Meteorologists say winter to be drier and warmer

After last year’s winter weather that one meteorologist at a conference last weekend called boring, this upcoming winter for the Pacific Northwest will be largely the same – a little drier and warmer than normal.

Four Portland weathermen spoke to a crowd on Oct. 27 at the Oregon Museum of Science and Industry. While one recapped last year’s weather, three offered their own predictions of what we can expect with this winter’s weather.

The weathermen offered their predictions at the 26 Annual Weather Forecast Conference, which is sponsored each year at OMSI by the Oregon Chapter of the American Meteorological Society (www.ametsoc.org/chapters/oregon).

In a disclaimer, Steve Pierce, Oregon AMS president, said the Oregon AMS doesn’t endorse any of the speakers. Still, each speaker defended his prediction from last year and all of those predictions were fairly close to what actually occurred during the 2017-18 winter.

The 2017-18 winter, the second consecutive La Niña winter, brought warmer and drier than normal weather to Western Oregon, according to Mark Nelson, meteorologist at KPTV/KPDX TV in Portland.

And this winter’s prediction is similar– to varying degrees warmer and drier than normal and with some variation – according to Tyree Wilde, meteorologist with the National Weather Service (NOAA) in Portland, Rod Hill, meteorologist with KGW-TV, and Kyle Dittmer, hydrologist and meteorologist with the Columbia River Inter-Tribal Fish Commission.

However, the difference in the forecast among the three weathermen is that Wilde and Hill are predicting that a mild El Niño will develop due to rising surface sea temperatures in the equatorial Pacific, while Dittmer is predicting an ENSO neutral year. According to NOAA, El Niño and La Niña together are called the El Niño Southern Oscillation (ENSO). Each is a periodic departure from normal sea surface temperatures (SST) in the equatorial Pacific Ocean.

“We see an El Niño developing in the equatorial Pacific,” Wilde said.

He predicted about a 75 percent probability that there will be a weak El Niño during the winter.

“No models show La Niña this year, and the El Niño should return to neutral by next summer.” He added that it could be the cooler central Pacific type of El Niño known as a Modecki El Niño.

In a weak El Niño, SSTs in the equatorial Pacific are only about 0.5 to 0.9 degrees Celsius higher than normal, whereas temperatures during a strong El Niño would be more than 1.9 degrees C higher than normal, according to Wilde.

He said that past El Niños have brought a variety of weather. Some have been dry and some have been wet with below normal precipitation in the Cascade Mountains.

His prediction for October, November and December this year is for above normal temperatures and below normal precipitation, as well as slightly below normal snowfall. Warmer and drier weather in January, February and March will shift to the Rockies, he said, while the Northwest will be more mixed. Still, he predicted slightly higher temperatures and lower precipitation than average, although mixed, and snowpack a little below average for the final winter months.

Hill said that historically and following the top five hot summers (2018 had 31 days in Portland when temperatures exceeded 90 degrees Fahrenheit), there has been only one wet winter: Typically precipitation has been near normal and a moderate El Niño has developed.

Hill’s prediction for Portland is for above normal temperatures (about 73 percent confidence), near normal precipitation, less than six inches of snow in Portland and the Willamette Valley, an 8 percent chance of a big snow storm and a 40 percent chance of a big wind storm with gusts to 60 miles per hour.

He also gave a 50/50 chance for normal snow pack on Mt. Hood, but there is cause for concern when looking at similar years: The snow year 2014-15 was a record dry year and the 2004-05 year was the second driest.

Dittmer said he looks at multiple indices when forecasting weather, including solar forcing, the multi-variable ENSO index and NOAA’s SST departure index, and he looks at the past 20 years of weather. With these variables, he is predicting an ENSO neutral year, but sometimes straying into El Niño territory one or two months.

"So I’m calling for an ENSO neutral with a flavoring of El Niño,” Dittmer said.

As the hydrologist for CRITFC, Dittmer also forecasts water supply, saying that it will be normal at The Dalles Dam. He predicts the January – July water supply forecast at the dam to be 101 million acre feet, which is 100 percent of normal.

“We should have an adequate water supply for fish,” he said.

As for snow, Dittmer said that “the personal economics are in your favor if you get a season ski pass this year,” although snowfall will be a little less than last year’s in the Cascades. He is predicting that Government Camp on Mt. Hood will see about 240 inches of snow, or about 117 percent of normal (November – May). Hood River could see 23 inches of snow, or 121 percent of normal.

Looking at a sea surface temperature map, Nelson showed what could be another warm blob developing in the Gulf of Alaska. However, he didn’t offer an interpretation or forecast of what the new blob may mean for either weather or Alaska fisheries.

Unusually warm ocean temperatures, referred to as "the Blob," encompassed much of the West Coast beginning about 2014, combining with an especially strong El Niño pattern in 2015. The warm conditions have now waned, although some after-effects remain.