El Niño hasn't left the building — it's just taking a few days to sober up between benders. But will it continue to deliver the precipitation punch in the gut the US West Coast was promised? One particular factor might determine California's fate. The National Oceanic and Atmospheric Administration (NOAA) has released its monthly El Niño update, which focuses on comparing various factors from past El Niños to determine if this one will be the most powerful yet. First we have to look at the way scientists "measure" El Niños:
The Oceanic Niño Index, the three-month-average sea surface temperature departure from the long-term normal in one region of the Pacific Ocean, is the primary number we use to measure the ocean part of El Niño, and that value for November — January is 2.3°C, tied with the same period in 1997-98.
So if we look at that single indicator by itself, this year is pretty much on track with 1997-1998. The values from the last month especially are practically identical.
But as NOAA rightly points out, this isn't the only factor that will guarantee the same perpetually stormy weather of El Niño 1997-1998. We also have to look at the atmospheric response — basically how those warm tropical waters affect the levels of clouds and moisture above them. One indicator says the 1997-1998 atmospheric circulation was much stronger than what we're seeing now.
As far as drought relief, what NOAA is keeping an eye on now is evidence of that atmospheric moisture heading in from the Pacific — which, when it's really cranking, turns into the "atmospheric river" you can see in the video below.
NOAA Climate.gov animation by Dan Pisut, NOAA Environmental Visualisation Lab, based on data provided by the University of Wisconsin/SSEC MIMIC.
This visualisation shows the month of January, when plenty of storms were streaming towards California in from the Pacific. February saw a shifting weather pattern that helped to push all that atmospheric moisture far, far north, perhaps because El Niño is so powerful. So, of course, even if this extra-huge El Niño does generate the precipitation promised, it still might toss us an atmospheric curveball when it comes to where exactly it will fall.