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February 2025 Disco/Obs Thread

Torch Tiger

By Torch Tiger,
in New England

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ORH_wxman

ORH_wxman

Posted
Posted
2 minutes ago, wx2fish said:

GFS is definitely more interesting next week. Warmer SWFE type look with a weak secondary. Would atleast keep the interior colder 

Phase with TPV in west-central Canada was a bit weaker/delayed this run (but not denied)....if we can weaken that further, then we'll keep better high pressure to our north...or at least have it take longer to slide east. Canadian shows this too....except even better.

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Typhoon Tip

Typhoon Tip

Posted
Posted
2 minutes ago, Sey-Mour Snow said:

CMC has a high impact winter storm verbatim wednesday several inches of snow and sleet to significant icing.. Interesting, not much support currently for that much precip.. 

technically still a needle thread pattern foot. 

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40/70 Benchmark

40/70 Benchmark

Posted
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Just now, Typhoon Tip said:

The 6th and the 9th look almost identical in the general 500 mb cinema of the 12z GFS run... 

Not sure how that will manifest and/or be different at the surface, but just looking at that one metric -

Family flies out of Logan on the 7th...lets keep that one clear, eh....

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Damage In Tolland

Damage In Tolland

Posted
Posted
2 minutes ago, 40/70 Benchmark said:

Honestly, though, Scott....the family keeping me busy has probably saved my MH because it allowed me to distance myself from all of this crap....they are taking off again in a week, so it would be nice to have an exciting late season stretch for reengagement

Is this the annual 3 month trip to Zimbabwe?

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40/70 Benchmark

40/70 Benchmark

Posted
Posted
2 hours ago, snowman19 said:

@CoastalWx You must be enjoying all of the out of control SSWE voodoo hype all over twitter and facebook right now. Spreading like wildfire. An exact replica/redux of February, 2018 is locked in and on the way lol

Uh oh...here comes the preemptive snowman defensive posturing when it appears possible that some of the weenies could feasibly be catching a break.  If "voo doo" is slang for widely varied outcomes that are difficult to predict, then sure...I guess you could call them that. But like I have been saying since August, we are at risk for  a warming event late this season.

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CoastalWx

CoastalWx

Posted
Posted
7 minutes ago, 40/70 Benchmark said:

Honestly, though, Scott....the family keeping me busy has probably saved my MH because it allowed me to distance myself from all of this crap....they are taking off again in a week, so it would be nice to have an exciting late season stretch for reengagement

I've been busy too. But I could use some winter. 

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ORH_wxman

ORH_wxman

Posted
Posted
4 minutes ago, 40/70 Benchmark said:

Uh oh...here comes the preemptive snowman defensive posturing when it appears possible that some of the weenies could feasibly catching break.  If "voo doo" is slang for widely varied outcomes that are difficult to predict, then sure...I guess you could call them that. But like I have been saying since August, we are at risk for  a warming event late this season.

There's pretty decent support for the 50mb split on guidance right now. We'll see how it looks in another few days...but pretty silly to just dismiss the idea.

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CoastalWx

CoastalWx

Posted
Posted
9 minutes ago, 40/70 Benchmark said:

Uh oh...here comes the preemptive snowman defensive posturing when it appears possible that some of the weenies could feasibly catching break.  If "voo doo" is slang for widely varied outcomes that are difficult to predict, then sure...I guess you could call them that. But like I have been saying since August, we are at risk for  a warming event late this season.

I will say that wasn't voodoo. Maybe he means all the posts that imply confidently how the pattern will change, be epic etc. We all know those posts can go overboard.

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brooklynwx99

brooklynwx99

Posted
Posted
6 minutes ago, CoastalWx said:

I will say that wasn't voodoo. Maybe he means all the posts that imply confidently how the pattern will change, be epic etc. We all know those posts can go overboard.

i don’t think anybody has said that on Twitter or wherever else. all i’ve seen is that it increases the -NAO risk, which is true when you have a -PNA and Scandi ridging 

MJO is also passing through the MC, which also often happens with -NAO episodes 

IMG_1492.thumb.png.d386e06fb77477e2dfde9bb605d44ee0.png

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LibertyBell

LibertyBell

Posted
Posted
18 minutes ago, 40/70 Benchmark said:

Uh oh...here comes the preemptive snowman defensive posturing when it appears possible that some of the weenies could feasibly catching break.  If "voo doo" is slang for widely varied outcomes that are difficult to predict, then sure...I guess you could call them that. But like I have been saying since August, we are at risk for  a warming event late this season.

because of high solar and +QBO?

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CoastalWx

CoastalWx

Posted
Posted
2 minutes ago, brooklynwx99 said:

i don’t think anybody has said that on Twitter or wherever else. all i’ve seen is that it increases the -NAO risk, which is true when you have a -PNA and Scandi ridging 

MJO is also passing through the MC, which also often happens with -NAO episodes 

IMG_1492.thumb.png.d386e06fb77477e2dfde9bb605d44ee0.png

Yeah a little NAO help there would press the PV south. 

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Typhoon Tip

Typhoon Tip

Posted
Posted

I suppose it doesn't matter how exactly and/or what precedes the splitting of the PV into SPV layout ... If it splits, it splits.  

The key is whether it involves/couples to the troposphere - the mechanism in which that happens is through stabilizing the UVM toward DVM, and that then physically drafts warm air from surrounding the PV domain into the elevated domain --> warm nodes at high altitudes and blocking results...  That's the very skinny on how that works. 

The thermal field projections off the GFS are not clear as to whether there is an actual thermal plume in the process of moving down in the column. There are warm layers, however - which could be the same thing just difficult to distinguish in the coarseness of the sigmas offered.  Unless someone has a different more liquid source:   https://www.cpc.ncep.noaa.gov/products/stratosphere/strat_a_f/

In any case, a split that couples would highly likely register as a -AO ...  I would suggest if that happens sooner rather than 3 weeks from now, that it is not an SSW but just a planetary reshuffling leading to a similar result.  

A -AO from either source bears no difference to middle latitudes after the fact.  It's a cold index mode and it comes down to where the hemispheric conveyors decide to layout for determining the mid latitude temperature distribution.

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40/70 Benchmark

40/70 Benchmark

Posted
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13 minutes ago, LibertyBell said:

because of high solar and +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%20QBO%20DJ.png
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%20QBO%20JF.png
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.
 
FM%20TEMPS.png
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.
 
DJ.png
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.
 
FM.png
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.
 
GEOMAG.png
 
 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. 
 
Solar:NAO.png
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.
 
color%20nao.png
 
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.
 
TOP%20SOLAR%20ANALOGS.png
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.
 
this.png
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.
 
 
outher%20qbo%20west.png
 
Warming%20Analogs.png
 
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:
 
 
AVvXsEiRrqm-d-7Fo4UpZwpac2oE29V5-psLjjH4

 

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.
 
AAO.png
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. 
 
DEC.png
 
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.
 
JF.png
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. 
 
March.png
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.
 
 
MESS%20UP.jpg
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. 
1b.gif
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.
chuck.png
 
 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.
AVvXsEgkTBaRBz_o4fbKw3i0CBNbm5aDTlZKmToA
 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.

 

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