September 2023 ENSO Outlook: An El Niño convo

I would not consider the positive phase of the PDO to be critical for El Nino's impacts - that's a bit like the tail wagging the dog. If we do see the expected El Nino impacts, particularly in the North Pacific and North America, then I would expect to see a shift toward a more positive PDO. However, if that occurs, it's likely a reflection of El Nino triggering the usual, stronger-than-normal Aleutian low, which then leads to changes of North Pacific sea surface temperatures consistent with the positive PDO. So, I generally would expect a shift of the PDO in the positive direction to accompany El Nino's expected impacts in the winter, but that doesn't mean that the positive PDO is the primary driver of the impacts.

El Niño usually contributes to a higher-than-average global average temperature (see this post). I expect that El Niño's contribution to what will likely be a record or near-record warm 2023 will only be part of the story, but it will definitely contribute.

Thanks for flagging this. I caught this in the article teaser, but missed it here. Tom is apparently reluctant to acknowledge the year is drawing to a close.

The likelihood that this coming winter resembles last winter depends on where you live, but I would say that it is unlikely that we will have a winter like last year in the U.S. (and many other global locations) overall. Last winter we were experiencing La Nina conditions, and as Tom reviewed last year, the U.S. climate anomalies resembled the expected La Nina impacts in many ways. This winter we are expecting El Nino conditions, and so most of the expected impacts are the reverse of that of La Nina. We also know that other less predictable factors will shape the coming winter, and there's no reason to expect that those more random factors will be the same as last year. 

So, stay tuned to CPC's seasonal outlooks, and check back in November when we have our annual Winter Outlook blog post.

Agreed! I love this post. :-) 

I agree with Bob that this event is not evolving like a typical Modoki event, as the sea surface temperature anomalies have been strongest in the eastern Pacific and gradually expanding westward. However, I do think there is an important kernel of truth in this comment, in that the strength of this event based on the Nino-3.4 index alone could given an impression that this event is stronger than it actually is, given that the global oceans outside of the tropical Pacific are also very warm. This could make it more challenging for rainfall anomalies to develop in the eastern Pacific like in other strong El Nino events (though this hasn't been an issue so far). I hate to plug my own paper, but the presence or absence of convection in the eastern Pacific could help to shape the large-scale climate pattern that develops this winter. 

Well done! :-)

Guest author Dr. Amy Butler wrote about this topic several years ago. As you can see from her post, there is an increase in probability of a weaker polar vortex and a late winter sudden stratospheric warming during El Nino, though the impacts tend to be stronger in Europe and Asia than in North America.

As I responded above, this event is not evolving like a typical Modoki event, as the sea surface temperature anomalies have been strongest in the eastern Pacific and gradually expanding westward. However, the global ocean warmth this year could make it more challenging for rainfall anomalies to develop in the eastern Pacific like in other strong El Nino events (though this hasn't been an issue so far). If that were to happen, then the tropical rainfall anomalies could look more like a Modoki event. However, given how warm and wet the eastern tropical Pacific is right now, I'm not expecting this to be the case at this time, but it's something to keep an eye on. 

It's a bit too early to tell, as this region does not have the strongest connection to El Nino relative to some other regions in the U.S. You can check CPC's seasonal outlook updates as well as some of the dynamical model guidance, like from the NMME. Some of the NMME models have been suggesting a relatively cool winter around that region (especially compared with last winter), which does happen in some El Nino winters, but not all models agree on this. 

Unfortunately, El Nino, on average, does not have a strong influence on weather in Chicago. It tends to be warmer-than-average to the north and cooler-than-average to the south during winter, so Chicago is in between the two temperature signals. El Nino does bring a slight tendency for drier-than-average winters in the region. Please feel free to check CPC's seasonal outlooks to see how they expect conditions to evolve over Chicago. 

CPC's current seasonal outlooks are pretty consistent with typical El Nino impacts over Idaho: elevated chance of below-normal precipitation and above-average temperatures this winter. So, there is a pretty good chance (but no guarantee) that this winter will not be as cold as last winter for this region.

The NOAA Climate Prediction Center does not monitor or forecast the particular El Nino type (e.g., Warm Pool/Central Pacific versus Cold Tongue/Eastern Pacific). I cannot speak for CPC, but I believe there are several reasons why. First, there are no universally accepted definitions for the two types of El Nino. Second, the type of El Nino is closely related to the strength (as discussed in this blog post), with weaker events typically resembling the Warm Pool/Central Pacific type and stronger events resembling the Cold Tongue/Eastern Pacific type. So, CPC's new ENSO Strength outlook provides some indication of El Nino type. The 70-75% chance that the Nino-3.4 index will exceed 1.5C provides a hint that the Cold Tongue/Eastern Pacific type may be favored.

With all that said, I recognize that there is still El Nino pattern variability even when we control for strength (e.g., the 2015/16 event was centered more toward the central Pacific than 1997/98 even though 2015/16 was one of the strongest events). This event has been warmest in the eastern Pacific, with the warmth gradually expanding westward, so that's another reason that this event may be centered farther east than most other recent El Nino events.

You can find the weekly (OISST), monthly (OISST and ERSST), and seasonal (ERSST) Nino region sea surface temperature data that NOAA monitors at this website. Specifically, the weekly OISST can be found here (latest weekly Nino 3.4 index of 1.6C). NOAA CPC does not regularly monitor daily Nino 3.4 sea surface temperature data. 

Keep in mind that the daily Nino 3.4 values that you find on Tropical Tidbits are based on CDAS Reanalysis, which is a product that combines observations with a climate model to fill in data gaps. The values from this reanalysis do not and are not expected to match up exactly with the official sea surface temperature data that NOAA monitors. The daily CDAS time series still can be a useful indicator of recent changes in the Nino 3.4 index, but as you can see, there can be substantial offsets between the values you see there and what is seen in the more purely observation-based OISST and ERSST products (but even those products can have substantial differences at times).

Over the past several months the trade winds have weakened in the east-central equatorial Pacific... this will likely continue through the course of the event which is favored to last at least through the Northern Hemisphere winter (March/April).   Sorry for the bad sailing news!

There are two ENSO prediction groups I'm aware of in Ecuador and Peru, who are also keeping tabs on potential implications in the local region.  

One is ENFEN (Peru) which you can find here:  

https://www.gob.pe/institucion/imarpe/noticias/834776-comunicado-oficial-enfen-n-14-2023-estado-del-sistema-de-alerta-alerta-de-el-nino-costero

And CIIFEN (Ecuador):  https://ciifen.org/el-nino-la-nina-ciifen/

I know both are monitoring closely the potential impacts, especially as we get into March-May 2024.  We will see if the far eastern Pacific/ coastal SSTs remain above average as we get into those seasons.  It is a much trickier and challenging prediction than predicting Nino3.4 which we focus on!