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. 

 

 

 

El Nino is officially here.

 

The National Oceanic and Atmospheric Administration has issued an El Nino advisory, announcing the official arrival of El Nino. There are several factors in place might make this El Nino different than other El Nino’s in the past.

The last El Nino event to impact the country was during 2018-19, this event was very weak. Since then, we had a triple dip La Nina, meaning a La Nina that covered three consecutive years.  

Nino region 3.4 is where we usually monitor the El Nino-Southern Oscillation (ENSO) for El Nino or La Nina. As I’ve said many times, an El Nino is when sea surface temperature anomalies reach 0.5 °C or warmer than average values for a three-month period.  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 3.4’s anomaly is at 0.98°C above average, meaning we’re on the cusp of a Moderate El Nino, Nino region 3 is at +1.1°C, Region 1+2 is much warmer at +2.6°C. 

The strength is determined by how much above average the water temperatures are in the Nino 3.4 region. The stronger the El Nino the greater it’s impacts. I posted in the blog, about what is a Super El Nino which you can find here.

Water temperatures 0.5ºC above average = Weak El Nino

Water temperatures 1.0ºC above average = Moderate El Nino

Water temperatures 1.5ºC above average = Strong El Nino

Water Temperatures of 2.0+ above average = Super El Nino

When we look at the subsurface water temperatures in the equatorial Pacific, we can see there is a lot of warmer than average water below the surface, coupled with those very warm SST off of Peru and Ecuador. While this is a good indicator of a strong El Nino down the road; they aren’t a 100% guarantee that a strong El Nino will develop.  When we look at the historic record, the SST in the equatorial Pacific is currently the 4^th warmest for May.  The top two May values were 1997 and 2015, both of these become super El Nino’s.  The El Nino of 1979 into 1980 lasted into the Summer of 1980, 1980 saw the third warmest water in the Central Pacific for the month of May. But that didn’t result in a strong El Nino, instead that El Nino was a weak Modoki El Nino.  A Modoki El Nino is when the SST in the central Pacific is warmer than in the eastern Pacific

This El Nino has started early based on the historic average. The early bird El Nino has formed roughly two months early.  The vast majority of El Nino’s are at their strongest during December to April, with the greatest impact during December through February, But the early start might make a difference in this. If the El Nino strengthens quickly it could affect both temperatures and rainfall this summer.

The Southern Oscillation Index (SOI)...

The SOI is a good indictor of how the overall atmosphere is responding to the ENSO. The more negative the SOI the stronger the El Nino. Sustained negative values below about –8 indicate an El Nino.

Over the last several weeks, both the equatorial SOI and traditional SOI were significantly negative.

The Madden-Julian Oscillation (MJO)...

The MJO is currently sitting in phase 3 and is very weak. The MJO is looking to transition to phase 4 and looks to stay there at least through the Middle of June. After that the models show it collapsing into the Circle of Death (COD) for the 2nd half of June and remains there for the foreseeable future. Phase 3 is typically a warm signal for the Northeast. But Phase 4 is a cool signal.  Once the MJO reaches the COD, it will loose most of its influence on the overall pattern, allowing other forces to be in control of the overall show. Seeing the MJO in the COD during the summer months is fairly typical due to the generally weaker trade winds. The MJO is looking to support overall temperatures staying below average to near average for much of June before allowing for more warming during July.

This should allow for the pattern over the CONUS to adjust to become zonal. Over the last several weeks, the pattern over the northern CONUS has been stuck in a roadblock. So, we’ve been having these upper-level lows (ULL) setting up and hanging around the Northeast.  The idea of these ULL spinning over the Great Lakes and Northeast is typical for El Nino. But lately this idea has been on steroids.  With the pattern more Zonal, we would have systems moving freely from west to east.  This would allow us to return to overall average/slightly below average temperatures across the Northeast, which would be a big change from the overall well below average temperatures we’ve been experiencing for the last few weeks.  So, with the El Nino, while we will see troughs over the Northeast, there shouldn’t be as many of them as we’ve seen the last several weeks. 

This general idea is supported by the CPC 8–14-day temperature and precipitation outlooks.

 

The Atlantic is also very warm...

Typically, El Nino creates more in the way of hostile atmospheric conditions of higher amounts of windshear. The higher windshear helps to disrupt tropical formation in the Atlantic Basin. Typically, during El Nino, the Atlantic sees cooler SST; the lower water temperatures are also unsupportive for tropical cyclone development.   This year Atlantic SST are much different. The warm SST are over a large part of the North Atlantic, including the Main Development Region. The combination of El Nino, the large amount of warm water in the north Pacific, and the very warm SST in the Atlantic Basin, is really nothing that we’ve seen before. So, we’re kind of in uncharted territory, when it comes to this year’s El Nino.   

The warmth in the Atlantic is going to help counteract the impact of El Nino on the 2023 hurricane season. This is one of the reasons My hurricane outlook is calling for average to above average tropical cyclone numbers in the Atlantic for this season.  

 

El Nino impacts for this Summer and upcoming Winter...

During El Nino years overall temperatures are warm across much of the CONUS, part of this has to do with the fact that typically during El Nino overnight temperatures are warmer when compared to afternoon temperature anomalies. This hanging on to the heat, helps to raise overall summertime temperature anomalies when they are averaged together.

In the summer months, the eastern U.S. typically sees cooler-than-average temperatures, with more in the way of dry condition, this is especially true for the Northeast. I showed this in my Summer Outlook which you can find here. Remember, the stronger the El Nino the more pronounced the impacts.

During the winter months, the northern tier of the CONUS including the Northeast it tends to be warmer than average, while the southern tier is colder than average. The Middle Atlantic region tends to see overall average to slightly below average overall temperatures. Precipitation is typically average to above average. But the temperatures make P-type is highly variable. Generally, snowfall is below average across the interior Northeast, this is largely due to the polar jet stream's diversion north, keeping the region warmer than average. The Middle Atlantic tends to due better on Snowfall during El Nino, typically seeing average to above average snowfall.

But the idea of this being a strong El Nino will have an effect on all of this. For the Northeast and northern Middle Atlantic Region, the phase of the MJO is as or more important than El Nino when it comes to snowfall in this region.

Here is a chart for cities in the Northeast and how the strength of the El Nino and the phase of the North Atlantic Oscillation (NAO) generally has on snowfall totals.

 

Showing snowfall from 1950 to 2017, broken down by El Nino, La Nina and neutral (neither El Nino nor La Nina) seasons, as well as those stronger El Nino seasons with a predominant positive (+) or negative (-) NAO.

In seven of the nine Northeast cities examined, strong El Nino seasons with a prevalent negative NAO produced the snowiest seasons compared to average.  The reason for this is when the NAO is negative it promotes a general pattern supporting Blocking near Greenland. Along with a better chance for the polar jet stream to push south, allowing for colder air at times. During strong El Nino’s the subtropical jet is typically very active and has a better chance of interacting with the northern Jet, when the polar jet is farther south.  This increases the odds for bigger Northeast snowstorms.

On the contrary, with the exception of Washington D.C., all other Northeast cities tended on average to see the least snow during strong El Nino and generally positive NAO.   The reason being the polar jet stream stayed eastward up across Canada keeping the cold air bottled up in Canada. These kept the subtropical jet stream from interacting with the polar jet, with a general lack of cold, meaning there were few chances for Northeast snowstorms.

That covers the latest on the developing El Nino, and how it could impact this Summer and a little glimpse of what it could mean for the Winter of 2023-2024.