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Interestingly the MEI data is tracking right along with 07-08 and 98-99 for the past 4-5 months, despite the SSTAs being quite a bit weaker through most zones. Well behind 2010-11 though, which is the strongest La Nina via MEI in the entire dataset going back to 1979. Also pretty close to 08-09 and 11-12.

If we're talking severe weather season strictly looking at these four years, there's quite a divergence between 07-08/98-99 (highly active seasons) and 08-09/11-12 (much quieter ones). The latter two show a poleward retracted jet in AMJ as opposed to the former.

image.thumb.png.03380dd0f2cb36592e92f551d3726508.png

image.thumb.png.b3da1e4c86cd44f116e920f0ae888c94.png

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Keep your eye on that cold spot in the North Pacific. 

Image

With some additional eastern Nino zone weakening and the north Pacific look, we could go to a Jan-Apr 2017 pattern fairly quickly.

The PNA is forecast to go negative for the first time in a while, so there do seem to be changes coming with Nino 4 taking over as the coldest Nino zone compared to averages. It is interesting to see the PNA (projected) flip coinciding perfectly with the Bering Sea Rule and then also the recent big SOI crash. Some kind of big system is coming I think.

pna.sprd2.gif

 

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572596772_ScreenShot2021-01-15at12_37_36PM.thumb.png.14b5a4cf6ad6fff47b6fd07d36023a40.png

Looks like Tropical Tidbits has their SSTA analogs up and running again. That would certainly be a favorable set for an active severe weather season, especially early season.

On the other hand, rapidly decaying Ninas in 3.4 over the past 20 years have been very unfriendly to the Plains in peak season, as such years consist of 2006, 2009, 2012, 2017, and 2018.

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5 hours ago, andyhb said:

572596772_ScreenShot2021-01-15at12_37_36PM.thumb.png.14b5a4cf6ad6fff47b6fd07d36023a40.png

Looks like Tropical Tidbits has their SSTA analogs up and running again. That would certainly be a favorable set for an active severe weather season, especially early season.

On the other hand, rapidly decaying Ninas in 3.4 over the past 20 years have been very unfriendly to the Plains in peak season, as such years consist of 2006, 2009, 2012, 2017, and 2018.

About as stark a contrast as you can get between those two sets of analogs. I sure as hell don't know what to make of it. Granted ENSO isn't the only large-scale driver of severe weather potential but it'd be much more confidence-inspiring to see things leaning more 1974/2008/2011-ish than 2006/09/12/18, although the line seems rather fine. Also, at least anecdotally, 2012 behaved nothing like the other years in that group being extremely warm and dry throughout the central CONUS from March through about September.

Also, shouldn't this be "2021 ENSO" by now? Seeing as we skipped over 2020.

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The JAMSTEC update has the eastern Nino zones continuing to warm into Summer, before reversing cooler after. No El Nino forms. 

But you do see this event warm out of a La Nina in the Spring, or even in February on the Jamsetc. The western areas never really warm out of the La Nina though. If the look below for Spring is right, almost think you could pull off a wet Spring in the Southwest with Nino 1.2 that warm. It's not that different from a cooled off 2017 look, where Nino 4 was cooler relatively to the eastern zones. Some pretty big storms that year in the Spring, including a couple blizzards.

Jamstec-Mar-May-2021

I think the Jamstec is trying to do something like a Spring 2008/2017 blend.

Image

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20 hours ago, raindancewx said:

Spring 2021 on the Jamstec also looks a lot like Spring 2001, 2012, 2014. 

:axe: re: Spring tornado chances. 2008/2017 would be more promising though.

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2 hours ago, andyhb said:

:axe: re: Spring tornado chances. 2008/2017 would be more promising though.

2014 wasn't bad considering the slow start (although frustrating for me since I missed the Pilger family by an hour and targeted Iowa the following day, but at least the opportunity was there). There were a number of high risks in 2001 but they generally busted.

2017 was meh, but actually one of the better post-2015 seasons, sadly. The event of the year locally happened before I was ready for it (February 28th).

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PDO update came in my email from Nate Mantua (the JISAO index).

