[June 2021 sea surface temperature departure from the 1991-2020 average. Image from Data Snapshots on NOAA Climate.] [From NOAA Climate written by Tom Di Liberto]  As things stand with the El Niño-Southern Oscillation (ENSO), neutral conditions are currently present in the tropical Pacific and favored to last through the North American summer and into the fall. But forecasters at NOAA’s Climate Prediction Center have issued a La Niña Watch, which means they see La Niña likely emerging (~55%) during the September-November period and lasting through winter.

Where we are:

I know you’re all excited for me to talk about La Niña, but I’m a killjoy, so bear with me for a second while I talk about the current state of the Pacific. In June, ocean surface temperatures were near the 1991-2020 average across the equatorial Pacific, including the all-important Nino3.4 region (check out this post for more on ENSO indices), which we use to monitor the state of ENSO. Specifically, the June sea surface temperature in the Nino3.4 region was 0.25 degrees Celsius below average, well within the ENSO-neutral range. Ocean temperatures in this region have been quickly returning to near-average conditions over the last several months, increasing by nearly half a degree Celsius since April and over a degree Celsius since last winter’s La Niña peak. But as we have said, so many, many times: there is more to ENSO than just the surface of the ocean. Putting on our snorkels, let’s dive beneath the surface of the Pacific, where things aren’t as near average but still firmly indicative of an ENSO stuck in neutral. Waters were slightly warmer than average, except for the eastern Pacific where cooler-than-average waters developed near the thermocline—the layer of water that marks the transition between the warmer upper ocean and colder deeper ocean. But overall, nothing to write home about. To finish off this trilogy of signs about our current ENSO-neutral Pacific, we look to the skies! After all, ENSO is a coupled atmosphere/ocean climate phenomenon. And for the past month, that atmosphere has been pretty darn neutral. Winds at both low and high levels of the atmosphere were pretty normal, and while thunderstorm activity was reduced near the dateline, things were mostly average elsewhere. [The official CPC/IRI ENSO probability forecast, based on a consensus of CPC and IRI forecasters. It is updated during the first half of the month, in association with the official CPC/IRI ENSO Diagnostic Discussion. It is based on observational and predictive information from early in the month and from the previous month. Image from IRI] There hasn’t been a more boring trilogy since Star Wars episodes 1-3 (yeah…I said it). But then again, that’s expected during neutral ENSO conditions across the Pacific.