Winter 20-21 Discussion

[wdrag]

Good Sunday morning everyone, Dec 27.

I won't repeat it here, but if you're interested..I've posted a topic in Met 101:  My own concern about the overuse of the term Arctic Air. 

Have a good holiday season. 

Walt

 

[raindancewx]

The CFS seems to be losing the big block over Greenland to some extent on its recent runs, or at least trending it east. The areas it has wetter than average in January are pretty well correlated to the +NAO phase in January.

[raindancewx]

January 2021 apparently has a 2007-08 winter look on the European.

[raindancewx]

Nino 4 in the prior winter and December SOI values are both good predictors for the NAO to go positive in February. Will be curious to see if that happens in February or if it sets up before. You have 1/20 years with a -NAO in February after Nino 4 is above 28.7C in the prior winter, and no meaningfully negative -NAO February years after the the SOI is above +12 in December. SOI is currently about +16 for the month, and Nino 4 was 29.20C or so last winter.

The +22 SOI in December 2011 and and the +26 SOI in December 2010 ate the NAO alive the following February. The transition in 2011 is kind of amazing since it ended a 14-month period with the NAO well into the negative phase (Dec 2009, +2010, +Jan 2011).

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii.table

2011  -0.88   0.70   0.61   2.48  -0.06  -1.28  -1.51  -1.35   0.54   0.39   1.36   2.52
2012   1.17   0.42   1.27   0.47  -0.91  -2.53  -1.32  -0.98  -0.59  -2.06  -0.58   0.17

[raindancewx]

Works for me. 

[raindancewx]

The models seem to like the first half of January 2021 as a clone of January 2008. What do you think? Do we get the cold of January 2008 too? This image of 2021 is from BAM's twitter.

I see a strong resemblance to the warm half of January 2008. So the question is whether the cold half is there too if the warm half verifies.

[raindancewx]

We actually pulled out a cold/wet month by the headwaters of the Rio Grande, which will help keep that river running for a while. Albuquerque will finish the month around 1F below the 1931-2019 average high, and with the coldest average low since 2009 or 2011, pending whether we drop to 25, 20, or 15 tomorrow. My idea for the winter has been that the northern mountains here would be "OK", and the southern mountains would get...jack. That seems about right so far. This storm really saved the northern snow pack for the green range at the end of the month.

 

 

[raindancewx]

My interior West cold idea for this winter has held up pretty well so far. This is your first third of winter 2020-21. 

[raindancewx]

As with December, I think the CFS & Canadian know a +WPO look weakly favors cold in the interior West but they can't' quite figure out where to place the cold spot. I like a colder blend of the CFS/Canadian looks for the month though.

[raindancewx]

On 10/10/2020 at 10:01 PM, raindancewx said:

https://www.scribd.com/document/479516526/Winter-2020-21-Outlook

That's why I have for the winter. The gist of it is:

+NAO La Nina - but likely negative in Dec/Mar -

Here is how I am doing so far. Most of the US verified within 3 degrees of the blend I had for December from October. The blend improved quite a bit compared to observations in the South, Midwest, Texas, and Southern Plains from 12/21 to 12/31.

 

[raindancewx]

Early part of January will verify warm for most. Will be curious to see how the later parts come in.

[raindancewx]

For anyone who remembers, there were several very powerful lows in the North Pacific late in December. One long-range forecasting theory is that lows in the Bering Sea/Gulf of Alaska area will 'appear' in the US 17-21 days later. If you buy that, the 938 mb low over southern Kamchatka is believed to correspond to about 35N over the Rockies (Albuquerque essentially), and will move east as a developing or rapidly strengthening storm. "Albuquerque lows" are often quite good snow storms for Colorado, but not necessarily where I am.

I'm attaching an image from late December and how it is supposed to correspond in the US spatially. We'd be looking at 1/14 to 1/18 for the Rockies, a day early West Coast if it comes west to east, and then around 1-2 days later for the Midwest/Northeast. I'm not a huge fan of this method. It does work quite well sometimes though.

 

[raindancewx]

[raindancewx]

There is now support from a big SOI crash for a system over the Southwest in the time frame you'd expect from the North Pacific timing I mentioned above.

Date	Tahiti (hPa)	Darwin (hPa)	Daily Contribution	30 day Av. SOI	90 day Av. SOI
8 Jan 2021	1013.12	1005.30	15.13	19.56	10.69
7 Jan 2021	1014.99	1004.95	25.58	19.23	10.68

[40/70 Benchmark]

On 12/31/2020 at 11:29 PM, raindancewx said:

Here is how I am doing so far. Most of the US verified within 3 degrees of the blend I had for December from October. The blend improved quite a bit compared to observations in the South, Midwest, Texas, and Southern Plains from 12/21 to 12/31.

 

Most missed the N plains....Pac jet and PNA coupler, but still a bit flukey IMO.

[raindancewx]

It's interesting looking back at the +NAO in November. The value was +2.54, and then -0.30 in December. So far, the winter correlations are far closer to what you'd get from looking at +NAO Novembers rather than -NAO December or January years.

You can see that the cold in the interior West and warm east look shows up after a +NAO November on the correlations map (blue = neg correlation to positive NAO, i.e. cold). That wasn't perfect for December, with Florida pretty cold and a lot of the South near average, but it's not bad for a map generated from one variable. CPC has the West heavily favored cold in the 6-10 day period, and it's already been cold in some places in the West for January to date. The new incoming cold may focus on the Northwest though, which again is consistent with the +NAO November.

[LibertyBell]

On 1/12/2021 at 10:38 PM, raindancewx said:

It's interesting looking back at the +NAO in November. The value was +2.54, and then -0.30 in December. So far, the winter correlations are far closer to what you'd get from looking at +NAO Novembers rather than -NAO December or January years.

