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#1301
Phil

Posted 16 May 2018 - 12:07 PM

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The interesting thing about that period compared to now is that we have much lower solar activity today. There was something else driving the deep -PDO/-ENSO circulation then.


Ironically, it was probably a response to the increase in solar activity in the 1940s, which warmed the WPAC and strengthened the Walker Cell, since the climate system was still recovering from the LIA and had plenty of warming left to do. Amazing how non-linear these things can be.
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#1302
Phil

Posted 16 May 2018 - 12:17 PM

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- Prolonged periods of high solar favor strong, single-yr niños and multi-yr niñas.

- Prolonged periods of low solar favor weak, multi-yr niños and single-yr niñas.

- Niña/-PDO is a regime of ocean heat uptake, which cools the atmosphere, while Niño/+PDO is a regime of ocean heat release, which warms the atmosphere.

- Short term/decadal effects of Niño/+PDO are a warmer atmosphere/upper ocean, but the long term effects are to release heat/cool the ocean/atmosphere system,

- Short term/decadal effects of Niña/-PDO are a cooler atmosphere/upper ocean, but the long term effects are to absorb heat/warm the ocean atmosphere system.

- This is why the MWP, and the majority of the middle Holocene, was dominated by -ENSO/-PDO, and it’s why the LIA, and the majority of the neoglacial late Holocene was dominated by +ENSO/+PDO.
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#1303
Mr Marine Layer

Posted 17 May 2018 - 04:52 PM

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Still a wide area below normal
 
cdas-sflux_ssta_global_1.png

Disagreement among the two maps.

http://www.ospo.noaa...p.5.17.2018.gif

#1304
Phil

Posted 17 May 2018 - 05:29 PM

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Disagreement among the two maps.

http://www.ospo.noaa...p.5.17.2018.gif


They use different climatology periods.
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#1305
TT-SEA

Posted 17 May 2018 - 05:49 PM

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Disagreement among the two maps.

http://www.ospo.noaa...p.5.17.2018.gif


He posted that a month ago... it must be a live link that is updating because the map is from today connected to a post from April 17th.

#1306
Mr Marine Layer

Posted 17 May 2018 - 07:28 PM

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He posted that a month ago... it must be a live link that is updating because the map is from today connected to a post from April 17th.

 

The one I posted is from today.



#1307
OKwx2k4

Posted 17 May 2018 - 10:47 PM

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They use different climatology periods.


Which climatology does NOAA use?

#1308
Phil

Posted 18 May 2018 - 07:21 AM

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Which climatology does NOAA use?


You mean the NOAA-OSPO/NESDIS dataset?

I believe it uses a 1985-1993 climatology period, which is much shorter/colder than the 1981-2010 climatology period utilized by OISST/CDAS.

Which is why I’ve grown less fond of OSPO/NESDIS in recent years, spatially speaking. The climatology period is no bueno..that era was all +PDO/-AMO..so that type of SSTA configuration today will not be well-represented.
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#1309
OKwx2k4

Posted 18 May 2018 - 10:17 AM

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You mean the NOAA-OSPO/NESDIS dataset?

I believe it uses a 1985-1993 climatology period, which is much shorter/colder than the 1981-2010 climatology period utilized by OISST/CDAS.

Which is why I’ve grown less fond of OSPO/NESDIS in recent years, spatially speaking. The climatology period is no bueno..that era was all +PDO/-AMO..so that type of SSTA configuration today will not be well-represented.


Yeah. Whatever alphabet soup name they want to call it. Lol. That's what I was referring to.

They just happened to pick the coldest background state they could find. Unreal sometimes what horse manure they shovel out as science these days.
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#1310
Phil

Posted 22 May 2018 - 10:54 AM

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Man, seems everyone is leaning El Niño now. NOAA, Accuweather, WxBell, many tropical meteorologists. And I’m here scratching my head..I just don’t see the necessary preconditionings for it.

We’ve had no reinforcing WWB activity, off-eq trades gave been consolidating, and the downwelling OKW has stalled and will cycle in a few months without mechanical reinforcement. And now we’ve got 2-3 weeks of enhanced trades upcoming. I’m lost. :huh:

Either I’m missing something everyone else is seeing, or there is widespread climate model hugging going on. As of now, I’m sticking with my call for a head fake and regression to a west-based warm-neutral.
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#1311
TT-SEA

Posted 22 May 2018 - 12:10 PM

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I hope it stays around neutral.   Best chance for a warm summer and a cold winter.   :)



#1312
Black Hole

Posted 23 May 2018 - 08:49 AM

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Man, seems everyone is leaning El Niño now. NOAA, Accuweather, WxBell, many tropical meteorologists. And I’m here scratching my head..I just don’t see the necessary preconditionings for it.

We’ve had no reinforcing WWB activity, off-eq trades gave been consolidating, and the downwelling OKW has stalled and will cycle in a few months without mechanical reinforcement. And now we’ve got 2-3 weeks of enhanced trades upcoming. I’m lost. :huh:

Either I’m missing something everyone else is seeing, or there is widespread climate model hugging going on. As of now, I’m sticking with my call for a head fake and regression to a west-based warm-neutral.

A lot of warm water below the surface and gradual warming has continued, especially west. I think el nino is possible but right now it doesn't look better than weak. 


BS Atmospheric Science University of Utah May 2015

PhD Candidate Atmospheric Sciences

 

--Emphasis on: Forecasting, Mountain Weather, Numerical Weather Prediction, Data Assimilation

 

Winter 2017/2018

Dec 4: 3.2", 16: 0.9", 20: 2.1", 23: 1.5", 25: 4.6"

Jan 6: 1.5", 20: 10.8", 25: 1.5"

Feb 19: 8.6", 20: 2.4", 23: 7.1", 25: .5"

Mar 4: 13", 15: 1.8", 17: 5.3", 25: 4.2"

April 12: 1", 17: 1.3"

Total: 69.3"

 

 

Winter 2016/17 Snow:
Nov 17: 3.2", 23: 1.6", 28: 9.2" (14)

Dec 1: .5", 16: 2.5", 25: 13" (16)

Jan 2: 5", 3: 2.4", 4: 7.7", 12: 1", 19: 1.2", 21: 13", 23: 6", 24: 1", 25: 3.7", 26: 2.5" (43.5) 

Feb 11: .5", 23: 6.5", 27: 4.5" (13.5)

Mar 5: 5.5" (5.5)

Apr 8: 2", 9: 1.8" (3.8)

May 17: 1" (1)
Total: 96.3"

Lowest Temp: 2F


#1313
Phil

Posted 23 May 2018 - 09:48 AM

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A lot of warm water below the surface and gradual warming has continued, especially west. I think el nino is possible but right now it doesn't look better than weak.


