2019 ENSO

[WestMichigan]

Sure is heading that way.  Interesting to see if it continues or not.

[raindancewx]

For reference. The European had a substantial warm up in Nino 3.4 (slightly different from CPC - they only show slight warming because they use a different baseline for what is average each month).

[raindancewx]

CPC is set to update its baseline averages in 2021 for El Nino and La Nina. It looks to me like the new winter average (DJF) in Nino 3.4 is going to be right around 26.63C for 1991-2020, whereas the 1951-2010 average is 26.50C.

Any event that can finish below 26.15C or so will be classified as a La Nina in 2020-21.

I've been pretty impressed with 2003/2010 for how close that blend is to the tropical pacific and has been for a while now. I'll have my winter outlook out in October - but this looks like an easier forecast than last winter to me. For the past three months, the subsurface is a very strong match to 1984, 2003, 2003, 2010 as a blend too.

My general sense is the NAO will be positive, with the PDO negative, and La Nina/near La Nina conditions. Solar activity has been increasing lately, but not dramatically. That's similar to 2009, when the absolute floor was in February. That's a bit of a wildcard. My current leading analog blend for winter has an ACE index around 160 for the Atlantic in 2020, which currently looks about right - we'll see it goes.

100-180W	May	June	July
1984	-1.11	-1.15	-0.25
2003	-0.85	0.13	0.53
2003	-0.85	0.13	0.53
2010	-1.00	-1.34	-1.36
Blend	-0.95	-0.56	-0.14
2020	-0.92	-0.62	-0.17

[raindancewx]

                Nino1+2      Nino3        Nino34        Nino4
 Week          SST SSTA     SST SSTA     SST SSTA     SST SSTA
 01JUL2020     21.1-1.1     25.5-0.5     27.3-0.1     29.1 0.3
 08JUL2020     21.1-0.8     25.3-0.5     27.2-0.1     29.1 0.3
 15JUL2020     20.2-1.5     25.1-0.6     27.0-0.2     28.8 0.0
 22JUL2020     20.2-1.2     25.0-0.5     26.8-0.4     28.7-0.1
 29JUL2020     20.1-1.1     24.7-0.7     26.3-0.8     28.4-0.4
 05AUG2020     19.8-1.2     24.6-0.6     26.3-0.6     28.4-0.3

Nino 3 has been in La Nina conditions for three months now. Nino 3.4 / 4 keep warming up each time a cold pulse reaches them. 

I'm starting to think this will be a "Nino 3" La Nina, but an official Neutral.  August is still cold below the surface so far, but barely. The level of coolness is actually very similar to last year, which is interesting since August looks very similar so far.

[raindancewx]

The latest subsurface update does look a bit better. European is still not 100% on board with a La Nina, but I've been expecting a ~26.0C Nino 3.4 in Dec-Feb, and that still looks about right, whether its a hair on the Neutral side or a hair on the La Nina side. The cold water has really thinned by South America though, and there is still a lot of warmth below Nino 4. To me there is some potential for a cool peak in Fall for Nino 3.4 - maybe to near -1.0 as the cold comes up - and then it warms fairly consistently through winter. There is some intense cold right now in Nino 3/3.4 but it isn't a very large or deep area. Once that surfaces, you'd expect the warmth west of it and below it to have a shot at coming up.

[StormchaserChuck!]

Subsurface definitely looks like a Weak Nina it usually drifts greater through October/Nov so maybe it will break -0.5.

[StormchaserChuck!]

No Super-El Nino watch for next year, I think. We've got a little bit out of "dead pattern" but still have a long way to go I think before anything greater than ~0.7 develops. Maybe we will transition to warmer waters in the Spring though. Pretty interesting. 

[raindancewx]

The subsurface is now pretty supportive of a La Nina compared to a few weeks ago, although I think the cooling will reverse to some extent over the next few weeks.

[StormchaserChuck!]

It certainly looks like a negative ENSO in Atlantic tropics right now. 

[StormchaserChuck!]

Some legitimate La Nina here, Long range models were showing a +PNA until today it switched to -PNA

 

I have that theory about subsurface trend = PNA state. 

