons averaged a DM -NAO, which is the most of the 3 datasets, due to the fact that lower heights to the north, which is typical of la Nina, are displaced to the west and away from the Davis Strait and Greenland.

DM H5:

 

 

This pattern also allows for the delivery of cold, albeit spilling west first, before bleeding east-southeastward...note 1973 and 2022 are each members of this composite, which lends credence to the idea of perhaps one winter month  averaging a - NAO in the mean or at least an extensive episode(s) of blocking. 
DM Temp anomaly:

 

 

 

This is a pattern that allows for a great influx of Pacific moisture with a slightly less prominent EPO ridging a bit further off of the west coast.
DM Precip anomaly:

 

 

 

 

 

This solution offers the greatest blend of cold and snow for the eastern US on average due to blend of ample cold and available moisture, however, the final composite, which is the mildest for the east coast, is also well represented.

The +EPO composite, which contains the MEI analog seasons of 1999 and 2011, features a more defined Pacific jet and thus a milder overall appeal. The presence of two of the analogs form the MEI data set is consistent with the notion of an overall mild DM period in the mean:

 

Only 28% of winter seasons averaged a -NAO for the DM period, which coupled with lower heights in the vicinity of Alaska, spells a very mild winter for the east in the DM aggregate mean.

DM H5:

 

 

 

DM Temp anomaly:

 

 

 

DM Precip Anomaly:

 

 

In Summary, the general implication of each of the data sets for the east coast winter season are as follows:

1) -EPO composite=cold and dry

2) -PNA composite=cold and wet (snowy)

3) Mild with moderate moisture influx biased north.

 

Here is a composite of all RNA composite members that are classified as basin-wide La Niña events given that this is the expectation for the coming season.

 

The general theme of deep RNA with occasional bouts of poleward Aleutian ridging and high latitude blocking continues.

 

Early Conclusions to be Drawn

The ongoing near record Pacific cold phase will continue to enhance the seemingly modest La Niña event per ONI, which will result in a very potent cool ENSO Walker cell throughout the coming winter. The fact that La Niña is expected to be central-based, as opposed to Modoki in conjunction with a prevalent  RNA pattern makes episode(s) of NAO blocking and poleward Aleutian ridging fairly likely. The latter is also supported by a very active north Atlantic Accumulated Cyclone Energy to date. However, the ability for cold air to reach the east coast will be limited and the milder periods will be far more frequent and intense than the wintry periods. 

 

Potential Analogs: 

Pacific Decadal Oscillation (PDO) Analogs: 1955, 1964, 1973, *1975, 1998, *1999, 2011, 2021, *2022 PDO Analogs

Pacific-North American  pattern (PNA) Analogs: 1964, 1973, 1998, *2007, *2022 

East Pacific Oscillation (EPO) Analogs: 1974, 1995, *2016 

West Pacific Oscillation (WPO) Analogs: 1954, 1973, 1988, *1999

Denotes strongest extra tropical pacific analog

Denotes strong extra tropical Pacific analog

* Denotes years that are also polar analogs

 

Preliminary Extra Tropical Pacific Analog Composite

Although there is a rather flat Aleutian ridge in the DM mean composite, it is expected that there will be intervals of such occurences that will coincide with episdes of +NAO and arctic intrusions focused over the west and midwest. The key for the mid Atlantic or the southeast to be more involved in said cold delivery will be to time an Aleutian ridge flex with a period of -NAO, which should be a fleeting occurence if at all. The season should average decidedly -PNA in the mean, however, some more extensive intervals of +PNA are possible mid season given what has been ascertained about the polar domain wth respect to NAO blocking being favored late in the season.

 

More updates to come-

[RUNNAWAYICEBERG]

Same “winter”…different year. 

[Snowcrazed71]

On 8/23/2024 at 6:59 PM, RUNNAWAYICEBERG said:

Same “winter”…different year. 

I've learned to not expect much, but also expect to expect surprises.

[weathafella]

It may be too early but a wooly bear caterpillar seen by my wife had an extremely narrow orange band indicative of a severe winter.  Not a prediction-just a folklore observation.

