raindancewx

Looks like another good snow event for Western Colorado and then the Plains. We'll get some good snows here in the mountains too. The Euro should start to have a good idea on precipitation totals for the majority of this event this time tomorrow. Large areas of NM & AZ may be able to pull out a wetter than average December if this verifies or trends wetter.

Amazing to think how warm this month would have been in the Northeast & Midwest without the -NAO and the snowstorms honestly. The WPO is a pretty big warm signal for the Northeast in December when positive and a cold signal for the interior West, so seems like we are seeing pretty canonical effects of its dirty work. The US had a warm November, but the warmth in Canada this month is impressive too.

Not a lock just yet, but increasingly looks like this December will finish with every day seeing a high below 60 degrees, and every morning seeing a low 32 degrees or colder. Both are pretty rare in December.

My best guess is the SOI finishes around +14 in December at the moment. If you match similar SOI years to December temperature observations in the US, I think a look similar to 1955, 1960, 2000, 2008 as a blend is likely for January. It's kind like a colder January 1989. The January look below is pretty similar to my winter forecast idea too. If the SOI goes a lot higher or lower by the end of the month, will have to change the mix to match observations. Jan WPO EPO PNA AO NAO D SOI 2008 0.92 -1.25 -0.32 0.82 0.89 13.3 2000 -0.21 -0.92 -0.82 1.27 0.6 12.4 1955 0.4 -1.32 0.4 -1.16 -1.84 11.5 1960 -0.03 -0.76 0.38 -2.48 -1.29 6.9 Blend 0.27 -1.06 -0.09 -0.39 -0.41 11.03

This is what I have for correlations for all the major indexes for January. You can see for New Mexico, it's at least possible all five will be favorable at the same time for cold in January. I don't expect all five to be favorable the whole month though, but it seems like they'll align at times. Blues and purples are negative correlations, greens and yellows are positive. The SOI is probably going to warm the south pretty quickly by February - which mechanism that is by is anyone's guess.

Looks to me like there is a non-trivial chance of seeing all the main indexes that support cold in New Mexico to be in the favorable cold positions in January. Essentially a +WPO and then blocking with a low by Alaska.

I appreciate that. I don't really use the indexes much, but if I do I use the +EPO that matches the index on the CPC site. I was just trying to point this out because when Weatherbell puts out their teleconnection stuff, I'm wondering if people are looking for the wrong sign of the EPO when they look for Eastern cold if they use a -EPO as ridging while CPC is using a +EPO as ridging. It's also possible Weatherbell is using a different calculation than CPC. This is one of the things I can't stand about Twitter, I see people reference the indexes but it's clear there is a 50/50 split on whether a -EPO or a +EPO is ridging by Alaska from different forecasters, I was trying to show that with the Wisconsin site earlier.

Date Tahiti (hPa) Darwin (hPa) Daily Contribution 30 day Av. SOI 90 day Av. SOI 24 Dec 2020 1010.81 1006.15 4.88 15.22 9.62 23 Dec 2020 1010.84 1004.25 14.89 15.16 9.75 22 Dec 2020 1012.31 1004.30 22.26 14.40 9.75 Big drop again. Another time to watch will be 1/3. Probably a weaker system though.

I know what it takes to make it cold in the East. I'm saying that the orange and reds up there are sometimes called a -EPO and sometimes called a +EPO. To give another example, this is from Weatherbell. They seem to be in the '-EPO' = heights by Alaska. But the index seems to be opposite on the CPC site. November 2014 has a +EPO on the index, but seems to fit the -EPO definition some people use. I don't get why people use different phases of the index to describe the same thing. I get what it does. That's not the issue. Does this clarify my point about the definition being variable? I get what it does, but it's just weird seeing it defined differently. EPO: Eastern Pacific Oscillation (https://www.weatherbell.com/glossary) A dipole pattern similar to the NAO in the Atlantic, but located in the eastern Pacific. There is a tendency for heights/pressures/temperatures to be higher to the north and lower to the south in the negative phase and lower to the north and higher to the south in the positive phase. The negative phase corresponds to widespread cooling over central and eastern North America and the positive phase to warming. CPC Definition: https://www.cpc.ncep.noaa.gov/data/teledoc/ep.shtml The East Pacific - North Pacific (EP- NP) pattern is a Spring-Summer-Fall pattern with three main anomaly centers. The positive phase of this pattern features positive height anomalies located over Alaska/ Western Canada, and negative anomalies over the central North Pacific and eastern North America.