[raindancewx]

               Nino1+2      Nino3        Nino34        Nino4
 Week          SST SSTA     SST SSTA     SST SSTA     SST SSTA

 03JUN2020     23.1-0.3     26.0-0.7     27.3-0.4     29.0 0.2
 10JUN2020     22.2-0.8     25.7-0.9     27.1-0.6     28.8 0.0
 17JUN2020     22.2-0.5     25.7-0.7     27.2-0.4     29.1 0.2
 24JUN2020     21.6-0.8     25.8-0.4     27.6 0.1     29.3 0.5
 01JUL2020     21.1-1.1     25.5-0.5     27.3-0.1     29.1 0.3
 08JUL2020     21.1-0.8     25.3-0.5     27.2-0.1     29.1 0.3
 15JUL2020     20.2-1.5     25.1-0.6     27.0-0.2     28.8 0.0
 22JUL2020     20.2-1.2     25.0-0.5     26.8-0.4     28.7-0.1
 29JUL2020     20.1-1.1     24.7-0.7     26.3-0.8     28.4-0.4
 05AUG2020     19.8-1.2     24.6-0.6     26.3-0.6     28.4-0.3
 12AUG2020     19.9-0.9     24.8-0.3     26.4-0.5     28.3-0.4

There is some erosion in the cold near South America, but still borderline La Nina conditions overall. If Nino 3 and Nino 4 remains above -0.5 though it is likely Nino 3.4 will warm up a bit eventually, for a little while anyway.. 

[raindancewx]

If La Nina persists into say, February, August is looking like the first La Nina month. Magnitude of the cold is La Nina, just have to see the duration now.

                Nino1+2      Nino3        Nino34        Nino4
 Week          SST SSTA     SST SSTA     SST SSTA     SST SSTA
 01JUL2020     21.1-1.1     25.5-0.5     27.3-0.1     29.1 0.3
 08JUL2020     21.1-0.8     25.3-0.5     27.2-0.1     29.1 0.3
 15JUL2020     20.2-1.5     25.1-0.6     27.0-0.2     28.8 0.0
 22JUL2020     20.2-1.2     25.0-0.5     26.8-0.4     28.7-0.1
 29JUL2020     20.1-1.1     24.7-0.7     26.3-0.8     28.4-0.4
 05AUG2020     19.8-1.2     24.6-0.6     26.3-0.6     28.4-0.3
 12AUG2020     19.9-0.9     24.8-0.3     26.4-0.5     28.3-0.4
 19AUG2020     19.5-1.1     24.3-0.7     26.0-0.8     28.4-0.2

There is still a lot of heat below the western part of Nino 4 that should move east or spread out with time, but the cold should hold on in Nino 3.4 through at least September. I still expect something a fall peak in severity and some of the ENSO models show that.

[raindancewx]

One thing to watch with the La Nina is when the event peaks. If you look at it on a constant 1951-2010 basis, the La Ninas that peak in the Fall (coldest Nino 3.4 relative to monthly average) are much colder in the US than the La Ninas that peak in the winter. In fact, none of the La Nina with a peak in the Fall are warm US wide, although 2011-12 was really only cold in NM and West Texas. There are some very hot winters included in the mix when you get a winter La Nina peak - 1998, 1999, 2005 are all in there. I'd imagine 1933, 1942, and 1949 are in the right grouping too, with 1938 in the left group.

[Snowstorms]

Most recent MEI value (JJ) was -1.0 which is borderline moderate La Nina. The new value for JA may come in higher as we've seen more progressive cooling across all ENSO regions through-out this month. Further cooling should continue over the next few weeks as a strong trade wind burst is expected next week esp over western ENSO regions. 

The new MEI v2 uses 5 variables compared to the old MEI which used 6. I prefer MEI as it takes into consideration all ENSO regions compared to ONI. 

[raindancewx]

Another thing is, when the ACE index is over 160 in the Atlantic heading into a La Nina winter, the composite pattern is very different from when the ACE is below 160. The recent La Ninas that were good for the West, 2000, 2011, 2016 - were all well below 160. While 1995, 2005, 2017 had values in the 200+ range and saw essentially no moisture or cold in the Southwest especially. The current ACE value is about 42 through 8/28. We're entering the peak of the Atlantic hurricane season, but it looks quiet through early September. so that 42 value should move closer to average than it is now. I don't really expect an ACE value under 80, but the meaningful point is around 150/160 - at that level is becomes almost impossible for the West to have a cold winter in a La Nina.

[StormchaserChuck!]

Good stuff. definite weak La Nina. I don't think anything major will fluctuate. 