You can see that the cold in the interior West and warm east look shows up after a +NAO November on the correlations map (blue = neg correlation to positive NAO, i.e. cold). That wasn't perfect for December, with Florida pretty cold and a lot of the South near average, but it's not bad for a map generated from one variable. CPC has the West heavily favored cold in the 6-10 day period, and it's already been cold in some places in the West for January to date. The new incoming cold may focus on the Northwest though, which again is consistent with the +NAO November.

It's interesting that the snowy pattern in the Mountainous West, which began early on in the fall looks to repeat itself.  This has been the region most resistant to long-term warning (on our continent anyway.)  On the other hand, if you look at a place like Chicago, which has had a pitiful winter, that looks like it will continue.

[raindancewx]

The PNA is supposed to flip 1/20 or so.

That makes sense given that we have real storms in the forecast again down here, which tends to happen when it flips. The other result is the cold should start to bleed into the Northeast. The long-term correlation of a +SOI December = Warm South February also appears to be setting up now as get near February following a +16 SOI reading in December (top five last 90 years).

[Roger Smith]

Do you perceive two different kinds of cold regime down there, like the anticyclonic type and the advection from far north type? 

This far north, we tend to do these two types simultaneously, either there's cold air of northern origin trapped over us, or we're in a mild Pacific flow.

This winter, it has been relatively mild (I'm only a few miles north of the 49th parallel here) but at my elevation a fairly decent snowfall. Quite a contrast locally, at my elevation 20-25 inches on the ground, down in the Columbia valley a few miles east of here, almost no snow, just partial cover and 2-4 inches where any at all. 

We just had some very strong winds from that low that came in off the ocean Tuesday night, a few large trees close to us coming down at daybreak.

[raindancewx]

The cold down here is kind of going as I expected. All of of my analogs had brief periods with intense storms in the Southwest - the problem is those periods are in different months. But they all also had extremely consistent dry periods. Either way favors cold - either cold highs or cold lows. The problem years are those like 2017-18, when you kind of had the subtropical jet over head to prevent extremely low dew points, but no impulses to bring rain or snow for months. The lows were kind of +1, and the highs were +5 generally in that pattern. This winter pattern so far is more like -1 or -2 for lows and 0 or -1 for highs overall.

Conceptually, the WPO, EPO, PNA, NAO, and AO all support or at least don't contradict cold in the Southwest in January if you look at their individual temperature correlations. So it has been cold here. The La Nina warm signal is about 2:1 for northern NM/northern AZ, and the dry signal is about 2:1 for northern NM/northern AZ. So it's never that surprising to me when we beat one of the long-term signals. For southern areas of the Southwest, the dry signal is far stronger than that, more like 4:1. 

What will impress me is if the forecast system(s) in the coming week can actually deliver a lot of moisture again to the Southwest. If that happens, there is a real chance the winter finishes wetter than average in some areas. It's very rare to beat both the warm and the dry signal in a La Nina out here. The Euro keeps trying. The mountainous areas had well above normal snow in the Fall, so I think my idea of 50-90% of normal snowfall for most of New Mexico and most of the Southwest is going to hold up pretty well for the cold season. Albuquerque looked like it could have some epic season for snow in October, but the systems since keep missing the airport, so they've only had 0.5 inches of snow since October. Most of the city is around 8-15 inches compared to the 5.0 or so at the airport.

Also wanted to mention: The Jamstec idea of a warmer Nino 1.2/3 in Spring, with Nino 4 still very cold looks realistic to me. If you look at years that match that solution, several of them, 2001, 2008, and 2012, have a passing resemblance to the temperature profile of Jan 1-15 this year.

 

[raindancewx]

WPC is pretty optimistic for total precipitation in the Southwest over the next five days. The setup isn't that different from the system around 12/10. But we'll see how it goes. Day 1-3 looks about right to me. Not sure about the day 1-5.

 

[raindancewx]

December started off as a terrible match to my main analog, 2007-08, but we've really moved toward it a lot in recent weeks. Not sure how much longer that will hold. But it's definitely a solid match for early January. Main misses are south TX and kind of the OR/CA/NV border area.

[raindancewx]

Decent storm today. Still snowing in the northern areas. More possible by the end of the month. Models are kind of going crazy with precipitation by the end of the month in Arizona. Droughts do end - but it will be interesting to see how much or how little we actually see. GFS is left, Euro is right. Will check back later and see if this has any validity. Arizona has had virtually no rain or snow this January.

Las Vegas, NM

Red River averages 135 inches of snow a year.

 

[Roger Smith]

Since we're comparing snow pictures ... I live about 20 paces left of this photo (taken a week ago, the trees have lost that snow cover from the windstorm last week, snow on ground is about the same today as then after a bit of a thaw and a bit more falling) -- this is a normal look for here in mid-January. 

 

[raindancewx]

I never really answered what you asked above. Our cold in the West is just inversions and moisture less lows with cold center passing through. I've had like six closed lows pass over me since mid-December and it still hasn't rained officially, or snowed officially at the airport here, even as a lot of the state has seen decent moisture overall. Some places seem to have legitimately picked up 0.5" or more with the storm today and yesterday.

Early on, December was a terrible match to 2007. But after 12/10 or 12/15 the pattern became similar. You can see a lot of the US is within one color in 2020-21 v. 2007-08, i.e. within two degrees. I had other analogs to warm up the Northeast & West from 2007-08, so we've actually been moving toward my blend. January 2008 is actually very cold late in the South, and it doesn't look too cold this year, so that will move my blend closer to observations since I've been running too warm in the South so far.. 

[raindancewx]

Droughts end. Keep your fingers crossed.

[PoZitron20]

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