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September 2016 ENSO update: Cooling our heels

Since the demise of the big 2015-16 El Niño in April, the tropical Pacific has been loitering around in neutral… and now forecasters think it’s likely to stay that way through the winter. For now, we’re taking down the La Niña Watch, since it no longer looks favorable for La Niña conditions to develop within the next six months.

What happened?

Over the last few months, sea surface temperature anomalies (the departure from the long-term average) in the Niño3.4 region have become more negative, which was expected.  Currently, the sea surface temperature in the Nino3.4 region is about -0.5° below the long-term average, according to the ERSSTv4 data.  

Line graph of Pacific sea surface temperatures in 2016 and for all previous moderate and strong El Niño events

Monthly sea surface temperature in the Niño 3.4 region of the tropical Pacific compared to the long-term average for all moderate-to-strong El Niño years since 1950, showing how 2015/16 (black line) compares to other events. Climate.gov graph based on ERSSTv4 temperature data.

This is the La Niña threshold! However, the second step of the La Niña conditions decision process is “do you think the SST will stay below the threshold for the next several overlapping seasons?” For now, the answer to this question is “no.”

In fact, the dynamical climate models are predicting that this month’s Niño3.4 index will be the low point, and sea surface temperatures will recover to near average over the next few months. There is still a range of forecasts, but all eight of the North American Multi-Model Ensemble models expect the negative anomalies to weaken toward zero.

Line graph of predicted probability of Pacific sea surface temperatures from September 2016 into summer of 2017

Climate model forecasts for the Niño3.4 Index, from the North American Multi-Model Ensemble (NMME). Darker purple envelope shows the range of 68% of all model forecasts; lighter purple shows the range of 95% of all model forecasts. NOAA Climate.gov image from CPC data.

What didn’t happen?

Here at the ENSO Blog, we talk a lot about the response of the atmosphere to the change in sea surface temperatures. That’s because it’s critical—you can’t have ENSO without the Southern Oscillation. Just like El Niño, La Niña requires an atmospheric response, and it just hasn’t happened over this summer.

The La Niña response is a stronger Walker Circulation. Even more than usual, cooler air sinks toward the surface over the cooler-than-average waters of the central and eastern Pacific. Meanwhile, the perpetually warm waters near Indonesia warm further, and the overlying air becomes even more warm and buoyant than usual, leading to more vigorous convection (rising air).

These opposing areas of vigorous rising and sinking air amp up the normal circulation across the tropical Pacific: at the surface, stronger-than-average winds blowing east to west, and high up in the atmosphere, corresponding stronger-than-average winds blowing west to east.  More rain falls over Indonesia, and less falls over the Central Pacific.

So far, there have only been some very weak indications of this intensification, like a small area of stronger-than-average upper level winds over a localized region of the central Pacific. Also, some extra rain over western Indonesia, and a narrow, but weak, strip of drier-than-average conditions over the cooler waters of the central Pacific.

Map of Pacific Ocean showing cloud patterns in August 2016

Blocking of outgoing longwave radiation (OLR) during August 2016. Blue shading shows areas where more clouds than average were present, indicated by greater-than-average absorption of surface OLR (less OLR exiting the top of the atmosphere). Climate.gov figure from CPC data.

But what needs to happen to really get La Niña conditions underway is for those stronger-than-average winds to blow across the surface of the equatorial Pacific, cooling the surface and helping to keep warm waters piled up in the far western Pacific. We’ve seen some weak bursts of this activity over the past few months, but nothing has settled in for the long haul.

Without this atmospheric feedback, the large area of cooler subsurface waters that we saw back in the late spring has decreased substantially. Yes, the surface has cooled, but there’s not much cool subsurface water left to extend or intensify the conditions. For fun, have a look at the subsurface during August of 1983, 1998—other years following a strong El Niño—and 2016.

What’s going to happen?

It’s certainly not impossible that La Niña could still develop; forecasters are putting the chances for La Niña somewhere around 40% through the early winter. And, while a strong La Niña developed immediately after the 1997/98 El Niño, there was nearly a year of slightly-below-average temperatures following the 1982/83 El Niño before a moderate La Niña eventually developed in October of 1984, further evidence that there are many pathways that the climate system can follow after a large El Niño event.

For now, though, most signs are pointing toward a stronger chance of remaining in neutral conditions for the time being. Between the model consensus and the current lack of atmospheric response, forecasters put the odds of staying ENSO-Neutral at 55-60%. Of course, we’ll continue to keep you posted on all the happenings (and non-happenings) in the tropical Pacific.

Comments

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I'm disappointed that this winter may not be a La Nina winter after all

Submitted by Charles Welsbacher on Thu, 09/08/2016 - 18:16

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Sorry you're disappointed. Why would you like there to be a La Nina winter?

