2021-2022 ENSO

[40/70 Benchmark]

On 7/19/2021 at 7:32 PM, raindancewx said:

Subsurface has flipped negative this week which is a good sign for a La Nina. July should be near neutral or slightly negative for the subsurface. Still need to cool the surface a lot though.

                 Nino1+2      Nino3        Nino34        Nino4
 Week          SST SSTA     SST SSTA     SST SSTA     SST SSTA 
 02JUN2021     23.2-0.4     26.6-0.2     27.6-0.2     28.8-0.2
 09JUN2021     23.2-0.0     26.7-0.0     27.8-0.0     28.9-0.1
 16JUN2021     23.3 0.4     26.0-0.5     27.2-0.5     28.8-0.2
 23JUN2021     22.9 0.2     26.3-0.0     27.6-0.0     29.0 0.0
 30JUN2021     22.6 0.3     26.2 0.0     27.5-0.1     28.8-0.1
 07JUL2021     22.2 0.1     26.0-0.0     27.4-0.0     28.9-0.1
 14JUL2021     22.2 0.4     25.9 0.1     27.2-0.1     28.6-0.4

Here is last year for comparison. We're nowhere near as cold overall. I know people talk about 2020-21 as a Moderate La Nina, but in winter, if you use 26.5C as average, it was a weak La Nina, and barely spent any time as a moderate. Only two months were -1.0C or colder v. the 1951-2010 monthly averages. We're running +0.2C or so warmer currently than 2020 in Nino 3.4, which finished at -0.9C (25.57C or so) in winter.

 03JUN2020     23.1-0.4     26.0-0.8     27.3-0.5     29.0 0.0
 10JUN2020     22.2-1.0     25.7-1.0     27.1-0.7     28.8-0.2
 17JUN2020     22.2-0.7     25.7-0.8     27.2-0.6     29.1 0.1
 24JUN2020     21.6-1.0     25.8-0.5     27.6-0.0     29.3 0.3
 01JUL2020     21.1-1.2     25.5-0.6     27.3-0.2     29.1 0.1
 08JUL2020     21.1-0.9     25.3-0.6     27.2-0.3     29.1 0.1
 15JUL2020     20.2-1.5     25.1-0.7     27.0-0.3     28.8-0.1

The current 'colder Nino 4' v. 'warmer' Nino 1.2/3 look is opposite July 2019/2020. Somewhat like 2012 and 2011. A blend of 2011/2012 is pretty close in all four zones currently.

 06JUN2012     24.7 1.3     27.1 0.3     27.8 0.0     28.6-0.4
 13JUN2012     24.4 1.3     27.1 0.5     27.9 0.2     28.6-0.4
 20JUN2012     24.3 1.5     27.1 0.6     28.0 0.3     28.8-0.2
 27JUN2012     23.8 1.4     27.1 0.8     28.1 0.5     28.9-0.1
 04JUL2012     23.2 1.0     26.8 0.7     27.9 0.4     28.8-0.2
 11JUL2012     22.6 0.7     26.6 0.7     27.7 0.3     28.8-0.2

 01JUN2011     24.3 0.7     26.8-0.0     27.5-0.3     28.4-0.6
 08JUN2011     24.2 0.9     26.7-0.0     27.5-0.3     28.4-0.5
 15JUN2011     23.8 0.8     26.6 0.0     27.4-0.3     28.4-0.6
 22JUN2011     23.2 0.5     26.5 0.1     27.4-0.2     28.4-0.6
 29JUN2011     22.9 0.5     26.1-0.1     27.4-0.2     28.6-0.4
 06JUL2011     22.2 0.2     25.8-0.2     27.1-0.4     28.5-0.5
 13JUL2011     21.9 0.1     25.7-0.1     27.1-0.3     28.5-0.4

