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Winter 2020-21 Discussion


CAPE
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4 hours ago, Rhino16 said:

I would not be surprised if the only decent snow that happens goes way south and misses us giving NC some snow... just because why not. Let’s hope 2021 is a little more friendly. We need some friendly flakes every once in awhile...

Me too. Here’s my winter snowfall map for the area ..EF27B84B-6090-4C50-8004-0FB57389EF3A.thumb.jpeg.c6f9192b0a7d9904228bb060b52a6f00.jpeg

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6 minutes ago, Chris78 said:

I think that looks like a few years ago when we were in the screw zone during a la Nina. We missed north and south that year.

And what's really frustrating is that we had to roll a nina AGAIN...twice in 4 years...right after a neutral year where the AO/NAO was record positive, smh Man I hope we can fluke/anomaly something this year...because I'm wondering if, with a nina this strong (or is it moderate), it won't leak over into the following winter as well...(can't imagine the numbers of the winter following a la nina are spectacular)

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Continuing to monitor trends in the LR guidance for HL +height anomalies, because it may be the only thing that can save us, along with some semblance of a decent Pacific for a time. Below is the extended GEFS for a month out- towards the end of November, and below that is the Euro(weekies) for approximately the same time period off of the free site. Crappy graphics but I think you can see the look is very similar, and would be an acceptable one heading towards Dec.

323245819_gefsblock.thumb.png.a0937935387bfc18cf1098670d742762.png

arctic.png.6838bfcc815974ea382f9fc92652107f.png

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3 minutes ago, CAPE said:

Continuing to monitor trends in the LR guidance for HL +height anomalies, because it may be the only thing that can save us, along with some semblance of a decent Pacific for a time. Below is the extended GEFS for a month out- towards the end of November, and below that is the Euro(weekies) for approximately the same time period off of the free site. Crappy graphics but I think you can see the look is very similar, and would be an acceptable one heading towards Dec.

323245819_gefsblock.thumb.png.a0937935387bfc18cf1098670d742762.png

arctic.png.6838bfcc815974ea382f9fc92652107f.png

Presently the polar vortex is strengthening but hopefully by the third week of November there are some signs that this may change - highly speculative the latest models from the GEFS shows the strengthening of the polar vortex currently. Actually some modeling posted by Simon at his strat site indicates a strong(er) pv for the next 46 days, which fits the seasonal models.

Dr. Amy Butler posted a cool scatter plot which shows in a Nina you can certainly have pv disruptions. And like the NAO hard to predict with skill. 

 

  

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14 minutes ago, frd said:

Presently the polar vortex is strengthening but hopefully by the third week of November there are some signs that this may change - highly speculative the latest models from the GEFS shows the strengthening of the polar vortex currently. Actually some modeling posted by Simon at his strat site indicates a strong(er) pv for the next 46 days, which fits the seasonal models.

Dr. Amy Butler posted a cool scatter plot which shows in a Nina you can certainly have pv disruptions. And like the NAO hard to predict with skill. 

 

The transfer of heat from the equatorial regions to the high latitudes is necessary to build anomalous heights there/warm the upper atmosphere and potentially weaken/disrupt the SPV, so it makes sense there is a  connection between the MJO and the AO. The QBO also has an impact as a modulator, and even though it is currently positive, it is only weakly so at this point. I don't know enough about the intricacies of the processes involved and the tendencies (eg location and magnitude of tropical forcing, ENSO state, QBO phase, etc). Above my pay grade. It's interesting, so keep us updated with the techno geek discussions on SW potential.

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56 minutes ago, CAPE said:

The transfer of heat from the equatorial regions to the high latitudes is necessary to build anomalous heights there/warm the upper atmosphere and potentially weaken/disrupt the SPV, so it makes sense there is a  connection between the MJO and the AO. The QBO also has an impact as a modulator, and even though it is currently positive, it is only weakly so at this point. I don't know enough about the intricacies of the processes involved and the tendencies (eg location and magnitude of tropical forcing, ENSO state, QBO phase, etc). Above my pay grade. It's interesting, so keep us updated with the techno geek discussions on SW potential.

