raindancewx

For the La Ninas since 1930, I found something like 0/18 are 'snowy' for NYC/Philly <150 ACE, and 5/10 are snowy >=150 ACE. It's not as important for Boston, but still preferential for higher ACE. Snowy here meaning more than +20% compared to average. One warning with the La Nina ACE stuff - the correlations aren't just for the NE, they are for the SW too. The correlation here is already likely to be pretty wrong for snow - although it's much weaker than for temperatures overall. The real strong La Nina ACE correlation here is Dec 16-Jan 15 highs. Albuquerque averages ~six inches of snow in La Ninas. But we've already had 4.4" officially. So if you throw out the La Ninas with less than 4.4" snow, you end up with a La Nina average of 8.1", which is near the long-term average of 9.6". Locally, 100% of years with measurable snow (10/10) see at least five months of measurable snow Oct-May. In years without October snow, it's more like 30%. That's the main effect. Years without October snow, tend to see 2-4 months of snow. These are my guidelines locally at this point - but you can see none of them really gel with the ACE index idea now. Basically: October + La Nina average the rest of the way --> 10.6" snow (4.4" + 6.2" --> +10%) La Nina with at least four inches of snow average 8.1" snow (4.4" + 3.7" --> -15%) October + Average of "five month" snow years from Nov-May --> (4.4" + 8.2" --> 12.4" snow (+30%) I'd say the 10.6" is the most likely, but 1/3 of La Ninas will see <3.7" in Nov-May, and 1/3 will see >8.2" in Nov-May. So I think the outcomes above are useful scenarios. My guess is snow tendencies won't change too much the next six weeks from the established pattern. Just a southward shift as winter arrives. Similar look through mid-January though.

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.

I never said 175 or 180 is a breaking point for the NE. It's a breaking point for what I forecast. The years well above 180 are all very hot here, and start to become the best analogs. My unweighted blend actually had about 155 ACE, but since I like 2007 I gave it half weight. It's not just not 1995 in my blend that does it either, I had 2003 in there which is almost identical to the ACE this year. What I did say is the top snowfall in the NE in La Nina years tend to cluster above 150 ACE. NYC/Philly in particular have literally no good snowfall years in a La Nina below 150 ACE. But it's about a coin-flip above 150. 1933, 1995, 2005, 2010, 2017 are the good ones for you guys I think. 2010 is not awful here, but I don't like it as an analog, and the others are very hot/dry here. This pattern is definitely a lot wetter/different here than the non-2010 years though. We've also already had more snow than all of those years just in October where I am.

My July-June snow anomaly map looks OK so far. Canada border with Idaho/WA to NW NM/Western Colorado, Midwest, and Northern New England were favored zones.

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.

SOI crash verified - Date Tahiti (hPa) Darwin (hPa) Daily Contribution 30 day Av. SOI 90 day Av. SOI 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 17 Nov 2020 1014.71 1009.05 17.69 5.38 8.25 16 Nov 2020 1014.73 1010.05 11.45 4.53 8.37

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.

December is favored to do what I expected in my outlook from October now that the earlier November idea of a late Nov -NAO seems to be off the table. Still think the NAO will go negative at some point in December, but I had December pretty warm anyway, and that still looks right to me.

This is what I get looking at non-El Nino Decembers following a November with a very positive NAO (top 1/3 +NAO for 1950-2019):

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.

