A Flowchart That Answers Once And For All Whether We're In An El Niño

Could we still see an El Niño this year? Yes, we could. In fact, it may have started already.


Top image: Current sea surface temperatures, as of today via NOAA

After the newest El Niño update yesterday — that conditions were still quite good for the potential of developing an El Niño this winter, either in the remainder of this year or the beginning of the next — NOAA's Climate Prediction Center took on an interesting question: Is it possible that an El Niño may have already begun?


With both the 65% likelihood that we're getting an El Niño sometime this winter and some anecdotal evidence (like California's sudden drought-interrupting rains), it certainly looks like a possibility.

So are we already in the midst of an El Niño? Not quite, concludes NOAA, but we are quite close. In a blog post on ENSO, NOAA sketched out just what was required for an El Niño to be confirmed with the help of this handy flowchart:

Illustration for article titled A Flowchart That Answers Once And For All Whether Were In An El Niño

Image: Glen Becker and Fiona Martin / NOAA/CPC

So have we met all those conditions? Some of them, but not all:

In a nutshell, the typical El Niño atmospheric response includes reduced rainfall over Indonesia, more rainfall over the central Pacific, and some weakening of the low-level easterly winds and upper-level westerly winds (the Walker circulation) along the equator. As of the beginning of this month, we have seen reduced Indonesian rainfall, but we have not seen more rain over the central Pacific (the opposite, in fact), and changes in the Walker circulation are unclear.


So not quite an El Niño yet. But, even though we are not calling an El Niño yet, that doesn't mean the rest of the world agrees. As NOAA notes, even though they're still not calling it an El Niño year, some other national weather services have done so:

El Niño impacts can emerge in different parts of the globe, even if the NOAA definition hasn't yet been formally satisfied. Different countries have different thresholds for El Niño, which are tailored to their specific interests. For example, the Peruvian National Committee on El Niño Studies (ENFEN) declared a "moderate coastal El Niño" in May of this year; SST anomaly in the easternmost Niño1+2 region is the primary metric for their declaration of coastal El Niño. Their event peaked in July, and is still ongoing.


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Unspiek Baron Bodissey