40/70 Benchmark

I'm not sure why La Nina has to automatically mean relentless blowtorch from latter January through March...I don't think that will be the case.

I said the month would start cold.

Ended up with 1/2".

.03" S- 30

@Allsnowis a quality, objective poster. Must read.

Much Milder Balance of December Before Potential Holiday Week Changes Winter 2024-2025 Thoughts on Track Warmer December Transition Marked by Light Weekend Snows It was conveyed in last month's Winter Outlook that the cold start to the month of December would likely be on borrowed time. "The colder pattern looks to be fleeting, as the month of December should turn very mild in short order with the passage of the MJO in phase 4. The mild regime should remain in place until at the very least mid month". While this concept does indeed still look to be valid, it will be a round of light snowfall that will actually herald in this transition to the warmer regime, as an added twist of irony. Snow will be of the nuisance variety with the potential for an inch to two of snowfall in the Worcester hills, and up to perhaps as much as 3" in the Berkshires. Accumulations across the rest of the region should be relegated to an inch or less, and any snow will melt quickly, thereafter given the imminent pattern change. The aforementioned light snowfall is obviously inconsequential as it pertains to longer term ramifications for the month of December and onward towards the New Year. Balance of December Update Although variability was anticipated to be the theme of December, the magnitude and length of the warmer interlude that will extend well beyond mid month was expected to outweigh the cold start, and that is precisely how the month appears to be evolving. Notice that December 1999, one of the milder members of the December forecast composite, is being reflected in the CPC forecast centered on December 14. This warmer shift, as earlier implied, is triggered at least in part by the translation of the MJO wave through phase 5 in the Maritime continent. These changes are reflected most prominently by the erosion of the North Pacific block, as evidenced by the precipitous and sudden rise in both the West Pacific and East Pacific Oscillation. It is also evinced by the recovery of the polar domain. As one would expect, this much mass flux will be accompanied by a significant storm system on Tuesday, however, it will be essentially all rainfall throughout southern New England with some snowfall possible across the ski resorts of northern New England. Thereafter, warmth should continue to prevail across much of the country through the holiday week, as the MJO eventually enters phase 6. What happens towards the end of the holiday week and in the vicinity of the New Year is what is somewhat more nebulous. New Pattern for New Year Possible The GFS suite continues to indicate that the MJO will advance into phase 7 prior to the New Year. However, other guidance hints of the possible decay of the MJO wave prior to reaching phase 7. This is crucial since phase 7 of the MJO in early January would imply a major transition to a colder pattern, marked by the redevelopment of poleward north Pacific ridging. Most long range guidance supports the aforementioned redevelopment of poleward ridging over the North Pacific and adjacent west coast, in conjunction with a strong polar vortex that is tilted favorably as to allow for the delivery of cold air over the northeastern US. This is a scenario that is very similar to the type of mismatch from the predominate MC forcing that took place in January 2022, which was cited in the Winter Outlook is a strong analog for January 2025. Note the similarity to the forecast progression of the MJO to its behavior from December 2021 into January 2022, implying a generally similar evolution, albeit potentially delayed and somewhat subdued. In conclusion, although the progression of the MJO wave into phase 7 for the onset of January may be slightly rushed on the GFS suite of guidance, it is unlikely to stagnate in the MC and should indeed reach the West Pacific and trigger a colder pattern beyond the new year.

https://easternmassweather.blogspot.com/2024/12/much-milder-balance-of-december-before.html

https://easternmassweather.blogspot.com/2024/12/much-milder-balance-of-december-before.html

Huge -WPO.

Maybe postpone the larger Funky's Deal for now and focus on a Clarke's gtg?

Henry's Weather will have to wait? Maybe, kinda? Can always change?? Keep asking questions until she's cute?

I can see it getting delayed some, but largely buy.