Yeah, that downwelling OKW did warm the subsurface. Though my concern is WWB activity has been lacking since its inception back in Feb/Mar, and if there’s no additional reinforcement before diffraction then there’s basically nothing to sustain the move into El Niño.

This upcoming trade burst will be key, IMO. If there’s no follow up WWB activity, then I highly doubt there will be enough fluid inertia left for a niño.
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#1314
Webberweather53

Posted 12 June 2018 - 02:50 PM

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I think this season being just before a major solar minimum will tip the balance and result in a failed El Nino attempt.  The failed attempt last year probably released some extra heat to make a Nino even more unlikely.  2019-20 on the other hand has a good chance of having a Nino IMO.

 

This claim doesn't hold water considering that the 2 largest El Ninos of the 19th century occurred within about 1-2 years before solar min in 1877-78 & 1888-89. All the other failed NINO attempts in the modern era like 2012 & 2017 featured a warm Atlantic coupled to warming that initiated in the far eastern Pacific before the rest of the basin, this year is the coldest in the entire OISSTv2 dataset in the Atlantic MDR and the central Pacific warmed before the far EP, completely different pattern and one that's not hostile to NINO growth.



#1315
Phil

Posted 12 June 2018 - 06:08 PM

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This claim doesn't hold water considering that the 2 largest El Ninos of the 19th century occurred within about 1-2 years before solar min in 1877-78 & 1888-89. All the other failed NINO attempts in the modern era like 2012 & 2017 featured a warm Atlantic coupled to warming that initiated in the far eastern Pacific before the rest of the basin, this year is the coldest in the entire OISSTv2 dataset in the Atlantic MDR and the central Pacific warmed before the far EP, completely different pattern and one that's not hostile to NINO growth.


I’d argue weak solar actually favors El Niño, or at least predisposes the IPWP to hold a more niño-friendly state during the crucial Feb-Jun period.

All else being equal, of course. Which often isn’t the case in the long term.
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#1316
Webberweather53

Posted 14 June 2018 - 12:59 PM

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For those that are interested (esp Phil), I made a few minor tweaks, further refined, and updated my ENS ONI index from the mid 19th century thru the present, putting it on my new website which was initially created to house a massive winter storm archive for NC (& still will obviously). I made the data (raw monthly NINO 3.4 SSTs, tri-monthly and standardized data, and ranks) easily accessible via Excel.

 

An intriguing distinguishing quality amongst most Super El Ninos in the observational record is the tendency to set new, successive, all-time monthly records in the NINO 3.4 region of the equatorial Pacific. 1877-78's record stood for over a century, lasting until 1982-83, which was later beaten by 1997-98 & then 2015-16. This doesn't take away from the fact that years like 1888-89 & 1972-73 weren't massive, but 1877-78, 1982-83, 1997-98, & 2015-16 certainly go the extra mile whereas those other 2 "Super" NINOs didn't as much. 

 

Enjoy!

https://www.webberwe...nino-index.html

 

screen-shot-2018-06-14-at-4-24-15-pm_ori

 

screen-shot-2018-06-14-at-9-14-47-am_ori


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#1317
Webberweather53

Posted 14 June 2018 - 02:32 PM

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The similarities between the mid-late 1870s and the last several years are getting borderline scary at this point. The progression is eerily similar, w/ 1880-81 producing a late blooming, weak El Nino after the Equinox that had trouble fading away after the winter, I think that's a very plausible scenario for 2018-19.

 

1875-76 & 2013-14: Cold neutral ENSO

1876-77 & 2014-15: Weak El Nino develops after the Equinox

1877-78 & 2015-16: "Super" El Nino

1878-78 & 2016-17: Cold neutral ENSO

1879-80 & 2017-18: Weak-Moderate La Nina

1880-81 & 2018-19: Weak El Nino develops after the equinox (?)

1876-1880 ENS ONI

 

Dfr0dOdXcAEZda1.jpg

 

 

 

2014-18 ENS ONI

 

Dfr0dOeX0AETSXR.jpg


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#1318
Phil

Posted 15 June 2018 - 08:14 AM

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Fantastic work as usual, Eric. Really do appreciate your ENSO reconstructions.

Definitely a fascinating evolution this year, as well.
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#1319
TigerWoodsLibido

Posted 15 June 2018 - 12:05 PM

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Crazy to me that 2 of the most impressive arctic/snow events for the Willamette Valley occurred in 68-69, a moderate Nino and 72-73, a mammoth Nino.


Springfield, Oregon cold season 18-19 Stats:

Coldest high: 48 (Nov 8)
Coldest low: 27 (Nov 11)
Total snowfall: 0"
Last accumulating snowfall: February 21-22, 2018
Last sub-freezing high: Jan 13, 2017 (31)
Last White Christmas: 1990

Personal Stats:

Last accumulating snowfall: March 6, 2017
Last sub-freezing high: Jan 13, 2017 (31)
Last White Christmas: 2008

My Twitter @353jerseys4hope


#1320
Front Ranger

Posted 15 June 2018 - 12:10 PM

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NWS fell for the head fake!!

https://www.nbcnews....ther-el-n883431

Cool anomalies soothe the soul.


#1321
TT-SEA

Posted 15 June 2018 - 12:28 PM

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Odd configuration... you can see the weak Nino forming in the ENSO regions but its uniformly warm to the north of the ENSO regions and cold to the south.

 

cdas-sflux_ssta_global_1.png



#1322
Phil

Posted 15 June 2018 - 12:44 PM

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Odd configuration... you can see the weak Nino forming in the ENSO regions but its uniformly warm to the north of the ENSO regions and cold to the south.

cdas-sflux_ssta_global_1.png


You can see the +PMM and -AMM clearly there. The colder IO is interesting too. The IO was the global SSTA hotspot for over 2 decades, and it sort of just flipped following the super-niño in 2016. Probably no coincidence that the IO and NATL have been heavily connected throughout the Holocene.

At the very least, we’re probably moving away from the particular seasonality of the axisymmetric forcing that has dominated since 1998, and into a new one.
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#1323
Guest_happ_*

Posted 19 June 2018 - 08:37 AM

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Does long term ocean warming have an effect on the frequencies of El Nino conditions?

 

https://twitter.com/borenbears

 

Attached Files



#1324
Phil

Posted 19 June 2018 - 12:51 PM

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Does long term ocean warming have an effect on the frequencies of El Nino conditions?

https://twitter.com/borenbears


Well, SSTAs in general as well as the ENSO system are both reflections of changes in circulation, heat budget structures, and their pseudo-entropic conduits to equilibration.