 02JUN2021     23.2-0.4     26.6-0.2     27.6-0.2     28.8-0.2
 09JUN2021     23.2-0.0     26.7-0.0     27.8-0.0     28.9-0.1
 16JUN2021     23.3 0.4     26.0-0.5     27.2-0.5     28.8-0.2
 23JUN2021     22.9 0.2     26.3-0.0     27.6-0.0     29.0 0.0
 30JUN2021     22.6 0.3     26.2 0.0     27.5-0.1     28.8-0.1
 07JUL2021     22.2 0.1     26.0-0.0     27.4-0.0     28.9-0.1
 14JUL2021     22.2 0.4     25.9 0.1     27.2-0.1     28.6-0.4

 

On 7/19/2021 at 7:32 PM, raindancewx said:

Subsurface has flipped negative this week which is a good sign for a La Nina. July should be near neutral or slightly negative for the subsurface. Still need to cool the surface a lot though.

                 Nino1+2      Nino3        Nino34        Nino4
 Week          SST SSTA     SST SSTA     SST SSTA     SST SSTA 
 02JUN2021     23.2-0.4     26.6-0.2     27.6-0.2     28.8-0.2
 09JUN2021     23.2-0.0     26.7-0.0     27.8-0.0     28.9-0.1
 16JUN2021     23.3 0.4     26.0-0.5     27.2-0.5     28.8-0.2
 23JUN2021     22.9 0.2     26.3-0.0     27.6-0.0     29.0 0.0
 30JUN2021     22.6 0.3     26.2 0.0     27.5-0.1     28.8-0.1
 07JUL2021     22.2 0.1     26.0-0.0     27.4-0.0     28.9-0.1
 14JUL2021     22.2 0.4     25.9 0.1     27.2-0.1     28.6-0.4

Here is last year for comparison. We're nowhere near as cold overall. I know people talk about 2020-21 as a Moderate La Nina, but in winter, if you use 26.5C as average, it was a weak La Nina, and barely spent any time as a moderate. Only two months were -1.0C or colder v. the 1951-2010 monthly averages. We're running +0.2C or so warmer currently than 2020 in Nino 3.4, which finished at -0.9C (25.57C or so) in winter.

 03JUN2020     23.1-0.4     26.0-0.8     27.3-0.5     29.0 0.0
 10JUN2020     22.2-1.0     25.7-1.0     27.1-0.7     28.8-0.2
 17JUN2020     22.2-0.7     25.7-0.8     27.2-0.6     29.1 0.1
 24JUN2020     21.6-1.0     25.8-0.5     27.6-0.0     29.3 0.3
 01JUL2020     21.1-1.2     25.5-0.6     27.3-0.2     29.1 0.1
 08JUL2020     21.1-0.9     25.3-0.6     27.2-0.3     29.1 0.1
 15JUL2020     20.2-1.5     25.1-0.7     27.0-0.3     28.8-0.1

The current 'colder Nino 4' v. 'warmer' Nino 1.2/3 look is opposite July 2019/2020. Somewhat like 2012 and 2011. A blend of 2011/2012 is pretty close in all four zones currently.

 06JUN2012     24.7 1.3     27.1 0.3     27.8 0.0     28.6-0.4
 13JUN2012     24.4 1.3     27.1 0.5     27.9 0.2     28.6-0.4
 20JUN2012     24.3 1.5     27.1 0.6     28.0 0.3     28.8-0.2
 27JUN2012     23.8 1.4     27.1 0.8     28.1 0.5     28.9-0.1
 04JUL2012     23.2 1.0     26.8 0.7     27.9 0.4     28.8-0.2
 11JUL2012     22.6 0.7     26.6 0.7     27.7 0.3     28.8-0.2

 01JUN2011     24.3 0.7     26.8-0.0     27.5-0.3     28.4-0.6
 08JUN2011     24.2 0.9     26.7-0.0     27.5-0.3     28.4-0.5
 15JUN2011     23.8 0.8     26.6 0.0     27.4-0.3     28.4-0.6
 22JUN2011     23.2 0.5     26.5 0.1     27.4-0.2     28.4-0.6
 29JUN2011     22.9 0.5     26.1-0.1     27.4-0.2     28.6-0.4
 06JUL2011     22.2 0.2     25.8-0.2     27.1-0.4     28.5-0.5
 13JUL2011     21.9 0.1     25.7-0.1     27.1-0.3     28.5-0.4

