40/70 Benchmark

You could also just burn my last two outlooks.....given the length, they should keep you warm.

Love that, but I think we need to treat any long range cold with skepticism this day and age.

I wonder if the ACE may also tie into that October MJO amplitude, as liberty suggested. That composite looks pretty -WPO to me, but also mainly -QBO.

There are all of the "extremely active" (ACE) La Nina seasons since 1950...can see the bouts of poleward Aleutian ridging and -NAO that I alluded to in my write up:

BTW, its still very active per ACE...bit of a misconception in relation to that. 2024 Accumulated Cyclone Energy [ACE] Basin Current YTD Normal YTD % of Normal YTD Yearly Climo* 2023** Northern Hemisphere 136.2100 210 64% 575 648 Western N Pacific 50.625 114 44% 298 266 Eastern + Cent N Pac 26.9875 66 40% 132 165 North Atlantic 56.31 21 268% 122 146 North Indian 2.2875 7 32% 23 60 Southern Hemisphere 169.958 209 81% 205 244 Global 269.3030 382 70% 780 881 *Yearly climatology from historical 1991-2020 Tropical cyclone best track datasets

I think a big ACE value correlated to more poleward Aleutian ridging.

I think the only wild card for mid season is Bluewave's October MJO rule...if the MJO isn't amplifed in October, then we roast mid winter.

I think the early season will be more Pacfic driven..ie Aleutian ridging and -EPO/WPO, though the PV shouldn't be too stout....then mid season it goes very warm with less of an RNA before perhaps blocking/big RNA late season.

Shake it up

Colder relative to what many susepect.

I feel like there have been some low key hints that raindance is going to be a bit more aggressive for the east than some may suspect.

I feel like we could see a Michael redux this fall.

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-

Here is my early stab at the extra tropical Pacific....will be expanded upon in a more exhaustive segment this fall as part of the whole outlook. https://easternmassweather.blogspot.com/2024/08/preliminary-assessment-of-extra.html

@bluewave or anyone....Do you have the piece on the new Pacific pattern designations...ie. Alaskan trough, etc...?

I have really been warming up to the 1973-1974 analog..especially with respect to the Pacific.

I thought last summer was rather cool around here....

This is an absolutely lethal match to the MEI analogs....uncoincidentally.

I didn't really look at all of that back in 2013....I would just watch the models for snow in season and measure when it fell.

Full disclosure.....gonna use this in my current blog piece. Thanks.

Not sure how early it was "obvious", but admittedly I only knew a fraction of the little that I know now, so....that was my first outlook attempt.

Any time you feel highly confident in racing to your laptop to convey seasonal throughts...pause, reflect and reconsider.

Yea, this is why I didn't entirely agree with notion that ENSO will not be a large factor this year....the entire hemisphere has been in a cold ENSO state for several years, which will allow it to be more influencial than implied by the ONI. We saw this in 2022. I feel like the point regarding less emphasis on ENSO was very valid last season with respect to the El Nino and certainly ENSO in general is not as prevalent a driver as it was 10-20 years ago.

Agree on 2017-2018, but 2014 was a bit more tricky in that it was entirely Pacific driven.....and I am willing to bet that most folks who went big expected a lot of NAO blocking, which includes myself.

Obviously this will be easier to pull off with latitude. If you didn't go well in 2007 or 2008, then you can probably pack it in save for maybe a fluke event.