So it’s not that warm SSTs affect ENSO. It’s that SSTAs and ENSO are affected by the aforementioned changes to relevant boundary conditions.
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#1325
Webberweather53

Posted 19 June 2018 - 05:57 PM

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Does long term ocean warming have an effect on the frequencies of El Nino conditions?

 

https://twitter.com/borenbears

 

In a general hand-wavy sense, increasing global temperatures in the late holocene would actually equate to less frequent NINO conditions because as the hadley cells further expand, they become less efficient and more reminiscent of NINA-esque conditions, there's likely also a lot more to it than we've been able to uncover. The ENS ONI and CPC's ONI that only uses ERSSTv5 use 30-year sliding base periods to try and remove the AGW signal in the data and even if the globe wasn't warming, I would still use a sliding base period or something of the like because they also indirectly make the observational background more relevant to each climate period in the process. This can include (but isn't limited to) the spatiotemporal coverage of observations, types of observational platforms, and magnitude and types of adjustments to these observations, etc.


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#1326
Phil

Posted 19 June 2018 - 06:13 PM

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In a general hand-wavy sense, increasing global temperatures in the late holocene would actually equate to less frequent NINO conditions because as the hadley cells further expand, they become less efficient and more reminiscent of NINA-esque conditions, there's likely also a lot more to it than we've been able to uncover. The ENS ONI and CPC's ONI that only uses ERSSTv5 use 30-year sliding base periods to try and remove the AGW signal in the data and even if the globe wasn't warming, I would still use a sliding base period or something of the like because they also indirectly make the observational background more relevant to each climate period in the process. This can include (but isn't limited to) the spatiotemporal coverage of observations, types of observational platforms, and magnitude and types of adjustments to these observations, etc.


Agree here. The Mid-Holocene is a great example of this warm globe ENSO/z-cell configuration. Persistent weak/moderate La Niña/-PDO type pattern shows up in literally all of the proxy interpolations, with a larger and more coherent WPAC warm pool as well.

Many papers suggest that multi-year niños are much more infrequent during warm climate periods. Not sure about super niño frequency, though. Maybe you would know more about that?
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#1327
Webberweather53

Posted 19 June 2018 - 06:28 PM

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Agree here. The Mid-Holocene is a great example of this warm globe ENSO/z-cell configuration. Persistent weak/moderate La Niña/-PDO type pattern shows up in literally all of the proxy interpolations, with a larger and more coherent WPAC warm pool as well.

Many papers suggest that multi-year niños are much more infrequent during warm climate periods. Not sure about super niño frequency, though. Maybe you would know more about that?

 

While I'm not entirely sure on the frequency of Super NINOs in a warmer climate and it's not easy to distinguish amongst those in the proxy records, the maximum potential intensity of El Ninos would probably increase barring that the globe warms and we continue along the path we're on w/ a steepening of the near-equatorial Pacific zonal SST gradient and a larger expanse of the basin above the general SST threshold to readily generate convection and thus generate true westerly winds that break down the wind-gravity balance (although some argue that this number also changes somewhat in a warmer climate). If an El Nino reminiscent of 1997-98 were able to completely breakdown this zonal SST gradient in a warmer climate where the SST slope is steeper, it would definitely be capable of becoming more intense. The efficiency of the Hadley Cells may make this more difficult to be realized. However, I don't think it's unreasonable to assume we'd have a higher ceiling even if the frequency of those extraordinary events somehow wasn't much different from today.


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#1328
weatherfan2012

Posted 19 June 2018 - 06:40 PM

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Well, SSTAs in general as well as the ENSO system are both reflections of changes in circulation, heat budget structures, and their pseudo-entropic conduits to equilibration.
So it’s not that warm SSTs affect ENSO. It’s that SSTAs and ENSO are affected by the aforementioned changes to relevant boundary conditions.

interisting that ocean warming was brought up as that is something that Robert Filex tends to talk about quite alot in interviews and in his book and on his site.

#1329
Phil

Posted 19 June 2018 - 09:11 PM

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Interesting to see the global SST anomaly decreasing in tandem with warming ENSO and the Arctic opening up for the summer. Not something you typically see at this time of year. Or at least not since the 80s/early 90s.

9Dazs1Z.png
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#1330
Phil

Posted 20 June 2018 - 10:39 AM

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While I'm not entirely sure on the frequency of Super NINOs in a warmer climate and it's not easy to distinguish amongst those in the proxy records, the maximum potential intensity of El Ninos would probably increase barring that the globe warms and we continue along the path we're on w/ a steepening of the near-equatorial Pacific zonal SST gradient and a larger expanse of the basin above the general SST threshold to readily generate convection and thus generate true westerly winds that break down the wind-gravity balance (although some argue that this number also changes somewhat in a warmer climate). If an El Nino reminiscent of 1997-98 were able to completely breakdown this zonal SST gradient in a warmer climate where the SST slope is steeper, it would definitely be capable of becoming more intense. The efficiency of the Hadley Cells may make this more difficult to be realized. However, I don't think it's unreasonable to assume we'd have a higher ceiling even if the frequency of those extraordinary events somehow wasn't much different from today.


Fascinating info. I guess that makes sense when you think about it. Having a loaded warm pool to draw from certainly can’t hurt...especially in interdecadal regimes of off-equator SST warmth. Or so I’m guessing. 🤓

I’m working on a study w/ a few peers on warm pool vacillations before and after the mid-Holocene transition. Too early in the process to draw conclusions, but the hypothesis is that the weaker meridional insolation/temp gradient in warm climate periods and high Obliquity periods weakens eddy fluxes and poleward transport of heat/moisture/mass from the middle latitudes, which has a cascading series of consequences on the structure of the planetary energy budget. These effects would be amplified over the hemisphere in which axial and apsidal precession are aligned to enhance the seasonal cycle, especially when eccentricity is elevated.

A weaker meridional temp/insolation gradient would also broaden/slow the Hadley Cells, reduce convective ventilation equatorward from 20N/20S, and favor a more Niña-like background state with a steroidal WPAC warm pool. It would also favor positive cold season annular modes, and an overall uptake of heat by the ocean/atmosphere system thanks to a reduction in tropical cloud cover and wind speeds between 35N/30S, not to mention an increase in cloud cover and H^2O around the winter pole, under the more positive annular mode.
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#1331
weather girl

Posted 23 June 2018 - 06:03 PM

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For whatever it's worth, probably nothing, I'm beginning to be a true believer of an El Nino later this year.  

 

 

Odd configuration... you can see the weak Nino forming in the ENSO regions but its uniformly warm to the north of the ENSO regions and cold to the south.

