On the second Thursday of every month, NOAA issues its analysis of the status of ENSO. This includes determining the Alert System Status. Although the current status remains the same i.e. La Nina Advisory, the forecast has been adjusted somewhat from last month. The forecast calls for the La Nina to continue but weaken during the Summer. Then it’s forecast to strengthen again in the Fall and Winter. The timing is shown in the NOAA discussion and the IRI probability analysis.
Of importance, the chances of a Triple Dip La Nina are still difficult to predict but seem to be higher than the estimate last month. I am not exactly sure how you define a Three-Peat. If it has to do with extending into early Winter the odds seem to be a bit higher. This is not likely to change the forecast for Winter but might change the forecast for next Spring. Finally, there is now less disagreement among meteorological agencies as to when this La Nina will end.
So I am referring to it as a Three-peat but it is not over until it is over. So it may not happen but it looks increasing as if it will.
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ENSO IMPACTS
The impact of the NOAA forecast for the slow or non-existent transition from La Nina to ENSO Neutral will show up next Thursday when NOAA issues its Seasonal Outlook. The NOAA ENSO Status Update provides an advance indication of how the Outlook might change. There is a lag between the ENSO state and the impact on U.S. weather. Thus the exact strength of the La Nina may not be very important in terms of the actual impact on Summer weather including the North American Monsoon (NAM). We may see some changes, in particular Winter and Spring of 2023, farther out in the NOAA Outlook that will be issued next Thursday. The chances that La Nina will extend into next Spring are slightly higher this month.
I have also reported on the Indian Ocean Dipole (IOD) because of the potential impact on world food production.
CLIMATE PREDICTION CENTER ENSO DISCUSSION
| We now provide a lot of detail. The detail is for those who will find it interesting. If your main interest was in learning what the current Status of ENSO was and how long will the current state last, you may not need to read the remainder of this article as that information has already been presented. If you are interested in how reliable the conclusion is and why one might accept the conclusion or be skeptical about the conclusion, continue to read. |
IRI CPC ENSO STATE Probability Distribution (IRI stands for the International Research Institute for Climate and Society)
Here are the new forecast probabilities. This information is released twice a month and the first release is based on a survey of Meteorologists, the second is based on model results. The probabilities are for three-month periods e.g. JJA stands for
June/July/August.
| It is important to realize that there is not much difference between ENSO Neutral with a La Nina Bias meaning the NINO 3.4 Index is close to -0.5C and a very weak La Nina where the NINO 3.4 Index is just slightly colder than -0.5C. The + and – thresholds are somewhat arbitrary. In Australia, they use + or – 0.8C as their threshold which appears to make more sense for that part of the World. Notice for JFM 2023 the probability of La Nina and ENSO Neutral is about equal. One way of looking at that is that the Nino 3.4 Index is likely to be close to -0.5C. But for FMA the probability for ENSO Neutral Exceeds that for La Nina. So maybe March is when the ocean conditions will be consistent with ENSO Neutral but the impact on our weather may lag a month or so. So we really seem to be looking a La Nina into Spring. |
Here is the forecast from the prior month.
| There is really no change in the probabilities for NDJ and DJF but since a month has gone by we are somewhat more confident in these further-out probabilities which is why I am concluding that we will have a Three-peat but that is not guaranteed. |
| I am not sure how you define a Three-Peat but if it has to do with extending into early Winter the odds seem to be about the same as last month but a month has gone by and the situation has not changed so it is more likely that the probabilities for NDJ 2022/2023 and DJF 2022/2023 are valid. This is not likely to change the forecast for Winter but likely to change the forecast for next Spring. But there is a delay in a change of phase in ENSO actually impacting CONUS weather. |
Now I am showing some prior month’s forecasts.
Analysis of the current and prior first and second Forecasts in each month.
IRI actually makes two forecasts a month. The first which is based on a survey of meteorologists is the one that NOAA relies on when they prepare their seasonal outlook. The second is a summary of the forecasts made by a set of computer models.
