ENSO Updates (2007 thru 2023)

[Eric Webb]

Another WWB is becoming increasingly impressive in the medium range over the far eastern Pacific and will help spur several tropical cyclones in the eastern Pacific basin within the next week or so. An easterly trade burst forecast on the GFS in the CP associated with the passage of the convectively suppressed phase of the MJO is weakening as verification nears. We may momentarily take our foot off the gas pedal with less favorable E Hem tropical forcing but subseasonal forcing will become more damped relative to ENSO as we close in on the fall. The speed of the MJO circumnavigating the global tropics will increase relative to normal as the traditional convectively active areas of the Maritime Continent and adjacent IO-WP warmpool begin to shut down and advection by the background flow (mid latitude jet) accelerates in concert with heightened Atmospheric Angular Momentum. What I’m essentially saying here is that the MJO actually moves faster during El Ninos than La Niñas and the global convective distribution and mid-latitude jet stream have a lot to do with it.

See Pohl and Matthews (2007) for more on this topic (AMS Journal hyperlinks aren’t working atm, this is a link to the abstract): https://scholar.google.com/scholar?hl=en&as_sdt=0%2C47&q=mjo+phase+speed+enso+&btnG=#d=gs_qabs&p=&u=%23p%3DRMN_e3289HYJ

[LarryWx]

The Eurosip has an obvious +ENSO bias however this should be a warning/lesson to all here that you shouldn't put all your eggs into one basket especially when it comes to ENSO. Forecasting ENSO based on large-scale conditions at hand is one thing, but forecasting the conditions based on the expected tendencies of the model that's predicting ENSO is definitely not the way to approach this because it implants another unnecessary layer of error into said forecast.

This is probably good advice but I still think it will be interesting to follow how Eurosip does. Also, keep in mind that Eurosip isn't just one model but instead is an ensemble of various models. And all I was emphasizing in these posts was trying to forecast ASO, not the ultimate event strength. I know you don't think ASO, itself, is important in the grand scheme of things and it may not be, but several here had been discussing ASO and that's what got me to jump in about that trimonth.

[Eric Webb]

The Eurosip has an obvious +ENSO bias however this should be a warning/lesson to all here that you shouldn't put all your eggs into one basket especially when it comes to ENSO. Forecasting ENSO based on large-scale conditions at hand is one thing, but forecasting the conditions based on the expected tendencies of the model that's predicting ENSO is definitely not the way to approach this because it implants another unnecessary layer of error into said forecast.

This is probably good advice but I still think it will be interesting to follow how Eurosip does. Also, keep in mind that Eurosip isn't just one model but instead is an ensemble of various models. And all I was emphasizing in these posts was trying to forecast ASO, not the ultimate event strength. I know you don't think ASO, itself, is important in the grand scheme of things and it may not be, but several here had been discussing ASO and that's what got me to jump in about that trimonth.

Yeah it’s not going to matter here if we have warm neutral ENSO or a weak El Niño in ASO for the Atlantic hurricane season. I’ve mentioned from the outset that even having a +PMM coupled with a cold Atlantic (even if there’s a La Niña ongoing) is enough to make conditions detrimental for TCG in the Atlantic MDR (1985 for ex). The Eurosip is an ensemble which not surprisingly akin to a herd of sheep is also underdispsersive and every ensemble member uses the same physics and paramaterizations that often misrepresent ENSO and lead its Niño bias. Quite frankly, I don’t find NWP models useful w/ ENSO and I rarely look at their forecasts because it either usually reaffirms what I already see evolving or they’re so late to the party with event evolution that it’s futile to use them to update/significantly tweak a forecast. The signs were already there as early as January and February that a Nino was going to try and develop. A +PMM coupled to a cold Atlantic at least 2 years removed from a preceding Super Niño with a large WP MJO event in late last winter were big warning signs of an impending Nino attempt, and the persistence of the +PMM and cold Atlantic well into the spring solidified my confidence that at least a borderline weak Niño would show up in 2018-19. Meanwhile models like the CFSv2 had their heads in the sand with some showing cold neutral conditions continuing to dominante the rest of the year.

[Kingarabian]

Latest sub surface snapshot shows continued robust warming of the warm subsurface pool, primarily under the EPAC:



There's clearly more warmth allocated to the EPAC portion of the this downwelling Kelvin wave. So it's surprising that Nino 1+2 remains this cool... especially when we consider how shallow that region is.

[LarryWx]

The June Eurosip recently updated and is a little warmer than the May update with low end weak El Niño (near +0.5 in Niño 3.4) for ASO averaged out with it warming to near +0.6 in Oct. This near +0.5 compares to near +0.35 for ASO in the May update.

