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Author Topic: Long Range Discussion: Winter 2020-2021  (Read 2478 times)

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Offline schneitzeit

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Long Range Discussion: Winter 2020-2021
« on: July 31, 2020, 10:05:17 PM »
We're four months from meteorological winter, and winter lovers nation-wide are apt to discuss what to expect this season.

So, let's talk about it.

La Niņa is expected to develop during the autumn months[1], though we're not entirely confident in that just yet as we are currently in an ENSO-neutral pattern. La Niņa events typically feature increased precipitation for the Tennessee and Ohio River Valleys, and commonly bring warmer than normal temperatures.

Last winter, we were stable in a weak/moderate El Niņo. You can see the trends since 2008 here (credit to NOAA):

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Another factor to examine is the North Atlantic Oscillation (NAO). This phenomenon is indicated by the pressure discrepancy between the subpolar and subtropical latitudes (on a map, Greenland and the Azores). A +NAO typically results in warmer than normal temperatures in the Eastern U.S. We witnessed this last year [2]:

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Yet another factor to analyze is the Madden-Julian Oscillation. This eastward-moving tropical convective system is classified into eight different phases, and it status affects our temperature and precipitation anomalies on a weekly basis. The MJO often traverses the Indo-Pacific Warm Pool every 30-60 days. [3] Take a look, for instance, at the phases of the MJO and their effect on our temperature during the winter months:

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More importantly, however, the MJO is more of a short-range tool, as it varies on a weekly basis. So one really couldn't use the status of the MJO for a long-range forecast, if I am not mistaken. But it's yet another tool that helps an amateur weather enthusiast like myself gauge the climate as we descend into the cooler months.


I have simplified a tremendously complex process, and the best insight we have at the present time is probably our seasonal La Niņa Watch. But I hope I have invited amiable discussion, and here's to, hopefully, a better winter than the recent ones our state as a whole has experienced. I know statistics just don't work this way, but let's be honest, we're past due for a decent winter.


Sources:

[1] https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml
[2]https://www.ncdc.noaa.gov/teleconnections/nao/
[3]https://www.climate.gov/news-features/blogs/enso/what-mjo-and-why-do-we-care#:~:text=The%20MJO%20consists%20of%20two,in%20the%20suppressed%20convective%20phase.


« Last Edit: August 01, 2020, 01:43:54 PM by schneitzeit »
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Offline snowdog

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Re: Long Range Discussion: Winter 2020-2021
« Reply #1 on: July 31, 2020, 11:15:50 PM »
Well, for better or worse, you now carry the burden of winter on your shoulders. May God have mercy on your soul.

Online BRUCE

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Re: Long Range Discussion: Winter 2020-2021
« Reply #2 on: August 01, 2020, 08:24:10 AM »
way early still... but I am going out. on a limb here, I am going with a warmer than average winter...
Come on severe wx season...

Offline StormNine

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Re: Long Range Discussion: Winter 2020-2021
« Reply #3 on: August 01, 2020, 10:42:28 AM »
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We are passed due for a colder and snowier winter and typically a La-Nina should mean an active northern stream although with a SE Ridge, but other factors may dominate the ENSO which looks to be a fairly weak La-Nina.  Just like the MJO and the strong Polar Vortex dominated the El-Nino last winter and the MJO and -PNA dominated the El-Nino in 2018-19. 

With the unusual warmth in the Maritime area/Indian Ocean that is still a strong signal for MJO phases 4-6 the least favorable phases.  Add the very warm Gulf of Mexico/Atlantic Ocean plus the tendacy for a La-Nina to have a ridge component plus recent trends/climate change then I just don't see how you can forecast anything but warmer than average. We at times are still struggling with that pesky ridge off the west coast of Alaska.

In order for us to get below-average we are going to need a strongly -NAO/-AO (we haven't seen a -NAO since 2012-13 and we will likely need a 2010-11 style NAO/AO combo or a super strong -EPO/+PNA with a weaker polar vortex-like 2013-14, 2014-15, or that late Dec/Early January period of 2017-18).

It isn't impossible for us to have a colder/snowier than normal winter but more things are on team warms side than team cools side.   

Offline StormNine

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Re: Long Range Discussion: Winter 2020-2021
« Reply #4 on: August 01, 2020, 10:48:28 AM »
Early Analogs:
1952-53
1983-84
2005-06
2016-17
2017-18

There may be some hope that December may be at least around average instead of a blowtorch like we are used to but either January and/or February go above to even way above average just on an analog approach.   

