What will Sisters' winter be like?

Predicting the weather is a tricky business. Just trying to figure out how the atmosphere will behave two or three days out is sometimes fraught with uncertainty.

Imagine, then, anyone so bold as to peer far beyond the normal forecasting horizon-say a month or even a season into the future. Yet, such was the case when a group of meteorologists and climatologists gathered together on Friday October 24, at the Oregon Museum of Science and Industry in Portland.

The event was the annual "what will the winter be like?" meeting put on by the Oregon Chapter of the American Meteorological Society. Four speakers shared with the audience what they think Old Man Winter has in store for the Pacific Northwest this season. They included Kyle Dittmer, hydrologist and meteorologist for the Columbia River Inter-Tribal Fish Commission, Pete Parsons, meteorologist for the Oregon Department of Agriculture, George Taylor, of Applied Climate Services and former state climatologist, and Steve Todd, meteorologist-in-charge at the National Weather Service in Portland.

Mark Nelsen, Chief Meteorologist for KPTV in Portland, began the proceedings by recapping the winter of 2007-08. The period from November 2007 through March 2008 was characterized by colder than normal temperatures and average precipitation amounts for many regions throughout western Oregon. November, however, was on the dry side and February was drier and warmer than normal. December was particularly wet as a string of cold storms swept in from the Pacific, producing frequent low-elevation snow.

A persistent westerly flow aloft brought significantly above-normal snowfall to the Cascades in December, January and March. This enhanced the rain shadow effect which produced drier than normal conditions in central Oregon, December being the exception when it was slightly wetter than average. Records at Redmond show that temperatures were near normal for the winter, but it was slightly colder in January and March. Except for a strong windstorm that impacted the northern Oregon coast in December, the Northwest was spared the extremes of Mother Nature, such as flood-producing rains from a Pineapple Express or very frigid temperatures from an outbreak of arctic air.

But that's old news. What lies ahead?

All of the weather prognosticators agreed that the best indicator of what our upcoming winter will be like is to look at what's going on in the mid-Pacific Ocean near the equator. When sea surface temperatures in this region are warmer than normal a few months before the onset of winter, we tend to have warmer and drier conditions.

This is known as an El Niño.

Conversely, when the water temperatures are colder than average, our winters are usually colder and wetter. This is called a La Niña. Currently, the ocean temperatures are near normal, meaning we are neither in an El Niño or a La Niña.

According to Todd, this neutral condition tends to introduce more variability in our winters, "...and we also tend to have some of our bigger Valley snow events."

Parsons believes that the odds of a severe cold snap throughout the Pacific Northwest go up during a neutral winter.

"The most likely time for a long cold snap is late December and January," he said.

Dittmer, who includes sunspot cycles to come up with his forecasts, foresees a cool and wet start to winter, with temperatures and precipitation trending to more normal values as the season progresses. He is also calling for three minor Willamette Valley snowfalls, "...all between one and half and three inches apiece."

Taylor thinks this winter will not be as protracted as last winter, stating, "winter will come early and leave early this year."

So, does anyone really know what our weather will be like several months from now? Probably not. The physics of the atmosphere is extremely complex, and our current understanding is simply not sufficient to permit pinpoint accuracy. But who's to say that scientific breakthroughs won't be made in the not-too-distant future that will result in much better weather and climate forecasts. Until then, weather is such fun to speculate about.

Ron Thorkildson is a retired meteorologist living in the Sisters area.