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[Global] Teleconnections: A Technical Discussion

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10 minutes ago, Isotherm said:

Significant caution needs to be exercised here, initially. The NAM modality shifted this past week courtesy of the strat-modulation [circa -2 SD now], and to a lesser extent, NAO diminution; however, there's been systemic, countervailing destructive interference, spasmodically this winter from the tropical Pacific which must be thoroughly recognized. The AO and NAO are modestly negative, but the NAO is not yet fully responding w/ a retrogressive Greenland block, due largely to unpropitious tropospheric receptivity via repeated diminutions in angular momentum and intermittent tropical forcing interference.

 

This present +ENSO event is now virtually gone -- SST's approaching neutral in ENSO region 3.4. Part of the reason why SOI responses have been meager, and the canonical walker cell has not been as robust as expected.

 

Further, the z50 QBO easterly shear stress and its influence on tropical forcing, coupled w/ the weaker El Nino event, and the SSW forcing, has allowed the MJO to circuit Nina-esque phases more frequently than I think most anticipated so far this winter.

 

Going forward, it's incontrovertible that the SSW-split has rendered the NAM altered, but lack of cooperation on the Pacific side has delayed significant winter storm opportunities on the East Coast. We are missing a favorable window this weekend - which is unfortunate - this weekend, w/ GWO/MJO circuits out of phases 8, 7, however, at least the Mid-west and Mid-Atlantic will be profiting from this recent pulse of felicitous tropical forcing.

 

Angular momentum declined once again over the recent week; however, we are reversing that now, with increase +EAMT, and we will see another modest +EAMT pulse this coming week which will further extend the Pacific jet January 15th-20th. Contemporaneously, the MJO will circuit back through phases 5-6-7 quite rapidly. Due to the torque and tropical forcing contributions, I would also anticipate the GWO to expeditiously circulate back toward phase 5/6 over the next week, and eventually back into 7 later this month.

 

This increase in equatorward momentum transport will alter the jet structure as we near January 20th. One will note on the h2 zonal wind maps on the EPS, the canonical "split" jet stream structure becomes much more evident after January 20th, and especially by Jan 22-24.

 

The significant Greenland blocking and concomitant stable PNA amplitude will occur when constructive interference finally realizes between the SSW after-effects, the GWO/AAM and the MJO. The pattern is now colder than normal, but this pattern truly elucidates strongly the importance of a semi-stable PNA structure for increased probabilities of the significant east coast winter storm. We are evolving toward a stable PNA structure, but not yet.

 

The SSW is already inducing benefits, but the recent AAM plummet implicates disconnect again right now (ephemerally). However, the AAM will increase and constructively interfere w/ the SSW going forward as extratropical torques improve. The MJO will adjunctively increase momentum over the next two weeks, but initially, as it traverses phase 5 in particular, energy may continue to bombard the West Coast such that it destructively interferes w/ stable PNA. Once the MJO pulse moves into phase 6, this will change - and MJO/GWO and SSW will all be acting in concert. This, to me, is probably after the 20th threat (closer to 22nd/23rd and onward).

 

To recapitulate:

 

-We miss another fairly conducive window this weekend, but other regions of the East receive a snowstorm

-The systemic issue so far this winter has not been the polar domain, but the Pacific domain, due in part to enhanced intraseasonal interference via a weaker +ENSO event than anyone anticipated [I thought about +0.8c trimonthly but it will be weaker], SSW enhancement, and less than optimal momentum responses

-the NAM/NAO have been and will remain negative, but the lack of a stable PNA implies a colder than normal pattern with reduced significant snow chance in the medium term initially

-the threat on the 20th may or may not produce, but there's a strong argument it doesn't, because the NAO has not properly retrogressed yet to countervail an unstable PNA, induced via unfavorable MJO passage

-equatorward momentum transport w/ increasing AAM, split flow regime begins after the 20th, and the MJO will thereafter constructively interfere too

-the stable PNA structure truly stabilizes 22nd+ 

 

Everything remains on track for a prolonged period of colder than normal and enhanced snow opportunities henceforth through winter. However, since we miss another favorable period this weekend, we're going to need to wait until revitalization of constructive interference once again. This may mean the initial short wave on the 20th/next weekend is rain followed by bitter cold. The 20th wave could set-up up the 50/50, further pump / retrogress the NAO as trop. forcing becomes improved, and PNA structure amplifies/stabilizes for the 22-23rd threat.

 

We've had a lot of poor luck snow wise this winter, and it's principally b/c of the Pacific domain, reverting frequently to Nina-esque proclivities.

