Unusual La Niña may be forming in the Atlantic: ‘almost unprecedented’

(NEXSTAR) – As we await the arrival of La Niña in the Pacific, there may be one already brewing in the Atlantic.

Researchers still need to collect temperature data throughout August to determine if a La Niña has in fact formed over the equator in the Atlantic Ocean, but this summer has already been unusual, said Franz Philip Tuchen, a postdoctoral associate with the Cooperative Institute for Marine and Atmospheric Studies.

The year started with record high sea surface temperatures, topping 86 degrees, before quickly and dramatically cooling off. This type of whiplash is more dramatic than any year before, Tuchen recently wrote.

“It’s almost unprecedented in the time series that we have, and that’s longer than 40 years,” he told Nexstar.

If the Atlantic sea surface temperatures stay where they were around June and July, it’ll officially constitute a La Niña in the Atlantic.

Unlike the La Niña patterns we’ve seen take hold in the Pacific repeatedly in recent years, we haven’t seen a La Niña in the Atlantic in over a decade. The last time we saw an Atlantic La Niña was the summer of 2013, Tuchen said.

Another big difference between Pacific and Atlantic La Niñas is the scope of their impacts. While a Pacific La Niña has global weather implications, including all around the U.S., “everything is a bit smaller” with an Atlantic La Niña, Tuchen explained. They don’t last as long and really only have regional weather impacts.

A strong La Niña would impact rain over northeastern Brazil and western Africa – the land masses closest to the equatorial Atlantic – but not here in the States.

Meanwhile, a La Niña in the Pacific usually means dry, warmer-than-average conditions across the southern half of the United States, more precipitation for the Pacific Northwest and Ohio Valley, and extra-cold weather for northern states. It can also fuel strong hurricanes.

That type of La Niña is favored to form this fall and strengthen as we head into the winter.