The 32nd annual Winter Weather Forecast Conference in the OMSI auditorium was similar to all the others – although the specific forecasts vary. This year it took place on Saturday, October 19, presented as usual by the Oregon Chapter of the American Meteorological Society.
The similarities were in having four featured forecasters, and on how much mathematics go into arriving at these winter predictions! Forecasting more than a week or so in advance is largely a matter of finding which years have had similar weather conditions to this year up to now – establishing “proxy” or “analog” years, and then averaging how the weather turned out in the winter at the end of those years to predict what will happen this winter.
Added in are specific indicators, such as the current status of the El Nino/La Nina conditions of the surface water temperature in the eastern Pacific, the sunspot activity of the sun, the ENSO trend, and other specific indicators that each forecaster follows. All made corrections for the warming climate trend before producing a forecast.
All the forecasters this year agreed that we seem to be in a “weak La Nina” situation, at least through January. The first presenting forecaster, Noah Alvix from Portland’s National Weather Service office, said the national forecasters for NWS have concluded the precipitation this winter would be “slightly above normal” all winter, with normal temperatures for the season through January, and slightly below normal temperatures in February through April.
The forecaster who presents every year, Kyle Dittmer of the Columbia River International Fish Commission, a former NWS forecaster, and a teacher of meteorology at two local colleges, went into great detail on the indicators he follows and what they have led him to forecast for this year – which amounted to better snow in the mountains, a bit more water in the rivers, and four snow events – two of them moderate (up to three inches) and two minor (an inch or less) in Portland.
Tanis Leach, a recent graduate of Oregon State in Meteorology, presented the densest mathematical analysis and also the most aggressive winter forecast of the day, with many slides elucidating the many factors he considers. His analog years go back to 1886 and 1915, his top recent analog years are 1992 and 2016.
His forecast is for rain above average this winter, “with a hyperactive year possible” – we could get 51 inches before the season is over, he said. He expects average temperatures to be 1.5” to 2” below normal, with the lowest temperature potentially reaching 13 degrees at some point, and he thinks there could be a decent windstorm peaking slightly over 50 m.p.h. in some parts of the Northwest. He thinks the most active weather will center between January 1 and February 15.
And the fourth forecaster was April Elliott, meteorologist with Avangrid Renewables, who went through her indicators and proxy years, but concentrated on the snow forecast: “Chances are high we’ll experience a snowstorm this winter” in Portland, she said. She agreed that “January to February hold the highest likelihood, but a snowstorm in December is also quite probable this year”. She thinks the annual winter snow accumulation for Portland might quite possibly be about a foot overall.
KPTV Meteorologist Mark Nelson, who starts out each year’s meeting by recapping what actually happened in the past winter, ventured his own generalized thoughts about the upcoming winter as he finished: “We are ‘due’ for a snowless winter (but probably won’t get one in a La Nina year), a major windstorm, and a widespread flood.”
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