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NW Fishletter #363, November 7, 2016

[8] Reappearance Of La Niña And The Blob Has NW Weather, Fish Implications

The combined ocean and atmospheric system reflected ENSO-neutral in September, meaning neither El Niño nor La Niña, but the trends now clearly lean towards La Niña conditions, the Climate Prediction Center said Oct. 13.

Forecaster consensus is now that La Niña has a 70-percent chance of developing in the Northern Hemisphere this fall and a 55-percent chance of persisting during winter 2016-2017.

In early September, the center, a branch of NOAA's National Weather Service, put the odds for a La Niña period at 40 percent. As a result, the weather service cancelled its La Niña watch, which had been in place for several months.

La Niña is any five-month stretch when sea-surface temperatures in the middle of the equatorial Pacific remain half a degree Celsius below normal. It often translates to stormy weather with colder and wetter conditions in the Pacific Northwest.

However, meteorologists warn, no two Las Niñas are alike.

The last La Niña hit in 2010-2011 and was relatively moderate. It was followed in 2015-2016 by an El Niño that produced hot and dry conditions across the Pacific Northwest and California.

In another unexpected reversal, NOAA climatologists are now saying the area of unusually warm water off the coast of Washington and Oregon, known as the "blob," has not dissipated.

The blob is produced by strong and persistent high pressure over the northeastern Pacific.

Earlier this year climatologists thought this large, warm-water area was gone, broken down by last winter's El Niño conditions.

"The blob has regained its strength," University of Washington professor and meteorologist Cliff Mass said on his blog.

"Its direct impact on our weather is modest," he said, "but it has implications for marine life."

Brian Burke, who studies ocean conditions and their effects on salmon and steelhead survival for NOAA Fisheries' Northwest Fisheries Science Center, told members of the Northwest Power and Conservation Council Oct. 11 that the blob, which began developing in 2013, has changed the ecology of the ocean and the food available to salmon and steelhead.

Burke said salmon were eating less nutritious species of fish.

The warm-water blob and its accompanying changes in the food web have also changed the behavior of sea lions, said NOAA researcher Robert Anderson at the October Council meeting.

Anderson said adult male sea lions are now entering the Columbia River to eat smelt and spring Chinook before they return to California breeding grounds in late spring. This year for the first time, more than 40 Steller sea lions were observed near Bonneville Dam in September, Anderson said.

On the question of how long the blob will last, Mass said it "may have some staying power." -Laura Berg

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Publisher/Editor-in-Chief: Mark Ohrenschall, Editor: Laura Berg
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