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La Nina Prediction For Northwest Winter Now Neutral, Could Mean Warmer-Than-Average Temperatures
Posted on Friday, September 16, 2016 (PST)

NOAA is reporting that summer temperatures across the contiguous United States, June through August of this year, were the fifth highest on record, and a forecast for a La Nina weather pattern emerging has been downgraded to a “neutral” forecast that could mean continued warmer-than-average temperatures in the Pacific Northwest through the fall and winter.


Climate and weather experts recapped summer weather on Thursday, showing that the Northwest states of Oregon, Washington, Idaho and Montana all experienced warmer-than-average temperatures over the summer. But temperatures were well below record highs in California and most East Coast states.


Meanwhile, below-average or near-average precipitation was recorded in Columbia Basin states, with the exception of much-below average rainfall in Idaho for the summer.


A U.S. Drought Monitor report issued Sept. 13 shows that “abnormally dry” conditions persist in Oregon, Washington, Idaho and Montana, with scattered pockets of “moderate” or “severe” drought conditions.


NOAA’s Climate Prediction Center issued an updated El Nino/La Nino forecast on Sept. 8, scaling back earlier predictions for a La Nina forecast for the fall and winter to instead a “neutral” forecast.


Overall, “neutral conditions are slightly favored (between 50 to 60 percent) during the upcoming Northern Hemisphere fall and winter 2016-2017,” the forecast states.


“La Nina would normally lead to cooler temperatures across the Northwest,” said Peter Rosencrans, head of forecast operations with the Climate Prediction Center. “We have changed our forecast to go with slightly higher-than-average temperatures in the Pacific Northwest.”


Complicating the forecast picture for the Pacific Northwest is “The Blob” — a large pocket of warm water that has persisted in the northern Pacific Ocean since 2013.


Asked how The Blob may influence El-Nino/La Nina forecasting, Rosencrans said it has an influence, but the primary drivers behind El Nino or La Nina weather patterns are very powerful influences of water temperatures that are monitored by zones in the rest of the Pacific, including the tropics.


Rosencrans said it’s somewhat of a chicken-or-egg situation. The Blob is known to mostly be caused by persistent high-pressure weather that curbs churning currents in the ocean, causing warm water to settle in.


“The problem is the blob is caused by a decrease in Pacific wind speeds … But if you get a couple of good storms go through it can really churn,” Rosencrans said. “We could go back to La Nina and the conditions that go with it. We go with the data and where that takes us.”


Just over the last week or so, it became apparent the warm water mass known as The Blob has been re-established in the Pacific off the Northwest coast, as noted by Cliff Mass, a professor of atmospheric sciences at the University of Washington.


Water temperatures off the Pacific Northwest were “slightly above normal. Nothing exceptional” since early July, Mass stated on his blog, showing corresponding graphics from NOAA. “But fast forward to a few days ago (Sept. 8) and you will notice MUCH warmer temperatures over the Northeast Pacific. The Blob is back.”


The potential for warmer-than-average fall and winter over Columbia Basin states, as noted in the latest Climate Prediction Center report — raises concerns of water supply for fisheries managers. Generally, it can cause below-average snowpacks, earlier runoff periods and warmer water temperatures in rivers that support salmonids.


In addition, recent research by NOAA Fisheries and University of California, Santa Cruz, scientists assessed marine ecology effects of the 2015-2016 El Nino pattern and The Blob for the first time.


“Last year there was a lot of speculation about the consequences of ‘The Blob’ and El Nino battling it out off the West Coast of the United States,” said Michael Jacox, lead author of the research. “We found that off California El Nino turned out to be much weaker than expected. The Blob continued to be a dominant force, and the two of them together had strongly negative impacts on marine productivity.”


The combination of El Nino and The Blob were shown to slow the flow of nutrients from the deep ocean, reducing the productivity of coastal ecosystems.


Water temperatures at or near five degrees above average are also believed to be responsible for sightings of warm-water marine life far to the north of their typical ranges, and the temperatures likely contributed to the West Coast’s largest harmful algal bloom ever recorded in 2015.


The current forecast for El Nino/La Nino neutral conditions can make forecasting at the regional level challenging, said Laurel McCoy, a meteorologist with the National Weather Service in Portland.


Neutral conditions can pave the way for powerful storm systems that can cause widely varying weather, McCoy said.


“The Climate Prediction Center is thinking we’ll probably have temperatures slightly above normal but precipitation could go either way,” she said.


The last La Nina pattern recorded was in 2013-2014, before it gave way to the El Nino pattern that influenced the region in 2015-2016.


More information on El Nino/La Nina and The Blob can be found at:


-- CBB, July 15, 2016, “Study: The Warm-Water ‘Blob,’ Combined With El Nino, Depressed Marine Productivity Off West Coast”


-- CBB, April 10, 2015, “‘Warm Blob’ Of Water Off West Coast Linked To Warmer Temps, Disruption Of Marine Food Web”


-- CBB, Dec. 18, 2015, “Study: In Warmer Ocean Years Juvenile Salmon Consume More Food, But End Up Smaller, Skinnier”

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