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
November -1.12
December  -0.90

 

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Nino 4 still looks like it will drop below 27.0C. I think we'll see Nino 3.4 and Nino 3 warm soon though. I've been looking at the years where the La Ninas are consistently colder the further West you go in Spring - some crazy years are in there. In other words, anomalies coldest in 4, then 3.4, then 3, then 1.2. Some east based El Ninos are that way, but it is mostly La Ninas.

                Nino1+2      Nino3        Nino34        Nino4
 Week          SST SSTA     SST SSTA     SST SSTA     SST SSTA
 23DEC2020     22.1-1.1     24.5-0.7     25.7-0.9     27.6-0.8
 30DEC2020     22.2-1.3     24.4-0.9     25.4-1.2     27.3-1.1
 06JAN2021     23.1-0.8     24.7-0.8     25.5-1.1     27.1-1.2
 13JAN2021     24.0-0.3     24.7-0.9     25.4-1.2     27.0-1.3

La-Nina-Subsurface-1-18-2021

 

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Compared to 1951-2010 averages, my guess is January finishes something like this in the four zones:

Nino 4:      -1.1C

Nino 3.4:   -0.9C

Nino 3:     -0.7C

Nino 1.2:  -0.5C

If my assessment is correct, the structure for the La Nina in January is much closer to a lot of the older La Ninas than the recent events. None of the six closest matches to January are in the past 20 years. A blend of January 2012 and 2011 is somewhat close and looks somewhat similar to the blend but colder in the West.

January-2021-Nino-zones

Jan Nino 4 Nino34 Nino3 Nino 12
2012 27.30 25.67 25.09 24.38
2011 26.92 25.00 24.40 24.08
Blend 27.11 25.34 24.75 24.23
2021E 27.00 25.55 24.80 23.80
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On 1/11/2021 at 2:24 PM, raindancewx said:

Keep your eye on that cold spot in the North Pacific. 

With some additional eastern Nino zone weakening and the north Pacific look, we could go to a Jan-Apr 2017 pattern fairly quickly.

 

This is what I was looking for when I made the January 2017 comparison. I don't know it if it will verify. But it's possible now, and this would have been hard to imagine a few weeks ago.

Image

Image

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The cold pool is actually retrograding a little bit

wkxzteq_anm.gif.c0fa9b720466efb360caaac5646b1150.gif

TAO_5Day_EQ_xz.gif

When I see this I think of an active severe thunderstorm season.

Warm pool still stronger though, I think well see some powerful Kelvin waves in the Spring. 

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We'll see how it goes. When I looked at the years that had a similar setup to what we see now at the surface, the tendency is for Nino 4 to remain cold pretty deep into the year, even as the other zones warm. Nino 4 getting reinforced by cold waters below the surface moving west and toward the surface is supportive of that.

The best subsurface matches for Nov-Jan are probably going to be 1995-96, 2007-08, 2011-12 as a blend, barring a huge last second change late January. That's a pretty typical La Nina look nationally for February.

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On 1/19/2021 at 2:30 PM, raindancewx said:

If my assessment is correct, the structure for the La Nina in January is much closer to a lot of the older La Ninas than the recent events. None of the six closest matches to January are in the past 20 years. A blend of January 2012 and 2011 is somewhat close and looks somewhat similar to the blend but colder in the West.

Jan Nino 4 Nino34 Nino3 Nino 12
2012 27.30 25.67 25.09 24.38
2011 26.92 25.00 24.40 24.08
Blend 27.11 25.34 24.75 24.23
2021E 27.00 25.55 24.80 23.80

CFS may radically change by the end of the month, but for now it is on board with the February 2011/2012 blend.

Image

Image

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image.thumb.png.e406ec788bb1a6ae94bcd37fdb044207.png

Did some skimming of SSTA data tonight and I'm intrigued by that warm pool centered at ~150˚W and 30˚S to the south of the cold SSTAs with the Nina. Based on looking into some previous analogs around this time, it seems like that strong meridional dipole is not present in years such as 2006, 2009, 2012, 2017, and 2018 (generally quieter severe seasons especially late season). It is more prevalent in several big Nina springs though, including 1974, 1976, and 2011.

