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Pattern shift points to less harsh winter

Thu., Sept. 24, 2009

Although fall officially started two days ago, many of us continue to enjoy the beautiful weather with very warm temperatures. While September typically brings normal high temperatures in the lower 70s, Spokane International Airport, as of early Tuesday, had observed nine days at or above 80 degrees, with three of those days at or above 90 degrees during the month.

Despite the great weather, I’m hearing this question more frequently: “What’s it going to be like for this upcoming winter?” Well, I don’t think we’re going to see seasonal snowfall totals anywhere near the record levels of the last two seasons.

The winters of 2007-08 and 2008-09 were undoubtedly two of the toughest in recorded history due to the heavy snowfall. During those years, we had a La Niña, the cooler-than-normal sea-surface temperature event in the south-central Pacific Ocean. There was also very low sunspot activity (storms on the sun) that may have contributed to the cold and snowy weather across our region and much of the northern U.S. and southern Canada.

This year, we still have the very low sunspot activity. With the exception of two days, Aug. 31 and Sept. 1, there have been no solar storms since July 11. However, there is a moderate El Niño along the West Coast of South America and the equatorial regions. The warmer than normal sea-surface temperature event should counteract the low solar activity for this upcoming winter season, giving us below-normal snowfall.

During El Niño years, many of the storms from the Pacific Ocean move to the south into California. About 70 percent of the time, the Inland Northwest experiences milder winter seasons with less snowfall when there is an El Niño. For example, during the past four El Niño events, in 2006-07 the airport received 34 inches of snow. In 2004-05, only 25.8 inches of snow fell. In 2002-03, only 21.2 inches were measured, with 18.3 inches of snow observed in 1997-98.

We’re already seeing the effects of the new El Niño as the subtropical jet stream has strengthened in recent weeks. As a result, the worst drought in the southeastern U.S. has been broken due to record rains. As much as 20 inches of precipitation has saturated parts of Georgia and been termed “100-year rains.”

In the near term, we should continue to see drier- and warmer-than-normal weather into early October. Showers should start to become more numerous by the middle of next month.

Contact Randy Mann at randy@longrange, or go to www.longrange for additional information.


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