 02JUN2021     23.2-0.4     26.6-0.2     27.6-0.2     28.8-0.2
 09JUN2021     23.2-0.0     26.7-0.0     27.8-0.0     28.9-0.1
 16JUN2021     23.3 0.4     26.0-0.5     27.2-0.5     28.8-0.2
 23JUN2021     22.9 0.2     26.3-0.0     27.6-0.0     29.0 0.0
 30JUN2021     22.6 0.3     26.2 0.0     27.5-0.1     28.8-0.1
 07JUL2021     22.2 0.1     26.0-0.0     27.4-0.0     28.9-0.1
 14JUL2021     22.2 0.4     25.9 0.1     27.2-0.1     28.6-0.4

Yea, I am pretty sold on a weak la nina.

Here is an excerpt from my blog...not the end all be all, but climo tidbits like that add confidence:

 

Climatology is also strongly opposed to the notion of an el nino. Currently, the ONI for the AMJ tri-monthly period sits at -0.5c. Dating back to 1950, there are only four years that featured a negative ONI value for the AMJ tri-monthly period and went on to develop into a classified el nino. 

They are:

1976: -0.3c

2018: -0.2c

1986:-0.1c

2006: -0.1c

Thus since 1950, no el nino event developed following an AMJ ONI value this low, which would make the development of an el nino later this year unprecedented. In fact, climatology actually favors the development of a la nina at this point. Only once since 1950 (1989 -0.6C) has there not been an official la nina registered during the autumn or winter following a AMJ tri-monthly ONI of -0.5c or lower.

[StormchaserChuck!]

I agree, I would go with a weak La Nina. It will be interesting to see what happens next in the subsurface, the CPC is forecasting a big +PNA. Maybe by early August we will be saying -0.5 as the ONI peak may be as far as we get. 

 

[raindancewx]

The top matches in Nino 3, 3.4, and Nino 4 for Apr-Jun are below. The July weeklies have 26.0C currently in Nino 3, well warm of the top Nino 3 matches for Apr-Jun. Nino 3.4 in July is a bit better, still trending like 1986 and 2001. The best Apr-Jun match overall is 1967. That winter is crazy (go look Dec 1967 US temps), and one of the very coldest Nino 3 winters on record even though 3.4 isn't that cold. The matches for 1967, 1986, 1996, 2001 are pretty solid for AMJ.

60-yr in green is the 1951-2010 average by month. My gut instinct after last winter was we'd have kind of a cold-neutral Modoki La Nina look to 2021-22. That's kind of where we are now - but it's unlikely to hold through winter.

July 1961 is also a fairly decent SST match in the Pacific/Atlantic. Terrible IOD match though, so probably won't hold.

[uncle W]

On 7/19/2021 at 4:43 PM, uncle W said:

the last time a second year la nina with a lull during the summer was 2011-12...there was a big gap between 2016-17 and 2017-18 la ninas..2008-09, 1984-85 and 1974-75...lets hope another la nina forms because of a neutral after nina winter scenario...1996-97 comes to mind...85-86 and 2001-02 too...

looking at the oni table I came up with years that were a second la nina winter but had a lull in between them...

year...DJF JFM FMA MAM AMJ MJJ JJA JAS ASO SON OND NDJ

2021 -1.0..-0.9..-0.8..-0.7..-0.5..-0.4?