Great post-only major question wrt to PNA stability is with pac energy continuing to slam into the west coast, couldn't this lead to a progressive result too? 

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14 minutes ago, Isotherm said:

Significant caution needs to be exercised here, initially. The NAM modality shifted this past week courtesy of the strat-modulation [circa -2 SD now], and to a lesser extent, NAO diminution; however, there's been systemic, countervailing destructive interference, spasmodically this winter from the tropical Pacific which must be thoroughly recognized. The AO and NAO are modestly negative, but the NAO is not yet fully responding w/ a retrogressive Greenland block, due largely to unpropitious tropospheric receptivity via repeated diminutions in angular momentum and intermittent tropical forcing interference.

 

This present +ENSO event is now virtually gone -- SST's approaching neutral in ENSO region 3.4. Part of the reason why SOI responses have been meager, and the canonical walker cell has not been as robust as expected.

 

Further, the z50 QBO easterly shear stress and its influence on tropical forcing, coupled w/ the weaker El Nino event, and the SSW forcing, has allowed the MJO to circuit Nina-esque phases more frequently than I think most anticipated so far this winter.

 

Going forward, it's incontrovertible that the SSW-split has rendered the NAM altered, but lack of cooperation on the Pacific side has delayed significant winter storm opportunities on the East Coast. We are missing a favorable window this weekend - which is unfortunate - this weekend, w/ GWO/MJO circuits out of phases 8, 7, however, at least the Mid-west and Mid-Atlantic will be profiting from this recent pulse of felicitous tropical forcing.

 

Angular momentum declined once again over the recent week; however, we are reversing that now, with increase +EAMT, and we will see another modest +EAMT pulse this coming week which will further extend the Pacific jet January 15th-20th. Contemporaneously, the MJO will circuit back through phases 5-6-7 quite rapidly. Due to the torque and tropical forcing contributions, I would also anticipate the GWO to expeditiously circulate back toward phase 5/6 over the next week, and eventually back into 7 later this month.

 

This increase in equatorward momentum transport will alter the jet structure as we near January 20th. One will note on the h2 zonal wind maps on the EPS, the canonical "split" jet stream structure becomes much more evident after January 20th, and especially by Jan 22-24.

 

The significant Greenland blocking and concomitant stable PNA amplitude will occur when constructive interference finally realizes between the SSW after-effects, the GWO/AAM and the MJO. The pattern is now colder than normal, but this pattern truly elucidates strongly the importance of a semi-stable PNA structure for increased probabilities of the significant east coast winter storm. We are evolving toward a stable PNA structure, but not yet.

 

The SSW is already inducing benefits, but the recent AAM plummet implicates disconnect again right now (ephemerally). However, the AAM will increase and constructively interfere w/ the SSW going forward as extratropical torques improve. The MJO will adjunctively increase momentum over the next two weeks, but initially, as it traverses phase 5 in particular, energy may continue to bombard the West Coast such that it destructively interferes w/ stable PNA. Once the MJO pulse moves into phase 6, this will change - and MJO/GWO and SSW will all be acting in concert. This, to me, is probably after the 20th threat (closer to 22nd/23rd and onward).

 

To recapitulate:

 

-We miss another fairly conducive window this weekend, but other regions of the East receive a snowstorm

-The systemic issue so far this winter has not been the polar domain, but the Pacific domain, due in part to enhanced intraseasonal interference via a weaker +ENSO event than anyone anticipated [I thought about +0.8c trimonthly but it will be weaker], SSW enhancement, and less than optimal momentum responses

-the NAM/NAO have been and will remain negative, but the lack of a stable PNA implies a colder than normal pattern with reduced significant snow chance in the medium term initially

-the threat on the 20th may or may not produce, but there's a strong argument it doesn't, because the NAO has not properly retrogressed yet to countervail an unstable PNA, induced via unfavorable MJO passage

-equatorward momentum transport w/ increasing AAM, split flow regime begins after the 20th, and the MJO will thereafter constructively interfere too

-the stable PNA structure truly stabilizes 22nd+ 

 

Everything remains on track for a prolonged period of colder than normal and enhanced snow opportunities henceforth through winter. However, since we miss another favorable period this weekend, we're going to need to wait until revitalization of constructive interference once again. This may mean the initial short wave on the 20th/next weekend is rain followed by bitter cold. The 20th wave could set-up up the 50/50, further pump / retrogress the NAO as trop. forcing becomes improved, and PNA structure amplifies/stabilizes for the 22-23rd threat.