[mreaves]

42 minutes ago, weathafella said:

It may be too early but a wooly bear caterpillar seen by my wife had an extremely narrow orange band indicative of a severe winter.  Not a prediction-just a folklore observation.

I saw one that was all yellow, no brown or orange 

[40/70 Benchmark]

Cosgrove has started touting 2007-2008.

[CoastalWx]

1 minute ago, 40/70 Benchmark said:

Cosgrove has started touting 2007-2008.

Deal with it?

[40/70 Benchmark]

Just now, CoastalWx said:

Deal with it?

I would love to deal with that.

[CoastalWx]

2 minutes ago, 40/70 Benchmark said:

I would love to deal with that.

Snow season has begun in the Sierra already. Please no more Baja troughs.

[40/70 Benchmark]

3 minutes ago, CoastalWx said:

Snow season has begun in the Sierra already. Please no more Baja troughs.

I saw that....nice.

[40/70 Benchmark]

Gotta be honest....I like this.

[40/70 Benchmark]

TBH, I think that CANSIPS weenie image would get the gradient a bit further south than 2007...

[40/70 Benchmark]

The only ugly month I see on the CANSIPS is January....reloads for Feb and March after a nice December. But even January doesn't lose the Poleward SAleutian ridging, so while shitty in the mean, I bet that is still a nice week mixed in there.

[40/70 Benchmark]

Man, this would feel like 1976-1977 after the past 10 years.

[tunafish]

Love hearing the 2007-2008 comparison.  

Just need to hold the look for another 2,400 hours.

[40/70 Benchmark]

23 minutes ago, tunafish said:

Love hearing the 2007-2008 comparison.  

Just need to hold the look for another 2,400 hours.

You probably aren't getting 140" again, either way lol

[512high]

11 hours ago, 40/70 Benchmark said:

You probably aren't getting 140" again, either way lol

TRUE!

 

But please better then my 2023/2024 31.5" total, I want to get excited, but don't want the rug pulled beneath my feet just yet !

[40/70 Benchmark]

11 minutes ago, raindancewx said:

August looks like the blend of the five years for most of the US, minus the unusual shot of cold air into the mountains of CA recently. This is fairly similar to what I get whenever I test features that are consistently showing up. Cold Plains, average / warm elsewhere. Actually a pretty cold December nationally.

 

13 hours ago, 40/70 Benchmark said:

Man, this would feel like 1976-1977 after the past 10 years.

 

[ORH_wxman]

Gonna need that Aleutian ridge to get poleward....if it can, then we get that nice -WPO to a neutral or negative EPO combo....and that will help give the arctic shots some bite to them so the airmasses aren't as stale. In recent winters, aside from the annoying deep western troughs, we've had a lot of +WPO which kind of gives us fake arctic airmasses even when the EPO goes a bit negative or the PNA goes positive. Obviously last year was an El Nino, but the La Nina of 2022-23 had this pattern....despite a -EPO and strong arctic ocean blocking, we had deep troughing over Kamchatka and far eastern Siberia which you don't want to see. You might be able to get away with that if you had a decent PNA, but once you add in the deep west coast trough, it was game over.

 

I know @Typhoon Tip and I have had discussions about the stronger WPO/Bering sea ridges being a good cold signal (and the opposite being a very strong warm signal). I've often talked to @CoastalWxabout the Bering Sea death vortex too....low heights there really suck for us.

 

In those colder La Nina years like '08-'09, '10-'11 and to a lesser extent '07-'08, we had the -WPO present with the big poleward Aleutian ridges....'07-'08 was kind of a hybrid, the meat of the Aleutian ridge was south but there were vestiges north of Bering and into the arctic ocean almost acting a block (esp in Dec 2007).

[40/70 Benchmark]

I don't think it's going to be a ++WPO like last year...

[40/70 Benchmark]

19 minutes ago, 40/70 Benchmark said:

John, I wonder if that excess of heat due to the current network of adjoining bathtubs across the globe could also help to beef up QPF this cold season, as well....even if progressive due to the velocity in the flow, some of these waves that amplify may be able to tap into that. I mean look at the Gulf......interesting to see how much of that is compromised by the balance of tropical activity this fall.

