Another El Nino update…

 

I wanted to post on the evolution of the developing El Nino

 

 

Sea surface temperature anomalies

 

 

El Nino…

The waters of the eastern and central Pacific Ocean are continuing to heat up; in fact, since NOAA issued an official watch, El Nino has been developing rapidly and looks to be building towards a strong El Nino. NOAA has us now at an El Nino alert.  Some of the indications are pointing towards and event that could rival or even surpass the intensity of the Super El Nino’s of 1997-1998 and 2015 -2016.

The Oceanic Nino Index (ONI) is NOAA's primary index for tracking the ocean part of the El Nino-Southern Oscillation ENSO) climate pattern. The ONI is the rolling 3-month average temperature anomaly in the Sea Surface Temperatures of the east-central tropical Pacific, near the International Dateline. As I said in my last blog post, found here. “Nino region 3.4 is where we usually monitor the ENSO for El Nino or La Nina. When looking at Nino 3.4, Index values of +0.5 or higher indicate El Nino. Values of -0.5 or lower indicate La Nina.

An El Nino alert is declared when Niño 3.4 anomaly exceeds +0.5°C for 3-month period. In order to be considered a full-fledged El Nino onset conditions must be met for 5 consecutive 3-month periods. So based on the data, we’re well on our way to a full-fledged El Nino.

When we look at the monthly Nino index in each of the four Nino regions, we see that they are all above 0.5 C.  Nino 4 …0.6°C above average, Nino 3.4’s anomaly is at 0.9°C above average, Nino region 3 is at 1.2°C above average, Region 1+2 is at 2.7°C above average.

 

 

When looking at the ocean analysis, we also have to look at the ocean anomalies below the surface, at depth. Below you can see the subsurface ocean anomalies across the ENSO regions, showing a strong warm belt, with the strongest anomalies in the eastern regions.

 

Given this we should reach actual El Nino status during this summer.   

 

All the models are indicating a high likelihood of moderate to strong El Nino event, with a few showing a super El Nino event. Super El Ninos feature anomaly temperatures in Nino 3.4 that are greater than 2C above average. If you want to read more on what a super El Nino is, click here.

The SST are warmer this year heading into El Nino, than they were for the Super El Nino of 2015-2016. This is another indication that this could be the strongest El Nino on record. 

Other Teleconnections…

Southern Oscillation Index (SOI)? The SOI measures the difference in air pressure between Tahiti, in the South Pacific, and Darwin, in the north of Australia. In its positive phase, pressures generally are lower than average in Darwin and higher than average in Tahiti. Sustained values of 1 or greater associate to La Nina. In the SOI’s negative phase, pressures tend to be higher than average in Darwin and lower than average in Tahiti. Sustained values of -1 or less correlate to El Nino

Looking at the SOI graph below, you can see the prolonged positive pressure phase, During the La Nina. But now you can see a fast shift into a negative pressure phase, indicating a shift into an El Nino mode.

 

Looking at the SOI chart, the three-month average Southern Oscillation Index is at -7.47.

The Indian Ocean Dipole (IOD)

IOD is the difference between the sea surface temperature of eastern Indian Ocean (Bay of Bengal) and the western Indian Ocean (Arabian Sea).

The wet negative phase of the IODs often, but not always, come at the same time as La Ninas, and the positive phase often happens at the same time as El Nino – meaning the IOD tends to exacerbate whatever ENSO is doing. But this relationship isn’t set in stone, and the IOD can also reduce the effects of ENSO if it’s in a different phase.

The IOD is currently neutral. All models suggest a positive IOD is likely to develop in the coming months. A positive IOD can exacerbate El Nino's impacts.

 The most recent IRI plume also indicates El Nino is likely to form during the May-July season and persist into the winter. The combination of a forecasted third westerly wind event in mid-late May, and high levels of above-average oceanic heat content, means that a potentially significant El Nino is very possible.

 

 

 

All of this is showing El Nino sticking around for the next several months. Based on the data the El Nino could continue to develop and strengthen right through winter 2023-2024.

 Looking back at the global ocean analysis from Coral Reef Watch, we see the very warm water in the Eastern and Central equatorial Pacific; we can also see the blob in the North Pacific, currently running well above average SST anomalies. Another area that is apparent is the North Atlantic. Notice a strong above average SST anomaly, spanning from the equator up to the polar circle. It’s this record warmth in the North Atlantic that is the most unusual thing going on, and is something to look closer at.   

 

The Atlantic Basin…

 

I’ve received questions in regard to El Nino and the early tropical activity in the Atlantic we’ve seen so far in June. Some feel the developing El Nino isn’t exerting influence on the pattern; citing the early activity in the Atlantic as proof of that Idea. They basically want to know if that is true?

 

 The global circulation and jet stream patterns are already coupling with the ocean-atmosphere influence of the developing El Nino.   During El Nino the southerly Pacific jet stream is amplified, this is certainly the case this year, with all the storms along the jet bringing lots of precipitation and cooler weather to the southern United States. Typically, during El Nino, the polar jet stream is usually further north and weaker, which limits a lot of the variability, that pattern has unquestionably been in place for the last few months, leading to the overly cool and dry weather the Northeast has experienced.

This is all part of the recent atmospheric setup over the North Atlantic. Over the past several months, we’ve had a persistent blocking pattern over the Labrador Sea, Greenland and Iceland.

This blocking setup in the high latitudes of the North Atlantic means that there is higher than average pressure closer to Greenland. Because of that there have been lower than average pressure near Bermuda and the Azores, which has been the case over the spring into Summer.  This atmospheric setup of the North Atlantic has been a big contributor to the above average water temperatures in the far north Atlantic and also in the tropics. As a result, parts of the North Atlantic Ocean are seeing exceptionally warm SSTs.  

As I outlined this setup as led to a weaker sub-tropical high (Bermuda High). Which in turn led to weaker easterly trade winds. Stronger winds increase upwelling of cooler water from below the surface.  But with the current setup, this allowed the tropical Atlantic Ocean to bake in late spring sunshine. The weak Bermuda High and lack of stronger trade winds, is the reason the wind shear hasn’t been as robust as is typical. It has also reduced the extent of Saharan dust over the tropical Atlantic leading to even higher water temperatures. The whole thing is a vicious circle.  This is very noticeable right now, in the Main Development Region in the tropical Atlantic. Where the SST are already at the level typically not seen until August and September.

So, while El Nino normally leads to fewer hurricanes and tropical storms, due to stronger wind shear. The setup in the Atlantic with the record warm SST, reduced shear and dust, is countering the El Nino leading to all the early activity we’re seeing in the Atlantic. So since the Atlantic is typically cooler during El Nino, the conditions this year, means we are entering uncharted waters, so this El Nino might be something we have not seen before.

.As I said in the What is a Super El Nino blog post, "Super El Nino’s seem to set a new plateau in regards to warming global temperatures". 

Well that's it, let me know what you think. If you like the post click like and also share the post with others.