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
Four Portland weathermen spoke to a crowd
Saturday, 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
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
“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
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 Niño’s have brought a
variety of weather. Some have been dry, some have been wet, but 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 6 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
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 (the
last slide of his presentation), 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 Nino pattern in 2015. The warm
conditions have now waned, although some after-effects remain.
Presentations are at https://oregonams.wordpress.com/2018/10/30/presentations-26th-annual-winter-weather-conference/
-- CBB, July 20, 2018, “Climate Forecast
Favors Onset Of El Nino, Could Mean Warmer Winter In Northwest,” http://www.cbbulletin.com/441141.aspx
-- CBB, October 27, 2016, “Expectations Of
Wetter Conditions, Mountain Snow Suggesting Basin Water Supply Above Normal,” http://www.cbbulletin.com/437864.aspx
-- CBB, October 30, 2015, “Winter Weather
Forecast Conference: Yes On Warmer Winter, Jury Still Out On Amount Of