[raindancewx]

If the weeklies end up jiving up with the monthly data, by CPC standards, August 2020 will be La Nina level cold in Nino 3.4 (they use a 1985-2014 basis). On an older baseline, still kind of borderline, but very close. What's interesting is using 1951-2010, Nino 4 was still +0.4C in July, and even if the weeklies are right and August finishes at 28.4C in Nino 4...that's still average for Nino 4 which implies that zone will hinder a stronger La Nina from developing. If the subsurface cold is to reverse in Fall (if the Western warmth isn't destroyed in the coming weeks), you'd probably see the subsurface monthly data start to match up with 2000, which had some pretty cold Fall weather as the subsurface peaked and then reversed early by historical La Nina standards.

[StormchaserChuck!]

I'd say the expectations now are that we have some warmer subsurface waters starting in March 2021. We may go Weak or Moderate El Nino, but I don't think anything strong will develop. It could also die out as that is the environment right now, but March-May 2021 is a warm subsurface ENSO signal. 

[raindancewx]

               Nino1+2      Nino3        Nino34        Nino4
 Week          SST SSTA     SST SSTA     SST SSTA     SST SSTA
 29JUL2020     20.1-1.1     24.7-0.7     26.3-0.8     28.4-0.4
 05AUG2020     19.8-1.2     24.6-0.6     26.3-0.6     28.4-0.3
 12AUG2020     19.9-0.9     24.8-0.3     26.4-0.5     28.3-0.4
 19AUG2020     19.5-1.1     24.3-0.7     26.0-0.8     28.4-0.2
 26AUG2020     20.0-0.6     24.2-0.7     26.1-0.7     28.6-0.1

Some warming this week in all zones in absolute SSTs outside Nino 3 which cooled. Still need Nino 3.4 to get colder than it is now for La Nina conditions in winter.

[raindancewx]

It's very difficult to get a good subsurface match for June-August that respects a) the big subsurface warm up in July, and b) the big subsurface cool down in August. A blend of 1984, 2003, 2010 has both rapid changes but isn't quite right on their severity, and has a fairly cool September for the middle of the US as the CFS/Canadian depicted for September.

https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ocean/index/heat_content_index.txt

Year	Jun	Jul	Aug
2010	-1.34	-1.36	-1.74
2003	0.13	0.53	0.03
1984	-1.15	-0.25	-0.22
Blend	-0.79	-0.36	-0.64
2020	-0.62	-0.17	-0.81

There is a strong correlation in the subsurface data for August to Nino 3.4 Dec-Feb temperature - the historical data (1979-2019) implies a 25.74C Nino 3.4 in winter, plus/minus 0.72C at 80% certainty. That's an 80% chance of a cold ENSO between +0.00C and -1.50C against 1951-2010 Nino 3.4 averages. Worth noting, the severity of the cold below the surface may be flat lining again, or even set to rise again. It is interesting to me that the cold peak in May has not be matched again, at least so far.

[raindancewx]

CPC has August Nino 3.4 SSTs 0.60C below the 1985-2014 average for Nino 3.4.The 26.3C value for August is still only 0.35C below the 1951-2010 average. Nino 4 is actually still about 0.1C above the 1951-2010 average in August (although a degree colder than last year).

The official ONI value for JJA is -0.4C. The Nino 3 and Nino 3.4 readings for August are the coldest they've been awhile but both were -0.35C against 1951-2010. Nino 1.2 was -0.75C in August against 1951-2010. The figure in Nino 3.4 for August is almost identical to August 2016, but that La Nina (and it doesn't even qualify as one by older standards such as 1951-2010) ended in January in a CPC/ONI sense.

I don't get the sense that this event will be as weak - the 2016-17 event finished with a 26.3C reading for Winter 2016-17 - the average in that zone is 26.5C long term and 26.58C for the CPC period - so the La Nina was over by then.

[Snowy Hibbo]

Just an extract from my early seasonal update about ENSO, thought the analog might interest some. Text not entirely relevant to the US, worthy of note on the analog is the SE ridge that comes along with it.

Quote

We are arguably looking at a more Central Pacific or Modoki based Nina if we are going to take this for face value. There is some research backing stronger precipitation in the Japan region during the winter during a Nina Modoki. But in general we see conditions from a Nina that favour snowfall in the Northern parts of the US and Canada. And for Europe, we see a +NAO type set-up, so wet for the UK and Northern Europe, snowy for the Northern Alps, and less snowy for the Southern Alps.