2011 -1.4..-1.2...-0.9..-0.7..-0.6..-0.4..-0.5..-0.6 -0.8 -1.0. -1.1. -1.0

2008 -1.6.-1.5...-1.3..-1.0..-0.8...-0.6..-0.4..-0.2 -0.2 -0.4 -0.6 -0.7

1974 -1.8..-1.6...-1.2..-1.0..-0.9...-0.8..-0.5..-0.4 -0.4 -0.6 -0.8 -0.6

1984 -0.6.-0.4..-0.3..-0.4.-0.5...-0.4..-0.3..-0.2 -0.2 -0.6 -0.9 -1.1

[raindancewx]

Exact Nino 3.4 July monthly figure will be interesting. From 1950-2020, the DJF value hasn't dropped off by more than ~1.8C from that level, and typically ~90%+ of the time, you'd get a smaller or much smaller drop off, even in a La Nina. ~27.25C in July and then a 1.75C drop to DJF would be around the 90-99th percentile for a drop, and still only as strong as last year. So a warmer cold ENSO event is the likely outcome. That said, 2017 had the 1.8C drop from July to DJF.

The CFS doesn't really favor anything more than a whisper of cold at the moment for what it's worth. But it changes all the time. It has a weak modoki La Nina or cold Neutral - a few days ago it had no blue in Nino 3.4/4 at all.

[StormchaserChuck!]

^Love the cold pool off of New Foundland. North Atlantic is -NAO for Winter right now... interesting to see what happens. 

[raindancewx]

My NAO method doesn't work until September finishes, but just as a gut take, I thought this would be another winter with significant NAO volatility. Historically, you don't get ever get -NAO in February after a warm Nino 4 February (one year lag v. 28.85C if memory serves) using the 1981-2010 NAO baseline. You don't have that issue this year. 

Locally, the tendency in cold ENSO years is for July/Dec, and Aug/Feb to be negatively correlated twins. So when July is warm, I look for a cold December (worked last year), and when August is warm I look for a cold February. We had all time record heat in August last year, and then severe cold in February. August looks much colder here than 2020, which is consistent with a warmer West late winter/March and/or -NAO February/March (probably as an El Nino begins to rapidly develop late winter if I had to guess). Generally if it is very wet in the Southwest the final week of July, you guys in the East get your big Christmas warm up with a big low moving out of the Southwest. The monsoon has been pretty unusual (and non-traditional) and robust this year, so we'll see how that goes soon enough.

[40/70 Benchmark]

13 hours ago, StormchaserChuck! said:

^Love the cold pool off of New Foundland. North Atlantic is -NAO for Winter right now... interesting to see what happens. 

I would not be surprised at a pretty decent spell of neg NAO over the course of the next few years....anecdotally speaking, it had become a real scarcity over the past decade.

[40/70 Benchmark]

12 hours ago, raindancewx said:

My NAO method doesn't work until September finishes, but just as a gut take, I thought this would be another winter with significant NAO volatility. Historically, you don't get ever get -NAO in February after a warm Nino 4 February (one year lag v. 28.85C if memory serves) using the 1981-2010 NAO baseline. You don't have that issue this year. 

Locally, the tendency in cold ENSO years is for July/Dec, and Aug/Feb to be negatively correlated twins. So when July is warm, I look for a cold December (worked last year), and when August is warm I look for a cold February. We had all time record heat in August last year, and then severe cold in February. August looks much colder here than 2020, which is consistent with a warmer West late winter/March and/or -NAO February/March (probably as an El Nino begins to rapidly develop late winter if I had to guess). Generally if it is very wet in the Southwest the final week of July, you guys in the East get your big Christmas warm up with a big low moving out of the Southwest. The monsoon has been pretty unusual (and non-traditional) and robust this year, so we'll see how that goes soon enough.

I think that is what is important with respect to the NAO...obviously, you would rather have it average negative, but variability is what fosters ample storm opportunity.

[uncle W]

I don't like the cold spot east of Virginia...it might not be there the next run...

[uncle W]

last year was the first time since 2010-11 that the nao was negative on average Dec and Jan...with an ao also negative no wonder NYC got a 10" snowfall in December and a bigger one Feb 1st...the last time NYC got a 10" snowfall or greater in Dec and Jan of the same year was in 2010-11...

[raindancewx]

Should probably start looking at cold-ENSO years with weakening drought in NM/TX/AZ in May-July given how wet we've been lately. This tends to happen pretty reliably after we get our 600 decameter bs down here (we had record cold and rain in June too after, similar to the wet period following a hot period/strong high now), not that anyone ever rolls those events forward.