Submitted by anthony.barnston on Thu, 09/08/2016 - 18:38

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I Love the warm winter we had last year and hot summer this year! Hope we have a repeat of the same for the next few years....!

Submitted by Anonymous on Thu, 09/08/2016 - 22:36

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It could rain a lot and still have warm summers like we had this past summer. That could make up for the loss in precipitation we need. Please more warm summers (with ample rainfall) in the Midwest and East coast! And please spare us the Polar Vortex winters....We hate it!

Submitted by More Sunshine on Fri, 09/23/2016 - 19:08

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I am in south- central Montana, near the Absaroka Bear tooth range. I was looking forward to La Nina for the additional moisture and potentially deeper snowpack it would bring to our region. These mild, dry winters we've had during el Nino are for the birds!! With a neutral ENSO, who knows what might happen!? We really need an above average snow year.

Submitted by T. Karcher on Thu, 09/08/2016 - 23:48

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It's not that you won't get a good snow year now, but just a slight shift in the odds for it getting lower. Even with a cool-neutral winter you could get good snow this winter. So don't give up hope at all. Also, climate impacts are not very tightly related to ENSO, but rather somewhat loosely related. I'm sure you can check your snow history, along with the ENSO state, over the last 20 years and see that is the case.

Submitted by anthony.barnston on Fri, 09/09/2016 - 11:00

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Probably a fellow skier/snowboarder :) Many US resorts have had a string of bad snow years, and people had high hopes that this one would deliver plentiful powder.

Submitted by anonymous on Fri, 09/09/2016 - 06:02

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As I said above, don't give up hope of a decent snow year. We could have cool-neutral ENSO conditions, which would be better for your snow than perfectly neutral condions. Also, there is still some chance for a weak La Nina even though it has dropped to below 50%.

Submitted by anthony.barnston on Fri, 09/09/2016 - 11:02

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also would love a La Nina to build up a fantastic snowpack so fire season stays lower - CA in particular would benefit from some... well, persistent and gentle rain! but NW could use replenishment of the ground water and snowpack as well!

Submitted by kcb on Fri, 09/09/2016 - 17:14

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If you click through the three charts in chronological order a warmer, shallower, more homogenous and easterly pattern emerges. I know, three charts is just anecdotal .... or is it?

Submitted by Bailey P. on Thu, 09/08/2016 - 20:27

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No, three charts is at least enough to give a suggestion, even if not conclusive. But exactly which charts are you referring to? It sounds like the subsurface equatorial temperature anomaly (depth-longitude cross section). Let us know if that's incorrect; "warmer" may not fit my hypothesis, unless you mean less cold.

Submitted by anthony.barnston on Fri, 09/09/2016 - 17:25

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Yes the three sub surface charts from '83, '98, and 2016. The cold water definitely warms, rises, shrinks, and moves easterly. Just open all three in separate tabs, chronologically, from left to right on your browser. Then click through.

Submitted by Bailey P. on Sat, 09/10/2016 - 10:34

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will the tropical instability waves further intensify in the coming months or has it reached its peak this year?

Submitted by Ana on Thu, 09/08/2016 - 22:08

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Although I have not directly observed the intensity of the instability waves week to week, I expect them to gradually become less intense as we go forward, because they are strongest when the temperature difference between the cold water right along the equator and the surrounding water is greatest. The time when this temperature difference was greatest was most likely a couple of months ago, when the warm waters from the El Nino were still hanging around but the much colder waters right at the equator appeared. Since then there has been more mixing of the two contrasting temperatures (which the waves facilitate) and the area of the cold water somewhat widened away from the immediate equator, and the warmth of the surrounding waters weakened.

Submitted by anthony.barnston on Fri, 09/09/2016 - 15:24

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I hate winter, especially that polar vortex crap that hit us 2 years ago. Hope it never snows in the Northeast/Midwest for many years to come. We can switch places with the west coast for a while. Give them a chance to recoup from the heatwaves theyve been having and send that heat to the midwest and East coast. We will be glad to have it!

Submitted by Karen on Thu, 09/08/2016 - 22:31

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Does this mean that we here in Southern California could have a normal winter? We have had no perception since February of this year. El Nino as you know gave us no real rain and we are entering our sixth year of sever drought. My wife and I live in the San Bernardino mountains in Lake Arrowhead and we haven't seen a normal winter or a winter at all since 2010-11. The forest is dying the lake levels are dropping to historic lows and it is our main source of drinking water we desperately need rain any chance of a break in this drought?