Here are five sets of those forecasts. For the first set, the initial forecast is also shown above. There is a pattern here. The chances of a Three-peat have increased each month and the survey of meteorologists has routinely been more convinced than the computer models that La Nina will persist. A possible reason for that is that some of the computer models are statistical models and from a statistical perspective a Three-peat is highly unusual.
I will let the reader sort out what can be learned from the above
What Does the NOAA Proprietary ENSO Model Forecast?
The above should auto-update. If it does not update you can click on it and it should update and enlarge. If that does not work you can click HERE. https://www.cpc.ncep.noaa.gov/products/people/wwang/cfsv2fcst/images3/nino34SeaadjPDFSPRDC.gif This model no longer shows La Nina continuing indefinitely. It had been showing that for some time but NOAA relies more on the IRI Forecast. But perhaps this model is now showing that we may become ENSO Neutral for next Spring or even the second half of Winter. It is actually a little more favorable towards La Nina right now.
Looking at Actual Current Conditions.
NOAA reports some derived data that describes the current situation and a forecast. But what if we want to form our own opinion? After all, meteorologists are looking at the actual current situation and making predictions.
This shows the current actual situation.
| Notice the cool water is almost all south of the Equator but the pattern extends to the west more than usual. To update this graphic click on it. If that does not work, Click Here https://psl.noaa.gov/map/images/sst/sst.daily.anom.gif |
| This is a forecast by Australian BOM. I could use a forecast by NOAA. It is forecast for October of this year. One can see the cooler water along and north of the Equator. |
Where is ENSO Measured?
You can mentally superimpose the Nino 3.4 area shown encompassing part of the yellow and part of the red areas in the above map and you can see that it is cool in the Nino 3.4 area especially South of the Equator. That is an oddity of this La Nina that is both westerly displaced and focused mostly south of the Equator. There is not much discussion of that and how that might impact our weather. It certainly explains why the NINO 3.4 Index is still in La Nina territory but warmer than last month.
One can also see that we remain in PDO-(Neg).
How About the Future?
ENSO is measured at the surface of the ocean because it is the surface that interacts with the atmosphere. But the surface changes over time so we pay a lot of attention to the subsurface. Here we are just looking at the Equator but from the surface down to 450 meters. And we are looking at the temperature anomalies (deviations from normal this time of year at the given depth and longitude). The Nino 3.4 Index is measured at the surface but the subsurface may become the future surface. There is anomalously cool water almost everywhere on the surface.
Here is what it looks like now. Does it look like it will soon be other than cool? It is complicated because we are looking at anomalies not absolute temperatures and we are only looking at a cross-section at the Equator when the Nino 3.4 Area extends five degrees north and south of the Equator but there is only so much information that can be presented in one graphic. Sea Surface Temperature Anomalies are only one component of ENSO but probably the most important component and La Nina is relative to SSTA is defined as -0.5C or colder.
Off to the west, the warm Indo-Pacific Warm Pool has receded from prior months but it is quite intense with maximum anomalies of 3 degrees Celsius. And we must remember that these anomalies are calculated based on the seasonal norms for water at that depth. So three degrees warmer than usual does not mean it is warmer than the water at the surface. So it will not automatically rise.
Mapping the details.
The data is a five-day average centered on the date shown.
| Has it changed much from last month? It is a truly amazing difference. Look where the warm anomaly is at around 120W. But the warm anomaly to the West has withdrawn and weakened. What should we make of this? |
I realize that is complicated. But it is important to understand. The analysis updates every five days but the graphics in this article are frozen. However, an updated version of this graphic can be found at https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ocean/weeklyenso_clim_81-10/wkteq_xz.gif. It comes with an upper graphic like the image shown above which is the temperature anomalies. It also has a lower graphic which is the actual water temperatures. Both are useful.
Another way to look at the same information
| It has kind of stabilized. Less warm than last month but not much change in the last couple of weeks. |
Are the changes significant? We need to look at additional information.
Another way of looking at the situation is the impact of the Oceanic Kelvin Waves.
What is below explains a lot.
