Washington state parched by one of driest summers ever

9/7/2006

Western Washington’s reputation as a soggy bastion for the web-footed is taking a beating this year, thanks to an unrelenting dry spell. And typically arid Eastern Washington is even more parched than usual.

Seattle-Tacoma International Airport recorded 2.12 inches of rain in the months of June, July and August, but only eight-hundredths of an inch of that total has come since July 1. It has been the second-driest July-August on record at Sea-Tac – in 1967, only 0.03 inch of rain was recorded for those two months.

The story is similar in many parts of the state, said Philip Mote, a University of Washington research scientist with the Pacific Northwest Climate Impacts Group and Washington’s state climatologist.

“The first half of June was pretty normal, and then the spigot just stopped,” Mote said. “We haven’t really had any of our normal rain since then.” A lot of places in Eastern Washington had only a small percentage of their normal precipitation during the last 90 days, zero to 25 percent of normal. It’s very dry.”

Bellingham had its driest July and August on record, with just 0.17 inch of rain, and Quillayute, on the Pacific coast, also had a record-dry July and August, with just 1.21 inches of rain.

It was the third-driest July and August at Chelan, the fifth-driest in Yakima and the sixth-driest in Hoquiam.

“It’s not just the total precipitation but the interval between precipitation events,” Mote said. “There were just dribs and drabs of rain in different parts of July and August. A lot of the time it was only a hundredth of an inch here or there.”

Even the rainy Olympic Peninsula has been severely affected. The sharply drier July and August held Quillayute’s total summer rainfall to just less than 4.5 inches, far below the normal of 8 inches.

“Unfortunately, the antiquated reporting process we have means there is a long delay before data from the best long-term weather stations reaches the Internet, so we cannot really diagnose an unfolding drought except at a handful of stations,” said Mote. “A month from now, the scope of this dry summer will be clearer.”

The reason for the dry spell, Mote said, might just be found in Alaska, where Juneau and Sitka are well above normal for the summer, particularly since Aug. 1. Sitka has received 21 inches of precipitation in the last three months compared with its normal of 13.5 inches.

“I’m speculating that the storms that usually wander south and miss Alaska during the summer just haven’t come our way like they usually do,” Mote said.

And it’s possible the fall and winter won’t bring much relief. Mote said scientists are keeping a close eye on conditions in the equatorial Pacific Ocean, where there are signs that an El Niño event could be brewing.

El Niño is the positive phase of a climate phenomenon called the El Niño Southern Oscillation. It has a dramatic impact on weather patterns around the world, and generally brings warmer, drier conditions to the Pacific Northwest.

Related Links
WA Dept. of Ecology WA Water Supply Information website WA Department of Ecology Water Resources Program
U.S. Drought Monitor
WRCC Standardized Precipitation Index
7-Day Average Streamflow Compared to Normal