Consistent with this warming, it has even higher pressures in the MDR for ASO from near 30W westward through the Caribbean and the GOM vs the already pretty high pressures shown in the May update. This update now has slightly higher pressure than the June ASO forecast for 2014. The June forecast for ASO 2015 is still somewhat higher with the pressures and is the only June forecast showing higher ASO pressures vs 2018. The message is clearly to expect a pretty quiet season in the MDR through the GOM overall with perhaps near normal north of 30-35N east of the CONUS to possibly up to near the NE US/SE Canada assuming this forecast has a decent clue.

Are you still thinking warm neutral for ASO? It's looking increasingly like El Niño to me

I just compared May and June Eurosip and found that June overall still averaged too warm for ASO by almost the same margin: +0.4 for June vs the +0.5 of May. Some Junes were significantly cooler than the respective May like 2017 and 2007 but others were slightly warmer and further away like 2012 (June 1.0 too warm vs May's 0.9 too warm), 2009 (June 0.4 too warm vs May's 0.2 too warm), 2008 (June 0.9 too warm vs May's 0.8 too warm), and 2005 (June 0.6 too warm vs May's 0.4 too warm).

Here is the list of years with June being available:

Year: Eurosip's June fcast verification for ASO 3.4
2017: 0.6 cooler (cold neutral occurred vs warm neutral prediction)
2016: 0.1 cooler (weak La Niña correctly predicted)
2015: 0.3 warmer (strong El Niño correctly predicted)
2014: 0.5 cooler (warm neutral occurred vs weak El Niño prediction)
2012: 1.0 cooler (warm neutral occurred vs moderate El Niño prediction)
2009: 0.4 cooler (weak El Niño occurred vs moderate El Nino predicted)
2008: 0.9 cooler (cold neutral occurred vs weak El Niño prediction)
2007: 0.1 warmer (moderate La Niña correctly predicted)
2006: 0.2 cooler (weak El Niño correctly predicted)
2005: 0.6 cooler (cold neutral occurred vs weak El Nino prediction)

So, 4 of these 10 June forecasts were pretty much correct (2016, 2015, 2007, 2006) for the ENSO phase for ASO with 2015 actually ending up 0.3 warmer. Perhaps that represents the upside risk, which would mean an actual SST of near +0.8 for ASO of 2018 max. Three were still 2 categories too warm: 2012, 2008, and 2005. Per the current OHC, 2018 is just a little cooler than 2009 and is a little warmer than 2006 and 2012. 2014 had been similar in May, but it plunged in June totally unlike the current case. 2017 was much cooler. So, the current OHC suggests ASO has a good chance to reach weak El Nino. The significant misses of the June Eurosips that predicted El Nino in ASO were 2014, 2012, 2009, and 2005. But 2014 can be thrown out since its OHC plunged in June. And 2012's OHC was near 0.3 cooler than 2018 is now. That leaves us with 2009 and 2005. 2005 was much cooler...so I can throw 2005 out. That leaves us with 2009 as the best analog, which as mentioned had a slightly warmer OHC. It also had a slightly warmer Nino 3.4 SST. As shown above, the June Eurosip for 2009 ended up 0.4 too warm for ASO 3.4 SST, which was +0.7. This all tells me that the coolest for ASO of 2018 3.4 SST may be around +0.1.

So, I'm currently in the +0.1 to +0.8 range for the ASO Nino 3.4 SST anomaly meaning either warm neutral or weak El Nino for ASO. My best guess for ASO: right on the border or near +0.4 to +0.5. This is a change from my prior prediction of warm neutral. Note that this prediction is taking into account current OHC and SST and, therefore, is not relying on just Eurosip.

[Eric Webb]

 https://twitter.com/MJVentrice/status/1011982117109223425

[Eric Webb]

We're definitely going to see an uptick in easterly trade wind activity for a good part of July as tropical forcing shifts back into the eastern hemisphere. The usual suspects will revert back into windshield wiper mode, proclaiming this somehow means something substantial for ENSO and will suddenly back away from their calls for a NINO or question everything they know about ENSO because the atmosphere isn't constantly NINO-esque, the reality is, this is rarely if ever true except in the strongest El Ninos (1982-83, 1997-98, & 2015-16, etc.). In the grand scheme of things, it really doesn't mean much either because subseasonal forcing will once again return back to the Pacific and W Hem in late July and early-mid August, leading to yet another WWB, and the subsurface OHC will subsequently respond, etc (I think you get the picture here). As long as that keeps happening on a semi-regular basis, we'll continue to our discontinuous progression towards a weak-moderate El Nino this year.




If you look at the cumulative trade wind behavior of most weak-moderate El Ninos, you see exactly what I described above. There's only quasi-regular, discontinuous WWBs before the September equinox before weak-moderate NINOs, with easterly trades even in some cases dominating over WWBs.

