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My idea for November has been that if we're to get a big storm it will be right at the end of the month. But it may actually be the first week of December. The European has been showing a pretty massive reversal in the SOI around 11/20. If we go from +10 or +20 to -10 or -20, you'll see something out here around Nov 30-Dec 2.

Right now, there is a huge high by Tahiti, but it's going to be replaced by a pretty strong low. Tahiti going from being at the edge of a 1039 mb high to a good storm moving through in essentially two days. This may not actually be the peak of the transition but we'll see soon enough what the Australians come up with for the SOI.

SOI-Crash-11-20-coming

SOI-Crash-11-20-coming-2

 

 

 

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14 minutes ago, raindancewx said:

My idea for November has been that if we're to get a big storm it will be right at the end of the month. But it may actually be the first week of December. The European has been showing a pretty massive reversal in the SOI around 11/20. If we go from +10 or +20 to -10 or -20, you'll see something out here around Nov 30-Dec 2.

Right now, there is a huge high by Tahiti, but it's going to be replaced by a pretty strong low. Tahiti going from being at the edge of a 1039 mb high to a good storm moving through in essentially two days. This may not actually be the peak of the transition but we'll see soon enough what the Australians come up with for the SOI.

SOI-Crash-11-20-coming

SOI-Crash-11-20-coming-2

 

 

 

And while still in fantasyland for the GFS, it does have a huge storm Dec 2/3 for NE Colorado

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The European has been showing a big precipitation event around 10 days from now. Would tie in well with the big time expected SOI crash today or tomorrow. 

The European has also been severely underestimating the current MJO wave. November 2000 has been very similar to the MJO wave this month. So we'll see if that continues. The big magnitude in phase 2 in 2000 was about two days earlier than this year, but it continued through phase 3 pretty easily.

MJO-11-11-v-11-19.png

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Any mention of November 2000 brings back the memories of how the Midwest descended into the cold-blitz of December 2000. I think my place got either synoptic snow or lake-effect snow every day that month.

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The Denver area could get some snow developing early Tuesday. Maybe this one will not be a total bust like the last potential snowstorm. WPC blended forecast has about 0.1" for me and 0.2" to 0.4" near Denver, better snowfall southwest towards the San Juan and Sawatch/mid Colorado.

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This is smoothed out and not particularly precise, but the Midwest Regional Climate Center has a pretty snowy fall to date for the US. It's kind of weird since it is also a pretty warm Fall overall, and not particularly wet. I had about 8.5 inches of snow in October (it was 7.5" the first two days, and I had to rush out to work the third day it snowed before I could measure), so it's a bit high in Albuquerque. I had an area from Western CO and NW New Mexico to the WA/ID border with Canada snowier than average (like most La Ninas, but a bit SE), and then northern New England and the Midwest snowier than average. Looks OK so far. Not sure what is going on with the snow in the South that is shown. I'm expecting the system shown in a week or so on the European to be a better system than these weak/moisture starved systems moving through the next few days.

Image

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Date Tahiti (hPa) Darwin (hPa) Daily Contribution 30 day Av. SOI 90 day Av. SOI
22 Nov 2020 1010.60 1008.90 -7.51 6.66 7.94
21 Nov 2020 1011.63 1008.30 2.86 7.21 8.15
20 Nov 2020 1013.38 1007.85 16.86 7.44 8.23
19 Nov 2020 1014.15 1008.10 20.17 6.99 8.14
18 Nov 2020 1014.69 1008.65 20.10 6.27 8.18

Another pretty massive crash in the SOI. That 24 point crash 11/20 to 11/22 is probably going to be a big, cold low around 12/1-12/3 over the Southwest and/or Colorado/Utah.

The mid-October SOI crash was similar in magnitude - and the storm came through the SW 10/25 to 10/28.

15 Oct 2020 1011.26 1009.50 -7.29 11.94 8.69
14 Oct 2020 1012.74 1010.20 -2.26 12.44 8.84
13 Oct 2020 1014.49 1010.00 10.31 12.58 8.77

I find anecdotally - I was starting to research this but I lost most of my non-essential research the other day when my computer died - the biggest, coldest, lows - the closed lows typically - tend to come after a big SOI crash that flips positive to negative. The crashes that go negative to more negative are usually super wet, and the crashes that go positive to less positive tend to be colder but moisture starved. It seems like the big crashes from positive to negative incorporate a big northern stream system that can tap into the subtropical jet essentially.

 

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Image

The years that are similar to snow this Fall since 1930 have generally been good for the West after the Fall too. A blend of 1947/1996 looks a lot like 2007, which I think will be a decent analog for snow the rest of the way (it hasn't been so far).

Image

The three days ending November 23 have each seen big SOI crashes (10+ points) in a two period - have to watch 12/1-12/3 for a big system or systems.

