ENSO Discussion

[Phil]

Then again, my earlier thoughts were for an integrated regime of constructive interference to develop in JFM of 2019..but since I overestimated the degree of autumnal warm pool dissociation and thermocline shoaling, that no longer looks to be the case, when the next bout of high amplitude MJO/mass circulation event occurs around the holidays following the NAM flip to negative. It will probably have the opposite initial effect on the ENSO state, though not nearly to the extent of 1987/88.

[Kayla]

Well that depends what parameters you use to define “slow walk”..SSTAs aren’t a good way to diagnose that. The anomalous suppression of the thermocline has not changed drastically over the last six months..it’s been suppressed for awhile. If we were observing a coherent amplification of the ENSO wavecycle then I’d be on the moderate/strong niño train as well. But that’s not the case.

 

I’m going to write up a detailed post on this later, but I’m still going with a borderline event as reflected by the trimonthly ONI from SON to JFM.

 

The trimonthly ONI is going to be solidly "El Niño" by SON. What are you defining as a "borderline event"?

 

The CPC defines a borderline event ONI number as +0.5 to -0.5. And again we should be solidly above +0.5C ONI by SON. 

[Phil]

The trimonthly ONI is going to be solidly "El Niño" by SON. What are you defining as a "borderline event"?

 

The CPC defines a borderline event ONI number as +0.5 to -0.5. And again we should be solidly above +0.5C ONI by SON.

The trimonthly ONI needs to be at/above +0.5C for five consecutive months, unless something has changed in the calculation since I left seasonal forecasting for paleoclimate research a few years ago. I don’t think that’s the case though.

[Kayla]

The trimonthly ONI needs to be at/above +0.5C for five consecutive months, unless something has changed since I left seasonal forecasting for paleoclimate research.

 

Yeah I understand. My point being is that you think the trimonthly ONI is going to drop below +0.5C between SON and JFM?

 

Bold call at this point if that's the case!

[Phil]

Yeah I understand. My point being is that you think the trimonthly ONI is going to drop below +0.5C between SON and JFM?

 

Bold call at this point if that's the case!

Yeah, hence my “perhaps I’ve blown a mental gasket” statement. And I’ve already had to recalibrate my projections since the failed MJO return in October, so maybe I’m still wrong.

 

What happens w/ the pattern between Dec 15 and Feb 1 will reveal a lot.

[Guest daniel1]

Then again, my earlier thoughts were for an integrated regime of constructive interference to develop in JFM of 2019..but since I overestimated the degree of autumnal warm pool dissociation and thermocline shoaling, that no longer looks to be the case, when the next bout of high amplitude MJO/mass circulation event occurs around the holidays following the NAM flip to negative. It will probably have the opposite initial effect on the ENSO state, though not nearly to the extent of 1987/88.

Is the NAM gonna flip negative?

[Geos]

Appears to be west-based... not sure if that is good or bad.    

 

And that warm pool off our coast keeps growing too.

 

 

Hopefully the el Nino can stay central basin based. I think Modoki el Nino act differently when it comes to the pattern in North America.

 

Also, hopefully the storminess in the NE Pacific can cool those waters off some. There has been some decrease in the last 7 days. 

 

[AbbyJr]

Does anyone know of a site that offers historical graphs where I can see the SST anomaly for both the Nino 4, 3.4, and 3 regions for years past? Tropical Tidbits have graphs for the current state, but it doesn't show what it was like back in 2003 on a given date.

[BLI snowman]

Does anyone know of a site that offers historical graphs where I can see the SST anomaly for both the Nino 4, 3.4, and 3 regions for years past? Tropical Tidbits have graphs for the current state, but it doesn't show what it was like back in 2003 on a given date.

 

Don't know about graphs but this gives you the weekly anomaly data back to 1990

 

http://www.cpc.ncep.noaa.gov/data/indices/wksst8110.for

[Jesse]

At this point we may as well just hope this Niño goes full blown and we can get it out of the way sooner. Maybe next winter will be the Niño fail.

[Phil]

Does anyone know of a site that offers historical graphs where I can see the SST anomaly for both the Nino 4, 3.4, and 3 regions for years past? Tropical Tidbits have graphs for the current state, but it doesn't show what it was like back in 2003 on a given date.

Eric Webb has a very detailed page reconstructing ENSO variability back into the 19th century.

 

https://www.webberweather.com/ensemble-oceanic-nino-index.html

[AbbyJr]

Thanks everyone for those links. 

[Webberweather53]

Well that depends what parameters you use to define “slow walk”..SSTAs aren’t a good way to diagnose that. The anomalous suppression of the thermocline has not amplified drastically over the last six months..it’s been suppressed for awhile. If we were observing a coherent amplification of the ENSO wavecycle then I’d be on the moderate/strong niño train as well. But that’s not the case.

