Science1 publisher2 min readPublished
NOAA gives 75% odds that this El Nino outranks every event back to 1950
The eastern Pacific is running 2.1 C above average on weekly NOAA data, past the 2 C mark for a super event. The official strength category comes from three-month averages, and the regional outlook comes with a caveat attached.
The Scientist · Science desk
What happened
- Weekly NOAA readings from the eastern Pacific put sea surface temperatures 2.1 degrees Celsius above average, past the 2 C mark that earns an event the informal label of a super El Nino.
- The agency also puts the chance of a very strong event emerging during the fall and winter at more than 90%.
- The Atlantic hurricane season passed its traditional peak without a tropical storm or hurricane, Ars Technica reported, in what is becoming a historically quiet stretch.
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Why it matters
- decision The Climate Prediction Center's outlook splits the country in two, so an operator with sites in California and in the northern tier is being handed two opposite winters and cannot plan both on one assumption.
- exposure NOAA's high-tide flooding note reaches West Coast coastal assets independently of rainfall totals. Port and shoreline operations are exposed even through a dry stretch.
- constraint A stronger event raises the certainty of the expected pattern without guaranteeing it. The 75% does not convert into a probability for any single site or seasonal commitment.
The 75% figure is a forecast about an index value. It is the chance that this event's sea surface temperature anomaly finishes above every El Nino in NOAA's rankings, which reach back to 1950, the earliest year the agency has data for historical comparisons [1]. The World Meteorological Organization's Global Seasonal Climate Update, released Sept. 3, carries multi-model forecasts for September-November 2026 [17]. That makes the comparison window 76 years wide [1].
How strong the event looks depends on how much smoothing goes into the number. The Climate Brink put the daily anomaly at 3.06 C on Sept. 20 [8], almost a full degree above the weekly value [2]. NOAA categorizes strength on three-month averages, because weekly data is more prone to temporary anomalies [3]. The official label will therefore come from the three-month average, not from the weekly and daily figures now circulating.
The European Centre for Medium-Range Weather Forecasts' models have the anomaly exceeding 3.5 C by the end of the year [7], which would put it 1.5 C past the super threshold [3]. Live Science reports that scientists have noticed this pattern strengthening rapidly in a way they have not seen before, intensified by human-driven climate change [18].
Warm water pools east in the equatorial Pacific and pushes the jet stream south [9]. The two most recent super events followed that same mechanism and left different lists of damage. The 1997-98 winter brought flooding in the Southeast, an ice storm in the Northeast and tornadoes in Florida, according to a National Climatic Data Center report [14]. The 2015-16 event's associated impacts included a historic hurricane season in the central North Pacific and record drought in the Caribbean, according to Climate.gov [13].
Some basin-scale effects are already in this year's record. CNN reported tropical storms in Hawaii attributed to El Nino, with warming in the waters where those storms typically form [15]. The index record does not indicate which of those two impact lists a given winter will resemble. El Nino has been officially underway since June 11 [5], and NOAA's bar for declaring conditions at all is 0.5 C above average, with wind, surface pressure and rainfall in the region also consistent [6].
What to watch
- NOAA's three-month average for the season, since the official strength category comes from that number and not from the weekly readings.
- Whether ECMWF's projection of an anomaly above 3.5 C by the end of the year verifies.
- Whether the Atlantic stays quiet through the rest of the season after passing its peak with no named storm.