 

cdas-sflux_ssta_global_1.png



#1332
Webberweather53

Posted 02 July 2018 - 09:59 AM

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We're following the weak-moderate satellite era El Ninos to script thus far, a weak-moderate El Nino still seems like a better call than none at all or a head fake based on what I'm seeing. We are about where I thought we would be several months ago and where we need to be at this point in time to see this solution verify. We'll take our foot momentarily off the gas pedal in the first half of July then the hammer is probably going to come down in late in the month and/or into early August as subseasonal forcing realigns w/ a bgd state that's steadily becoming more NINO like. It's also worth mentioning that most weak-moderate El Ninos in the satellite era were dominated by prolonged periods of easterlies near the dateline before the Equinox but that did little if anything to halt their momentum into the boreal winter. As long as we continue to see WWBs w/ every subseasonal forcing shift into the Pacific, even if there are formidable easterlies for prolonged stretches of time in between, we'll continue moving forward. 



#1333
Phil

Posted 02 July 2018 - 11:53 AM

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Funny, I actually thought we’d be farther along by now, even in my head-fake scenario. I still can’t find a conduit to the dateline WWB action necessary to pull us over the finish line. Or at least not in time to counter EPAC diffraction.
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#1334
Webberweather53

Posted 02 July 2018 - 04:44 PM

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Funny, I actually thought we’d be farther along by now, even in my head-fake scenario. I still can’t find a conduit to the dateline WWB action necessary to pull us over the finish line. Or at least not in time to counter EPAC diffraction.

 

Most of the satellite era weak-moderate events saw limited dateline WWBs until we got into October and the conduit with most of those events rested on the PMM which is still large and positive atm. I don't see the head fake scenario playing out unless the Atlantic warmed up a lot in the next few months. Considering we just set a new record low -AMM last month, I don't think that's going to happen.

DhHjIhDXkAAdOL7.jpg

 

DhHjIihX0AEwzTN.jpg


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#1335
Phil

Posted 02 July 2018 - 05:13 PM

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Interesting. How do the thermocline sloshes in those years compare to this year re: timing and amplitude?

My gut instinct is that our pair of OKWs will complete their half-life cycles ~ 3 weeks before the equinox. That feels like unfavorable timing to me without a WWB/warm pool tap before then. But it’s definitely not a confident prediction.
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#1336
Webberweather53

Posted 02 July 2018 - 07:06 PM

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Interesting. How do the thermocline sloshes in those years compare to this year re: timing and amplitude?

My gut instinct is that our pair of OKWs will complete their half-life cycles ~ 3 weeks before the equinox. That feels like unfavorable timing to me without a WWB/warm pool tap before then. But it’s definitely not a confident prediction.

 

Another weak downwelling KW is crossing the International Dateline atm in the wake of these other KWs and we appear to be tapping into the warmpool yet again.

wkxzteq_anm.gif

 

 

In terms of warm water volume along/east of the dateline, we're running close to 2009, 2004, & 2002 atm, and behind 1997 & 2015 obviously. The evolution of thermocline suppression, OKW behavior, and Eq trade wind distribution seems to be closely mirroring 2009 although we have an advantage thus far w/ weaker dateline easterlies.

 

 

July 2002 BOM subsurface analysis

 

IDYOC002.200207.gif

 

2009

IDYOC002.200907.gif

 

This year

IDYOC002.201807.gif


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#1337
Phil

Posted 02 July 2018 - 09:15 PM

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You think there’s enough fluid inertia there to delay the backslosh? I guess we’ll see.
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#1338
Webberweather53

Posted 02 July 2018 - 10:00 PM

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You think there’s enough fluid inertia there to delay the backslosh? I guess we’ll see.

 

When a downwelling Kelvin Wave reaches the eastern boundary, it returns as a slower moving, westward propagating off-equatorial Rossby Wave. This means the "black slosh" from a KW is often much slower and arduous than the other way around. Likewise, when upwelling Rossby Waves generated from a westerly wind anomaly in the CP reaches the western boundary, it returns as an upwelling Kelvin Wave and typically terminates an El Nino.

 

I'm under the impression that you were incorrectly assuming that when a Kelvin Wave reaches South America it returns westward as a Kelvin Wave too and propagates at the same speed as it did before hitting South America and this somehow means it's completed its half cycle.

 

This is actually not true at all.

 

In fact, when a downwelling KW reaches the eastern boundary it's only about 1/4th of the way through it's life cycle because the Rossby Wave that's generated from the Kelvin Wave reflection propagates at one third (~1 m/s) of the Kelvin Wave phase speed (~3 m/s). This also means this backslosh you're referring to due to a refracted Kelvin Wave returning as a Rossby Wave is actually 3x slower than the downwelling Kelvin Wave that triggered it, meaning that it would take about 6 months for a RW generated at the western boundary to return and pass the CP (even then the RW is still suppressing the thermocline because the downwelling KW generates a downwelling RW, both of which constructively interfere w/ one another and generate the quasi-stationary and then eventually the slowly westward propagating SST configuration in the Eq Pacific.). Another KW is crossing the dateline now and will likely reach South America sometime near the beginning of September. It will take about another 5-6 months after that KW hits South America for it to pass the dateline again as Rossby Wave, certainly seems like we're doing fine w/ maintaining forcing thru the solstice.

 

Also keep in mind that NINO termination usually occurs as Rossby Waves refract against the western boundary and return as upwelling Kelvin Waves and not by downwelling RWs being generated at the eastern boundary. There's still a lot of downwelling in the WP atm as yet another weak-moderate Kelvin Wave is passing the dateline and the westerly wind anomalies aren't really that strong (as is often true in most weak-moderate El Ninos). All of this evidence along with what I already discussed in my previous comparisons to satellite era El Ninos does suggest that...

a ) We will not see termination of this event any time soon

b ) We're drawing directly from the West Pac Warm pool w/ another downwelling KW in progress

c ) We do in fact have enough WWB forcing to trigger an El Nino (semi-regular modest WWBs w/ each subseasonal forcing pass is sufficient for weak-moderate El Ninos leading into boreal winter)

d ) a conduit (the strong +PMM) to manipulate and maintain the forcing


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#1339
Phil

Posted 02 July 2018 - 11:30 PM

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When a downwelling Kelvin Wave reaches the eastern boundary, it returns as a slower moving, westward propagating off-equatorial Rossby Wave. This means the "black slosh" from a KW is often much slower and arduous than the other way around. Likewise, when upwelling Rossby Waves generated from a westerly wind anomaly in the CP reaches the western boundary, it returns as an upwelling Kelvin Wave and typically terminates an El Nino.

I'm under the impression that you were incorrectly assuming that when a Kelvin Wave reaches South America it returns westward as a Kelvin Wave too and propagates at the same speed as it did before hitting South America and this somehow means it's completed its half cycle.