 

I’m going to write up a detailed post on this later, but I’m still going with a borderline event as reflected by the trimonthly ONI from SON to JFM.

 

I don't want to sound mean at all because I think you're an extremely smart dude, but I think you've been living in a little denial lately... A moderate El Nino is indeed possible and what we're seeing is "coherent" amplification up to this point anyway haha. If you actually looked at every other El Nino with a thermocline that was as suppressed as this one currently is they were all moderate or strong El Ninos, and that's no surprise. SSTAs are one of the best ways to define that because they evolve relatively slowly over periods of several weeks-months and are the source of energy for deep convection that drives circulation changes globally. Even when weekly SSTAs are above +1 to even 1.5C in some cases, that is definitely not a slow-walk towards warm ENSO with the event developing after the solstice as you initially anticipated (which was a legitimate scenario imo until about several weeks ago), and there are other indicators which corroborate the fact we're already in an El Nino and/or have been for a while. Is it possible we fade back towards warm neutral very late this winter or better yet near the equinox? Absolutely, but it seems far more likely historically speaking we intensify thru the spring equinox and end up w/ a formidable El Nino already at hand next summer. It would certainly be quite an anomaly for us to end up back in neutral and stay there for the remainder of 2019 & into 2020 esp given where we stand wrt SC 24, but it can't be entirely ruled out either given what happened in 1880-81.

[Phil]

Hey man, I hope I’m living in denial. It would mean more snowfall in my backyard.

 

And SSTAs evolve slowly? That’s a new one for me. The subsurface certainly evolves “slowly” by comparison, but how that translates to the surface depends on the nature of wind stresses/hydrostatic coupling, which remains unimpressive.

[Webberweather53]

Hey man, I hope I’m living in denial. It would mean more snowfall in my backyard.

 

And SSTAs evolve slowly? That’s a new one for me. The subsurface certainly evolves “slowly” by comparison, but how that translates to the surface depends on the nature of wind stresses/hydrostatic coupling, which remains unimpressive.

 

I'm not going down this rabbit hole with you again. Yeah they actually do if you looked at the e-folding scale of the anomalies, there's a significant subseasonal component but most of the variance is explained over periods of several months or more. It's supposedly unimpressive yet we're getting SSTAs > 1-1.5C in the NINO 3, NINO 3.4, & NINO 4 regions of the tropical Pacific & the thermocline is suppressed enough to support a borderline moderate-strong El Nino. Again you're living in denial lol

[Phil]

[Webberweather53]

Well, I guess we’ll find out eventually.

 

And the SSTAs themselves are pretty bouncy, even if their boundaries are preconditioned over longer periods of time. Personally, I try to avoid extrapolating from them on timescales like this.

 

The reason the SSTAs are this high is mainly related to low frequency variations in the thermocline and the warming is occurring simultaneously w/ an easterly trade wind burst over the basin atm as tropical forcing shifts into the Eastern Hemisphere. Hence, this doesn't look like a temporary change.

[Webberweather53]

The warm water volume anomaly in the east-central Pacific was 6th highest on record for October, only surpassed by moderate or strong El Ninos and safely inside moderate NINO territory if you use ranked percentiles. A weak or moderate El Nino is the most likely solution for the upcoming winter, we have more than enough gas in the tank to squeeze out at least one tri-monthly > +1C even if there's considerable damping from this point forward.

[Geos]

A write-up on Modoki el Ninos. 

 

http://firsthandweather.com/3796/winter-2018-2019-discussion-modoki-el-nino/

[Brian_in_Leavenworth]

You can see in this Hovmoller in early October and in early November the two westerly wind anomalies that led to the increases in positive SST anomalies.  But it is also showing a possible cooling of the anomalies in the next week.  

 

http://www.atmos.albany.edu/student/ventrice/real_time/timeLon/u.anom.30.5S-5N.gif

[Phil]

The reason the SSTAs are this high is mainly related to low frequency variations in the thermocline and the warming is occurring simultaneously w/ an easterly trade wind burst over the basin atm as tropical forcing shifts into the Eastern Hemisphere. Hence, this doesn't look like a temporary change.

But the ongoing cell (more subsidence/trades just west of the dateline) is one that would trigger an upwelling wave, if it were to continue. Cuts off the warm pool draw and increases Indonesian throughflow.

 

I know it’s an intraseasonal cycle tied to the -EAMT conjunct poleward cycling +AAM from the subtropics, but that’s not a quick process either. I think we peak early this year.

[Phil]

The warm water volume anomaly in the east-central Pacific was 6th highest on record for October, only surpassed by moderate or strong El Ninos and safely inside moderate NINO territory if you use ranked percentiles. A weak or moderate El Nino is the most likely solution for the upcoming winter, we have more than enough gas in the tank to squeeze out at least one tri-monthly > +1C even if there's considerable damping from this point forward.