 

5 minutes ago, Typhoon Tip said:

oh shit yes.  of course.  

not intending condescension there ( ha)  

no but just as a base physical consequence to more warm air, it evaporates more water. that means the ambient atmosphere holds more water mass - such that all events in that same ambient medium will avail.  that very basic concept is why rain rates have been increasing around the world in close correlation with cc ...etc.  no question remains re that connection.

based upon that facet, increasing ( non dispersive ) ohc, and then inducing a mechanism to release it ( ensuing winter) - that's sort of what i was 'hinting' at with that 'restoring going the other way' thing a while ago.  etc

 

One thing I am certain of is that Canada will be colder this year than it has been the past few years, which means that even assuming another amplifying hydro-bomb blasts inland due to a western displaced baro-zone...there will be a hellacious front-ender on the coast as an appetizer. This is something we have been deprived of lately due to prohibitive warmth and bad timing.

[weatherwiz]

I don't think I am going to get to a winter outlook this year (never even got to a review of mine from last year lol). Anyways, I have been going about composites and ENSO breakdowns in a totally different manner. 

I was doing something with La Nina...and since I go back to 1900 and the climate division maps only allow up to 30 inputs, obviously I can't input every event. So I just did one set from 1900-1950 and the other from 1951-present. 

But its all based off of the climatological period. For instance, if you change the climo period for the second map...

I don't know what the point of this post was but was just doing something and the result made me go urghhh

[40/70 Benchmark]

On 8/28/2024 at 6:05 PM, ORH_wxman said:

Gonna need that Aleutian ridge to get poleward....if it can, then we get that nice -WPO to a neutral or negative EPO combo....and that will help give the arctic shots some bite to them so the airmasses aren't as stale. In recent winters, aside from the annoying deep western troughs, we've had a lot of +WPO which kind of gives us fake arctic airmasses even when the EPO goes a bit negative or the PNA goes positive. Obviously last year was an El Nino, but the La Nina of 2022-23 had this pattern....despite a -EPO and strong arctic ocean blocking, we had deep troughing over Kamchatka and far eastern Siberia which you don't want to see. You might be able to get away with that if you had a decent PNA, but once you add in the deep west coast trough, it was game over.

 

I know @Typhoon Tip and I have had discussions about the stronger WPO/Bering sea ridges being a good cold signal (and the opposite being a very strong warm signal). I've often talked to @CoastalWxabout the Bering Sea death vortex too....low heights there really suck for us.

 

In those colder La Nina years like '08-'09, '10-'11 and to a lesser extent '07-'08, we had the -WPO present with the big poleward Aleutian ridges....'07-'08 was kind of a hybrid, the meat of the Aleutian ridge was south but there were vestiges north of Bering and into the arctic ocean almost acting a block (esp in Dec 2007).

I think we are going to have something similar to this second group with respect to the N PAC.

[40/70 Benchmark]

Looks like December has the most favorable NAO on the EURO...slightly negative..January around neutral and then a toaster bath for Feb. PNA is also servicable in December before tanking.

 

[CoastalWx]

Anybody have a link to the EC seasonal forecasts? Mainly 500mb heights. It's through ECMWF.int but I don't have an hour to parse through that site.

[SnowGoose69]

1 hour ago, 40/70 Benchmark said:

Looks like December has the most favorable NAO on the EURO...slightly negative..January around neutral and then a toaster bath for Feb. PNA is also servicable in December before tanking.

 

Saw JB's Euro seasonal post and it makes no sense IMO.  I don't see why you'd basically have a nationwide torch in a weak Nina following a moderate Nino, there really is no track record of that ever happening.  If want to go purely off the ENSO you'd say 54-55 83-84 92-93 16-17 seem to be the closest matches of weak Nina following Mod or greater Nino.  None of those were nationwide torches at all.  I guess the problem is 2 were in a +PDO ERA.  16-17 is the only thing remotely close to that Euro seasonal US temp anomaly forecast and even the west was way colder.