Sorry, I wasn’t trying to suggest the KW itself refracts back westward upon reaching the EPAC. That wouldn’t make physical sense without some kind of barrier to restrict meridional evacuation. So the bathtub analogy is technically incorrect.

But when the OKW reaches the EPAC and diffracts into the two off-equator oceanic rossby waves, it aids equatorial upwelling behind the tail as water evacuates poleward, as I’m sure you know.

Hence the importance of a healthy follow-up OKW.
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#1340
Jesse

Posted 02 July 2018 - 11:32 PM

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giphy.gif


Does this count as a healthy follow up OKw?

#1341
OKwx2k4

Posted 02 July 2018 - 11:43 PM

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Does this count as a healthy follow up OKw?


Guess not. Lol. I'll remove it. Sorry about that. It was a good post. Didn't think a "like" covered it so I did that.

#1342
Phil

Posted 02 July 2018 - 11:46 PM

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Sorry, I wasn’t trying to suggest the KW itself refracts back westward upon reaching the EPAC. That wouldn’t make physical sense without some kind of barrier to restrict meridional evacuation. So the bathtub analogy is technically incorrect.

But when the OKW reaches the EPAC and diffracts into the two off-equator oceanic rossby waves, it aids equatorial upwelling behind the tail as water evacuates poleward, as I’m sure you know.

Hence the importance of a healthy follow-up OKW.


And does the +PMM actually aid the development of the niño, or is it largely a result of the low frequency state of circulation that favors warm pool discharges?

I’m more convinced of the latter. Too much off-equator convection can actually interfere with El Niño development, in the canonical sense. Some of the most prolific +PMMs like 1980 and 2014 were very anemic in the ENSO department.
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#1343
Jesse

Posted 02 July 2018 - 11:46 PM

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Guess not. Lol. I'll remove it. Sorry about that. It was a good post. Didn't think a "like" covered it so I did that.


Just a joke.
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#1344
Webberweather53

Posted 03 July 2018 - 05:50 AM

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Sorry, I wasn’t trying to suggest the KW itself refracts back westward upon reaching the EPAC. That wouldn’t make physical sense without some kind of barrier to restrict meridional evacuation. So the bathtub analogy is technically incorrect.

But when the OKW reaches the EPAC and diffracts into the two off-equator oceanic rossby waves, it aids equatorial upwelling behind the tail as water evacuates poleward, as I’m sure you know.

Hence the importance of a healthy follow-up OKW.

 

I see where you're coming from but the latter isn't true either. When a Kelvin wave reflects onto a boundary it returns as a rossby wave of the same sign. Meaning that these downwelling Rossby Waves created by reflection of the KW at the eastern boundary also suppress the thermocline. What actually enhances near-equatorial upwelling during El Nino events is the westward flowing surface currents which are in the same sense as earth's rotation generating cyclonic wind stress curl anomalies that augment Sverdrup transport, in effect increasing poleward export of water from the equator. Those westward propagating off-equatorial Rossby Waves actually do contribute to some extent to retaining heat in the Eq Pacific because their westward propagation contributes to anticyclonic wind stress curl that offsets the Equatorial discharge induced by the equatorial westerly current. In any case, I don't think we're having much issue generating more downwelling oceanic Kelvin Waves because another one has entered the fray as aforementioned, it will initially be met with destructive interference but when sub seasonal forcing realigns w/ the base state that's becoming more NINO like late in July and into August, this downwelling wave will likely intensify before reaching South America.

 

 

And does the +PMM actually aid the development of the niño, or is it largely a result of the low frequency state of circulation that favors warm pool discharges?

I’m more convinced of the latter. Too much off-equator convection can actually interfere with El Niño development, in the canonical sense. Some of the most prolific +PMMs like 1980 and 2014 were very anemic in the ENSO department.

 

 

I've discussed this at length numerous times, but the answer is yes literature shows that the PMM in both NWP simulations and observations contributes to the triggering of about 2/3rds of all El Nino events, is vital to the seasonal phase locking of ENSO, and when coupled with the negative phase of the SPMM increases the probability of central pacific/modoki El Nino. This year's +PMM regime is bigger than any that has ever been observed during the satellite era and the subsurface warming is way stronger than either 1980 & 2014 ever were, being more on par w/ moderate El Ninos like 2009 & 2002, which suggests that the former years may not be an adequate comparison here. Not every +PMM event will trigger an El Nino, however the probability of an El Nino is likely significantly higher when its coupled w/ a -AMO. 1980 and 2014 actually featured near or above normal SSTAs in the tropical Atlantic by this point in the summer, this year's SST anomalies have been rivaling the coldest years of the last -AMO regime in the 1980s & 1990s. Why does a cold tropical Atlantic matter for ENSO? 

 

A colder Atlantic is certainly more favorable to El Nino for several reasons, cooler MDR SSTs means the easterly trades are stronger which favors air/mass more readily piling into South America, where a major anomalous upward branch of the Hadley Cell is juxtaposed during El Ninos, essentially meaning that a cold AMO superimposes itself to some extent onto the larger-scale NINO circulation. A colder Atlantic also means there's one less ocean basin that's competing for upward motion on the global scale, affording the Pacific a greater chance to steal the show per say. In addition, the cold phase of the AMO pulls the ITCZ in the Pacific equatorward, again favoring El Nino (Sung et al (2015)). A seiching mechanism related to the Atlantic Meridional Overturning Circulation has also been proposed but it's much more elusive.

 

Here's a few excerpts from literature I've sifted through in the past few months that provide verification of this cold AMO-NINO relationship.

 

"The results show that the tropical Atlantic warming associated with the positive AMO phase leads to a

westward displacement of the Pacific Walker circulation and a cooling of the tropical Pacific Ocean, thereby

inducing anomalous descending motion over the central tropical Pacific. The descending motion then

excites a stationary Rossby wave pattern that extends northward to produce a nearly barotropic anticyclone

over the North Pacific."

https://www.ess.uci....k.JCLI.2017.pdf

 

"The long-lasting cold surface conditions of North Atlantic, i.e., the negative phase of Atlantic Multidecadal Oscillation (AMO), can intensify the El Niño–Southern Oscillation through the enhanced air-sea coupling under the increased central-to-eastern tropical Pacific mean sea surface temperature. However, the impact of warmer mean sea surface temperature (SST) is more efficient in the intensifying El Niño than La Niña, because of the nature of the exponential growth of atmospheric convection to SST change. Moreover, the farther eastward shift of the atmospheric convection during the negative AMO leads to the stronger El Niño due to the longer delayed negative feedback by oceanic waves. Therefore, the AMO mainly influences El Niño intensity rather than La Niña intensity."