Submitted by Dr. Roy A. Teel Jr. on Thu, 09/08/2016 - 23:41

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It means that the chances for Southern California to have deficient rainfall is lower than it would be if we still believed a La Nina would be coming. The new set of seasonal forecasts for winter will be issued next Thursday (see http://www.cpc.ncep.noaa.gov/products/predictions/90day/ ) and they will likely show a lower chance for the "below normal" rainfall category due to the weakening in the outlook for La Nina. It is good news for you. But I know your drought is serious and getting a healthy rainfall season is important, so we need more than just making a poor rainfall outlook more of a normal one.

Submitted by anthony.barnston on Fri, 09/09/2016 - 14:57

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Possible yet to forecast likely conditions in the west for 2016 –'17? Does sustained neutral conditions suggest an average weather year?

Submitted by Dromio on Fri, 09/09/2016 - 00:14

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The new set of seasonal forecasts for winter will be issued next Thursday (see http://www.cpc.ncep.noaa.gov/products/predictions/90day/ ) and they will likely show a lower chance for the "below normal" rainfall category in central and southern California due to the weakening in the outlook for La Nina. In the Pacific Northwest it could mean a reduction in the likelihood of above normal rainfall. In general, the teleconnection pattern associated with La Nina will probably be weakened, and will show less areal coverage. But you should check the forecast next Thursday, since there are other factors determining the West's winter climate besides ENSO, that the dynamical model predictions should pick up.

Submitted by anthony.barnston on Fri, 09/09/2016 - 15:05

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Not necessarily. The new set of seasonal forecasts for winter will be issued next Thursday (see http://www.cpc.ncep.noaa.gov/products/predictions/90day/ ) and they will likely show no preference for above normal or below normal temperatures in the Northeast, as last month's forecasts for winter did. But I'm only guessing and you should check.

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I'm disappointed that La Nina might not develop too. I'm in Malaysia, and we face this terrible transboundary haze from Indonesia's forest fires every year, normally from July to early October, when Indonesia faces its dry season. Last year's El Nino caused severe haze, with no respite until the dry season ended. But this year we've been having more rainfall, I wonder if there's a connection between the SST and the amount of rainfall in Malaysia, and parts of Indonesia (Sumatera, Kalimantan). By the way, is the first graph updated frequently, or only drawn for this blog's purposes? If it's available for public viewing, where can I find it?

Submitted by Maxis on Fri, 09/09/2016 - 03:19

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Even without a named La Nina this coming winter, things already look a lot better for you this year, as Indonesia has been having more rain this year than last, and a bit more than average due to the near-La Nina conditions. The current nearly borderline La Nina conditions should persist a bit longer, such as another 2 months, before weakening toward mid-neutral toward winter. But it's the next couple of months that matter for your haze conditions, so I think calling off an official La Nina for later in the year (Nov, Dec, ...) is not as bad for you as it might seem.

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Prediction of LA Nina or El Nino is easy when you use solar cycles. My earlier thoughts were no strong La Nina would occur this time because of the Declining solar cycle. During 1998 post the Supper el nino solar was increasing and that is why the strong La Nina occured. https://mobile.twitter.com/VWeatherWatcher/status/752881226181144576

Submitted by @njsnowfan on Fri, 09/09/2016 - 09:06

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There is no solid scientific evidence linking the phase of the 11-year solar cycle to ENSO. There is also no plausible physical mechanism connecting the solar cycle to ENSO. (How would it work?) So I would argue that any relationship between the two that you have found, is due to luck using a small sample size. There was once a theory that El Nino is triggered by volcanic activity, and that is another example of an idea that bit the dust once more data became available.

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Emily, Excellent commentary once again from this blog. We (Paul Pastelok and myself) are looking forward to hearing your presentation(s) again this year up in Bangor next month.

Submitted by Brett Anderson… on Fri, 09/09/2016 - 13:37

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Looking at the historical ONI-values from 1950 and onward reveals that only twice a La Niña have developed if the ONI-value in July-August-September was above -0,5. The last time was back in 1984 when the ONI-value didn't dropped below -0,5 until September-October-November. The result was a moderate La Niña. The other case is from 1967, a very late case, when the ONI-value didn't drop below the threshold until November-December-January(!) The result was a weak La Niña. GFS forecast a strong easterly wind burst to emerge in the next couple of days. Let's see if it will have any real effect.

Submitted by Knight on Fri, 09/09/2016 - 16:17

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I would like to know what will be the effects of having a neutral ENSO this season in central South America. Last year, we had an exceptionally dry year. Should a neutral ENSO take place, will the rain season be as expected? (Current predictions are for a wet year and we really need rain here).