"As it approached midday, the snow deph reached the high end of thy stocking with drifts approaching mid scrotum"-

@GaWxJust for clarity as to where I stand on this, here is the appropriate section from my November release. The Polar Domain Primary Modern Polar Domain Analogs: 2022-2023, 2016-2017 Secondary Archaic Polar Domain Analogs: 2007-2008, 1999-2000, 1975-1976, 1970-1971 Influence of ENSO on the Extra Tropical Atmosphere It is evident in the graphic below that Modoki, or basin-wide La Nina events, such as this one is likely to be, often feature the seasonal nadir for the NAO near the bookends of the season in December and March. In contrast, east-based events are more likely to feature mid season NAO blocking and accompanying cold. The behavior of the NAO is the reason why December is the coldest month of the CP la Nina composite, as the NAO is only moderately positive in the composite, while it is highly positive in January and February. The NAO averages slightly negative in November and March. Contrary to the CP la Nina years, the month of December is the most mild month of the EP composite because the NAO is neutral-negative, and is very negative the rest of the winter before ascending slightly in March. Thus the orientation of La Nina can play a vital role in not only the aggregate NAO value of the winter season, but also the overall progression. This is due both the aforementioned modulation of the Hadley Cell via convective forcing patterns and the oceanic circulation patterns that feedback into the Atlantic via subtropical jet bridges to sustain said forcing patterns. Zhang et al 2014 verify through several atmospheric simulations that CP la Nina favors an extratropical response redolent of a positive NAO configuration across north America and the north Atlantic. And EP La Nina favors negative NAO during the winter season due to a diametrically opposing atmospheric and oceanic circulation pattern. It is suggested that the subtropical jet bridges the connection between ENSO and the NAO. Essentially, the circulation pattern of the CP la Nina strengthens the Pacific subtropical jet, which augments the Atlantic jet and creates an anticyclonic circulation. This circulation configures SSTs in such a manner as to reinforce positive NAO through a wind-evaporation-SST feedback. The EP event has a diametrically opposed circulation pattern that weakens said subtropical Pacific jet, which in turn diminishes the Atlantic jet and fosters the development of an cyclonic circulation that sustains negative NAO via said wind-evaporation-SST feedback. This likely played a role in why the more eastern biased, strong hybrid la Nina season of 1955-1956 featured both high latitude blocking and poleward Aleutian ridging, while other years within the dataset, such as 1999-2000 and 1975-1976 were so much milder with a notable dearth of blocking. In fact, Zhang even referred to basin-wide events as "hybrid" or "mixed" events, since they often display characteristics of both east-based and Modoki events. Due to the fact that this season is likely to feature a central-based, hybrid event of weak intensity with a moderate ocean-atmosphere interface, odds favor a +AO and NAO consistent with a fairly strong polar vortex in the mean. The months of December and March may be most prone to an episode(s) of -AO/NAO. However, variance in this data set is high, thus it is imperative to consider alternative outcomes. Obviously, weaker SST anomalies present within more marginal La Nina events have a reduced ability to couple with the atmosphere, thus other extra tropical factors play a more prominent role. This means that the correlation of the NAO to the structure of La Nina is reduced in weaker ENSO events. This is also why some weaker CP events, such as the 2008-2009 and 2000-2001 events, did not feature a very prominent positive NAO signal and were thus more prone to episodes of blocking. Likewise, the minor EP event of 2005-2006 was relatively mild, despite some blocking episodes. Note that the extremely positive NAO value reflected during the moderate Modoki season of 2011-2012, which in conjunction with a very consolidated polar vortex and cold phase of the Pacific undoubtedly played a role in the very mild character of that winter. Clearly there are other factors at play with respect to the modulation of the polar domain that are independent of ENSO and are very worthy of consideration in their own right. One such consideration. Quasi Biennial Oscillation (QBO). Role of the Tropical Stratosphere on the Polar Domain The system of cycles and oscillations that occur throughout the tropical atmosphere extends high above the waters of the ENSO region. And all of it plays an integral role in modulating the atmosphere across the entire span of the globe. The Quasi Biennial Oscillation (QBO) is an atmospheric phenomenon marked by a circuit of zonal winds measured at 30mb and 50mb, which run in dual bands throughout the equatorial stratosphere. Each band oscillates from an east to west direction with height, while propagating downwards until its dissipation at the top of the tropical tropopause. Currently the QBO is ascending and is nearing its westerly peak at both the 30MB and 50MB levels. This past summer, Eastern Mass Weather identified the year 2016, 2020 and 2022 as three primary QBO analogs when considering both the 50MB and 30MB levels and this preliminary analysis remains valid. October 