Offline StormNine

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Re: Long Range Discussion: Winter 2020-2021
« Reply #5 on: August 09, 2020, 07:15:57 AM »
The Euro Monthlies are pretty much 2016-17 for the November-February timeframe.  Not too dissimilar from my outlook.  It looks like the Polar Vortex may be locked in the poles as well according to that.   

Offline TNHunter

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Re: Long Range Discussion: Winter 2020-2021
« Reply #6 on: August 09, 2020, 07:48:02 AM »
The Euro Monthlies are pretty much 2016-17 for the November-February timeframe.  Not too dissimilar from my outlook.  It looks like the Polar Vortex may be locked in the poles as well according to that.

I would take that. We had a couple snow days that year and duck season was a great one!

Offline schneitzeit

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Re: Long Range Discussion: Winter 2020-2021
« Reply #7 on: August 14, 2020, 08:30:46 PM »
August 13th Update from NOAA:

La Niņa development probability has increased to 60%.

Source: https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml


Model averages from last month:

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Our suspicion of a Weak to Moderate La Niņa are coming to fruition.
« Last Edit: August 14, 2020, 08:34:12 PM by schneitzeit »
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Offline schneitzeit

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Re: Long Range Discussion: Winter 2020-2021
« Reply #8 on: August 16, 2020, 10:37:55 PM »
Hoping we can get a -NAO this winter, or at least for part of it. We haven't had that in a long time, as evidenced by this chart. A negative NAO, on average, produces better winter weather down here. Take a look:

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In recent years, the good winter of 2010-2011 that witnessed a snowy December for TN featured a strong -NAO. Other examples include the record-breaking snowy winter of 1959-1960. You can also see when January 1985 had a -NAO.

The past several winters have all had +NAO patterns, which can make it trickier for snowmakers in Tennessee.
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Offline Nashville_Wx

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Re: Long Range Discussion: Winter 2020-2021
« Reply #9 on: August 16, 2020, 11:49:01 PM »
I do not think it ultimately matters that much to be honest if you look at it in a IMBY prospective. Events are rarely state wide. Most snowfall events are even localized to area of counties. Winter 40 miles from here could be epic while I see 2" of snow for the year. I am done looking at the fine details this far out. Long range during winter should be 120hr out for TN. Where snowfall rides on 1-2 degree many of times its all a matter of luck really. It could really be that simple guys. No year is really better than another unless you are looking regionally. When is the last time that has happened? Vanilla way to look I know as it takes the fun out of forecasting. But snowfall in TN is many times hopes and dreams.
« Last Edit: August 16, 2020, 11:51:32 PM by Nashville_Wx »


Offline StormNine

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Re: Long Range Discussion: Winter 2020-2021
« Reply #10 on: August 17, 2020, 08:34:09 AM »
As far as what we really really want snow we can have a favorable pattern and strike out (alas I-40 from Nashville to Memphis in 2013-14) and we can have a not as favorable pattern and sneak in some storms (alas 2015-16 or Chattanogga last Feb).

Obvisously the more favorable a winter you have the more oppurtunities you have but nothing is a 100% guarantee in the South. 

Offline TNHunter

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Re: Long Range Discussion: Winter 2020-2021
« Reply #11 on: August 17, 2020, 09:29:05 AM »
About the only thing that is close to guaranteed in a Tennessee winter is that us in Northwest Tennessee will USUALLY cash in at least once or twice while the rest of the state strikes out.  Lol now I just jinxed us and we will repeat last winter and watch Chattanooga actually cash in.

Offline StormNine

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Re: Long Range Discussion: Winter 2020-2021
« Reply #12 on: August 17, 2020, 11:56:58 AM »
About the only thing that is close to guaranteed in a Tennessee winter is that us in Northwest Tennessee will USUALLY cash in at least once or twice while the rest of the state strikes out.  Lol now I just jinxed us and we will repeat last winter and watch Chattanooga actually cash in.

Last winter we struck out.  In matter of fact there were places in Indiana that didn't even see 1 inch of snow total last winter.   

Offline schneitzeit

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Re: Long Range Discussion: Winter 2020-2021
« Reply #13 on: August 17, 2020, 12:42:21 PM »
Last winter we struck out.  In matter of fact there were places in Indiana that didn't even see 1 inch of snow total last winter.

I was in a sweet spot last year. I managed to get 3" over the course of the winter.
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Offline schneitzeit

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Re: Long Range Discussion: Winter 2020-2021
« Reply #14 on: August 17, 2020, 12:43:33 PM »
I have higher hopes for this winter than last.
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