I took a wide selection of Nina Modoki/Central Pacific years, and we see pretty similar themes. A strong Aleutian high, which pushes troughing into Northern and Western North America. A strong +NAO and therefore jet stream coming off the NA Continent towards the UK and Europe. And finally a +AO, indicated by the trough over the Arctic. All this points to a strong snow season for the Western and Northern US, as well as the Northern Alps.

 

[StormchaserChuck!]

That's quite an extreme Strong-Nina composite, I'm not saying the N. Pacific ridge won't build as strong, but that's right in the prime NPH spot. 

[raindancewx]

One thing I've been looking at lately is how the ACE Index relates to severe cold outbreaks in La Ninas in the Southwest.

In general, there are more cold days in lower ACE La Ninas if you use 10F below average in Nov-Feb as the threshold. But it doesn't hold super well for the rarer, more intense cold waves. Current ACE index is 45 - and we're about half way through the season now.

The chart shows subsets, i.e. 1933-34 had four days in Nov-Feb that were at least 10F below average, of which, one was 15F below average.

Cold Days Nov-Feb in Albuquerque by ACE Index
La Nina	ACE Index	<=-10F	<=-15F	<=-20F
1933	258.6	4	1	0
1938	77.6	25	10	3
1942	62.5	3	0	0
1949	96.4	10	2	0
1950	211.3	11	5	4
1954	110.9	6	2	0
1955	158.2	12	5	2
1956	56.7	8	3	0
1964	169.8	10	3	0
1970	40.2	8	6	5
1971	96.5	11	7	1
1973	47.9	15	5	3
1974	68.1	21	10	4
1975	76.1	10	4	0
1983	17.4	5	2	0
1984	84.3	15	3	2
1988	103.0	13	2	2
1995	227.1	1	0	0
1998	181.8	4	0	0
1999	176.5	1	0	0
2000	119.1	11	2	0
2005	250.1	3	0	0
2007	73.9	10	0	0
2008	145.7	2	0	0
2010	165.5	11	7	3
2011	126.3	2	0	0
2016	141.3	3	0	0
2017	224.9	0	0	0

Weatherbell has this for the winter, if anyone is curious - fairly typical low-average ACE La Nina winter look.

[raindancewx]

                 Nino1+2      Nino3        Nino34        Nino4
 Week          SST SSTA     SST SSTA     SST SSTA     SST SSTA
 01JUL2020     21.1-1.1     25.5-0.5     27.3-0.1     29.1 0.3
 08JUL2020     21.1-0.8     25.3-0.5     27.2-0.1     29.1 0.3
 15JUL2020     20.2-1.5     25.1-0.6     27.0-0.2     28.8 0.0
 22JUL2020     20.2-1.2     25.0-0.5     26.8-0.4     28.7-0.1
 29JUL2020     20.1-1.1     24.7-0.7     26.3-0.8     28.4-0.4
 05AUG2020     19.8-1.2     24.6-0.6     26.3-0.6     28.4-0.3
 12AUG2020     19.9-0.9     24.8-0.3     26.4-0.5     28.3-0.4
 19AUG2020     19.5-1.1     24.3-0.7     26.0-0.8     28.4-0.2
 26AUG2020     20.0-0.6     24.2-0.7     26.1-0.7     28.6-0.1
 02SEP2020     18.9-1.6     23.6-1.3     25.8-0.9     28.4-0.3

Pretty strong drops across the board this week. I still like at least an initial peak for the La Nina intensity in the Fall. But as long as Nino 4 is much warmer (by anomalies and actual temperatures), it will be hard for Nino 3.4 to cool too much I think. Look at  2010 or 2007 which peaked around 25.0C in Nino 3.4 -

01SEP2010     18.8-1.7     23.4-1.5     25.1-1.7     27.2-1.5

05SEP2007     19.4-1.1     23.7-1.2     26.0-0.8     28.3-0.4

I actually like 2007 as an analog, but I'll have more on what I expect in the coming weeks for the winter. We're way warmer than 2010 at this point though.