It's probably to some degree why this CDAS-derived SSTA analog product from Tropical Tidbits is essentially grouping a who's who of Nina springs with a lot of tornadoes/severe weather, including some with very large outbreaks.

image.png.c5ce00b04be0e1951ca1df3b8f7669a2.png

You can see the SSTA dipole present in the Southern Hemisphere in the mean here.

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One thing I try to match on is MJO timing. So we'll probably be in MJO phase 7 on 2/1. Some cold ENSO years with high-magnitude phase 7 on 2/1 (1/30-2/3 is my threshold for timing):

February 2018, 2012, 2006, 1993, 1990, 1989. If you ignore the early February timing requirement 1999, 2001, 2008, 2017 had amplitude phase 7 too. A lot of El Nino years do too.

I did some research the other day: If you get a wet January in a La Nina in the Southwest (seems likely now for at least large portions of Western NM, Arizona, and parts of Utah, and Colorado, Nevada, and California), it does seem like the SW Spring dry signal weakens a bit, but remains. My guess is the weak systems we've been getting all winter won't make it through in the Spring, and it will just be a handful of very powerful upper level lows, probably cold cut off lows that occasionally tap Gulf of California moisture, that bring precipitation. That's probably pretty tornadic if the north is cold and the south is warm, with all the dry and wet air mixing, and it does make me think maybe the WPO will hold on a bit longer than forecast. 

The right images are what I call the "wet Southwest La Nina" January composite. The left images are the "mixed Southwest La Nina" January composite - where some places are wet and others very dry. The right image seems a lot closer if California gets as much rain and snow as they are forecast to by Friday.

Image

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I'd be more impressed if the subsurface cold pool was not strengthening as it pulled back. (research shows the subsurface of ENSO has more + correlation to the 500mb pattern and surface temps than surface ENSO SSTs).

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Also can a moderator change the title of this thread, considering it is certainly no longer 2019?

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Nino 4 dropped below 27.0C this week. Except for one week in January 2012, this is the first time for that since the 2010-11 event. We'll see if it continues to trend colder. This event is still similar to 2011-12. However, the 26.9C was the coldest reading in Nino 4 of 2011-12. We're still fairly close to 2007-08 in Nino 4, and that event kept Nino 4 dropping erratically into February. If that happens, we'll drift away from 2011-12 as a good match. 

                Nino1+2      Nino3        Nino34        Nino4
 Week          SST SSTA     SST SSTA     SST SSTA     SST SSTA
 16DEC2020     22.0-0.8     24.3-0.8     25.6-0.9     27.8-0.7
 23DEC2020     22.1-1.1     24.5-0.7     25.7-0.9     27.6-0.8
 30DEC2020     22.2-1.3     24.4-0.9     25.4-1.2     27.3-1.1
 06JAN2021     23.1-0.8     24.7-0.8     25.5-1.1     27.1-1.2
 13JAN2021     24.0-0.3     24.7-0.9     25.4-1.2     27.0-1.3
 20JAN2021     23.9-0.8     25.2-0.6     25.5-1.1     26.9-1.4
 14DEC2011     21.5-1.2     24.1-1.0     25.6-1.0     27.4-1.1
 21DEC2011     22.1-1.0     24.5-0.7     25.6-1.0     27.2-1.3
 28DEC2011     22.6-0.9     24.4-0.9     25.5-1.1     27.1-1.3
 04JAN2012     22.7-1.1     24.6-0.8     25.5-1.0     27.2-1.2
 11JAN2012     23.7-0.5     24.8-0.7     25.6-1.0     27.1-1.2
 18JAN2012     24.0-0.6     24.9-0.8     25.4-1.2     27.1-1.2
 25JAN2012     24.6-0.4     25.2-0.7     25.5-1.2     26.9-1.3

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Levi's site has the La Nina getting it's ass kicked in the eastern zones, while Nino 4 remains very cold. We're not really in a La Nina in Nino 1.2 or Nino 3 anymore if you go by his figures.

La-Nina-weakens

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According to Jae-Heung Park's paper "Mid-latitude leading double-dip La Nina" published last year, it is very likely to get a double peak event considering the very cold Nino 4 region and a meridionally expanded easterly wind anomalies.