2024 50MB QBO: 9.54 & rising 2022: 5.13 & rising 2020: 6.94 & rising 2016: 4.53 & rising October 2024 30MB QBO: 11.64 & rising 2020: 10.80 & rising 2016: 12.83 & rising 2022: 10.93 & rising Given that the QBO will be westerly both the 30 and 50mb levels during the 2024-2025 winter season, the state of the tropical stratosphere dictates that blocking is more likely to occur earlier in the season before dissipating by mid season, which is congruent with history concerning hybrid, or "mixed-type" La Niña seasons. This is evidenced by the December-January 500mb composite for all cool ENSO seasons with a westerly (positive) QBO, similar to this season. Note the slight blocking signature in the vicinity of Greenland, as well as the pronounced poleward ridging near Alaska. This aligns with earlier analysis of the West Pacific. W QBO/Cool ENSO DJ H5 Thereafter, any semblance of blocking vanishes later in the season, like the other composites, which supports the notion of a Pacific driven mid-season MC mismatch period akin to January 2022. W QBO/Cool ENSO FM H5 This is why most of the eastern US warms appreciably during the second half of winter in the general W QBO/cool ENSO dataset. W QBO/Cool ENSO FM Temp Anomalies This same trend for early season blocking is noted with respect to the primary QBO analog composite of 2016, 2020 and 2022. 2016-2017, 2020-2021, 2022-2023 DJ H5 Interestingly enough, in the analog composite, while certainly decreased in the aggregate relative to the December-January period, blocking appears to reassert itself late. However, it seems to be largely negated by the very deep Western CONUS troughing that is related to the Western Pacific Warm pool, which doomed last season's outlook. This was alluded to in the extra tropical Pacific analysis, and was wonderfully illustrated during the 2022-2023 season. This more recent tendency for southeast ridging to adjoin NAO blocking is predominately why the aged polar analogs are considered secondary to the more modern day analogs. 2016-2017, 2020-2021, 2022-2023 FM H5 The subtle trend for the polar vortex to become at least somewhat disturbed once again later in the season is confirmed through a consideration of solar data in conjunction with the aforementioned QBO analysis. Influences of the Solar Cycle on the Polar Fields The impact of the solar cycle and the stratosphere on the earth's atmosphere continues to be a work in progress and much like seasonal forecasting in general, it is still very much a frontier science. Traditionally, research correlated high levels of solar activity near solar max, such as will be the case for winter 2024-2025, to a stronger polar vortex and thus milder winters for much of North America and Europe. There are a multitude of theories as to why this is the case, however, most of these theories cite drivers such as UV radiation and total solar radiation (TSI), which closely mirror sunspot activity, as responsible for increasing ozone levels and temperature in the equatorial stratosphere. This warmer tropical stratosphere then results in a stronger latitudinal gradient and a cooler polar stratosphere (stronger polar vortex) via a modulated Brewer-Dobson cycle. The issue with these theories is that the peak levels of the aforementioned potential drivers of the solar-stratosphere connection coincide with solar max. And most recent research cites stronger drivers that do not coincide with solar max, such as geomagnetic energy and solar winds, which peak during solar flux or, about one year after solar max in terms of peak UV and TSI . (Maliniemi et al, 2014). Malimiemi et al theorize that geomagnetic energy makes its way into the polar region via the process of energetic particle precipitation, which then produces nitrogen oxides in the the upper atmosphere that have a protracted period of time to descend downward and increase ozone during the polar winter in the absence of any sunlight, which cools the stratosphere and strengthens the PV. This more closely corroborates both with other recent research, which cites drivers that do not peak at solar max as defined by UV and TSI (geomagnetic energy peaks approximately one year after solar max), as well as the research of Malimiemi et al (2014), which found that the declining phase of the sunspot cycle remarkably consistently produces the spacial pattern of surface temperature anomalies related to the positive NAO during the last 13 solar cycles" (Maliniemi et al, 2014). This makes sense since the geomagnetic energy peak that Maliniemi et al cite as the main driver behind the connection between the solar cycle and polar domain lags solar max as defined by UV, TSI and sunspots by approximately one year, which is during the declining phase that so strongly correlates with the +NAO response in their research. This implies that winter 2025-2026 and 2026-2027 will be more favorable for a stronger polar vortex than the impending winter season, which is also consistent with other recent studies of seal level pressure patterns that revealed a +NAO pattern lagging solar max by approximately 2-4 years. The work of Maliniemi et al also showed that this relationship is not at all dependent on overall sunspot activity due to intra-cycle variability. Mean winter NAO index values for the four cycle phases, averaged over cycles 11 to 23. The red line represents the overall mean value of wintertime NAO (0.05). Bars represent the 95% confidence