Sierra could use strong El Niño winter
August 7, 2004
Snap. Crackle. Pop.
Weather stations up and down the Sierra Nevada that measure moisture show the forests are the driest they’ve been in 30 years, officials say.
“They are coming near records or breaking records every day,” said Jack Blackwell, regional forester for the U.S. Forest Service, Pacific Southwest region. “It’s our fifth year or sixth year of drought and we’re probably looking at another dry one coming up.”
But maybe not.
The National Oceanic & Atmospheric Administration expect El Niño conditions to develop during the next three months.
An El Niño is a warming of the Pacific Ocean off South America that influences global weather patterns. Some years it produces a wetter than normal winter in the Sierra while in others it has resulted in average or below-average precipitation.
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“If a strong El Niño were to develop it would give us a good chance for more snowfall and help alleviate some dry conditions we’re seeing,” said Brian Brong, a weather forecaster in the Reno office of NOAA. “But for us to get rid of the drought and dry conditions we’ll need several years of above-average snowfall.”
Jan Null, adjunct professor of meteorology at San Francisco State University, said information announced by NOAA should be taken lightly.
“The middle of the Pacific ocean is warmer than normal right now,” Null said. “But it’s right at the minimum threshold, as cold as an El Niño could be. It’s a very iffy proposition right now.”
El Niño walloped the basin in 1997, causing floods at South Shore on New Year’s Day and leaving more than 51 inches of precipitation in its wake that year. The average annual precipitation – or water content drawn from snow and rain – for the basin is about 35 inches, said Tom Cylke, a meteorologist for the National Weather Service in Reno.
Dry winters are bad for the ski industry because they leave less snow to ski and board on. Dry times, however, mean good times for bark beetles. In the late 1980s, with Tahoe in the midst of an extended drought, the insects devoured nearly one-third of the conifers in the basin.
The standing dead trees increased the danger of wildfire and many of them had to be removed by helicopter. There are no signs that a widespread beetle infestation is developing in the basin. But any forest packed with too many trees, like conditions are in the basin, is more vulnerable to bark beetles.
“People blame the insects,” Blackwell said, “but really there are too many trees for the available moisture in the soil.”
The last and probably the largest sign that things are dry in the basin is the level of Lake Tahoe. The office of the Federal Water Master in Reno estimates the lake will drop to its rim – 6,223 feet above sea level (on Monday it was about six-tenths of a foot above 6,223) – before the end of September. Last year the lake reached its rim Nov. 20.
– Gregory Crofton can be reached at (530) 542-8045 or by e-mail at firstname.lastname@example.org