Along the Equator in the eastern Pacific Ocean, the El Niño climate phenomenon has been coming on strong in recent weeks.
You can see that strength in the image above, which shows how temperatures at the ocean surface vary from normal right now. El Niño's fingerprint is seen in that broad yellow, orange and red swath along the Equator, indicative of abnormally warm water.
We're Now in Strong El Niño Territory
"El Niño is currently chugging along, and forecasters expect it to continue for the next several months, with a 62 percent chance of lasting through April–June 2024," notes University of Miami scientist Emily Becker. Moreover, it has crept across the threshold for what is regarded unofficially as a “strong” event.
Strong El Niño's are more likely to influence winter weather patterns over North America in a distinct way that you can see here:
As the map shows, much of the southern tier of North America tends to be wetter than normal, whereas the northern tier tends to be drier. (The impact, which is most likely to emerge during strong El Niño's, is distilled in this graphic.)
Right now, as we approach winter in the Northern Hemisphere, is it beginning to look a lot like El Niño? For an answer, check this out:
I think you'd have to agree that based on the map, which shows recent precipitation patterns, the answer is, no, not yet.
And there's something else about this El Niño that's looking a tad weird. To understand how, check out this animation:
The two frames of the animation show how circulation of air and moisture in the atmosphere typically responds to changes in the ocean during an El Niño.
Without El Niño, the usual atmospheric pattern, called the Walker circulation, consists of rising air and associated rain storms over the far western Pacific Ocean. Up high in the atmosphere, winds blow west-to-east, and then air plunges toward the surface over the cooler eastern Pacific. The circulation is completed by the trade winds, which typically blow from the east to the west near the surface.
But this Walker circulation pattern weakens during an El Niño. With very warm sea surface waters shifting from the west toward the central and eastern Pacific, the updrafts of air and associated rainstorms shift along with it.
The result is less rain to the west, and more to the east. In addition, the trade winds slacken during an El Niño, and sometimes they even reverse. This enables even more warm water to creep toward the east along the Equator, strengthening the overall effect.
"We’ve observed all of these characteristics of the weaker Walker circulation lately, indicating that El Niño’s engine is fully engaged," Becker says.
But experts quoted by Washington Post meteorologist Matthew Cappucci say a few weird anomalies bear watching. For one, there’s an unusual blob of warm sea water in the western Pacific — where it doesn't really belong during an El Niño. This may be linked at least in part to human-caused climate change.
You can see it here:
As was depicted in the previous animation, energy flowing from warm ocean waters into the atmosphere tends to send updrafts of moist air billowing upwards. When the air rises high enough and thus cools, moisture condenses and falls out as rain.
According to University at Albany scientist Paul Roundy, quoted by Cappucci, this is what's happening right now over the warm blob. And that, he posits, is causing less rain to fall in the eastern Pacific than one would expect during an El Niño.
This is potentially important because what happens in the equatorial Pacific Ocean doesn't stay there. These events influence large-scale atmospheric circulation patterns, including the jet streams that carry weather systems across North America. And so if the current somewhat unusual patterns continue, we might not see the typical impacts of a strong El Niño here in North America.
But it's also important to keep in mind that the climate phenomenon's impact on our temperature, rain and snow is most distinct during the winter. And that means El Niño still has plenty of time to begin influencing weather patterns here in the classic way.
Stirrings From the Deep
In fact, El Niño may soon be getting an additional boost in the form of a gargantuan wave of warm sea water that is sloshing beneath the surface toward the eastern Pacific.
The animation above shows the evolution of subsurface Pacific waters along the equator between early September and the end of October. During that time, warmth from the deep surfaced in the eastern Pacific, helping to reinforce El Niño. The animation also shows what appears to be a followup wave of particularly warm water heading toward the surface — where it's likely to keep feeding the climatic phenomenon.
With the heart of winter fast approaching, we won't have to wait long to see how this all plays out.