Since there's a non-linear relationship only between +SSTAs and convection in the east-central equatorial Pacific, this also means that equivalent periods and magnitude of anomalous easterly and westerly winds in the Pacific actually don't have the same effect on ENSO! For example, if you had a couple weeks of strong easterly trades followed by a couple weeks of WWBs, the net, cumulative effect of this trade wind behavior would not cancel out equally, it would actually push ENSO closer to El Nino conditions. Why does this apparent discrepancy exist in the first place? Keep in mind that the mean SSTs east of the International Dateline in the Equatorial Pacific are too cold to readily sustain convection, during El Nino events the warmer than normal SSTs actually cross a threshold of ~28C or so wherein convection can be generated. This convection non-linearly/exponentially amplifies and reinforces the pre-existing SST anomaly (Bjerknes Feedback). This mechanism doesn't operate in La Ninas because again, the sea surface is too cold to support convection in the east-central Pacific. This is also why for example, the strongest El Ninos are stronger than the biggest La Ninas, and is also why the transition from El Nino to La Nina conditions occurs more frequently than the other way around because the Bjerknes feedback is more efficient in El Ninos! The spatial scale of the convective anomaly associated w/ El Ninos is more localized than during La Ninas (near-equatorial Pacific in NINOs vs almost the entirety of the east-central Indian Ocean, Australia, Indonesia, SE Asia, and the Western Pacific in NINAs). This too contributes to the efficiency of the Bjerknes feedback and even the variance in CONUS weather (more variability in La Ninas vs El Ninos), but that's a discussion for another time.


2002 5S-5N 850 hPa trade anomalies thru June 27





2004 5S-5N 850 hPa trade wind anomalies thru June 27





2006 5S-5N 850 hPa trade wind anomalies thru June 27





2009 5S-5N 850 hPa trade wind anomalies thru June 27





This year's 5S-5N 850 hPa trade wind anomalies thru June 27




I would also like to remind everyone that the RMM MJO index only uses the first EOF pair of upper and lower level zonal winds & OLR, the 3rd EOF (leading mode of variability) is actually what describes the advancement towards El Nino conditions, if this was included in the RMM MJO index, our perceived relationships between the MJO & ENSO would be much different than they currently are.

[Ntxw]

From Mike Ventrice

 https://twitter.com/MJVentrice/status/1012693038374817792

[TheStormExpert]

 https://twitter.com/MJVentrice/status/1013415609009344513

[Kingarabian]

BOM has Nino 3.4 up to +0.53. CFSv2 has been spot on.

[Ntxw]

0.4C again later this morning at the update on the weeklies. Nino 4 hits 0.5C

[cycloneye]

Text of CPC weekly update of 7/2/18 that has Niño 3.4 remaining at +0.4C.

http://www.cpc.ncep.noaa.gov/products/a ... ts-web.pdf

[cycloneye]

@webberweather
This yr is following the satellite era weak-moderate El Ninos to script so far. Majority of these El Ninos were also triggered by a +PMM which received little resistance w/ a cold Atlantic. Also note the -SPMM in the preceding summer, this is usually a precursor to modoki El Nino

 https://twitter.com/webberweather/status/1013842857831038979

[NotSparta]

Looking at the CFS, I'm thinking maybe the peak of this El Niño event will be moderate rather than weak-moderate

[Eric Webb]

The current amplitude, evolution, and timing of the downwelling Kelvin Waves in the Equatorial Pacific is closely mirroring 2009 this year and another downwelling KW is passing the international dateline atm which will further suppress the thermocline and maintain the heightened OHC thru the Equinox. Ironically this is about the same time when another major downwelling wave formed in 2009 and crossed the central Pacific.

This Year



2009



For more subsurface maps see: http://www.bom.gov.au/oceanography/oceantemp/sota.shtml

[Eric Webb]

Here comes the aforementioned downwelling KW passing the international dateline in the CPC analysis at the end of the loop.

[NotSparta]

In addition, the 200mb VP pattern is expected to become Niño-like over the next few weeks, meaning faster progress towards Niño conditions

[cycloneye]

@BenNollWeather
Sea surface temperature (SST) anomalies in the Pacific are warmer than average along & north of the equator and cooler than average south of the equator.

SSTs are more anomalously warm in the central Pacific than in the east near Peru -- this is an important factor to monitor.



 https://twitter.com/BenNollWeather/status/1014090239143337984

[hamburgerman7070]

I think the million dollar question aside from if a niño is present in fall/winter is will we or could we have a set up that favors cold air to come south, which was prevalent in 2009-10 niño.

[TheStormExpert]

I think the million dollar question aside from if a niño is present in fall/winter is will we or could we have a set up that favors cold air to come south, which was prevalent in 2009-10 niño.

Niño or not you still need a -NAO/+PNA setup to usher in the colder air repeatedly. -AO wouldn’t hurt as well.