[raindancewx]

                Nino1+2      Nino3        Nino34        Nino4
 Week          SST SSTA     SST SSTA     SST SSTA     SST SSTA 
 09JUN2021     23.2-0.0     26.7-0.0     27.8-0.0     28.9-0.1
 16JUN2021     23.3 0.4     26.0-0.5     27.2-0.5     28.8-0.2
 23JUN2021     22.9 0.2     26.3-0.0     27.6-0.0     29.0 0.0
 30JUN2021     22.6 0.3     26.2 0.0     27.5-0.1     28.8-0.1
 07JUL2021     22.2 0.1     26.0-0.0     27.4-0.0     28.9-0.1
 14JUL2021     22.2 0.4     25.9 0.1     27.2-0.1     28.6-0.4
 21JUL2021     22.1 0.6     25.2-0.4     26.8-0.5     28.5-0.4

Haven't run it yet, but we'll interesting finding years with +May, +Jun, -Jul subsurface readings. We're probably going to flip into a Modoki La Nina in August, and then it may spread east later.

[George001]

woah, we are already down to -.5 in nino 3.4 over the past week. That’s already low end weak Nina territory and the negatives in the subsurface have strengthened rapidly. I didn’t think the Nina would develop this quickly, could the models be underestimating the strength of the La Niña? I’m starting to think we are going to see a moderate La Niña in the fall. 

[raindancewx]

You can see compared to last year, this event has developed differently. 
Western origin in 2021 v. Eastern origin in 2020. Nino 1.2 and Nino 3 were 
both very cold already last year. But, Nino 4 was still pretty normal.

Last year shifted from being coldest East to coldest West.
My current sense is you won't see a big shift to the Eastern Zones coldest. 
But that's something to look for in the coming months.
 
 10JUN2020     22.2-1.0     25.7-1.0     27.1-0.7     28.8-0.2
 17JUN2020     22.2-0.7     25.7-0.8     27.2-0.6     29.1 0.1
 24JUN2020     21.6-1.0     25.8-0.5     27.6-0.0     29.3 0.3
 01JUL2020     21.1-1.2     25.5-0.6     27.3-0.2     29.1 0.1
 08JUL2020     21.1-0.9     25.3-0.6     27.2-0.3     29.1 0.1
 15JUL2020     20.2-1.5     25.1-0.7     27.0-0.3     28.8-0.1
 22JUL2020     20.2-1.3     25.0-0.7     26.8-0.5     28.7-0.2

 09JUN2021     23.2-0.0     26.7-0.0     27.8-0.0     28.9-0.1
 16JUN2021     23.3 0.4     26.0-0.5     27.2-0.5     28.8-0.2
 23JUN2021     22.9 0.2     26.3-0.0     27.6-0.0     29.0 0.0
 30JUN2021     22.6 0.3     26.2 0.0     27.5-0.1     28.8-0.1
 07JUL2021     22.2 0.1     26.0-0.0     27.4-0.0     28.9-0.1
 14JUL2021     22.2 0.4     25.9 0.1     27.2-0.1     28.6-0.4
 21JUL2021     22.1 0.6     25.2-0.4     26.8-0.5     28.5-0.4

 

For my purposes, La Nina conditions in July or August should be 0.5C below the reading

observed from 1951-2010. So for July, that's 26.54C or colder, and 26.15C or colder for August.

CPC uses 26.79C as -0.5C for July and 26.36C as -0.5C for August using the most recent 30-year period. I think those thresholds are too warm to sync correctly with La Nina conditions.

You can see sort of see that with the cold south look for this month.