The European has been showing a big SOI crash (big high by northern Australia, big low by Tahiti) around 11/20 that lasts for a days. Most recent SOI value was over 20 - the highest in a while - so we could see a 20-40 point crash in a short period that should shake everything up quite a bit around 12/1. The subsurface actually warmed this week too, it wasn't just a surface warming - still similar to 2007 in that regard which weakened in December from an earlier peak and then briefly rallied stronger in January. We're still not particularly close to the very highest Atlantic ACE seasons, but the composite at 180 ACE in a La Nina for 1931-2020 is not exactly a cold look. It's interesting though - four of the five "cold Neutral" years in the 140-220 range are still very much a like the 80-160 ACE La Nina composite. A lot of the years on the left also have extremely high solar activity, which we don't have this year. So if you take the cold-ENSO, low solar, similar ACE years, you get this look: Here are some strengths for the blend: 1932: Only other year on record with a category five hurricane in November in the Atlantic. (Cuba Hurricane of 1932). Snowed into the valleys of the Southwest in October. Fairly similar (but much colder) look to October (coldest Plains/Central). 1964: Delta was similar to Hilda in October, and the first half of November looks a lot like 1964 high temperatures nationally. Followed a weak El Nino like this La Nina is. 1996: Snowed into the valleys of the Southwest in October. Can't really think of any other particular similarities off the top of my head. This was actually the most recent "Major" snowstorm for Albuquerque in October, with several inches. Actually, the way the Jamstec depicts Summer next year in the tropical Pacific is very similar to how the 1997 El Nino developed - so that's another feature in favor of the year. 2008: Big Gulf of Mexico activity like this year, and some months have similar spatial patterns for temperatures (notably not great in Oct-Nov which were very cold in the SE). Pretty good QBO match. 2010: Bad match for the Gulf of Mexico hurricane activity. Similar QBO, followed an El Nino. Very different for blocking patterns and La Nina development. Not a fan of the year overall. 2016: Similar QBO, followed an El Nino. Main issue is the cold patch in the north Pacific (+PDO), and warm Nino 1.2. Also much weaker La Nina. Matthew was the first landfalling October hurricane in a while on the US mainland (Sandy was subtropical). The 1961-62 winter is a good QBO match, with similar types of Atlantic hurricane activity, and similar on NAO trends in the predictive periods for winter. But it had higher solar activity - but it looks almost identical to the six year composite. The six year blend actually looks a lot like November (although too cold).

Nino1+2 Nino3 Nino34 Nino4 Week SST SSTA SST SSTA SST SSTA SST SSTA 07OCT2020 19.5-1.2 23.4-1.5 25.5-1.2 27.8-0.8 14OCT2020 19.6-1.2 23.6-1.3 25.3-1.4 27.8-0.9 21OCT2020 19.9-1.1 23.8-1.2 25.3-1.4 27.8-0.8 28OCT2020 20.0-1.1 23.5-1.5 24.9-1.7 27.9-0.7 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 Pretty nice little warm up this week just about everywhere at the surface. Now well behind 2007 and 2010 for this week. Unlikely to last though. 10OCT2007 18.8-1.9 23.3-1.6 24.9-1.8 27.7-1.0 17OCT2007 18.6-2.2 23.5-1.4 25.3-1.4 27.9-0.7 24OCT2007 19.2-1.8 23.5-1.4 25.3-1.4 27.8-0.8 31OCT2007 19.7-1.5 23.2-1.8 25.2-1.5 27.8-0.8 07NOV2007 19.3-2.1 23.0-2.0 25.0-1.6 27.5-1.1 14NOV2007 19.2-2.3 23.2-1.7 25.2-1.5 27.3-1.3 06OCT2010 18.7-1.9 23.2-1.7 24.8-1.9 27.1-1.6 13OCT2010 18.9-1.9 23.0-2.0 25.1-1.6 27.1-1.6 20OCT2010 19.1-1.8 23.2-1.7 25.1-1.6 27.0-1.7 27OCT2010 19.8-1.3 23.6-1.4 25.2-1.5 27.0-1.6 03NOV2010 19.7-1.6 23.4-1.6 25.2-1.4 27.0-1.6 10NOV2010 19.5-1.9 23.5-1.5 25.2-1.4 27.2-1.5

The North Pacific actually looks like it is starting to respond to the La Nina with a lot of cooling in recent days. Would also say the PDO is trending toward a more normal looking negative phase. It looks to me like the centering of the La Nina will continue to slowly shift West for a while. Don't really expect eastern Nino 3 or Nino 1.2 to cool back down again for a while. One of the odder things about this even is how little the North Pacific has changed to date. I included 2019-20 as an analog almost solely because I suspected the little circled area would show up (presumably from high pressure persistence - I'd have to look).