Here is a weird question for everybody. When I look at the EPO index, it is clear the positive phase is the one that is correlated to cold in the Central/East. But then I see sites where the EPO in the negative phase is supposed to do that. I know what the EPO is and what it does, but did CPC change the definition of which phase was positive? There seems to be a common split, where some people refer to the -EPO as "good" for cold in the East and others refer to +EPO as "good" for cold in the East, even though they are clearly talking about the same thing, where one is named incorrectly. This is Nov 2014, 2018, 2019 which all have major +EPO phases on the CPC index. But according to a site like the one below (not picking on them it just popped up), should be a -EPO. When people talk about a positive or negative EPO...are people even talking about the same thing? Phases seem to be defined oppositely in some places. On the same index from CPC, Nov 2016 is negative and very warm in the places that are cold below. https://psl.noaa.gov/data/correlation/epo.data 2014 1.11 0.31 1.24 0.05 0.77 -0.69 0.33 -1.03 0.20 -0.66 3.21 -99.90 2015 1.27 1.18 1.13 -0.35 0.49 1.72 0.23 -0.28 -1.38 0.33 -0.94 -99.90 2016 -0.35 0.23 0.24 1.47 0.14 1.26 -0.36 -0.42 -1.41 -0.84 -1.43 -99.90 2017 0.39 0.21 -1.04 1.04 -0.72 0.50 0.00 -1.65 -0.46 -0.58 0.41 -99.90 2018 0.66 0.23 0.30 -0.18 -0.98 0.05 -0.16 -0.78 -0.83 1.17 1.42 -99.90 2019 1.07 1.20 2.11 0.67 0.32 1.74 0.10 -1.18 -1.50 -0.47 1.93 -99.90 2020 -0.60 -1.79 0.44 1.54 0.04 -0.69 -1.97 -2.39 0.06 0.57 -0.66 -99.90 https://www.wisconsinwx.com/teleconnections

The 30-day SOI has run up to +14. If we hold at +10 to +18 like in December 2007, you should see pretty strong warmth develop in the South either in or by February. None of the years in the +10 to +18 SOI range are cold in the South in February. It's arguably the strongest correlation for the SOI of the entire year. The coldest major +SOI December years are still 'slightly warm' in the South the following February.

Those four years above as a blend are very warm for January. I've been looking at the January cold-ENSO years following two El Nino winters. Those are pretty cold in the West pretty reliably. 1929-30/1930-31 El Ninos ---> Jan 1932 1957-58/1958-59 El Ninos --> Jan 1960 1968-69/1969-70 El Ninos --> Jan 1971 (may look warm in the West, but featured a record cold shot and record warmth) 1976-77/1977-78 El Ninos --> Jan 1979 1986-87/1987-88 El Ninos --> Jan 1989 2014-15/2015-16 El Ninos --> Jan 2017 I think I'd add 3.0F to this in the Plains for lack of snow cover and +1.5 everywhere else since the analogs are centered on the 1970s.

When I did my forecast for winter, I knew 2007-08 had a +WPO just from looking at temperature patterns in Asia and the US, but I didn't realize there was a formalized index for it. It's a weird time frame to do a forecast, but the WPO is super useful for trying to figure out if Feb-Apr will be cold or warm out here. In the meantime, CPC still has the Western US cold for a while, especially the interior. I was doing an analysis of my analogs earlier today for 12/1-12/21 v. US observations. I'm pretty close in a lot of the eastern Midwest, Northeast (outside Maine), interior West, and the edges of the South (VA, Arkansas, Oklahoma). I'm not close at all Northern Plains and Deep South, but the deeper we get into the month, the more the month has looked like my blend. One of the ideas in my forecast was at least some cold periods in the interior West this winter, based on low sea ice in the Summer + cold ENSO. That's at least partially right. If you use Albuquerque as a proxy, we haven't hit 60 this month. Even on a 'warm' day like today when we'll be mid-50s, it was 22 in the morning, which prevents the highs from getting out out control. I'm curious to see if the areas outside the Northern Plains and Deep South can trend toward what I had more by the end of the month.