[raindancewx]

To me, and this isn't my forecast - I'll link it here when I finish by 10/10/21 - the CFS SST anomaly forecast looks like a blend of 1960-61, 1967-68, 2011-12, 2012-13, 2016-17 and 2020-21, with weak La Nina Modoki peaking NDJ, around 150W at it's core. I warmed up the oceans by 0.2C to account for the warming from the average analog date of 1997 (~0.2C of warming for 24 years). It's hard to match that level of warmth east of Japan - I think it will spread out more than what the model shows. The weaker tendency for cold ENSO by South America looks correct to me. December 1960 / 1967 are actually stupid cold in some places nationally, but it gets wiped out by the other years for the default "warm Nino 4" look we so often see in recent Decembers. That said, I do think something similar to December 1960 is possible nationally if things break a certain way over the next few months. These winters where all four Nino zones are convective-ly shut down or diminished seem to be the most volatile of the cold ENSO years.

[George001]

What would you guys say the chances the La Niña increases in strength more than expected and becomes similar in strength to the 2010-2011 La Niña? I’m thinking it could strengthen more than expected due to the cooling in the enso 3.4 region being more than most models had us by now, the increasing soi, active tropics, and rapidly cooling subsurface.

[raindancewx]

Right now, 2013 is a decent match for SSTs globally. It's amazing how different the weeklies, tropical tidbits, and these maps all look frankly. I would say we're behind 2013-14 still at the surface, and I don't consider that year a La Nina for winter. That cold water off western North America is the main issue with 2013.

[StormchaserChuck!]

That is one heck of a -PDO, image looks like it's the dominant pattern this Winter. Even if it's very cold, the surface should not be as cold. We also have a good +IO, I doubt we see dominant 4-5-6 MJO waves though. 

[raindancewx]

One thing 2013 has going for it outside the tropics is the y/y transition in the Arctic. The 2012 and 2020 sea ice extent were both very low with dis-favorable patterns up there in Summer. We seem to be in a better pattern for the ice retention in Summer 2021 - so far anyway  - similar to how Summer 2013 was. I had used 2012-13 as a double weighted analog last year ahead of winter, mostly for precipitation patterns nationally rather than temperature patterns, so it's been interesting to see 2013 is still a decent match. July 2013 is pretty similar to the temperature spatial pattern of July 2021 nationally, and drought nuking rain of July 2013 has been present in the Southwest. I kind of "knew" this was coming, which is why I was so annoyed in that "look it's hot SW" climate thread from June when it was obvious we are entering our wettest Summer pattern in literally years.

Here is Albuquerque for July 2021 v. July 2020:

[raindancewx]

Subsurface heat content for May-July 0-300m below 100-180W in the Tropical Pacific best matches 1981, 1987, 2014, 2014 as a blend. The blend of those four features big drops in the subsurface at similar magnitude to 2021 in May-->June, June-->July. Historically, for 1979-2020, most years around -0.3 to -0.4 in July subsurface readings do end up as La Ninas, but quite a few in that area are Neutrals. A lot of years are borderline too, with only 1-3 months 0.5C or colder than the 1951-2010 average in Nino 3.4. When I talk about a Neutral that's what I mean. I'm pretty sure the surface will drop to La Nina cold levels - just not convinced it will be long enough for an official event yet. Last year, you already had the subsurface very cold in Apr-Aug prior to the surface getting cold enough to be in a La Nina in late August.

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

 07JUL2021     22.2 0.1     26.0-0.0     27.4-0.0     28.9-0.1
 14JUL2021     22.2 0.4     25.9 0.1     27.2-0.1     28.6-0.4
 21JUL2021     22.1 0.6     25.2-0.4     26.8-0.5     28.5-0.4
 28JUL2021     22.1 0.8     25.1-0.4     26.7-0.4     28.7-0.1

We're seeing a very nice Summer locally, with cool to near average highs in May, June, and July, wet conditions and somewhat warm lows. Total year to date 90 degree highs here are running below the 100 year median and average. Part of that to me is that La Nina doesn't seem to switch on until ~26C in winter, and even in August it's ~26.15C (26.65C is average for 1951-2020). So we're just not that close yet at the surface, with 27.0-27.1C likely to be the monthly number for July.

[StormchaserChuck!]

Not warm subsurface except inthe Spring, March-May there will be a warming trend. I wouldn't be surprised if we don't go La Nina though. 

