As fall arrives, a ‘triple-dip’ La Niña looms

WATERTOWN — Autumn and the equinox arrives at 9:03 tonight in the region, and on its heels will be a climatological rarity.

For the third year in a row, we should expect to feel the effects of La Niña. The World Meteorological Organization says the three-peat would become this century’s first “triple-dip” La Niña, spanning three consecutive Northern Hemisphere winters (Southern Hemisphere summers).

“It’s pretty rare to have a third La Niña in a row,” said Jessica L. Spaccio, climatologist at Cornell University’s Northeast Regional Climate Center in Ithaca.

La Niña, translated from Spanish to “little girl,” is a natural ocean-atmospheric phenomenon marked by cooler-than-average sea surface temperatures across the central and eastern Pacific Ocean near the equator. It’s the opposite of El Niño (“little boy”) which features warmer-than-average sea surface temperatures in that region.

The cooler waters from La Niña affect the location of jet streams, which impacts North America.

“Right now, it has a high probability (91%) of continuing through the fall — September, October and November,” Ms. Spaccio said. “The probability goes down for January through March.”

The National Oceanic and Atmospheric Administration reports the chances of La Niña continuing decreases to 54% from January to March 2023.

La Niñas, Ms. Spaccio said, can have various effects, but other weather-making elements must be considered.

“Last year a moderate La Niña in Watertown in December there was kind o