 

"The SST anomalies in the El Niño years during AMO periods were stronger;"

 

"El Niño events were more significantly enhanced than La Niña events during AMO periods. The asymmetric development of the ENSO during the different AMO phases is related to thewarmer and wetter basic state of the central-to-eastern tropical Pacific, as shown in both the observations and the CM2.1 model output. Owing to the nonlinear properties in the SST-convection relationship, the warmer mean state of the SST in the central-to-eastern tropical Pacific enhances the sensitivity ofatmospheric convection to the same SST anomaly"

https://agupubs.onli...02/2015GL064381

 

 

Also given this year's +PMM is the strongest and one of the longest lived events that's ever been observed, this only gives me more confidence that this +PMM will trigger an El Nino this year. 

 

 

You would be right that the current +PMM and -SPMM configuration does limit the maximum intensity of El Ninos especially in the canonical sense because the cold SE Pacific is a reflection of cumulative southern hemisphere mid-latitude RW activity and the trade wind anomalies in the subtropical SE Pacific propagate equatorward via WES feedback (described in Min (2015)) and affect the eastern portion of the equatorial basin onlyHowever, the presence of this -SPMM doesn't limit the total probability of El Nino because it says nothing about the central Pacific and the dateline region which is in a favorable regime for warming right now. The base of the +PMM connects to the equator near the dateline, favoring westerly wind anomalies near the edge of the warm pool, and on its own, favors central Pacific El Nino. Like its counter part in the southern hemisphere, these westerly wind anomalies in a +PMM propagate towards the equator ultimately favoring El Nino, and the net ekman transport induced by the west - southwesterly wind anomalies generated in a +PMM transport water towards the eastern boundary region and the equator closer to the dateline, again favoring El Nino. The PMM in a general sense acts as effective red background noise "energizing" low frequency variance in the tropics, thereby exciting ENSO (see Lorenzo et al (2015) linked below).

 

All of the above evidence, literature, and current observations suggest that a weak-moderate central Pacific El Nino is most likely in 2018-19. Furthermore, the observational record in addition to the expected intensity of this El Nino (if one were to form) also argue that the probability of another El Nino in 2019-20 is higher than long-term average (~30-33%).

 

To close this post I'll reiterate that according to the ENS ONI, since 1865, 50-60% of first year-weak moderate El Ninos are followed immediately by another El Nino. In about 85% of those cases where another El Nino occurred in the following year, the 2nd El Nino was stronger than the first one. Keep this in mind going forward.

 

pac.gif

 

There's lots of literature on this topic, I'm only showing a few pieces I've read through.

 

 

https://agupubs.onli...29/2007GL030302

 

https://journals.ame...CLI-D-16-0063.1

 

https://journals.ame.../2008JCLI2473.1

 

https://agupubs.onli...02/2015GL066281

 

https://agupubs.onli....1002/grl.50571

 

https://agupubs.onli...29/2001GL013435

 

 

"The majority of ENSO events in both nature and the coupled model are preceded by MM events."


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#1345
Webberweather53

Posted 03 July 2018 - 06:36 AM

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If you compare the subsurface temperature anomalies to years like 2012, last year, 2014 wherein a significant NINO (or in the case of 2014 strong NINO) head fake occurred, we're blowing them out of the water (no pun intended :) ) with exception to 2012.

 

2012 is an interesting case study because neither a +PMM or cold Atlantic were present during the summer of 2012, and furthermore most of the intense +SSTAs were confined to the far EP unlike this year. The warm tropical Atlantic, -PMM, and where the greatest warming initiated in the Eq Pacific were tip offs of a NINO head fake in 2012. I use 2012 as a prime example w/ similar subsurface warming and a bgd climate to this year to showcase how the PMM and tropical Atlantic as I discussed above are important in determining ENSO evolution. I believe based on observations & literature (some of which I linked above) that they provide valid, easy to recognize clues wrt forthcoming ENSO behavior and are reliable warning signs of either impending El Ninos or head fakes, 2012 just solidifies this rationale.

 

This year however couldn't be more different atm from 2012 outside of the subsurface and is following the recipe of success w/ a cold Atlantic, +PMM, and initiating in the Central Pacific, I'll explain why the latter is important below.

 

anomnight.7.2.2012.gif

 

 

 

 

 

 

If you also were to analyze the early evolution of all these head fakes, they all observed vigorous eastern Pacific warming early on in their lifetimes, whereas this year seems to be following a completely different path with the most intense +SSTAs based in the central Pacific. We know that the climatological SSTs near the dateline are closer to the threshold necessary to readily generate convection. The implications of this are that weak events based in the CP like this year instead of the EP (as was the case initially in 2012, 2014,  & 2017) are more likely to generate convective feedback that non-linearly reinforces and grows the pre-existing SST anomaly. What this may also mean is that pound for pound, the North Pacific Meridional Mode may be a more effective generator of El Nino than the SPMM and having a +NPMM/-SPMM is more favorable than -NPMM/+SPMM because the base of the NPMM is directly connected to the edge of the warm pool whereas the SPMM is confined to the eastern Eq Pacific, limiting its potential for non-linear feedback unless a strong or extraordinary El Nino like 1982, 1997, &/or 2015 is observed.



#1346
OKwx2k4

Posted 03 July 2018 - 08:38 AM

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Thank you for the great write ups and for sharing information. Both incredibly impressive and fascinating.

#1347
Phil

Posted 03 July 2018 - 08:46 AM

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I see where you're coming from but the latter isn't true either. When a Kelvin wave reflects onto a boundary it returns as a rossby wave of the same sign. Meaning that these downwelling Rossby Waves created by reflection of the KW at the eastern boundary also suppress the thermocline. What actually enhances near-equatorial upwelling during El Nino events is the westward flowing surface currents which are in the same sense as earth's rotation generating cyclonic wind stress curl anomalies that augment Sverdrup transport, in effect increasing poleward export of water from the equator. Those westward propagating off-equatorial Rossby Waves actually do contribute to some extent to retaining heat in the Eq Pacific because their westward propagation contributes to anticyclonic wind stress curl that offsets the Equatorial discharge induced by the equatorial westerly current. In any case, I don't think we're having much issue generating more downwelling oceanic Kelvin Waves because another one has entered the fray as aforementioned, it will initially be met with destructive interference but when sub seasonal forcing realigns w/ the base state that's becoming more NINO like late in July and into August, this downwelling wave will likely intensify before reaching South America.


But ERW’s suppress the thermocline poleward of the equator rather than along it...without follow-up downwelling OKW activity, how can you conserve mass and momentum after an OKW diffracts into an ERW without a relative cessation of equatorial downwelling (in the absence of follow-up OKW activity)?