intervals. Perhaps more germane within the context of the coming winter is that the study found that both the solar max and the ascending portion of the solar cycle are weakly correlated to a colder pattern redolent of the -NAO, although this is more dependent on intra-cycle variability of activity. There is a modest negative correlation with solar minimum, which was the case in the QBO analog year of 2020-2021. These relationships between solar behavior and the NAO are evident in the graph above, with reds, denoting +NAO, very evident in the declining phase of the last several solar cycles. And Blue, indicative of -NAO, prevalent in the ascending portion of the cycles. What can also be deduced from the graphic above is that while solar max seasons are not as favorable as the ascending phase of the cycle for incidences of high latitude blocking, nor are they as hostile as the descending seasons. Thus winter seasons such as 2024-2025, which are near solar max, are not entirely devoid of blocking, however, nor is this season as prone to an intense round of late season blocking the magnitude of March 2023 given that the solar cycle was still ascending at that point. Be that as it may, solar max seasons are not entirely hostile to incidences of a disturbed polar vortex and this is evident when considering the best solar analogs of 1970 and 1999. There was a split of the polar vortex on January 17, 1971, a displacement on March 20, 1971 and a displacement on March 20, 2000. While there was an easterly QBO evident during the 1970-1971 winter, the polar vortex displacement that took place in March of 2000 occurred during a westerly QBO, as will be the case this season. Thus the latter displacement seems worthy of more consideration for the coming season. When considering the three primary QBO analogs of 2016, 2020 and 2022 within a solar context, although none took place during solar max, 2022 was the closest, followed by 2016 and 2020, the latter of which is a poor solar match having taken place near solar minimum. Given that the QBO analog of 2020-2021 took place near solar minimum, the early January 2021 SSW is of least relevance as a viable analog occurrence this season. However, the February 2023 SSW, which is a better solar analog, lends more support to a later season potential polar vortex disruption along the lines of March 1971 and 2000. This notion is supported by research on high solar, westerly QBO seasons, which lends credence to the late winter/early spring displacement scenario. The postulation of a modestly disturbed polar vortex during the month of December, followed by a recovery during the middle portion of the winter, prior to a more substantial displacement of the polar vortex during either February or March is well supported by research on moderate, basin-wide La Niña events taking place near a solar maximum with a westerly QBO. Such an evolution would also be consistent with the 2022 type of preferred mismatch during January 2025, which would be Pacific driven (-WPO/-EPO and/or +PNA and accompanied by a fairly strong polar vortex (+AO/NAO). This preliminary conclusion is based upon a constellation of historic data can be checked against observed, concurrent data in real time. Observations During 2024 That Inform Behavior of the Polar Fields During Winter 2024-2025 The Role of Atlantic Accumulated Cyclone Energy The primary reason why the tropics are so crucial to what ultimately transpires here in the mid latitudes is because it is here that the earth's energy budget is set, and it is the subsequent redistribution of said energy from the tropics, throughout the mid latitudes and all the way to the poles that is the very essence of weather. All types of weather and everything involving the atmosphere, from storms to oscillations, and ocean currents play a role in the redistribution of said heat in an effort to achieve an illusory balance that will never be reached. Aside from ENSO, perhaps the most prolific re-distributors of this heat are topical cyclones. Given that heat transported poleward can also increase atmospheric heights, it stands to reason that the amount of energy transported poleward by tropical cyclones during the summer and into the fall can have some baring on what transpires at the higher latitudes during the ensuing cold season. A graphic configured by @RaindanceWX, who is a highly recommended follow: Note the tendency for the delivery of cold to the northern tier via a fairly cold source region in the absence of NAO blocking. This lends credence to the concept gleaned from the solar data that early NAO blocking may be more ephemeral in nature, with consolidation of the polar vortex thereafter across the mid Atlantic and southeast. Although the season is still in progress, the final Accumulated Cyclone Energy (ACE) value is already above average at 159.8 with more activity potentially on the horizon. The poleward redistribution of heat that this entails is more likely to foster the development of the higher latitude ridges that can contribute to deviation from the MC like regime, as was the case in January of 2022. While this certainly does not ensure ample AO/NAO blocking, it does provide more reason to doubt an excessively strong polar vortex in the DM seasonal mean, which is supported by additional events from around the globe during 2024. In fact, most skilled seasonal forecasters are those that devise methods that incorporate both an exhaustive