YAKIMA — The summer of 2007 was the driest on record for the east slopes of the Cascades in central Washington, though the region still managed to escape the drought conditions and catastrophic forest fires that typically accompany dry years.
Precipitation at five Yakima Irrigation Project reservoirs this summer was recorded at 18.91 inches between April and September, just 43 percent of average. The previous record low was 20.72 inches in 1939. Record-keeping began in 1912.
But the good news is that all irrigators received a full supply of water and the central Washington fire season was one of the quietest in years.
Officials say the reason is a combination of timing and luck.
Richy Herrod, deputy fire management officer for the Wenatchee-Okanogan National Forests in Wenatchee, said there was much less lightning activity to spark large fires this summer. When lightning or human-caused fires did get a start, the weather conditions weren’t right for fires to quickly spread because there was more moisture in the air and winds were light.
Total acreage burned in the Okanogan and Wenatchee forests, and on land managed by the southeast region of the state Department of Natural Resources, was 14,777 acres, compared with 293,137 acres in 2006.
The southeast region covers Chelan, Kittitas, Yakima and Klickitat counties.
“Part of it was sort of luck. A lot of things have to line up to get large fire growth,” he said. “Dry fuels are just part of the recipe.”
Herrod said the lack of lightning appears to be related to a weather pattern called the four-corners high pressure system, which tends to pull subtropical moisture in a northeasterly pattern toward the Northwest. The system centers on the area where the states of Utah, Colorado, Arizona and New Mexico meet.
That system, while generally in the same location this year, appeared to wobble slightly, said Bob Tobin, senior forecaster for the National Weather Service in Spokane, which tracks fire weather. The change sent more of the moisture stream toward eastern Oregon, northern Idaho and Montana, areas that saw more lightning and more wildland fires this summer.
Whether 2008 turns out the same remains to be seen. The national Climate Prediction Center, charged with estimating long-term weather patterns, predicts a La Nina weather phenomenon will affect weather in the western United States this winter.