A potentially ‘historic’ El Niño may become the biggest on record, NOAA says
It is expected to dampen Atlantic hurricane numbers
The rapidly developing El Niño is likely to become a “historic event” that could become the most-intense in the period of record, the government’s Climate Prediction Center said Thursday.
The El Niño warming in the tropical Pacific, coupled with how it is affecting the atmosphere, is all but certain to have dampening effects on the Atlantic hurricane season, researchers said.
While it is likely to be disruptive and destructive during the next several months, during the tropical storm season it may mean fewer scares for East and Gulf Coast and Caribbean residents, and perhaps fewer flooding threats in the Philly region.
El Niño already is making its presence evident thousands of miles away in the Atlantic Basin, said Philip Klotzbach, tropical storm specialist at Colorado State University. Colorado State’s forecast methodology has been the prototype for the outlooks issued by the National Oceanic and Atmospheric Administration and commercial companies.
In his update last week, Klotzbach predicted the season would produce nine named storms, those with winds of at least 39 mph — down from 13 in the April outlook. NOAA also subtly trimmed its numbers. The long-term average is 14.
Even with above-normal temperatures that usually would be favorable for storms in the hurricane-development regions of the Atlantic, what’s going on in the Pacific is going to dominate, he said.
“El Niño is definitely the story of this season,” he said, and NOAA says the Pacific warming is likely to persist through April.
(Even The Farmers’ Almanac has noticed. The winter outlook it has cooked up appears to be right out of the El Niño recipe book, calling for wetness and storminess in the South, typical of El Nino. Helpfully, it said the forecast up our way is “tricky.”)
How does warmth in the Pacific affect Atlantic hurricanes?
El Niños, which occur every two to seven years as part of a natural process, agitate the overlying air and disrupt atmospheric circulation worldwide. It is part of the so-called El Niño Southern Oscillation, or ENSO, and since oscillations do oscillate, El Niño periodically shares the stage with La Niña, during which the waters are cooler than normal.
The climate center reported Monday that in the key El Niño region of the east-central Pacific, sea-surface temperatures over a 2.4 million-square-mile area were more than 3 degrees Fahrenheit above normal.
That air-ocean interaction generates strong west-to-east upper-level “shearing” winds that can keep tropical storms from maturing into hurricanes.
Klotzbach said that last week, the 30-day average of wind shear in the western Atlantic was higher than in any other 30-day period dating to 1979.
Other players in the atmosphere affect tropical storm activity, but El Niño “usually becomes the dominant factor,” said Matt Rosencrans, the weather service’s lead hurricane forecaster.
During the top six most-intense El Niños in records dating to 1950, tropical-storm numbers were significantly below normal.
Is this El Niño yet another symptom of a warming planet?
“There is still considerable debate in the scientific community on how warming may affect ENSO behavior,” said Michelle L’Heureux, physical scientist with NOAA’s Climate Prediction Center and the head of the ENSO team.
El Niños likely have been occurring for eons, but the period of record dates only to 1950 because “much fewer observations” are available before then, she said.
“It would take much more research to compare El Niño events in the older records,” she added.
El Niños in which the temperatures reached 3.6 degree Fahrenheit — averaged over three-month periods — occurred in 1965-66; 1972-73; 1982-83; 1991-92; 1997-98, and in 2015-16.
The warmest three-month average, 4.3 degrees Fahrenheit, was recorded in the 1982-83 event, and the climate center sees a 69% likelihood that this will exceed that level.
But L’Heureux cautioned that “intense El Niño events are not totally unexpected.” The top six list shows that they have reappeared every 10 to 15 years.
Thus, she said, “There’s a reasonable argument we were due.”
What might all this mean for the Philly region’s weather?
Tropical storms or their remnants “are especially notorious for flash-flooding impacts” in the region, said Sarah Johnson, warning coordination meteorologist in the weather service’s Mount Holly office.
In 2020 and 2021, the region was affected by six such storms or remnants, including the devastating Ida, in September 2021.
The 2020 season was quite active, and 2021’s hyperactive. Logically, fewer Atlantic storms would reduce the odds of remnants heading this way.
With the exception of 2012, the year of Sandy, Johnson said that all the years with below-average flash-flood warnings issued by the Mount Holly office coincided with seasons in which no tropical storms or remnants have affected the region.
We wouldn’t mind an encore.