analysis of what has happened throughout history under fairly similar conditions with what is actually happening in reality, and how the hemisphere evolved following similar occurrences in the past. Forecast confidence can be increased when the results are congruent. Major Disruption of Antarctic Polar Vortex Lends Support to Polar Analog This past summer featured a major SSW occurring over Antarctica, as evidenced by the extremely negative Antarctic Oscillation (AAO) that was observed, which is the southern hemispheric cousin of the Arctic Oscillation here in the northern hemisphere. Looking back at similarly extreme -AOO episodes during fairly comparable La Niña events, the year 2007 stands out as a stronger, basin-wide La Niña that featured a -2.63 AOO value during the month of July. The behavior of the polar domain during the ensuing winter of 2007-2008 is interesting in that it behaved fairly similarly to the progression of the solar/stratosphere composite. While the season finished with a fairly robust polar vortex in the mean (+.79 DM AO/+.51 DM NAO), the month of December featured an elongated polar vortex that kept the northeast cooler, while deep western CONUS troughing kept a southeast ridge fixed in place. Deep western CONUS troughing became the predominate driver of the pattern mid season, as the PV lifted northward and heights rose through the eastern US, which is expected early and late in the season this year. The season drew to a close with a textbook high solar/westerly QBO SSW on February 22, 2008, which led to considerable warming throughout the polar stratosphere during the month of March, which is congruent with the theme of other polar analogs. It is noteworthy that the 2007-2008 season is both a poor solar and QBO analog, however, this does not entirely negate the value of what is a strong ENSO match working in conjunction with similar behavior of the southern hemisphere during the northern hemisphere summer to potentially yield a result similar to the solar max/W QBO dataset. Note the support for the +EPO/-WPO configuration that was strongly emphasized in the analysis of the extra tropical Pacific, however, for adjustments for the modern tendency of the southeast ridge to be more prevalent would need to made assumed. It is prudent to consider each individual season of this six year composite as an individual ensemble member with slightly perturbed initial conditions in one manner or another. The mean aggregate DM AO of the dataset is +.41 & DM NAO is +.54. This is remarkably consistent with the subsurface formula derived by @stormchaserchuck1 at Americanwx.com weather forum. The index is a measurement of May 1 - Sept 30 SSTs in the North Atlantic. It's correlated to following November-March NAO/AO (+6 month lag). The index is a composite of 2 areas in the North Atlantic (blue box - red box). Because the northern area has more volatility, the total dataset, SSTs and NAO were normalized by multiplying the total historical absolute number of both, and dividing it by each other. When blue box is cold SSTs, a negative NAO is implied for Winter. When red box in warm SSTs, a negative NAO Winter. For comparison, and red box is 65% value of blue box anomaly (so -1 blue +0.65 red is same thing). Visa versa. The index this year from May 1 - Sept 30 is +0.52, making it a 50% chance of having the DJFM NAO -0.04 to +1.04. This compared to the mean DM NAO value (.54) of the Eastern Mass Weather polar analog composite, which is also in alignment with the rather unremarkable signal from the both the Eurasian Snowcover Advance Index (SAI) and the Snowcover Extent Index (SCE) vourtesy of Dr. Judah Cohen. The Eastern Mass Weather 2024-2025 forecast for the AO is between .26 and .56 and the NAO between .38 to .68, with the most favorable period for a modestly disturbed polar vortex being in December (albeit largely negated by a MC driven Pacific), and the greatest likelihood for a major disruption in February or March.

I certainly woudn't be suprised if one took place, as you could probably gather from my write up...but I'm just saying its not as glaring a signal as 2022. I agree conditions aren't as hostile as some are implying.

Yes, I am saying ascending is better than solar max.

I hit 14 a few times, but I def radiate....

Yea, fair enough...social media oriented communicative patterns and decreasing reading comprehension aren't a great combination.

Not what I am saying...talking about max vs ascending...the hostility towards blocking due to solar wind dispersed electrogeomagnetic particles isn't much of a factor for a couple of years post max.

Yea...airmass is blase. Its just that we are so conditioned to warmth in December that its noteworthy.

I am quite confident that we well given my research using @bluewave's data regarding usage of the MJO behavior to diagnose periods of deviation from said MC forcing. This is especailly true since La Nina is finally getting the jolt that you and I have been calling for.

Actual SSW is somewhat dubious, but I don't expect an extremely +AO/NAO, either.

Its more the wind...which iroically enough is part of the reason it didn't actually get very cold.

Yea, that one was def. a brown shit-stain....like I said.

Yea, I'm not a fan of posting extreme images. I defintely would have had some qualifiers such as "while this of a scanrio is unlikely, its does lend support to the return of poleward ridging in the Pacific".