ENSO Updates (2007 thru 2023)

[Ntxw]

https://psl.noaa.gov/enso/mei/

MEI data for AS came in at +0.6.

I forgot, what does a Positive MEI mean? An El Nino?

Scales similar (but not 1:1) like ONI. Yes positive MEI is warm ENSO, but the +0.6 means the atmosphere is weakly coupled like a weaker event.

https://psl.noaa.gov/enso/mei/

[Teban54]

 https://twitter.com/WorldClimateSvc/status/1710357043456942555

[cycloneye]

The weekly update from CPC.

The latest weekly
SST departures are:
Niño 4 1.2ºC
Niño 3.4 1.5ºC
Niño 3 1.9ºC
Niño 1+2 2.6ºC

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

[zzzh]

Very interesting.

[cycloneye]

80% of having el Niño March thru May 2024.

https://www.cpc.ncep.noaa.gov/products/ ... disc.shtml

ENSO Blog:

https://www.climate.gov/news-features/b ... e-big-cats

Since we’re sure El Niño will be operating into the winter, the next question is “how strong will it get?” Strength definitions, which usually also use the Niño-3.4 Index, are unofficial, since it’s not like an El Niño with a peak Niño-3.4 Index of 1.5 °C is going to have noticeably different impacts than one with a peak Niño-3.4 Index of 1.4 °C. However, as I mentioned above, the stronger the El Niño, the more likely it will affect global temperature and rain/snow patterns in expected ways. This is because a larger sea surface temperature change leads to a larger shift in the Walker circulation, making it more likely that El Niño will affect the jet stream and cause a cascade of global impacts.

The unofficial definition of a strong El Niño is a peak 3-month-average Niño-3.4 Index of at least 1.5 °C. El Niño is a seasonal phenomenon, and that 3-month-average Niño-3.4 Index (called the Oceanic Niño Index or ONI) is important for making sure that the oceanic and atmospheric changes persist long enough to affect global weather and climate. A peak ONI of 2.0 °C or more is considered “historically strong,” or “very strong.” We’ve only seen four of these in our historical record, dating back to 1950.

Forecasters give this event a high chance of qualifying as a strong event, based on our climate model predictions and the current conditions. “Hey wait,” you’re saying. “Isn’t the September Niño-3.4 Index already 1.6 °C?” And indeed it is, but the 3-month-average for July–September was 1.3 °C. That said, we have a 75% chance that the ONI will reach or exceed 1.5 °C in November­–January (typically the peak season). We actually have a slightly higher chance, 83%, that we will reach that threshold in September-November, which is on our doorstep.

[Dean_175]

Hovmoller diagrams have shown increased a and fairly consistent weakening of the trades and even some moderate WWBs since mid September and the GFS is hinting at another WWB in the next couple of weeks. This will help push another pulse of warm water east and is reflected in the CFS model's forecast of a further strengthening to a monthly anomaly around 1.8-2.2C. Looks like the atmosphere is finally responding more. The warmest waters are near the dateline as opposed to the west Pacific, which helps shift the Walker circulation.

[Kingarabian]

Looking at the PDO, Waters are still too warm east of Japan but the waters off the NW Pacific have finally responded to El Nino.

[Kingarabian]

Hovmoller diagrams have shown increased a and fairly consistent weakening of the trades and even some moderate WWBs since mid September and the GFS is hinting at another WWB in the next couple of weeks. This will help push another pulse of warm water east and is reflected in the CFS model's forecast of a further strengthening to a monthly anomaly around 1.8-2.2C. Looks like the atmosphere is finally responding more. The warmest waters are near the dateline as opposed to the west Pacific, which helps shift the Walker circulation.

Yeah latest CFS has jumped back up and now shows this event peaking just below 2.0C. Big change vs its peak at about +1.6C from about a month ago

[Ntxw]

Say what you will about coupling etc. Outside of the extreme anomalies (82, 97, 15) this is a pretty good event SSTA wise. To get ~2C from the dateline all the way to east is impressive.

[cycloneye]

The weekly CPC update has Niño 3.4 at +1.6C:

Niño 4 1.3ºC
Niño 3.4 1.6ºC
Niño 3 2.0ºC
Niño 1+2 2.6ºC

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

[Kingarabian]

Successive WWB's to close out the year.

[dexterlabio]

Successive WWB's to close out the year.

https://i.postimg.cc/x8QcY0rd/u-anom-30-5-S-5-N.gif

Wouldn't this help the chances of a second-year Niño?

[Dean_175]

Looking at the GFS, we are possibly seeing signs of jet coupling in the nino3.4 region, with enhanced pacific jet into the southeast US. Typical El Nino winter in the CONUS?

[Dean_175]

Successive WWB's to close out the year.

https://i.postimg.cc/x8QcY0rd/u-anom-30-5-S-5-N.gif

Wouldn't this help the chances of a second-year Niño?