What about the WWV anomaly between 160E and 160W? That’s the area I usually focus on.

[Geos]

Going back down.

 

 

[TT-SEA]

Going back down.

 

 

 

Very good news!

[OKwx2k4]

I still say that based off destructive interference alone, no Niño. There is well more than enough evidence to support suppression by surface wind anomalies.

[luminen]

I still say that based off destructive interference alone, no Niño. There is well more than enough evidence to support suppression by surface wind anomalies.

 

Maybe so but "it" seems to want to go into + territory. If a strong one is avoided this season then it seems more likely a full blown Niño will occur next year. Hopefully I'm wrong on all accounts though. 

[AbbyJr]

But the ongoing cell (more subsidence/trades just west of the dateline) is one that would trigger an upwelling wave, if it were to continue. Cuts off the warm pool draw and increases Indonesian throughflow.

 

I know it’s an intraseasonal cycle tied to the -EAMT conjunct poleward cycling +AAM from the subtropics, but that’s not a quick process either. I think we peak early this year.

Do you think we have already peaked or perhaps will pick later in November?

[Webberweather53]

Another downwelling oceanic Kelvin Wave has formed in response to the WWB ~120-150E late in October west of the dateline and will be reinforced by an equatorial Rossby Wave this week.

[Webberweather53]

The downwelling wave that's formed west of the dateline in response to the late October WWB from 120-150E will be shielded from destructive interference this week thanks to an equatorial Rossby Wave seeding the KW w/ more westerly wind anomalies & will enhance thermocline suppression on the leading edge of the wave.

[Phil]

Another downwelling oceanic Kelvin Wave has formed in response to the WWB ~120-150E late in October west of the dateline and will be reinforced by an equatorial Rossby Wave this week.

That tiny thing? Feels like it will do more to stave off any upwelling wave/move to niña than strengthen the ongoing event, since the EPAC wave is about to enter its diffraction phase.

[Webberweather53]

That tiny thing? Feels like it will do more to stave off any upwelling wave/move to niña than strengthen the ongoing event, since the EPAC wave is about to enter its diffraction phase.

 

It seems subjectively tiny to you atm because it literally just formed and will actually continue growing west of the dateline thanks to an atmospheric equatorial Rossby Wave moving across the dateline this week which will deposit more westerly momentum into it. It's certainly a far cry from the upwelling wave you keep promising is coming . Btw, the thermocline is being suppressed down to at least 250m, it's not a trivial downwelling wave like you're making it out to be & again it will only grow from here in the coming week as it approaches the dateline.

[Black Hole]

It seems subjectively tiny to you atm because it literally just formed and will actually continue growing west of the dateline thanks to an atmospheric equatorial Rossby Wave moving across the dateline this week which will deposit more westerly momentum into it. It's certainly a far cry from the upwelling wave you keep promising is coming . Btw, the thermocline is being suppressed down to at least 250m, it's not a trivial downwelling wave like you're making it out to be & again it will only grow from here in the coming week as it approaches the dateline.

Can you explain to me about these " atmospheric equatorial Rossby Waves". What do they look like on a chart, how are they formed, and what all do they do? How do they relate to Oceanic Kelvin waves? Thanks!

[Webberweather53]

Can you explain to me about these " atmospheric equatorial Rossby Waves". What do they look like on a chart, how are they formed, and what all do they do? How do they relate to Oceanic Kelvin waves? Thanks!

 

Atmospheric equatorial rossby waves are typically formed (like most convectively coupled waves) from deep convection and they radiate westward from their heating source, often exhibiting a pronounced axisymmetric equatorial structure with gyres of the same sign (cyclonic or anticyclonic) straddling the equator, the speed of these waves is a function of distance from the equator, with faster westerly propagation closer to the equator and vis versa and on average they travel at about a third of the speed of a Kelvin Wave. In the case where twin cyclones are axissymmetric wrt the equator and propagating westward as an equatorial Rossby Wave, they produced westerly wind anomalies at the surface which disrupts the wind-gravity balance in the equatorial Pacific, ultimately producing a Kelvin Wave in order to restore this balance because the eastward wind is slower. Zonal advective feedbacks, those related to convection, and the underlying "elasticity" of the thermocline (in our current climate) all contribute to non-linearities in the system wherein the contribution from anomalous westerly wind of the same magnitude and duration as a corresponding easterly wind anomaly will actually push the equatorial Pacific slightly towards El Nino instead of being dead-on neutral. It's one major reason why even in years like 2014 which had one pronounced westerly wind burst over a period of several months which were actually dominated by easterlies still ended up w/ net +SSTAs in the Eq Pacific. In a warmer climate where the static stability of the upper ocean increases due to disproportionate warming rates in the upper vs middle-deep oceans actually stiffen the thermocline and dampen non-linearities that currently exist in the system, such that the strongest El Ninos will actually be as strong as the largest La Ninas instead of today where we find "Super" Ninos like 1877-78, 1982-83, & 1997-98 having greater amplitude over monster La Nina events like 1973-74, 1916-17, etc

[Webberweather53]

That tiny thing? Feels like it will do more to stave off any upwelling wave/move to niña than strengthen the ongoing event, since the EPAC wave is about to enter its diffraction phase.