 

We've had a lot of poor luck snow wise this winter, and it's principally b/c of the Pacific domain, reverting frequently to Nina-esque proclivities.

 

Thank you for your honesty.

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26 minutes ago, wxmd529 said:

Great post-only major question wrt to PNA stability is with pac energy continuing to slam into the west coast, couldn't this lead to a progressive result too? 

 

 

Yes; it's high risk. The most likely scenarios w/ an unstable PNA and non-retrogressed downstream block are either warmer/coastal hugger or simply deamplified and weaker. The stable, amplified PNA structure is needed for the more optimal big storm scenario. 

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30 minutes ago, Isotherm said:

 

 

No problem. I recognize that we're nearing that point in the winter in which everyone's hoping the next storm threat is "the one" because the clock is ticking with regards to winter's life, but unfortunately, since we're missing another favorable window this weekend, we may need to wait for the next burst of constructive interference. This next pulse of constructive interference will last much longer as the AAM/MJO/SSW after effects operative adjunctively, and the SSW induced impacts after this historic split/destruction will certainly persist in the troposphere through all of February, and potentially even longer.

So do you think we might have another color maybe stormy March due to the SSW?

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1 hour ago, Isotherm said:

 

 

No problem. I recognize that we're nearing that point in the winter in which everyone's hoping the next storm threat is "the one" because the clock is ticking with regards to winter's life, but unfortunately, since we're missing another favorable window this weekend, we may need to wait for the next burst of constructive interference. This next pulse of constructive interference will last much longer as the AAM/MJO/SSW after effects operative adjunctively, and the SSW induced impacts after this historic split/destruction will certainly persist in the troposphere through all of February, and potentially even longer.

Just my pennies worth but after you said that the SSW would not affect your long range forecast then admitted it had a big effect on the accuracy of your December forecast I stopped reading any further.

A SSW like the one we are having ( just had) changes the whole dynamics of the atmosphere to say otherwise or stick with a pre SSW forecast is in my opinion very unwise.

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In some ways this is reminding me of 2014/15 when interseasonal interference destructively interfered with ENSO(which kept NOAA from declaring a Nino til March). After a favorable Nov. that Winter didn't produce until late January-Feb(and boy did it snow in Boston!). Many were calling for a pattern change in late Dec. as well.:)

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I am very worried about guidance showing the MJO going into phase 5. Even though were getting a negative EPO the ridge WAR is coming up the east coast thanks to the MJO. 

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16 hours ago, Isotherm said:

 

 

You're conflating issues.

 

1)Material impact on the winter forecast

 

2) Material impact on the atmosphere

 

These are two disparate issues. You misinterpreted my remarks. What I said was that the occurrence or non-occurrence of a SSW event this winter, would not materially change the forecast of colder/snowier than normal. However, nowhere did I assert that SSW events do not impact the atmosphere in a material way.

 

What happened was that the SSW aided in a significant interruption of the pattern, which, if it had not occurred, I contend that late Dec/early January would have been colder/snowier due to less intraseasonal influence.

 

The impact of the historic SSW is part 1: a delay of the initiation of the favorable snow pattern, but consequently, part 2: a prolonged favorable pattern once it begins.

 

And yes, if there were no SSW this winter, we still would have a colder/snowier than normal second half of winter. But because of the SSW, the ceiling is increased on the potential for the upcoming 6 weeks.

 

Hopefully, this clarifies, and you can see that my comments are absolutely not inconsistent, and not what you claim them to be.

I was not saying you have been inconsistent rather surprised that you do not think this SSW will affect your forecast going forward. Apologies if my post caused any ill feeling.

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Do you guys think this downwelling SSW event will eventually cause the TPV to loop as far south as the Great Lakes/upstate New England and perhaps bring Florida a widespread hard freeze?

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Modelling seems to have lost what solidarity it had on the Pacific-Atlantic pattern sharpening up 22nd+, hopefully this is just model shortfalls as opposed to actual ones being picked up on.

 

Another cause of uncertainty is present for NW Europe, as there's little consistency with respect to how much the positive GPH anomalies just N and NE of the UK are able to work down from the lower stratosphere and, D8-D10, disrupt the incoming major trough associated with the polar vortex drain out of Canada.

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@Singularity, interesting. Can you please share more info? Things look pretty much perfect to me. Or, were you speaking about Europe specifically? Thanks :) 

gfs-ens_z500a_nhem_65.png

gem-ens_z500a_nhem_65.png

eps_z500a_nh_61.png

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