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Spokane, Washington  Est. May 19, 1883

Jennings: “El Nino” affects area ski hill conditions

Bill Jennings Correspondent

I skied in boot top powder again Saturday, an experience I’ve been getting used to this winter. Meteorologists say we’re about halfway through the snow accumulation season in the inland northwest. Despite the snowfall angst brought on by the emergence of the strongest El Niño in recorded history, the winter of 2015-16 has been a pleasant surprise. So what’s going on?

During a typical El Niño year, temperatures are above normal and precipitation is below normal – not a good recipe for skiing and riding. But the “signal,” as meteorologists like to say, for temperature tends to be stronger. Precipitation is the wild card. Even with El Niño, temperatures are often cool enough at higher elevations for precipitation that does arrive to fall as snow.

California usually can expect to be drenched as El Niño drives a strong subtropical jet stream along a southerly path. The Pacific Northwest gets left relatively high and dry. But this winter the subtropical jet has been pushed north of its typical path. I found a possible explanation on The California Weather Blog, written by Daniel Swain, a PhD candidate in the Department of Earth System Science at Stanford University.

The effects of El Niño on our climate are partly the result of the “Hadley circulation,” a chain of events linking the tropics to the mid-latitude atmosphere. Warmer than usual ocean temperatures in the eastern tropical Pacific increase thunderstorm activity there, pumping a lot of heat into the upper atmosphere. This tropical air flows north and falls back to Earth around the latitude of Hawaii. Enhanced Hadley circulation during an El Niño increases the temperature differential between the tropics and the Gulf of Alaska, causing the jet stream to strengthen and aim south.

According to Swain, the Hadley circulation during this El Niño is stronger than expected. The descending air on its northern side is falling closer to California, which means that the enhanced temperature differential is occurring farther to the north than during previous strong El Niños. As a result, subtropical ridges forming between Hawaii and California have been more pronounced, pushing the jet stream across Northern California and the Pacific Northwest, rather than Southern California.

As scientists, meteorologists are reluctant to speculate about why the atmospheric response to El Niño this year has been different than what is usually expected. But Swain wrote, “It’s impossible to ignore the fact that global temperatures in late 2015 and early 2016 have reached their highest levels in human recorded history.”

Both NASA and the National Oceanic and Atmospheric Administration (NOAA) analyze trends in global temperature, based upon thousands of weather stations and ocean buoys distributed throughout the world. The two agencies released a report Jan. 20 showing 2015 as the warmest year since record keeping began in 1880. The strong El Niño’s persistence into this year raises the possibility that 2016 could set another record.

Could it be that our “normal” expectations for El Niño winters will have to change in the future? Taking into account the great skiing I’ve enjoyed up to this point, it’s tempting to think that maybe climate change isn’t such a bad thing. But that would be wishful thinking, based on an assumption that the climate is done changing. We can’t expect the conditions of the last few months to be the way it’s going to be.

Because of last winter’s bust, the persistent snowfall we’ve enjoyed so far may seem like an anomaly. But the snowpack is still slightly below normal. SNOTEL (snow telemetry) is an automated system of more than 730 climate sensors in the western U.S. operated by the Natural Resources Conservation Service. According to its readings, the snowpack as of Jan. 30 was 91 percent of normal in eastern Washington and most of north Idaho.

Going forward, the seasonal outlook hasn’t changed much from earlier forecasts: warmer than normal temperatures with a weaker signal for precipitation. However, John Livingston, Meteorologist in Charge of the National Weather Service in Spokane, once said he could tell me what the weather will do for the next 15 minutes, but anything further out is just an educated guess.

Perhaps Punxsutawney Phil had the answer. The celebrated groundhog predicted an early spring after failing to see his shadow Tuesday. Enjoy the snow while you still can.