 

Also need to remind you that the diffraction phase occurs nowhere near as fast as the growth phase w/ a downwelling Kelvin Wave approaching the eastern boundary region due to the differences in the Kelvin Wave & equatorial Rossby Wave phase speeds which I discussed in an earlier comment to you a few months ago.

[Phil]

It seems subjectively tiny to you atm because it literally just formed and will actually continue growing west of the dateline thanks to an atmospheric equatorial Rossby Wave moving across the dateline this week which will deposit more westerly momentum into it. It's certainly a far cry from the upwelling wave you keep promising is coming . Btw, the thermocline is being suppressed down to at least 250m, it's not a trivial downwelling wave like you're making it out to be & again it will only grow from here in the coming week as it approaches the dateline.

Relative to the diffracting EPAC wave, hard to argue (IMO) that this one is anywhere close to the amplitude of the prior one. Would you agree?

 

FWIW, I’m not seeing/predicting a consequential upwelling wave either. Still leaning towards a multiyear warm event, with a niño in 2019/20. Or, if I’m wrong about the eventual amplitude of this current ENSO event, then maybe a neutral in 2019/20 and another niño in 2020/21. But the low frequency evolution of the IPWP clearly seems to favor +ENSO for the long haul.

[Phil]

Also need to remind you that the diffraction phase occurs nowhere near as fast as the growth phase w/ a downwelling Kelvin Wave approaching the eastern boundary region due to the differences in the Kelvin Wave & equatorial Rossby Wave phase speeds which I discussed in an earlier comment to you a few months ago.

Of course, but the diffraction and poleward displacement of water across the equatorial EPAC boosts thermocline shoaling and destructively interferes with eastward propagating downwelling waves in the near term.

 

Regardless, whether this ends up a weak niño or warm neutral feels like splitting hairs to me (it might very well end up stronger than I thought..we’ll see). I’m more interested in whether the aforementioned developments and evolution of other external parameters can force a series of WWB events in JFM and produce a stronger niño next year.

[Phil]

[Black Hole]

Atmospheric equatorial rossby waves are typically formed (like most convectively coupled waves) from deep convection and they radiate westward from their heating source, often exhibiting a pronounced axisymmetric equatorial structure with gyres of the same sign (cyclonic or anticyclonic) straddling the equator, the speed of these waves is a function of distance from the equator, with faster westerly propagation closer to the equator and vis versa and on average they travel at about a third of the speed of a Kelvin Wave. In the case where twin cyclones are axissymmetric wrt the equator and propagating westward as an equatorial Rossby Wave, they produced westerly wind anomalies at the surface which disrupts the wind-gravity balance in the equatorial Pacific, ultimately producing a Kelvin Wave in order to restore this balance because the eastward wind is slower. Zonal advective feedbacks, those related to convection, and the underlying "elasticity" of the thermocline (in our current climate) all contribute to non-linearities in the system wherein the contribution from anomalous westerly wind of the same magnitude and duration as a corresponding easterly wind anomaly will actually push the equatorial Pacific slightly towards El Nino instead of being dead-on neutral. It's one major reason why even in years like 2014 which had one pronounced westerly wind burst over a period of several months which were actually dominated by easterlies still ended up w/ net +SSTAs in the Eq Pacific. In a warmer climate where the static stability of the upper ocean increases due to disproportionate warming rates in the upper vs middle-deep oceans actually stiffen the thermocline and dampen non-linearities that currently exist in the system, such that the strongest El Ninos will actually be as strong as the largest La Ninas instead of today where we find "Super" Ninos like 1877-78, 1982-83, & 1997-98 having greater amplitude over monster La Nina events like 1973-74, 1916-17, etc

Thanks for the explanation. Which charts do you find best to track these equatorial rossby waves? I know the kelvin waves can be seen with the anomalously warm ocean temperatures propagating eastwards. 

[OKwx2k4]

Thank you guys all for writing that stuff out. I can usually tell you what something is going to do or show and explain(atmosphere,ENSO,etc...), but I can't touch an explanation like that for the "how?". Thank you.

[Geos]

Hard drop in the 3.4 index. el Nino throwing in the towel?...