We described Oceanic Kelvin Waves in the article some months ago but let’s just say they are near-surface waves confined to the Equator which can move warm water east and help end a La Nina. The downwelling phase of such a wave is shown in red and the upwelling phase is shown in blue. The recent Kelvin Wave made it look more likely that we would transfer to ENSO Neutral. But it turned out to be a fairly weak Kelvin Wave not followed by another one although we might see one forming in this graphic.
| The onset and evolution of the recent Kelvin Wave explain most of the changes in the probabilities from one release to the next so I think the Meteorologists may not have been paying as careful attention to this as they might have. Looking at the top image you see that the downwelling Kelvin Wave has played out and there is only a trace of an upwelling wave. So not much is happening. You have to look at the Hovmoller carefully since it is showing things over time. The dates are shown. And we are mostly interested in what is currently taking place between 170W and 120W and what we can expect to happen as the wave progressed to the east. |
Two months ago
Three months ago
Four months ago.
Looking at the Wind Anomalies. This is another way to try to understand what is happening and this is another Hovmoller chart. I am pretty sure they used to create these charts with a plotter and every day the roll would unwind and there was one more day’s worth of data added. The format remains and it still works pretty well.
My conclusion is we do not know yet when this La Nina will be over if ever. I take that back, La Nina can not persist forever but there could be a Triple Dip which would cause a lot of problems.
| This is a Hovmoller graphic. It is sort of what comes off of a plotter so the most recent information is at the bottom and the earlier information is at the top. Easterlies tend to be associated with La NIna since the Warm water in the IndoPacific Warm Pool can not move east. |
From the NOAA ENSO Blog
A good resource is the posts by Emily Becker. I have extracted some of the graphics but you can click on the below to read her full post.
There has been an interesting graphic for some months now in the NOAA ENSO BLOG which was written by Emily Becker. All La Ninas since 1950 which had a double-dip are shown. The black line is our current La Nina.
She has a new graphic this month.
And here is the same graphic from last month or the month before.
–
| The black line which is the current La Nina turned up a bit but it seems to be with the two-year La Nina’s that three-peated. |
What do Other Meteorological Agencies Say
I do not have the time or resources to check what all of the various meteorological agencies have to say on this. NOAA publishes (or is it IRI) what they call a plume of forecasts from many models not just those operated by the U.S. Last month those models seemed to show that ENSO Neutral with a strong bias towards La Nina was most likely. By a strong bias, I mean the forecast was for Nino 3.4 to be in the lower end of the ENSO neutral range. But the updated version of this “plume” will be published with the second IRI report so I do not have it now. But I do have a report from the Australian Meteorological agency (BOM which shows a subset of models.
BOM
And this is what it looked like last month but it only went out to October.
| Again there is not much change. This is a small set of models but a good one and it is important to remember that the new model results are for one month later. They still show a lot of variabilities but they all show NIno 3.4 to be negative and notice that the Australian threshold is -0.8 so all of these models are showing Nino 3.4 to be less than -0.5C in November or is it December as the title is confusing. |
IOD (Indian Ocean Dipole)
This impacts mostly India and Australia but all nations that border the Indian Ocean. This article https://iaseasy.in/indian-ocean-dipole-positive-negative-and-neutral-iod/ provides some insight but was written when a positive IOD was expected and this is a negative IOD which is generally good for Australia but bad for India. It covers both positive and negative IOD’s.
This shows the Walker Cycle for IOD Negative which is predicted.
| It is important to understand the Walker Circulation pattern of where moisture is rising (from warm water) and later falls as precipitation. |
Here is IOD Neutral
Here is IOD Positive
And here is how the Index is calculated (The SWIO is another Index not used to calculate the IOD the index of which is sometimes called the DMI)
| The index is calculated as the monthly difference between the western (10°S-10°N, 50°-70°E) (WTIO) and eastern Indian Ocean (10°S-0°, 90°-108°E) (SETIO) sea surface temperature departures from average. |
JAMSTEC
I have not yet received the JAMSTEC Seasonal Outlook which contains their ENSO forecast. I have used the Australian Bureau of Meteorology (BOM) information instead
