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The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883

El Niño conditions heading our direction

Michelle Boss Correspondent

El Niño is in the news again. The waters in the equatorial Pacific are warming, and somehow this event will affect weather all across the U.S. and across the globe as well. The amount of rain in Southern California, the amount of snow here in the mountains, the number of storms in the Midwest, even the frequency and intensity of hurricanes in the Atlantic will be affected by the El Niño phenomenon. A basic understanding of the roles that heat and water play in our atmosphere will help you see how this little “fever” in one area of the Pacific could make a difference in the weather across the Inland Northwest.

The sun is the source of power that fuels our weather. This heat energy is needed for thunderstorms, hurricanes and even blizzards. The sun does not directly heat the air, though. The sun heats the Earth’s surface, which heats the air above it. It is the differential heating from one place to another that results in the movement of air masses we know as warm and cold fronts. Land masses heat up and cool down quickly when compared with bodies of water. Whereas land surfaces absorb energy in a relatively shallow layer, bodies of water, through mixing, can transfer heat energy to great depths. With water making up approximately 70 percent of the Earth’s surface, ocean-atmosphere interactions become very important in influencing the weather on a global scale. With that in mind, it makes sense that when ocean temperatures change, that change affects the atmosphere above it. A study of El Niño years throughout the last century has shown a general correlation with El Niño conditions to particular weather patterns across the Inland Northwest. Research has shown that during many El Niño winters the weather was warmer and drier than usual.

In an El Niño, or warm episode year, changes in the jet stream steer storms to the south into California or cause storms headed our way to weaken. The winter of 2004-05 is a good example, where warmer and drier weather were the rule from November into February. However, not all El Niños are of the same intensity, which is measured by the degree of ocean warming that occurs. It turns out that during very strong El Niño years, in particular the winter of 1982-83 and 1997-98, the weather turned out to be milder but wetter than usual. In both 1982 and 1983, Coeur d’Alene received between 30 and 31 inches of precipitation, with the normal being 26.11 inches. Snowfall for the winter of ‘82-‘83 was only 42 inches, with the normal being nearly 67 inches. In 1997, Coeur d’Alene received 32.98 inches of precipitation and then 28.37 inches in 1998. Snowfall, however, for the ‘97-‘98 season was only 30 inches. Those strong El Niño years brought plenty of rain but not so much snow.

So far, this year’s El Niño is a weak one, but according to the National Oceanic and Atmospheric Administration’s lead El Niño forecaster, it could strengthen to a moderate event by winter. With that in mind, it looks like we have a pretty good chance of seeing warmer-than-normal weather this winter. As far as precipitation goes, don’t count the ski season a bust just yet. Milder weather may mean rain for the valley locations, but the mountains could still get a fair share of snow. I for one wish skiers all the snow in the world in the mountains, though I’d much prefer to deal with rain on the roadways in Spokane and Coeur d’Alene.

Next week, as we get ready to enter the month of October, we’ll take a look at the climatology of autumn in the Inland Northwest.