Submitted by Sam on Fri, 09/09/2016 - 21:31

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The IRI's updated forecast for South America will be released this Thursday. The ENSO forecast driving this new updated forecast is for cool-neutral SST conditions in tropical Pacific. Probably the tendencies forecast from last month will continue, but more weakly. The forecast will be available at: http://iri.columbia.edu/our-expertise/climate/forecasts/#Seasonal_Clima… and South American can be selected.

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What type of winter could we expect in Southern California under neutral conditions? Hopefully some rain?

Submitted by Jill Hortz on Mon, 09/12/2016 - 11:56

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Please see comments and discussion above about southern California. A little less gloomy than if the La Nina were still being predicted. See the CPC's coming forecast (URL given above).

Submitted by anthony.barnston on Mon, 09/12/2016 - 20:38

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Any advice for southern Arizona precipitation-wise? Do I keep the umbrella in the car? I hope it will be needed occasionally .

Submitted by Mike anderson on Tue, 09/13/2016 - 19:37

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The current seasonal outlooks for southern Arizona through the winter slightly favor a drier than average winter, but that certainly doesn't mean no rainfall at all.  Would expect you'd get some use of it, but probably not enough to pull you out of drought.

Submitted by mike.halpert on Mon, 09/19/2016 - 12:43

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What drives the decrease in global temperature after a La Nina emerges? If it is the SST, then will there be a short term cooling?

Submitted by Aaron Shunk on Wed, 09/14/2016 - 02:47

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Global temperature departures are likely to fall at least a bit from the very elevated range they're currently at, but it's quite doubtful that the decrease will result in a short term cooling.  Given the background increase in global temperature we'veobserved over the last 40-50 years, the decrease we'd expect to see with the end of El Nino (and possibly the development of La Nina) is still likely to leave global temperatures well above normal.  A piece on the "Beyond the Data" blog explores some of this here:

https://www.climate.gov/news-features/blogs/beyond-data/how-will-el-ni%…

Submitted by mike.halpert on Mon, 09/19/2016 - 12:56

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Appreciate the explanation for the switch to a La Nada forecast . . . simple . . . I like it! However, maybe worth mentioning that a number of other countries appear to be concluding differently . . . but they do their studies differently. Any thoughts about relationships between RRR and the blob to La Nina, e.g., is there an ongoing blob or RRR off our coast? Primary interest is re: this winter's precipitation forecast for CA. Thanks!

Submitted by rfernando@mwdh2o.com on Mon, 09/19/2016 - 14:09

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You're absolutely right that other countries can come to different conlusions on the ENSO status (though I only know of one right now: Japan).  The main reason for this is that we all have different thresholds with respect to ENSO.  Why is that?  ENSO is a very complex phenomenon that cannot be simply distilled to one number and impacts each country differently.  In our ENSO guidebook we're "cool-neutral" at the moment, but one of the main reasons we dropped the watch is because we're favoring Neutral in the near future.  I just updated the ENSO blog with a new post that provides some more info on why we made that decision, so check it out:  

https://www.climate.gov/news-features/blogs/enso/incredible-growth-2015-16-el-niño-followed-incredible-shrinking-la-niña

... and, as always, forecasters will update our consensus outlook next month when the new round of data comes rolling in.  This is a borderline situation, which is one of the hardest forecasts to make (in contrast 2015 was easy as pie because the El Nino was so strong and obvious).  

For upcoming precipitation and temperature outlooks, check out the CPC webpage here:

http://www.cpc.ncep.noaa.gov/products/predictions/long_range/

Submitted by michelle.lheureux on Fri, 09/23/2016 - 14:23

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I think we saw the influence of El Nino more so at least here in the Southwest US back starting in May 2015. Above normal rainfall through southern California and southern Arizona.. and it was a modest monsoon season. The big El Nino event that was supposed to happen for the winter of 2016 never really materialized.. guessing based on the atmosphere not responding as it should to El Nino. Given neutral conditions expected across the Pacific I presume the weather pattern should be what passes for normal for most of North America. The only thing I think will be noticeable is early autumn cooler than normal storms and somewhat above normal precip for the western states. It is already becoming evident. Could this also mean an early winter ?

Submitted by Jason on Thu, 09/22/2016 - 03:05

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What are the likely effects for weather in southern Oregon? El Nino brought much needed higher rainfall amounts and way too much fog last winter. A very dark winter. Summer again brought record temps (100s) after a cooler and wetter June and cooler July. Thank you.

Submitted by Grants Pass on Thu, 09/29/2016 - 16:48

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Hi mjd,

Interesting thought, but La Nina doesn't have location-based classifications like El Nino does, in part because the magnitude of La Nina events (as measured by the size of the Nino3.4 index) tends to be smaller than El Nino events. 

Submitted by emily.becker on Mon, 10/10/2016 - 10:37

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