There would have to be another OKW to continue modulating the shoaling of the thermocline after the first ERW transition, no?

I've discussed this at length numerous times, but the answer is yes literature shows that the PMM in both NWP simulations and observations contributes to the triggering of about 2/3rds of all El Nino events, is vital to the seasonal phase locking of ENSO, and when coupled with the negative phase of the SPMM increases the probability of central pacific/modoki El Nino. This year's +PMM regime is bigger than any that has ever been observed during the satellite era and the subsurface warming is way stronger than either 1980 & 2014 ever were, being more on par w/ moderate El Ninos like 2009 & 2002, which suggests that the former years may not be an adequate comparison here.


Fascinating stuff man. I’ve read contradicting literature on this, however. Because a +PMM is largely a result of a weaker and/or poleward displacement of the NPAC high, which is indicative of stunted Indo-Pacific exhaust and a narrower longitudinal component of the Walker Cell, which would already favor WWBs/warm pool discharges to begin with under said state of transfer.

The +PMM can’t just manifest on its own accord..it has to be triggered by something. IE, it’s technically a result of the same warm pool/convective dynamics that play a role in modulating ENSO/thermocline shoaling in the first place.

I think it’s safe to say the process begins with changes to circulo-convective modes, initiated peripherally, which modulate the boundary conditions governing of the structural evolution of the west-Pacific warm pool.

I’d argue (and there is literature to substantiate this as well) that the +PMM is more of a positive/constructive feedback to a westward dislocation of the warm pool itself which aids the efficiency of discharge, rather than a dominant forcing on its own, unless it’s an overwhelmingly anomalous signature with a clear sign in the OHC/off-eq thermocline.

FWIW, as with most +PMMs, the signature becomes quite shallow in the presence of OKWs..barely even reflects in the anomalies right now. So it’s easily subject to intraseasonal disruption..IE it’s sustained by supportive peripheral boundary conditions.

mnth_hc_hcdiff_glb_xy.gif

Not every +PMM event will trigger an El Nino, however the probability of an El Nino is likely significantly higher when its coupled w/ a -AMO. 1980 and 2014 actually featured near or above normal SSTAs in the tropical Atlantic by this point in the summer, this year's SST anomalies have been rivaling the coldest years of the last -AMO regime in the 1980s & 1990s. Why does a cold tropical Atlantic matter for ENSO?

[size=4][font=arial][color=rgb(51,51,51)]A colder Atlantic is certainly more favorable to El Nino for several reasons, cooler MDR SSTs means the easterly trades are stronger which favors air/mass more readily piling into South America, where a major anomalous upward branch of the Hadley Cell is juxtaposed during El Ninos, essentially meaning that a cold AMO superimposes itself to some extent onto the larger-scale NINO circulation. A colder Atlantic also means there's one less ocean basin that's competing for upward motion on the global scale, affording the Pacific a greater chance to steal the show per say. In addition, the cold phase of the AMO pulls the ITCZ in the Pacific equatorward, again favoring El Nino (Sung et al (2015)).


That’s certainly fascinating, but I’m having trouble connecting with what you’re predicting.

The +PMM does the opposite of the -AMO/-AMM, and displaces/broadens the Pacific ITCZ poleward east of 150W. And if both the Atlantic and the equatorial EPAC are cold, and there’s subsidence centered over South America as a result, trades in the EPAC along/east of 120W would be stronger, all else being equal, no? And the zonal SSTA gradient across the Pacific should be stronger as well.

So it’s no surprise that the recent Atlantic SSTA warming occurred in conjunction with stronger westerlies developing over the EPAC. There was an earlier CCKW passage that aided lift/divergence aloft across the EPAC domain.

This post is getting too long for my phone, so I’ll have to respond to the rest of the literature you sited in a followup post. But thank you for the fantastic reading and analysis..I really do enjoy these discussions.
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#1348
Black Hole

Posted 03 July 2018 - 08:59 AM

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If you compare the subsurface temperature anomalies to years like 2012, last year, 2014 wherein a significant NINO (or in the case of 2014 strong NINO) head fake occurred, we're blowing them out of the water (no pun intended :) ) with exception to 2012.

 

2012 is an interesting case study because neither a +PMM or cold Atlantic were present during the summer of 2012, and furthermore most of the intense +SSTAs were confined to the far EP unlike this year. The warm tropical Atlantic, -PMM, and where the greatest warming initiated in the Eq Pacific were tip offs of a NINO head fake in 2012. I use 2012 as a prime example w/ similar subsurface warming and a bgd climate to this year to showcase how the PMM and tropical Atlantic as I discussed above are important in determining ENSO evolution. I believe based on observations & literature (some of which I linked above) that they provide valid, easy to recognize clues wrt forthcoming ENSO behavior and are reliable warning signs of either impending El Ninos or head fakes, 2012 just solidifies this rationale.

 

This year however couldn't be more different atm from 2012 outside of the subsurface and is following the recipe of success w/ a cold Atlantic, +PMM, and initiating in the Central Pacific, I'll explain why the latter is important below.

 

 

 

 

If you also were to analyze the early evolution of all these head fakes, they all observed vigorous eastern Pacific warming early on in their lifetimes, whereas this year seems to be following a completely different path with the most intense +SSTAs based in the central Pacific. We know that the climatological SSTs near the dateline are closer to the threshold necessary to readily generate convection. The implications of this are that weak events based in the CP like this year instead of the EP (as was the case initially in 2012, 2014,  & 2017) are more likely to generate convective feedback that non-linearly reinforces and grows the pre-existing SST anomaly. What this may also mean is that pound for pound, the North Pacific Meridional Mode may be a more effective generator of El Nino than the SPMM and having a +NPMM/-SPMM is more favorable than -NPMM/+SPMM because the base of the NPMM is directly connected to the edge of the warm pool whereas the SPMM is confined to the eastern Eq Pacific, limiting its potential for non-linear feedback unless a strong or extraordinary El Nino like 1982, 1997, &/or 2015 is observed.

 

Appreciate your thoughts and time writing this and other posts.

In this and the previous post you talk about +PMM, and then I assume this is divided into NPMM and SPMM in your quoted post. I have a general sense about these from context, but can you define these in terms of SST anomalies (or otherwise) for me. I want to have a better sense of what you are getting at.

El nino modoki tends to be associated with warmer and drier winters in the Great Basin region where i live, from what I have seen anyway. Any early thoughts on that? I think el nino modoki often is associated with an enhanced monsoon season in the SW. Hopefully we see that this year.  


