La Niña getting strong, expected to stay for fall | National

The National Oceanic and Atmospheric Administration predicted Aug. 11 that a La Niña has a strong chance of staying through the end of the year, but may fade in the middle of winter.

La Niña, linked to cool and wet weather in the Northwest, has prevailed the last two winters. La Niña rarely reigns for three consecutive winters. That has occurred only twice since 1950.

NOAA said this La Niña has a 60% chance of remaining in place through December. By January, the chances of a La Niña drop to 47%.

The La Niña should influence fall and early winter weather, though the rarity of a third-straight La Niña makes long-range forecasts difficult, Washington State Climatologist Nick Bond said.

“There have been so few cases, we can’t really generalize,” he said. “Right now, I’m very guardedly optimistic that we’ll have a decent start to the water year,” which begins Oct. 1.

Below-average sea-surface temperatures along the equator in the Pacific Ocean trigger a La Niña. Above-average temperatures trigger an El Niño.

A La Niña is linked to cool and wet weather in the northern tier of the U.S., but warm and dry seasons in the southern tier. La Niña exerts its greatest influence in the winter.

A month ago, NOAA anticipated La Niña might fade in the fall but come back in the winter. In July, however, the ocean cooled, after warming toward normal in June.

NOAA now estimates an 86% chance the La Niña will stay through September and an 80% chance though October.

By January, it’s a tossup whether the sea-surface temperatures will be cool or neutral. NOAA sees almost no chance for an El Niño to form.

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