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23 hours ago, mayjawintastawm said:

5.1” here. Good moisture content too, probably the wettest event in at least a couple of months!

Looks like the middle of Denver got 0.6" liquid equivalent or a bit more.

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On 11/21/2020 at 10:19 PM, raindancewx said:

Another pretty massive crash in the SOI. That 24 point crash 11/20 to 11/22 is probably going to be a big, cold low around 12/1-12/3 over the Southwest and/or Colorado/Utah.

The mid-October SOI crash was similar in magnitude - and the storm came through the SW 10/25 to 10/28.


I find anecdotally - I was starting to research this but I lost most of my non-essential research the other day when my computer died - the biggest, coldest, lows - the closed lows typically - tend to come after a big SOI crash that flips positive to negative. The crashes that go negative to more negative are usually super wet, and the crashes that go positive to less positive tend to be colder but moisture starved. It seems like the big crashes from positive to negative incorporate a big northern stream system that can tap into the subtropical jet essentially.

There's a chance that the Southwest will get two closed low pressures at 500mb, without getting much snow out of it, for any state.

I read Joe Bastardi's weather discussion for a few years. He constantly mentioned the daily SOI as a source of change in the subtropical jet stream. But I always have had a hard time tracking equatorial disturbances toward the US. 

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We'll see. Even from 48 hours ago, there was nothing like this depicted on the models:

GFS-12-3-2020

When I did my outlook, it seemed like 12/10 would have been the time frame for a big December system, but we seem to be getting a lot of things that happened similarly in 2007 at time frames that are 2-3 weeks off. There were big drops in the SOI late Nov and Dec 2007, but not all of them preceded big systems. It's definitely a decent indicator for low passages but not as reliable for actually identifying storms with...moisture.

2007-v-2020.png

In 2011, it actually got so cold down here that a couple systems missed northern New Mexico because they were too far south, some of the things I look at are somewhat similar to 2011, have to watch for that too.

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00Z run 11/26 from the GFS has 40 hours of snow for New Mexico starting around six days from now. It's basically dead on to the SOI crash time frame. I'm sure it will change, but the trend is good.

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Not a drop of rain or a flake of snow in town. But it has been snowing in some spots.

I can't believe they went with a winter weather advisory in town. I'm not fully convinced we'll get more than T. I've been assuming T-0.10" total, with some of it as snow if it came overnight.

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I check in once in a while at opensnow.com.  The site is mountain snow/skiing oriented but is a good place to track storms heading into Colorado. Or in this case, the lack thereof.

 Unfortunately  they are seeing little if any snow for CO (and the West in general) until late December. Seems as though a huge high pressure ridge is setting up shop again over the west (does it ever really go away?).  What causes these ridges to keep building and hovering over the west?

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The north Pacific orientation changes with the ENSO/PDO states. Actually think some of the mountains will see decent snows this week given the little impulses depicted to dive down. When I look at 2007-08, the pattern depicted for early December is similar to about 11/20-11/26 in 2007. If we keep running say 10 days behind 2007, then the bigger storms (at least down here) of Dec 2007 would show up late December instead of mid-December.

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On 11/21/2020 at 9:19 PM, raindancewx said:
Date Tahiti (hPa) Darwin (hPa) Daily Contribution 30 day Av. SOI 90 day Av. SOI
22 Nov 2020 1010.60 1008.90 -7.51 6.66 7.94
21 Nov 2020 1011.63 1008.30 2.86 7.21 8.15
20 Nov 2020 1013.38 1007.85 16.86 7.44 8.23
19 Nov 2020 1014.15 1008.10 20.17 6.99 8.14
18 Nov 2020 1014.69 1008.65 20.10 6.27 8.18

Another pretty massive crash in the SOI. That 24 point crash 11/20 to 11/22 is probably going to be a big, cold low around 12/1-12/3 over the Southwest and/or Colorado/Utah.

Looks like it will get pretty cold in this time frame. Not sure about moisture yet. My wild card is this system may be able to tap some moisture from the Gulf of California even if the subtropical jet isn't there. But the models don't really show it. But usually the storms that are strong that get far enough south can do it. The last system missed Albuquerque, but areas south and west had a pretty decent little snow event, with 0.05-0.20" liquid falling as snow.

Dec-3-storm-11-29-GFS

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Finnster, here’s a pretty detailed article on the so-called Ridiculously Resilient Ridge (RRR) https://weatherwest.com/archives/5982. While the RRR is generally very bad for places like California, a western trough that’s too deep and too far west can be less than ideal for us here in CO, especially on the east side of the Rockies. Along the Front Range, we often seem to do best with a trough that’s centered east of CA, along with some blocking in the Atlantic (negative NAO).

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