A quick look at each Nov 1-15 from 1950-2019 shows that the current spatial look to November is fairly rare in that period. I only found six good matches nationally - 1964, 1975, 1978, 1987, 2011, and 2015. You're looking for something like this, but ideally warmer than 2011 was. The best match may be 1964 overall. Here is a look at the unweighted six year blended highs - 1964, 1975, 1978, 1987, 2011, 2015 for ten US cities 11/1-11/15: Boston: 59.9F v. (55.2+65.3+56.1+54.6+60.1+60.9)/6 --> 58.7F Richmond: 69.8F v. (70.2+72.9+68.7+66.6+65.0+66.1)/6 --> 68.3F Jacksonville: 78.7F v. (75.2+76.6+74.9+74.7+72.7+81.1)/6 --> 75.9F Detroit: 61.9F v. (64.0+61.3+58.7+55.3+59.4+60.9)/6 --> 59.9F Chicago: 62.9F v. (64.0+61.3+58.7+55.3+59.4+60.9)/6 --> 59.9F St. Louis: 67.3F v. (71.7+65.3+65.9+65.1+65.6+65.7)/6 --> 66.6F Billings: 51.0F v. (50.0+58.2+42.5+56.5+45.1+51.0)/6 --> 50.6F Albuquerque: 63.0F v. (61.1+66.7+63.7+61.9+56.9+58.7)/6 --> 61.5F San Diego: 72.7F v. (70.3+70.9+69.3+70.3+67.9+73.1)/6 --> 70.3F Seattle: 52.7F v. (48.3+53.7+50.3+56.5+51.2+52.3)/6 --> 52.1F The blend has a cold West look to December as a composite. The ten city average "error" for the Nov 1-15 blend is about 1.6 degrees. I find blends that close over a large area of the US usually hold for a little bit - but we'll see.

Cold morning lows have been a bit ahead of the analog schedule (black v. brown) so far for Albuquerque. Still behind last year though. It's a shame we didn't hit 100 lows <=32F last year with how cold in got in Oct-Nov. But we had super warm lows in March and barely any lows <=32F in Spring.

In 2000, the MJO increased in amplitude in phase 2 in mid-November like the models are showing, but then continued on through the subsequent phases. The increase in amplitude in phase 2 this year is not depicted to continue after that. I don't think I buy that completely, but we'll see soon enough. Very curious to see what the weekly data shows on Monday - think the eastern zones may be warming again, as some top layer cold seems to be thinning, but it is still pretty cold below the surface. I keep waiting for the MEI update too, they say on their website by the 10th of the month...but no update yet.

The GFS has been showing a much further south track than the European for the storm around 11/20. Will be interesting to see how that turns out. My winter blend implied November could be one of the wetter cold season months for NM/CO/AZ/UT, but would probably be late month if it did show up.

CPC has that warm December look through at least mid-month that we've become so familiar with over recent years. It's funny - the MJO is actually almost identical to 2000 (also a La Nina) right now but we're not getting anything like 2000 for actual weather with the Arctic behaving differently. But of course Nov/Dec 2000 are very cold.

I don't know if it applies area wide for the SW USA, but for Dec-Feb, Albuquerque is about 3F below the 1891 to 1920 high / 1951-2010 high in 1893-94. I'm sure we'll be very warm here in March though as we always do, so the map is probably about right for Dec-Mar. My main issue with 1893-94 is how dry it is here. It's like 0.25" for the entire winter. We do get dry La Nina years for sure (2017-18 most recently), but they tend to have a super-wet September (like 1893 and 2017) or a super high ACE value (180-280 like 1893 and 2017). 1988-89 is close to an inch here for winter, which is much more likely to me, that's ~25% below average for precipitation, but that year also had a very wet September, which almost always precedes an extremely dry period from Oct-May here in a La Nina. The 1988-89 winter is also super cold in the SW mid-Dec to mid-Jan: I find for temperatures, high elevations in the SE & SW are also slightly colder in low-solar winters than high-solar winters, and both 1893-94 and 1988-89 are pretty high for solar. The 1988-89 winter also followed a ~record wet monsoon. The long and short of it is I think maybe the blend is a bit colder than you realize in the West, and that precipitation patterns will probably be pretty different even though I largely agree with the overall temperature look. 1988-89 is pretty snowy deep into the SW. I have no idea how to get a temperature or snow map of 1893. The blend of 1988/1893 is actually a near perfect match on the current ACE value which does intrigue me somewhat, even though both years have very high solar activity.