No, second year El Nino events are usually events that begin without much atmospheric coupling (like 2014) or begin late in the year like 1986 and therefore have abnormal coupling to the seasonal cycle. It will help push some more warm water east to boost the peak of this year but not likely to produce warm ENSO next year. There is decent model support for the creation of a subsurface cool pool that will spread eastward in 2024, possibly leading to La Nina, but almost certainly ending El Nino. Going by climatology, this event has been strong enough for long enough to produce negative feedback and the end of the event next year. Despite being a positive feedback coupled interaction, ENSO events are self limiting/are part of an oscillation and El Nino does not typically extend to two northern hemisphere winters. For example, while there was WWB activity in early 2016 and early 1998, both years evolved into La Nina due to changes in the distribution of Pacific equatorial ocean heat content. Since 1950, only one strong (>1.5C ONI) El Nino was followed by another El Nino (1957 was strong and 1958 was weak).

In short, a WWB now is just an indication the atmosphere is responding typically to an El Nino ocean.

[Category5Kaiju]

Successive WWB's to close out the year.

https://i.postimg.cc/x8QcY0rd/u-anom-30-5-S-5-N.gif

Wouldn't this help the chances of a second-year Niño?

Not necessarily; it's actually kind of rare to get consecutive years with El Nino. El Ninos tend to go strong and then diminish over one year, while La Ninas don't tend to go as strong but can oftentimes last consecutive years.

[dexterlabio]

Successive WWB's to close out the year.

https://i.postimg.cc/x8QcY0rd/u-anom-30-5-S-5-N.gif

Wouldn't this help the chances of a second-year Niño?

No, second year El Nino events are usually events that begin without much atmospheric coupling (like 2014) or begin late in the year like 1986 and therefore have abnormal coupling to the seasonal cycle. It will help push some more warm water east to boost the peak of this year but not likely to produce warm ENSO next year. There is decent model support for the creation of a subsurface cool pool that will spread eastward in 2024, possibly leading to La Nina, but almost certainly ending El Nino. Going by climatology, this event has been strong enough for long enough to produce negative feedback and the end of the event next year. Despite being a positive feedback coupled interaction, ENSO events are self limiting/are part of an oscillation and El Nino does not typically extend to two northern hemisphere winters. For example, while there was WWB activity in early 2016 and early 1998, both years evolved into La Nina due to changes in the distribution of Pacific equatorial ocean heat content. Since 1950, only one strong (>1.5C ONI) El Nino was followed by another El Nino (1957 was strong and 1958 was weak).

In short, a WWB now is just an indication the atmosphere is responding typically to an El Nino ocean.

But the atmosphere-ocean coupling seems to be happening only now. Many people would argue that the atmosphere for the past few months was not really El Niño-like with the lack of true WWBs in the Pacific, this in contrast to the warm Niño regions.

As you said, second year Niños seem to happen when the atmospheric response occured late in the game. This is definitely just a speculation though.

[tolakram]

I've seen people argue, but is there any professional grade material that indicates this was an unusual start to el nino?

[cycloneye]

I've seen people argue, but is there any professional grade material that indicates this was an unusual start to el nino?

Maybe this CPC Enso Blog post answer your question?

https://www.climate.gov/news-features/b ... y-inducing

[zzzh]

ASO ONI is 1.5.

[Category5Kaiju]

Wouldn't this help the chances of a second-year Niño?

No, second year El Nino events are usually events that begin without much atmospheric coupling (like 2014) or begin late in the year like 1986 and therefore have abnormal coupling to the seasonal cycle. It will help push some more warm water east to boost the peak of this year but not likely to produce warm ENSO next year. There is decent model support for the creation of a subsurface cool pool that will spread eastward in 2024, possibly leading to La Nina, but almost certainly ending El Nino. Going by climatology, this event has been strong enough for long enough to produce negative feedback and the end of the event next year. Despite being a positive feedback coupled interaction, ENSO events are self limiting/are part of an oscillation and El Nino does not typically extend to two northern hemisphere winters. For example, while there was WWB activity in early 2016 and early 1998, both years evolved into La Nina due to changes in the distribution of Pacific equatorial ocean heat content. Since 1950, only one strong (>1.5C ONI) El Nino was followed by another El Nino (1957 was strong and 1958 was weak).

In short, a WWB now is just an indication the atmosphere is responding typically to an El Nino ocean.

But the atmosphere-ocean coupling seems to be happening only now. Many people would argue that the atmosphere for the past few months was not really El Niño-like with the lack of true WWBs in the Pacific, this in contrast to the warm Niño regions.

As you said, second year Niños seem to happen when the atmospheric response occured late in the game. This is definitely just a speculation though.

What's interesting though is that the super-long models, namely the CANSIPS and the CFS, seem to agree that there will be a noticeable cooling of the equatorial EPAC by the middle of next year.