Developing ‘Super’ El Niño Could Match California’s Great Deluge of 1997-98

Current El Niño conditions appear likely to become comparable to the “great” El Niño of 1997-98, according to an experimental prediction system used by the National Science Foundation’s National Center for Atmospheric Research.

“Our forecast system has shown that it can do a remarkably good job of accurately hindcasting past El Niño events when we’ve tested it using historical data, which gives us high confidence in this forecast,” said NCAR scientist Stephen Yeager, who helped lead the modeling effort.

The 1997-98 El Niño was one for the California record books.

It began with an October 1997 hurricane fueled by El Niño slamming into Acapulco, causing massive flooding and hundreds of deaths.

Then, in December, more than 7 inches of rain fell in parts of Orange County in a single day. Mudslides destroyed homes, and major roads were jammed with debris. And, February 1998 brought  13.68 inches of rain to downtown Los Angeles.

Here in the San Joaquin Valley, the great El Niño swelled rivers beyond their capacity, flooding both farmland and cities. According to National Weather Service records, the 1997-98 rain season ended with Fresno receiving 20.16 inches.

Putting that into perspective: the all-time Fresno rain season total is 23.57 inches, set in 1982-83. In the 2022-23 precipitation season that set numerous records for rainfall and snowpack, Fresno had 17.94 inches of rain, according to NWS records.

Related Story: El Niño Is Coming, and There’s a Strong Chance It Could Be a Doozy

‘Only Time Will Tell If We’re Accurate’

Weather, of course, is fickle and often fools meteorologists. In this specific case, Yeager acknowledges that NCAR’s modeling is predicting a more robust El Niño than other climate systems.

“Our system is predicting a warmer event than many other systems,” Yeager said. “But it isn’t out of the realm of possibilities. Only time will tell if we’re accurate, but we believe our system has something to offer and we’re excited to be able to contribute this knowledge to the conversation going on right now about the impacts El Niño may have in the coming months.”

In August 2015, meteorologists warned of a developing El Niño that could potentially match the 1997-98 El Niño. While 2015-2016 did end four years of drought in California, El Niño failed to carry 1997-98’s precipitation punch. However, the following rain season saw Fresno receive 17.20 inches — about 6.20 inches more than normal.

During strong El Niños, the subtropical jet stream sends a train of storms over Southern California and the southern United States. But “great” El Niños shift the entire jet stream over all of California, resulting in massive rainfall and a huge Sierra snowpack — as the state experienced in 1982-83 and 1997-98.

The Seasonal-to-Multiyear Large Ensemble (SMYLE) prediction system accurately hindcasted past El Niños, as shown in this graph. NCAR scientists have run the system in real-time to predict the strength of this winter’s El Niño, which is forecast to be on par with the 1997-98 event. (NCAR)