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Let's Talk About SSW's as We Watch One Unfold


Eduardo

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So it seems like there is a solidifying consensus among reliable pro's here and elsewhere that a major SSW event will take place over the next week.  In fact, some have stated that this has the potential to be a historic event.  Many of us have seen the term "SSW" thrown around before and perhaps understand it to varying degrees.  To some of us, the subject is an arcane one.

To me, this seems like an especially teachable moment for those of us who are interested in expanding our knowledge of the subject, so I figured I would open a thread for experts to share their knowledge in hobbyist's terms (as best they can) and perhaps weigh in on what we are seeing day-to-day as the impending event progresses. 

 

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It is really going to be interesting to see what is going to happen with this SSW event. Talk has been really starting to pick up with this and there is also alot of differences in opinions by meteorologists and hobbyists on how this will effect the pattern and sensible weather especially in the eastern half of the country. 

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12 hours ago, SnowGoose69 said:

They rarely have no impact across the US unless we are in an absolute ratter of a pattern.  The January 2012 event had no impact here because the dominant longwave pattern was just so atrocious and the vortex impacted Europe.  We can usually count on at least minimal positive impacts 

Having one so late in the season might mean it has more of an impact for inland areas in terms of snow though might delay spring for everyone.  Could have a March like we had last year?

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50 minutes ago, Snow88 said:

This is just wrong

How does a negative nao not produce ×

winter storms ?

Probably because the remaining pattern is bad.   It’s too early to know but I have a feeling (and the latest weeklies support it somewhat) that we end up with a semi zonal pattern or lousy ridge out west so that despite the -NAO it’s still very hard to get any sort of great pattern for cold or storms 

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Some good stuff so far everyone.  I had some time to nose around the internet for some information.  Seems like there is a great deal of disagreement concerning, not so much the magnitude of the upcoming event, but the orientation(?) of it and thus which portion of the northern hemisphere is likely to see increased wintry weather as a result of it.

Found this short video though, which I found to be a simple explanation of the physics at work:

Also, @Isotherm, I frequently see you reference "wave 1" and "wave 2" mechanics.  Would you oblige us in a layperson's explanation of what you mean by this?

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Wave-1 and 2 are distinct atmospheric circulation patterns whereby we have "one" notable ridge and trough signal, or "two" ridges and troughs throughout a given spacial domain. 

Certain tropospheric patterns constructively interfere or enhance wave-1 resonance by nature of the fact that they project upon the climatological wave-1 or wave-2 circulations. 

This has been almost a perfect progression for a major SSW, and we're seeing that. Wave-1 preconditioning/displacement and elongation with a follow-up wave-2 split with ridges pressing on the Atlantic and Asian sides.

The current SSW is one of the most severe we've ever experienced due to it's zonal mean wind reversal and duration (7-10+ days). The upwell of the wave-2 implicates strong coupling w/ the stratosphere and downwell feedback will be rapid.

Thus, as MJO continues, u-div through the E hemisphere, and the circulation anomalies propagate downward, the AO/NAO will reverse by late February, and the Pacific should improve.

Late feb (last week) into march will produce a snowstorm in my opinion.

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Wave-1 and 2 are distinct atmospheric circulation patterns whereby we have "one" notable ridge and trough signal, or "two" ridges and troughs throughout a given spacial domain. 
Certain tropospheric patterns constructively interfere or enhance wave-1 resonance by nature of the fact that they project upon the climatological wave-1 or wave-2 circulations. 
This has been almost a perfect progression for a major SSW, and we're seeing that. Wave-1 preconditioning/displacement and elongation with a follow-up wave-2 split with ridges pressing on the Atlantic and Asian sides.
The current SSW is one of the most severe we've ever experienced due to it's zonal mean wind reversal and duration (7-10+ days). The upwell of the wave-2 implicates strong coupling w/ the stratosphere and downwell feedback will be rapid.
Thus, as MJO continues, u-div through the E hemisphere, and the circulation anomalies propagate downward, the AO/NAO will reverse by late February, and the Pacific should improve.
Late feb (last week) into march will produce a snowstorm in my opinion.


Thank you isotherm for the clear explanation. Two questions:
1. When would you expect we begin to see your thoughts start showing up on the ensembles, as they adjust to this SSW event?
2. May I ask, what is it that you do? I’m really curious. You are one of the most articulate and semantically gifted posters on this forum.


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The video above touches on a concept that is very important in the SSW discussion, and that is the downward movement phenomenon.

I drafted up this annotation the other day in a sub-forum, to help elucidate what is meant by that. 

The two images below: the left is a downward movement of warm anomaly; the image on the right is a non-downward propagating warm event. 

SSWp.jpg.f68742e8d86e7dfd200cc8d7b68ea8c8.jpg

 

There is an important distinction between these two variations of what happens post the initial onset of the warm intrusion phenomenon.  The one on the left is more obviously correlated to a negative Arctic Oscillation, per an ~ 20 day lag.  The one the right ...not as well to put it diplomatically. 

In fact, we have seen the AO's be sensitive over winters of the past to more tropospheric mechanical influences ... rising and/or falling into persistent modes in the absence of any obvious stratospheric anomalies, warm or cool. It is probably important not to hang one's hat (so to speak) on this particular modeled occurrence until its form and behavior can really be assessed.   

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3 hours ago, Isotherm said:

Wave-1 and 2 are distinct atmospheric circulation patterns whereby we have "one" notable ridge and trough signal, or "two" ridges and troughs throughout a given spacial domain. 

Certain tropospheric patterns constructively interfere or enhance wave-1 resonance by nature of the fact that they project upon the climatological wave-1 or wave-2 circulations. 

This has been almost a perfect progression for a major SSW, and we're seeing that. Wave-1 preconditioning/displacement and elongation with a follow-up wave-2 split with ridges pressing on the Atlantic and Asian sides.

The current SSW is one of the most severe we've ever experienced due to it's zonal mean wind reversal and duration (7-10+ days). The upwell of the wave-2 implicates strong coupling w/ the stratosphere and downwell feedback will be rapid.

Thus, as MJO continues, u-div through the E hemisphere, and the circulation anomalies propagate downward, the AO/NAO will reverse by late February, and the Pacific should improve.

Late feb (last week) into march will produce a snowstorm in my opinion.

Most of this is over my head, so I appreciate the educational post. The timeline here jives with my second favored seasonal window of March 1-14.

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