[Fred Gossage]

6 hours ago, raindancewx said:

                 Nino1+2      Nino3        Nino34        Nino4
 Week          SST SSTA     SST SSTA     SST SSTA     SST SSTA
 01JUL2020     21.1-1.1     25.5-0.5     27.3-0.1     29.1 0.3
 08JUL2020     21.1-0.8     25.3-0.5     27.2-0.1     29.1 0.3
 15JUL2020     20.2-1.5     25.1-0.6     27.0-0.2     28.8 0.0
 22JUL2020     20.2-1.2     25.0-0.5     26.8-0.4     28.7-0.1
 29JUL2020     20.1-1.1     24.7-0.7     26.3-0.8     28.4-0.4
 05AUG2020     19.8-1.2     24.6-0.6     26.3-0.6     28.4-0.3
 12AUG2020     19.9-0.9     24.8-0.3     26.4-0.5     28.3-0.4
 19AUG2020     19.5-1.1     24.3-0.7     26.0-0.8     28.4-0.2
 26AUG2020     20.0-0.6     24.2-0.7     26.1-0.7     28.6-0.1
 02SEP2020     18.9-1.6     23.6-1.3     25.8-0.9     28.4-0.3

Pretty strong drops across the board this week. I still like at least an initial peak for the La Nina intensity in the Fall. But as long as Nino 4 is much warmer (by anomalies and actual temperatures), it will be hard for Nino 3.4 to cool too much I think. Look at  2010 or 2007 which peaked around 25.0C in Nino 3.4 -

01SEP2010     18.8-1.7     23.4-1.5     25.1-1.7     27.2-1.5

05SEP2007     19.4-1.1     23.7-1.2     26.0-0.8     28.3-0.4

I actually like 2007 as an analog, but I'll have more on what I expect in the coming weeks for the winter. We're way warmer than 2010 at this point though.

Both were officially strong La Nina episodes, with 2010-2011 being a bit more robust.  Both peaked with 3.4 at  -1.6C or lower and held -1.5C or lower for three or more trimonthly periods.

https://origin.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ONI_v5.php

[raindancewx]

My primary issue with 2007-08 is that Nino 4 eventually cooled off a lot too - to around 27.0C. It took an enormous amount of subsurface cooling to do it though.

https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ocean/index/heat_content_index.txt

YR    MON   130E-80W   160E-80W   180W-100W 

2007    8     -.16      -.42       -.68
2007    9     -.35      -.69      -1.03
2007   10     -.52      -.87      -1.19
2007   11     -.54      -.97      -1.19
2007   12     -.49      -.87      -1.08

In the current setup, the subsurface cold seems to be slowly thinning, not deepening like in 2007.

[Snowstorms]

2 hours ago, raindancewx said:

My primary issue with 2007-08 is that Nino 4 eventually cooled off a lot too - to around 27.0C. It took an enormous amount of subsurface cooling to do it though.

https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ocean/index/heat_content_index.txt

YR    MON   130E-80W   160E-80W   180W-100W 

2007    8     -.16      -.42       -.68
2007    9     -.35      -.69      -1.03
2007   10     -.52      -.87      -1.19
2007   11     -.54      -.97      -1.19
2007   12     -.49      -.87      -1.08

In the current setup, the subsurface cold seems to be slowly thinning, not deepening like in 2007.

Subsurface anomalies are still relatively cold across much of the ENSO regions with the exception of Nino 4 as you mentioned. However, one thing to keep in mind is that 2007 had similar subsurface anomalies across far western ENSO regions to date. We should see continued trade winds blowing over the ENSO regions with another strong easterly burst coming next week. We'll see what impact that has, but regardless the SOI is now in Nina territory. The MJO is expected to remain weak/inactive as per models so this La Nina will continue to strengthen over the next few weeks. As it stands right now, I suspect this Nina will peak in the winter as did 2007. 

[raindancewx]

This stuff is surprisingly hard to find, but the trend in 2007 at the subsurface was pretty clearly to rapid cooling. There was a brief plateau, and then the bottom really fell out in September

In any event, 2007 is the much better match, not just in the tropics, but certainly in the local weather. It makes more sense too, it's a ~27.3C El Nino transitioning to a ~25.0C La Nina in 2007, while 2010 was like a 28.1C El Nino to a 25.2C La Nina - much bigger change for only a year. To stay on pace with 2007, I think you'd have to see the subsurface fall to -1.0 at least by the end of the month.

[StormchaserChuck!]

Yeah.. we aren't in anything Strong. There is a threshold in ~ONI -0.8 that is a whole different Pacific pattern, more dominant. This right now is kind of "lean toward -PNA".