El Niño just leveled up to super status. Here’s what that means for the weather
By Meteorologist Mary Gilbert, CNN
(CNN) — An already-strong El Niño just turned super as the phenomenon crosses into unprecedented territory.
The natural climate cycle has been strengthening at a breakneck pace since it was first declared in June and is stronger now than it’s ever been on this date. And isn’t done bulking up yet.
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Forecasters have thought for months that El Niño would become very strong or “super” by this fall. The key measure of its strength has now crossed that threshold and will continue to soar higher.
As a refresher: El Niño is characterized by warmer–than–average water temperatures along the equator in the Pacific Ocean. The warmer water triggers corresponding shifts in the atmosphere that have a domino effect on weather patterns around the globe.
An active Pacific hurricane season that’s churned out multiple threats for Hawaii, a hurricane-less Atlantic hurricane season to date and Indonesia’s overwhelming wildfires are just a few effects of this very strong El Niño.
The stronger an El Niño is, the more likely it is to influence these types of weather patterns — but it doesn’t guarantee more extreme impacts.
Turning super
To capture El Niño’s strength, National Oceanic and Atmospheric Administration forecasters measure how far above normal sea surface temperatures are in a specific region of the Pacific, using a metric called the Niño 3.4 Relative Oceanic Niño Index, or RONI.
The latest weekly RONI value just hit 2.0 degrees Celsius, 3.6 degrees Fahrenheit, above average. This is the threshold for “very strong,” the highest official category set by forecasters. That’s also when El Niño gains its unofficial “super” moniker.
These weekly values from NOAA capture a reliable snapshot of El Niño’s strength in real-time, which is crucial because of just how fast the event is gaining ground.
This time a year ago, a weak La Niña — El Niño’s cool counterpart — was in place, and only a handful of other years have had such a rapid flip to a potent El Niño, including the strongest ever event from 1982 to 1983.
Even so, using the weekly values is a slight departure from the norm.
NOAA’s most widely recognized strength metric is a three-month rolling average RONI. The rolling average’s purpose is to smooth out choppy short-term changes in data in favor of capturing a cleaner long-term average; that value updates once a month.
This is how a climate record that dates back decades is built, but the delayed data means it’ll take weeks for that reading to truly capture how super-sized El Niño is right now.
Breaking new ground
This isn’t a normal event: In addition to being the strongest El Niño on record on this date, it’s ultimately likely to become stronger than any event before it.
By the end of the year, El Niño has a 75% chance of peaking as the strongest event since records began in 1950, according to NOAA’s latest forecast issued last week.
This year’s El Niño is also happening in a much hotter world than previous record-setting events due to climate change. One look at sea surface temperatures from this year compared to past record events shows just how much fossil fuel pollution has rewritten the rules.
Climate change has literally changed the metric used to monitor El Niño. This event is the first to be captured by NOAA’s aforementioned RONI, which was first implemented in February.
The old metric took sea surface temperatures at face value, but RONI subtracts out how much warmer the Pacific Ocean is because of climate change to get the “true” strength of El Niño.
Even so, this El Niño continues to clear hurdles in its pursuit of record-breaking strength later this fall or early this winter.
Past, present and still to come
Winter is when El Niño is forecast to hit its peak strength and is also typically when its influence on global weather is most pronounced, but it’s already left many calling cards behind this summer as it strengthened rapidly.
It was, and continues to be, a major factor in both the Atlantic and Pacific hurricane seasons. In the Atlantic, it’s taken storm-killing wind shear to extreme levels and kept it there, even at what should be the busiest time of the season. That’s created a record-long wait for the season’s first hurricane.
El Niño has prevented that same type of wind shear over the exceptionally warm Pacific and activity exploded. Sixteen storms, including two Category 5 hurricanes, have formed and thrived in the eastern and central parts of the ocean so far, with Hawaii alone facing three tropical systems in less than a month.
Fourteen of those storms originated in the East Pacific, which, with two and a half months of the season still to come, will likely blow past its average seasonal storm total of 15.
Elsewhere, Indonesia is battling widespread wildfires and conditions could deteriorate further: El Niño years make the country drier than usual, which leaves plenty of tinder-dry vegetation for blazes to consume and limited rainfall to help fire crews tamp down ongoing activity.
El Niño also raises global average air temperatures above levels already being increased by climate change and was a factor in making this summer such a scorcher around the globe. This August was Earth’s hottest on record and could mark the start of a record-breaking warm stretch that would likely culminate in a record-hot 2027 — and possibly 2026 — globally.
It’s clear El Niño is already a major player, but it will hit its full stride in the months ahead, right on time to dictate winter weather across the US.
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