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Mountain West Discussion

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On Wednesday, a 500mb low will develop and slosh around under the blocking scenario. Normally this would be a big storm for us as it would have brought in moisture from the Pacific, but it's kind of a non-event this time.

uJJL3DE.png

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There it is guys - the big wet storm of 12/10/2007, right on time. It actually starts much earlier than this 174 hours in terms of precipitation. The first moisture would be ~150 hours on the Euro from now. This is the last two runs. Was shown on the prior run too.

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On 11/30/2020 at 12:11 AM, raindancewx said:

There it is guys - the big wet storm of 12/10/2007, right on time. It actually starts much earlier than this 174 hours in terms of precipitation. The first moisture would be ~150 hours on the Euro from now. This is the last two runs. Was shown on the prior run too.

 

 

Maybe the Euro will bring this storm back. I am rooting for you to have your SOI change prediction come true, and I'm rooting for any precipitation in the Southwest whatsoever.

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I actually don't think that Euro storm is going to come back as depicted unfortunately. The GFS has had something similar a bit later though.

The SOI thing I've mentioned - that's the systems now. The crash was 11/21-11/23, and the rule is you wait ten days.

It more or less did work as it is snowing across our northern mountains pretty heavily (really squalls with low qpf snow). There is a low over the area in the correct time frame too.
But the NAM and HRRR were hinting at snow even down here earlier today. There is a winter weather advisory out, and the local NWS learned their lesson this time, waiting for the snow to actually develop before issuing an advisory. I want to see how December goes, but I find replicating July-December precipitation patterns is a good predictor for Jan-June. So if this holds up, there is a pretty strong precipitation signal for January here. Each blue period is wetter than average.

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The 12/1-12/5 high for the city as currently forecast looks ~top 20 for cold for the past 100 years. So some cold and some snow isn't a terrible way to start of a La Nina down here. I'm much more concerned about the Spring than the Winter for moisture. December has a bunch of ways it can be wet regardless of the outcome the next ten days. 

MJO phase five is usually pretty good in December, La Nina rapidly weakening would be good, another SOI crash could help. I'm a little bit optimistic for March too, just because every year we've seen snow in October in the city has seen snow in March. The years with October snow have all seen storms come through in the time frames we've seen them this year. The weird pattern of a lot of early cold days is unusual too (highs <=55), but it has some similarities to 1936 when I looked.

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Let's try this again: There was another big SOI crash today. As far out as it is, the three models I look at all have a day ten storm tapping subtropical moisture. Are they going to be right, or even close this far out? No. But...this is the first time they've all had something depicted that far out since the October storm.

Date Tahiti (hPa) Darwin (hPa) Daily Contribution 30 day Av. SOI 90 day Av. SOI
2 Dec 2020 1014.81 1008.05 15.78 8.74 7.73
1 Dec 2020 1014.91 1007.10 21.23 8.99 7.70
30 Nov 2020 1013.51 1006.20 28.18 9.24 7.69

There was an associated SOI drop in this time frame in December 2007 ahead of a big storm.

2007 332 1012.91 1006.95   19.59 (Nov 28)
2007 333 1013.66 1009.50    8.14 (Nov 29)
2007 334 1013.05 1010.90   -4.65 (Nov 30)(-23 in two days)
2007 335 1012.80 1010.30   -6.33 (Dec 1) (-15 in two days)

Ten days later in Albuquerque:

Date Hi Lo Mean Dpt HDD CDD Precip Snow  
2007-12-10 40 32 36.0 -0.7 29 0 0.49 T 0
2007-12-11 43 33 38.0 1.5 27 0 0.24 0.3 0

Too early to expect anything useful from the models, but it is rare to see something on all three so far out here. The GFS has actually had something around 12/11 for a while already...but I had been ignoring it.

12-11-storm-SOI-drop

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The airport of course got literally nothing. But areas north and west of it in the metro did very well overnight. So that SOI crash from 11/21-11/23 did well here. I had a dusting.

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