September-February Weather Update: El Nino

Here is a look at the latest sea surface temperature anomaly map. Notice all the orange and red off the west coast of South America? That is the current El Niño...

The blue shaded area that is sandwiched between the warm North Pacific and the El Niño warmth, hasn't changed much as of late. This temperature gradient is important in fueling the southern branch of the jet stream, which is likely to become more enhanced over the next few months. The graphs below show the various models and their forecasts for how strong El Niño will be from October through February. The red, vertical, dashed line is the minimal level to achieve El Niño status. The models are well beyond that line, and the overall mean of the models runs from 1.8 to 2.2 degrees C above average in the main ENSO region. That equates to a strong El Niño...

What happens beyond February? Well, historically El Niño will typically weaken pretty rapidly as we get into spring. That doesn't necessarily mean this one will follow suit, but the models do show it weakening after February. That means we will still likely have some sort of El Niño influence as we head into spring. However, I doubt it will be nearly as strong as what we will see from now through winter.

So, we know we have an El Niño and we know we have a strong El Niño. So, what type of El Niño do we have right now? Well, there are three different types and are shown below...

The graphic above shows (from top to bottom) where the warmest water resides with each type of event, what the upper level weather pattern does with each type of event, and the temperature anomalies associated with each type of event. As of right now, we are dealing with a Traditional or east-based event, because the warmest water is positioned right off the west coast of South America. Could this event start as one type and evolve into another type? Absolutely. Some of the El Niño events of the past have done just that...start as a traditional event and morph into a hybrid or modoki type event. This is somewhat common when we have a negative Pacific Decadal Oscillation, which we still have... See the graph below to see just how negative.

Since the late summer of 2020, the PDO has been in a negative state. Could we moderate the PDO as we move through the winter? It is possible, yes... Could we switch phases completely as we move through winter? It is possible, but pretty unlikely... I would really like to see that change taking place now, in order to achieve that phase change

So, what are we left with when it comes to analog years? Remember, an analog year is a year from the past that matches up similarly with the weather pattern drivers we are seeing now. So, we have a pretty strong traditional / east-based El Niño and one that is likely going to get stronger. The image below shows precipitation anomalies, from October through March, for the years since 1950 that had a strong traditional / east-based El Niño. You can see the years listed...

The green/blue represents wetter than average, while the yellow/red represents drier than average. This fits pretty well with what a strong, traditional / east-based El Niño does...keeps the southern tier of the country quite a bit wetter than average. There are other areas that receive moisture too, with the drier than average region mainly confined to the Pacific Northwest and parts of the Northern Rockies.

The image below is looking at the same thing, but takes into account ALL types of El Niño events since 1950. You see the expanded number of years listed...

Pretty much shows the same thing, but the drier than average areas are a little more prominent. Pacific Northwest, and parts of the eastern Corn Belt.

Now, let's look at the years since 1950 that had a strong traditional / east-based El Niño and a PDO that was quite negative. Again, we are looking at precipitation anomalies from October through March. You get only two years...1951-52 and 1972-73.

Generally speaking, you get many of the same things...midsection and southern parts of the country end up wetter than average, with a few dry pockets. The one area that showed up drier than average that I didn't expect was central and southeast Texas. Typically, El Niño blesses that region with some great moisture. And to be clear, I'm not saying the next several months will end up that way for central and southeast Texas. However, it does underscore what I have said many times before...every El Niño event is different and can cause unexpected impacts. That is one reason we have to be cautious about what we do, and not put all of our eggs in one basket.

So, what is going to happen? Well, I'm not sure anyone knows at this point. The models do not favor this particular event evolving into a modoki El Niño. However, it could evolve to a hybrid type of event, which would still resemble much of what a traditional / east-based event brings. The models that I sent out to you last week largely show what we would expect during a traditional / east-based  El Niño. I don't have any reason to argue against the models at this time, but it is something I am watching very closely.
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I am sure you will have questions, so please...let me know if you do.

Brian

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