September 12, 2010 in Idaho Voices

Strong La Niña may bring wetter-than-normal fall to area

Michelle Boss
 

Most people associate the fall season with things like “back-to-school” and college football. Seeing as we’re in the midst of these things, the cloudy skies and cooler temperatures might seem right on track. But summer is not officially over yet, and we typically don’t see the most dramatic cascade into cooler, wetter weather until about the first week of October. Average highs are still supposed to be in the mid-70s with average lows in the upper-40s. This past week we’ve seen afternoon temperatures consistently about 10 degrees below normal. Fortunately, for gardeners, most areas have not seen overnight lows drop below freezing.

The latest information from the Climate Prediction Center indicates that La Niña strengthened in August and would last at least through early 2011. For the fall season, La Niña conditions usually mean wetter-than-normal weather for the Pacific Northwest. For the tropical Atlantic, a more active hurricane season is usually forecast during La Niña years. Using a calculation called ACE, for accumulated cyclone energy, which measures the combined strength and duration of tropical storms and hurricanes, August activity was about 60 percent above normal. While there have been three hurricanes so far, Alex, Danielle, and Earl (the last two considered major hurricanes), it should be noted that even tropical storms that do not reach hurricane status can be very dangerous and result in fatalities as well as millions of dollars in damage.

Islands and coastal areas usually receive the brunt of tropical storms’ winds and water, but torrential rains and associated flooding can occur much farther inland, when the storm is nothing more than a remnant area of low pressure. This was the case with Tropical Storm Hermine, whose remnants produced tornadoes in both Texas and Oklahoma, with at least one tornado in the Dallas area. Flooding was responsible for at least two fatalities in Texas, and heavy rains are expected to impact folks from Arkansas to as far north as Kansas.

Locally across the Inland Northwest, September is usually a dry month. Average precipitation in Spokane is similar to July, about .76 inches. Coeur d’Alene sees a bit more rainfall, averaging 1.58 inches, which is about 50 percent more than what is seen in July. The latest computer models, however, do not show much in the way of wet weather through this upcoming week. If you’re thinking of getting your sprinklers blown out sooner than later, don’t count on mother nature to pick up the job of keeping your lawn watered. It does look like some milder weather is on the way, which should bring us highs back into the mid-70s. Enjoy it while you can!

Michelle Boss can be reached at weatherboss@comcast.net.


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