From the Cliff Mass Weather Blog
Cliff Mass
The media and social media are abuzz with talk about the upcoming “Super” El Niño, with forecasts of low snowpack, drought conditions, and massive wildfires (see sample below).
My local newspaper and some amateur social media are making similar claims.
Few of these scary claims are supported by the facts: in reality, the outlook is quite favorable for our region if a “Super El Niño” continues to develop.
Let me prove this to you.
Surprisingly, there is nothing called a “Super El Nino” in the scientific world.
If the temperature anomaly (difference from normal) of the ocean surface in the tropical Pacific is 1.5 to 2 C above normal, it is called a strong El Niño. More than 2C, a very strong El Niño. The media calls this a “super”; the scientific community does not.
Below is the latest forecast by NOAA. They are predicting a very strong El Niño this autumn (peaking around 2.2 C above normal).
There is little doubt we will get a very strong El Nino, but this is not unprecedented, with others occurring in 1982-1983, 1997-1998, 2015-2016, and 2023-2024 (others have occurred before as well).
A KEY point is that very strong El Niños are very different animals than their more moderate cousins. With different impacts.
Moderate to strong El Niños are typically associated with less snowpack and drier-than-normal conditions.
Very strong El Niños bring near-normal snowpack and plenty of moisture.
Thus, our water resources are generally fine with very strong El Niños like the upcoming winter.
Want the proof?
Below is a plot of precipitation from October to April (our wet season) since 1980. The red arrows indicate very strong (“super”) El Nino years, and the yellow line is the average of the period (1980 to today).
Very strong El Niño years are NOT particularly dry… their average is a bit ABOVE NORMAL.
Let’s check out a few sites, looking at April 1 snowpack (which is generally the date used for evaluations).
Crystal Mountain Ski area (around 6000 ft)? Snowpack during very strong El Niños is nearly normal (horizontal line) during such years.
The much lower Stampede Pass (4000 ft)? Same story.
Even LOWER at Snoqualmie Pass (below). Same story…nearly normal snowpack during very strong El Niño years!
Very strong El Niño years have near-normal snowpack in our mountains. I could show you a dozen other locations: same story.
What about temperature? Over Washington State at the surface, very strong El Niño years are about 1°F above normal, although one was below normal (2024).
With normal rain and mountain snow during a very strong El Nino year, the expectation is that there will be plenty of water next year for our region’s needs.
So those predicting drought, drastically reduced snowpack, and enhanced wildfires over the region will have a lot of the proverbial egg on their face next summer.
So what exactly does a very strong El Niño do to the larger-scale atmospheric circulation around here? I am a weather scientist and am curious!
Below is the average of the upper-level heights at 500 hPa (think pressure at 18,000 ft), showing the difference from normal for October through March of a very strong El Niño year. Purple is much lower than normal heights/pressure (a strong trough).
Mama mia! A HUGE intense low-pressure area over the north Pacific!
Let’s look at the local implications of this intense pattern by examining the difference from normal in the winds around 5000 ft for such a very strong El Nino year (below).
There are greatly enhanced winds from the southwest offshore, bringing in lots of moisture into the West Coast. That means more precipitation. NO DROUGHT.
To demonstrate this, below is the difference in precipitation from normal for such very strong El Niño years. A lot more precipitation over the West Coast, with the greatest increase over northern CA and southern Oregon.
Our region will be a bit warmer than normal, but the additional moisture should result in near-normal snowpack in the mountains above 3500 ft. Lots of water to fill reservoirs and moisten the soils.
No problem.