BS Atmospheric Science University of Utah May 2015

PhD Candidate Atmospheric Sciences

 

--Emphasis on: Forecasting, Mountain Weather, Numerical Weather Prediction, Data Assimilation

 

Winter 2017/2018

Dec 4: 3.2", 16: 0.9", 20: 2.1", 23: 1.5", 25: 4.6"

Jan 6: 1.5", 20: 10.8", 25: 1.5"

Feb 19: 8.6", 20: 2.4", 23: 7.1", 25: .5"

Mar 4: 13", 15: 1.8", 17: 5.3", 25: 4.2"

April 12: 1", 17: 1.3"

Total: 69.3"

 

 

Winter 2016/17 Snow:
Nov 17: 3.2", 23: 1.6", 28: 9.2" (14)

Dec 1: .5", 16: 2.5", 25: 13" (16)

Jan 2: 5", 3: 2.4", 4: 7.7", 12: 1", 19: 1.2", 21: 13", 23: 6", 24: 1", 25: 3.7", 26: 2.5" (43.5) 

Feb 11: .5", 23: 6.5", 27: 4.5" (13.5)

Mar 5: 5.5" (5.5)

Apr 8: 2", 9: 1.8" (3.8)

May 17: 1" (1)
Total: 96.3"

Lowest Temp: 2F


#1349
Webberweather53

Posted 03 July 2018 - 09:09 AM

Webberweather53

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But ERW’s suppress the thermocline poleward of the equator...without follow-up downwelling OKW activity, how can you conserve mass and momentum after an OKW diffracts into an ERW without a relative cessation of equatorial downwelling (in the absence of follow-up OKW activity)?

There would have to be another OKW to continue modulating the shoaling of the thermocline after the first ERW, no?


Interesting stuff man. I’ve read contradicting literature on this, however. Because a +PMM is largely a result of a weaker and/or more poleward NPAC high, which is indicative of stunted Indo-Pacific exhaust and a narrower Walker Cell, which would already favor WWBs/warm pool discharges to begin with.

The +PMM can’t just manifest on its own accord..it has to be triggered by something. IE, it’s trchnically a result of the same warm pool/convective dynamics that play a role in modulating ENSO/thermocline shoaling in the first place.

So I’d argue it’s more of a positive/constructive feedback than a dominant forcing unless it’s an overwhelmingly anomalous signature with a clear sign in the OHC/off-eq thermocline.

FWIW, as with most +PMMs, the signature becomes quite shallow in the presence of OKWs..barely even reflects in the anomalies right now. So it’s easily subject to intraseasonal disruption..IE it’s sustained by supportive peripheral boundary conditions.

mnth_hc_hcdiff_glb_xy.gif


That’s certainly interesting, but a +PMM does the opposite, and displaces/broadens the Pacific ITCZ poleward east of 150W. And if both the Atlantic and the equatorial EPAC are cold, and there’s subsidence centered over South America as a result, trades in the EPAC along/east of 120W would be stronger, all else being equal, no? And the zonal SSTA gradient across the Pacific should be stronger.

So it’s no surprise that the recent Atlantic SSTA warming occurred in conjunction with stronger westerlies developing over the EPAC. There was an earlier CCKW passage that aided lift/divergence aloft across the EPAC domain.

This post is getting too long for my phone, so I’ll have to respond to the rest of the literature you sited in a followup post. But thank you for the fantastic reading and analysis..I really do enjoy these discussions.

 

The EQ RWs suppress the thermocline most appreciably a few degrees from the equator but to reiterate once again, because of the anticyclonic wind stress curl generated from the westward current associated w/ these waves, it actually offsets the anomalous discharge promoted by an eastward flowing equatorial current. This is an important connection to make because its related to the discharge-recharge hypothesis that explains why westward flowing currents and surface winds in La Nina charge the Eq Pacific w/ warm water and limit poleward discharge. Similarly westward propagating, slower moving Eq Rossby Waves generated by downwelling KW activity also offset the poleward discharge during NINOs which is a crucial mechanism that terminates them. There's lots of literature on this topic.

 

As far as the PMM is concerned, you're really getting into a chicken-egg argument here. Again the PMM is generated by cumulative mid-latitude RW activity in the preceding winter that leaves a seasonal footprint which persists into the following spring. The depth of the anomalous warming associated w/ a PMM isn't as important as the surface reflection which affects low-level trades in the central and NE subtropical Pacific, you can easily have instances where it doesn't extend to an appreciable depth yet still yields similar forcing, additionally the mixed layer isn't that deep at this time of the year there barring the occasional TC so it likely won't matter all that much. The tropical forcing component from the warm pool is only one component to that RW activity which creates the PMM. The ITCZ is pushed poleward of its climatological position only in the eastern Pacific during +PMM, whereas because the base of the PMM extends directly onto the equator in the central Pacific the ITCZ actually remains close to the equator near the edge of the warmpool where non-linear feedbacks can take over and reinforce the SST anomaly and remotely force +SSTAs in the EP thru WWBs. (remote SST forcing component is larger than the local piece in the EP). The ITCZ juxtaposition in the Eastern Pacific doesn't matter as much because non-linear convective feedbacks don't occur here except in the strongest El Ninos, this is exactly why most weak EP-based NINOs in the modern era have failed as stated earlier.



#1350
Webberweather53

Posted 03 July 2018 - 09:30 AM

Webberweather53

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Appreciate your thoughts and time writing this and other posts.

In this and the previous post you talk about +PMM, and then I assume this is divided into NPMM and SPMM in your quoted post. I have a general sense about these from context, but can you define these in terms of SST anomalies (or otherwise) for me. I want to have a better sense of what you are getting at.

El nino modoki tends to be associated with warmer and drier winters in the Great Basin region where i live, from what I have seen anyway. Any early thoughts on that? I think el nino modoki often is associated with an enhanced monsoon season in the SW. Hopefully we see that this year.  

 

Sure thing. Yeah when I refer to +PMM it's usually the North Pacific Meridional Mode (NPMM) because this was first recognized by Chang and Vimont and likely plays a more prominent role in determining total ENSO probability. There are several reasons to believe if an El Nino occurs this year it'll be central pacific based/modoki. Namely...

A: Since 1976 almost every (successful) El Nino has started in the central Pacific

 

B: +NPMM/-SPMM configuration we have right now w/ warm water in the tropical and subtropical North Pacific (+PMM), and cold water in the SE Pacific (-SPMM) has been to shown to favor modoki over canoncial/classical El Nino.

See Min (2015) for more on this: https://journals.ame...CLI-D-16-0063.1

 

C: ENSO flavor is moderately related to intensity. Weak-moderate El Ninos like we're expecting this year are more likely to be modoki/CP-based than Strong-Super events (obviously we know this isn't always the case however).


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