Boston is still running close to 3x the 30-year average for snow totals for the date. That's not really sustainable for the long-term, since you won't get 120+ inches of snow this Oct-May. Question is whether there is an extended quiet period or you just slowly move back toward average with relatively normal totals from here on, say, 30-40 inches from 12/22-5/31. My hunch with this year has always been that each region of the US would see 2-3 big storms and a bunch of little storms. I don't have data to back that up, it's just my sense of things. You've arguably had two in the Northeast - the big Nor'easters in Oct/Dec, two in the Rockies - the Sept/Oct storms, one in the Midwest - the late Nov storm. If you look at what the models forecast for December, it's pretty clear the Canadian at least had some idea of what was going to happen. A +WPO, +PNA, -AO, -NAO December looks like this, but of course even in the south a lot of areas are now running a bit above average, and it's actually been fairly cold out here. Something like ~30th coldest December 1-21 high so far in 100 years, even after a few relatively warm days recently. It's kind of amazing how much warmer the look is compared to the composite, and it seems like that's the main issue with the seasonal models. They aren't bad at identifying the 'looks' up above.

I'm starting to see a lot of speculation about an active tornado season. One thing that is against that is the current WPO / Nino 4 blend. The WPO is a very strong signal for a cold SW / warm Central US in April if it is positive, and the opposite if negative. A blend of a +WPO December and a cold Nino 4 December (27.6C or so) is unusual. The blend I get is something like this: That favors a pretty -WPO in April, which is actually a warm Southwest/cold Central pattern, i.e. not real tornadic. The WPO correlations change dramatically in May. But if you want a big tornado season, you should be rooting for the WPO to hang on positive through April. WPO Feb Mar Apr 1953 1.38 0.58 -1.86 1972 -2.26 -1.87 -0.01 1985 -1.12 1.81 -0.53 2008 0.01 -1.35 0.28 2009 1.71 0.22 0.02 Blend -0.06 -0.12 -0.42

The Euro still has a system in the time frame you'd expect after the SOI crash. I would expect something to come through. I realized yesterday there is monthly data for the West Pacific Oscillation. We flipped from an extremely negative WPO in October to a positive WPO in November-December. That's useful for preventing winter warmth out here. I hope it continues in Feb-Apr, because it's a very strong cold signal for the Southwest in that time frame. The WPO correlation to the US in October and what actually happened in October is basically uncanny, it's a powerful little index at certain times.

I realized yesterday that there is monthly data for the WPO, the West Pacific Oscillation, which is actually super powerful as a predictor in some months. Check out October (-2.44 was actually the WPO September reading, should say -1.18 on the graphic for Oct): Since October, the index has been positive. Check out December, v. the rolled forward +WPO, +PNA, +AO, +NAO blend for November: I don't think the +WPO, +PNA, -AO, -NAO December look is right for January. It looks pretty off to me. But we can see. The look is essentially January 2000, which didn't have the +WPO or +PNA, and I'd bet on both continuing at least a bit in January. Arctic is probably wrong too. But just thought I'd show the composite. The WPO is actually very powerful at out here for Feb-Apr, so I am hoping it stays positive.

Nino1+2 Nino3 Nino34 Nino4 Week SST SSTA SST SSTA SST SSTA SST SSTA 04NOV2020 20.3-1.0 23.6-1.3 25.1-1.5 27.8-0.8 11NOV2020 21.2-0.3 24.1-0.9 25.7-1.0 27.9-0.7 18NOV2020 21.0-0.7 23.6-1.4 25.2-1.5 27.9-0.7 25NOV2020 21.0-1.0 23.7-1.3 25.3-1.3 27.9-0.7 02DEC2020 21.8-0.5 24.4-0.7 25.5-1.1 27.6-1.0 09DEC2020 22.4-0.1 24.3-0.8 25.4-1.2 27.7-0.8 16DEC2020 22.0-0.8 24.3-0.8 25.6-0.9 27.8-0.7 I don't know that Nino 1.2 averages really change as rapidly as depicted, but that's the only region that cooled off by actual temperatures this week. Nino 3.4 is at 25.5C for the month, which is about -1.0C for 1951-2010. Nino 4 is still pretty cold. Nino 1.2 averages 22.58C for 1951-2010 in December, so that's still the laggard in terms of coolness. The 20.86C last month was about -0.6C against 1951-2010.