There was a study published years ago that found that a positive QBO becomes a problem for high latitude blocking once it gets over +10 (don’t quote me but I believe that was the threshold given) during the winter months. The stronger the +QBO gets, the more it promotes strong westerlies/zonal flow

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2 hours ago, snowman19 said:

There was a study published years ago that found that a positive QBO becomes a problem for high latitude blocking once it gets over +10 (don’t quote me but I believe that was the threshold given) during the winter months. The stronger the +QBO gets, the more it promotes strong westerlies/zonal flow

I'm good with QBO 101. But thanks.

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44 minutes ago, uncle W said:

2010-11 had a plus 10 on the QBO scale and got extreme blocking Dec and Jan...2008-09 and 2016-17 had a high QBO and both winters were good in the NYC area despite little blocking...1966-67 had a high QBO with some blocking and major snowstorms...

There is a generally accepted connection between the easterly(negative) phase of the QBO and disruption/weakening of the SPV, but any direct correlation between QBO phase and HL blocking episodes seems a bit more nebulous. It may be that winters with sustained blocking are more associated with easterly QBO due to increased likelihood of a weaker SPV, and this leads to development of a sustained -AO.  By the same token, if the SPV remains more intact, but not an absolute beast (say in a somewhat weak westerly QBO), with no coupling to the troposphere/towards the surface, periodic HL blocking episodes may still occur.

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25 minutes ago, BTRWx's Thanks Giving said:

I'm really struggling to find analogs for a nina that had low heights over the northern plains along with above normal heights over northeast Pacific in October.  Also, Europe tends to be above normal.

1557370142_Oct2020500mb.gif.cb8b6dd3b7d4fa654a8413589b61b28a.gif

All things considered, this is not a bad comparison!  Two great snow seasons

274895689_Oct1995_2013500mb.png.8118a8f43e6c7ad6185231c728621230.png

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21 minutes ago, uncle W said:

the QBO was dropping from plus to minus in 1995...this year could be different...

That tends to be the case with the "legit" blocking winters. Doesn't mean we can't get some HL help though. SPV is not likely going to be disturbed in the near term based on current forecasts. WAFz looks minimal over the next 10 days. Unless the SPV becomes becomes a persistent, giant blue ball of death over the coming weeks and couples to the troposphere, there is still the possibility of HL + h5 heights developing towards the end of November as the long range GEFS and EPS are suggesting. Time will tell, as always.

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5 minutes ago, EasternLI said:

Interestingly enough, the qbo that year actually was westerly below 30mb to the tropopause. This year actually looks to do that as well albeit with a thicker vertical profile. Also interesting in that 2007-08 was completely different then this year. Merely a couple observations. Cheers.

PysojQU.png

Q2uxKnq.png

That oddity in the regular cycle in 2016-17 really stands out. Makes one wonder if that sort of thing will become more prevalent. I suppose it could have simply been related to the strong Nino during that period, or maybe a sign of things to come.

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46 minutes ago, CAPE said:

That oddity in the regular cycle in 2016-17 really stands out. Makes one wonder if that sort of thing will become more prevalent. I suppose it could have simply been related to the strong Nino during that period, or maybe a sign of things to come.

Yeah, I've seen a couple papers that attributed it to the super Nino. A more recent paper goes into some greater detail. I can't help but wonder if the powerful +IOD event last year played some role in the odd behavior of this year. 

https://acp.copernicus.org/articles/20/6541/2020/

In addition to the anomalous behavior in the tropical lower stratosphere in 2015/2016, we explored the forcing of the unusually long-lasting westerly zonal wind phase in the middle stratosphere (at 20 hPa). Our results reveal that mainly enhanced Kelvin wave activity contributed to this feature. This was in close relation with the strong El Niño event in 2015/2016, which forced more Kelvin waves in the equatorial troposphere. The easterly or very weak westerly zonal winds present around 30–70 hPa allowed these Kelvin waves to propagate vertically and deposit their momentum around 20 hPa, maintaining the westerlies there.

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7 hours ago, uncle W said:

2010-11 had a plus 10 on the QBO scale and got extreme blocking Dec and Jan...2008-09 and 2016-17 had a high QBO and both winters were good in the NYC area despite little blocking...1966-67 had a high QBO with some blocking and major snowstorms...

Thanks for the info...love your work. But keep in mind all 4 of those years you cite were pretty sucky for snow here.  67 was ok but not really compared to the period it was in.  The other 3 were all below normal and frustrating as we missed almost every storm just to our northeast.  Nina’s are a lot less hostile in NYC than our area. 

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