A flat blend of 1954 and 2005 is a good match for the three variables I listed above up until about 180 ACE, especially with the solar activity rising fairly rapidly now. That was why I centered the ACE at 135 in my outlook, you can justify the look I want up to about 175 ACE, after that it's not really a likely outcome for the winter anymore. All that said, only the Caribbean is really warm enough to support a big hurricane at this point in the Atlantic and the tropical storms don't add much ACE. The Northern Gulf of Mexico is like 25C right now. The PDO hasn't really changed from October to November on the Nate Manuta index - https://oceanview.pfeg.noaa.gov/erddap/tabledap/cciea_OC_PDO.htmlTable?time,PDO January -0.23 February -0.68 March -0.82 April -0.57 May 0.09 June -0.08 July -0.38 August -0.28 September -0.70 October -0.69

The UKMet November update is warmer than last month for the winter. Looks like most of their recent November outlooks for winter have been bad for the US though. If that colder look in Western Canada verifies though, someone in the US should at least see impressive cold snaps if nothing else. The look is pretty dry along the Mexican border, but it would only be slightly dry where I am, which is more or less what my analogs had too. I would say the SE tended meaningfully drier on the new run in addition to the warmer look overall for the US. On their probabilistic outlook, Texas is most favored to be drier than average, with the NW & Ohio Valley most likely wet. Only California to Montana has a better than 20% shot of being colder than average on the new run, a smaller area than before.

With the ACE index over 160 now, the La Nina composite favors essentially the entire continental US above average for temperatures. That said, I don't think it should be compared directly, since a lot of storms this year never would have been named or correctly observed at a higher intensity like this year. So I'm treating the current reading like it is still about 150 by historical standards, which is still somewhat cooler in the Northwest. The ACE index is high enough now that places like NYC and Philly have a decent shot a snowy winter - you really can't get a snowy winter in those spots in a La Nina if the ACE is below 150. Even so, the odds are not great. The ten highest ACE La Ninas are 50/50 for above average snow in NYC, but the correlation is pretty direct, and those ten winters average ~200 ACE which is highly unlikely even with two tropical storms out there right now. I have an experimental regression for La Ninas winter highs here. Even at 160 or 170 ACE (favoring a hot SW in a La Nina), it favors a fairly cold winter here because we hit 90 degrees so early, which is where all the cold La Ninas are clustered locally. If you try to match on the three inputs, solar, ACE, and when we first hit 90, a blend of 1954 and 2005 is pretty close.

The local NWS likes a blend of 2007-08, 2010-11, 2016-17 for the winter. That blend is actually very wet for the West - that's my main issue with it. http://www.weather.gov/media/abq/Briefings/202021WinterOutlook.pdf

The local weather service likes 2016-17, 2010-11, 2007-08 as analogs for the winter. https://www.weather.gov/media/abq/Briefings/202021WinterOutlook.pdf

I'm on board with what Roger said - there should be a storm that comes through the West like the October system that runs up the coast at some point, but it would be cold enough for most areas to see snow. It does look like he is using 1975-76 as the main year. Would be cool to see that Spring, pretty sure it snowed down to El Paso last week of April 1976. That was my issue with 1975-76 when I looked - I don't know that we'll transition into an El Nino next year. I don't have a good feel on that at all. The MJO in 1975 isn't terrible compared to this year, but its off by 2-3 weeks timing wise I'd say heading into December. That's one of the reasons I didn't give 2007 full weight in my outlook, it's been off for the MJO timing for a while now. The little heat core max over Nebraska and Missouri is very 1975-76, it's usually warmest in a La Nina in Texas, the Southwest or the Southeast, so it's likely that is the year used at least in part. December is probably the easiest to see as 1975, he's got Florida/New England near average with the heat in Montana like here - The winter of 1975-76 actually did have one very cold period nationally though. With the north Pacific and north Atlantic warmer than in 1975-76, I'd imagine this period would be pretty snowy in some places with more moisture available. I think 1975-76 is probably the right idea (though I don't buy the core of the heat over NE/MO), but with the MJO different I'd expect at least a somewhat different progression. You can see for instance October 1975 was pretty warm in the middle of the country, while it was pretty cold this year. October finished looking a lot like 1954 or even 1959 if you try to find a one year match, and those years do get pretty cold out here like Roger said.