 

-27cd268520b15bc.png

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The SOI was +15.85 for January 2021. That's the fifth highest January reading since 1932, behind 1939, 1962, 1974, 2011. Top SOI matches for Nov-Jan still look like 1938-39, 1950-51, 1961-62, 1998-99, 2007-08. As a blend, you get a cold West February from those years. February 1962 is a pretty extreme pattern if that's the kind of look we get.

The new Canadian will be out tomorrow. I'm not sure if it will show the look in that paper for Feb-Apr or not. My expectation is Nino 4 stays cold for a while, while Nino 1.2/3 both see at least a month or two above average. Spring/Summer will be pretty interesting if Nino 4 remains both coldest and the most extreme of the four regions. I'd really like to see that plume of cold water in Nino 4 push into the waters by the "Box C" zone on the Modoki calculation. That area is fairly well correlated to cold in the West and it never seems to get cold. 

If you look at the coldest Nino 4 January years from 1950-2019, below 27.5C in January, 17/18 warmed from the January reading to the next Dec-Feb. The exception is naturally 1955, which is actually a decent analog to current conditions, but it was 27.4C in January, not 27.0C or so like this January.

Nino4 Jan DJF Gain
1974 26.3 27.56 1.26
1976 26.58 28.19 1.61
1989 26.6 28.49 1.89
1999 26.64 26.97 0.33
1971 26.65 27.79 1.14
2008 26.87 27.48 0.61
2011 26.92 27.37 0.45
1950 26.94 27.15 0.21
2000 26.99 27.46 0.47
1956 27.04 27.77 0.73
1951 27.21 28.3 1.09
1965 27.23 28.74 1.51
2012 27.3 28.28 0.98
2009 27.37 29.41 2.04
1955 27.41 27.05 -0.36
2001 27.43 28.68 1.25
1963 27.45 28.33 0.88
1984 27.49 27.59 0.10

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The new Canadian trended the La Nina weaker/warmer for February-April. It does have a brief return to neutral conditions in Summer before another La Nina develops next Fall.

Image

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Wants to torch the southwest/south-central States for spring too, not ideal for severe weather potential.

I do wonder if it's killing the Nina in the western zones too quickly though.

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The weeklies have caught up to the look on the Tropical Tidbits map. A lot of weakening this week. If Nino 4 continues to warm up too, this event is going to end fairly soon, at least for a bit before resuming. The Eastern zones have warmed out of a La Nina this week.

                Nino1+2      Nino3        Nino34        Nino4
 Week          SST SSTA     SST SSTA     SST SSTA     SST SSTA
 30DEC2020     22.2-1.3     24.4-0.9     25.4-1.2     27.3-1.1
 06JAN2021     23.1-0.8     24.7-0.8     25.5-1.1     27.1-1.2
 13JAN2021     24.0-0.3     24.7-0.9     25.4-1.2     27.0-1.3
 20JAN2021     23.9-0.8     25.2-0.6     25.5-1.1     26.9-1.4
 27JAN2021     24.6-0.4     25.7-0.2     25.9-0.7     27.1-1.1

The subsurface heat dropped to -0.99 in January from -0.94 in December. But the peak was still -1.11 in October for this event. 2007-08 had an Oct-Nov peak and then a second, stronger peak in January at the subsurface. This event had a weaker second peak. The best blend I could come up with was 1995-96, 2005-06, 2007-08 for Nov-Jan. You get slight subsurface weakening in December followed by slight strengthening in January.

Image

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

I haven't finished writing it up yet, but my outlook for Spring is probably going to be based on a blend of 1954-55, 2007-08, 2011-12, as an SST/US Weather/solar match with 1978-79 thrown in to account for a very +NAO in November transitioning to a -NAO Dec/Jan. That NAO behavior is very unusual in a La Nina. The blend of the four years, 1955, 1979, 2008, 2012, looks like a colder version of what the Canadian shows for February. The near-record +NAO November correlations should have input on how the Spring evolves. One effect of a very +NAO in November is NM/TX tend to be cold/wet late Spring at a pretty high correlation.

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