[raindancewx]

These are the top SOI matches to 2021 for May-July from 1931-2020 (+3.9, +0.0, +16.3 in 2021 for each month respectively).

I had used Spring 1979 as an analog for Spring 2021, given that the cold-ENSO 1978-79 winter followed two El Ninos near/following the solar minimum (1976-77, 1977-78) and had ~record +NAO/AO values in November before transitioning to a huge cold period in late winter. NAO was +3.0 or something insane in Nov 1978 before dying later on. Was pretty similar in 2020 and I knew that by the time I did the Spring Outlook in February. The 7th closest SOI match (really a ~ three-way tie between 1936, 1939, and 1960) is 1960, and the 1959-60 winter was also very similar at times (Dec/Feb) for temp patterns nationally, and 1960 has worked sporadically as a match in Spring/Summer 2021. If you don't know, 1936 and 2011 are both very hot Summers nationally, so interesting to see them both show up as top matches. July 1960 had incredible heat in the Northwest, similar to 2021. The "look" that is supposed to happen in August nationally is fairly similar to August 1939, 1936 blended toward 1939, and then maybe a touch colder overall.

SOI             May         June      July     Distance (less = closer to 2021)

1979          +4.0        +4.5         +13.6     (warm-Neutral winter)  (7.2 off)

2011         +2.1        +0.9          +9.1      (La Nina winter)             (9.8 off)

2010         +10.5      +1.3          +18.7    (La Nina winter)             (10.3 off)

1974         +10.6      +1.7          +11.1    (La Nina winter)             (13.5 off)

1939         -0.4         -1.8           +7.5      (El Nino winter)               (14.9 off)

1936        +4.7         -1.8           +3.9     (warm-Neutral winter)      (15.0 off)

Blend:       +5.3        +0.8          +10.7  

2021        +3.9         +0.0          +16.3

[StormchaserChuck!]

We last had a pretty good SOI/SST difference (higher SOI vs warmer SST, cold ENSO) in 2011-2012. 

https://www.pmel.noaa.gov/tao/drupal/assorted_plots/images/soi_110w_drupal.gif

[bkviking]

While I’m a long term hobbyist - I wonder why a negative PDO is contributing to such an extreme PNA+ this summer. Is this normal for season? Does the advance of winter in northern hemisphere change the likely blocking index by then? 

[40/70 Benchmark]

13 hours ago, bkviking said:

While I’m a long term hobbyist - I wonder why a negative PDO is contributing to such an extreme PNA+ this summer. Is this normal for season? Does the advance of winter in northern hemisphere change the likely blocking index by then? 

Intuitively, I would say that it is likely due to the wave lengths being so much shorter during the summer....the teles are much weaker and more diffuse, so many of the "rules" are broken.

[CheeselandSkies]

Interestingly, positive PDO was attributed as a main reason some of the tornado seasons in the early-mid 2010s were rather lackluster. Now we have a negative PDO but this A/M/J was similarly quiescent in the Plains/Midwest. Thoughts @andyhb?

[StormchaserChuck!]

Yeah, it seems like the whole Pacific Jet is drying up. 

[raindancewx]

Compared to last year, Nino 3 (and 1.2 also) are still much warmer at the surface, while Nino 4 is colder.  The ONI values / raw SST data for July updated, so the matches above are the closest objective matches. I then compared the observations to the 1951-2010 average for the blend, and 2021 itself. It won't last long in Nino 3.4, but 1986 is currently the top match for the three zones. The SOI/SST matches I've shown recently, including 1967, 2011, 2013, 1979, etc, have all shown up again. These years are generally cold Augusts, so it will be interesting to see how that plays out.

[andyhb]

On 8/4/2021 at 8:46 AM, CheeselandSkies said:

Interestingly, positive PDO was attributed as a main reason some of the tornado seasons in the early-mid 2010s were rather lackluster. Now we have a negative PDO but this A/M/J was similarly quiescent in the Plains/Midwest. Thoughts @andyhb?

Without further analysis, I'd have to think that the La Nina decaying quite early may have been a factor.