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 slightly lower 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 lower. This is not likely to change the forecast for Winter but might change the forecast for next Spring. Finally, there is now more disagreement among meteorological agencies as to when this La Nina will end.
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 less this month. But the possibility of a Triple Dip should be of considerable concern. We will learn more about what NOAA thinks next Thursday.
I have also reported on the Indian Ocean Dipole (IOD) because of the potential impact on world food production. We also discuss this year’s hurricane season to the extent it is impacted by La Nina.
CLIMATE PREDICTION CENTER ENSO DISCUSSION
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. MJJ stands for
May/June/July.
| 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. |
Here is the forecast from the prior month.
Looking at DJF which heads into 2023, In now looks like Equal Chances of La Nino and ENSO Neutral.
Here is the prior version issued in April
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 a bit lower. This is not likely to change the forecast for Winter but likely to change the forecast for next Spring.
Prior Analysis
Sometimes it is useful to compare the current forecast to prior forecasts. 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 four 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 the 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.
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.
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
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? Yes. The cool anomalies are not quite as cool and the warm anomalies have extended a bit farther to the east.
And two months ago at about this time in the month. The warm anomaly actually advanced east a bit last month.
And let us look at the situation three months ago.
At that time it looked like the situation could quickly change. It does not look like that now.
And this is what it looked like four months ago. There was a lot more warm water at depth but it is not there now.
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 cool than last month but not much change the last couple of weeks.
Are these changes significant?
Another way of looking at the situation is the impact of Oceanic Kelvin Waves.
And a month ago
And two months ago.
The above explains a lot.
We described Oceanic Kelvin Waves in the article two 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. |
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.
What Are the Chances of a Three-Peat?
What does NOAA Say
We discussed that both two months ago and last month. But there was an interesting graphic and comment in the NOAA ENSO BLOG today 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.
As you can see from the graph, April 2022 was the coldest of the nine second-year La Niña events on record, for this time of year.
She has a new graphic and the resolution is not good but it shows that May although it has warmed a bit is nonetheless the coldest May for a repeat La Nina year.
Emily Becker in her Blog Post has a more up-to-date version but it is more difficult to read.
Notice the value for May is the lowest for any two-year La Nina repeat.
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
This just goes through October and it shows the BOM proprietary model back into neutral range by then but three models are still in La Nina range. The key is that they are talking about October and the information they provide only goes out that far. The ECMWF is a very well-respected model. It is indicating ENSO Neutral by then.
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. |
Sea Surface Temperature
This is a forecast for September of this year. It is related to the ENSO forecast for BOM. It is a very interesting pattern.
JAMSTEC
I have not yet received the JAMSTEC Seasonal Outlook which contains their ENSO forecast.
From the NOAA ENSO Blog, some insight into this year’s Hurricane Season
Emily Becker usually writes a blog article when NOAA issues their ENSO Update and here is the link to her post: https://www.climate.gov/news-features/blogs/june-2022-enso-update-how-does-your-garden-grow
Here is what she says about the upcoming Hurricane Season
That provides some useful insight.