The +NAO Nov, -NAO Dec thing is pretty unusual if it verifies, regardless of ENSO - but there are no La Ninas with the combo. These are the only years to do it since 1950. You can see it is a mixed bag for January. Of the years in the chart 1953 is closest to US conditions for Nov-Dec. Also very curious to see the weekly data tomorrow. Should give a good idea if December is really going to finish warmer than November in Nino 3.4. The SOI is around +13 for the past 30 days despite the big crash recently. Has been similar to 2007-08 since October on that indicator. https://www.longpaddock.qld.gov.au/soi/

Will be interesting to see how the winter transitions after December. Currently looks like Dec 2017 and Dec 2018 as a blend.

My winter forecast included the idea that the NAO would go negative in December and then revert positive for Jan-Feb based on 'NAO analogs' which match the 2020 NAO in predictive periods to similar behaving predictive periods. Will be curious to see how that goes. The NAO is a much more important as a national feature for Jan-Apr than at other times.

Date Tahiti (hPa) Darwin (hPa) Daily Contribution 30 day Av. SOI 90 day Av. SOI 20 Dec 2020 1011.45 1005.80 10.02 12.80 9.49 19 Dec 2020 1012.11 1002.50 30.57 13.03 9.54 18 Dec 2020 1012.34 1002.05 34.10 12.68 9.35 17 Dec 2020 1013.64 1003.35 34.10 12.22 9.08 16 Dec 2020 1013.54 1004.30 28.65 11.67 8.85 Keep your eyes on the end of the month. That's a pretty massive drop for one day. The SOI is still positive, so it's probably a northern stream system with some pop if something is going to come through. The SOI crashed pretty hard in a very positive month about this time (12/18-12/19) in 2018 ten days before the end of the month system. 2018 352 1014.64 1006.70 21.90 2018 353 1013.25 1008.05 7.68 This is late 2016 - 2016 355 1010.63 1002.35 23.66 2016 356 1010.94 1003.25 20.60 2016 357 1009.60 1005.95 -0.36 2016 358 1007.23 1006.85 -17.33 Pretty hard to find 20 point drops in a day at this time of year.

Date Tahiti (hPa) Darwin (hPa) Daily Contribution 30 day Av. SOI 90 day Av. SOI 20 Dec 2020 1011.45 1005.80 10.02 12.80 9.49 19 Dec 2020 1012.11 1002.50 30.57 13.03 9.54 18 Dec 2020 1012.34 1002.05 34.10 12.68 9.35 17 Dec 2020 1013.64 1003.35 34.10 12.22 9.08 Those 20 point crashes are rare...but fun usually. No idea if this will work, but if you run objective "closest high" matches for 22 US cities and then pull out the most common top-10 close matches as analogs, you get a pretty good map for December, followed by an extremely warm US winter. I would say, very generally, either 2011 or 2012 or both were common western matches, while 1999, 2011, 2017 were more likely in the East. Overall, 2001 was the year that most commonly appeared as a top 10 match, which surprised me a bit.

Nino 4 in the prior winter is fairly predictive of what the NAO does in February. Bodes better for February 2022 in the East with Nino 4 likely to finish in the low 27s. But Nino 4 was 29.19C last winter. Not a good sign for this year. Above 28.7C in Nino 4 the prior winter, only 1 in 20 winters is below -0.2 for the Feb NAO. February NAO averages +0.6 for years following Nino 4 over 28.7C in winter, but averages -0.1 in the remaining colder years. This is your +NAO La Nina composite - although I'd expect a somewhat different result.

I use this for snowfall data. Locally it is imperfect and has some small data issues, but it's 99% right. https://xmacis.rcc-acis.org/