La Niña prepares to soak Pacific Northwest
November 2, 2010
By Warren Kagarise
The extended forecast calls for La Niña.
La Niña means unusually cold temperatures in the Pacific Ocean near South America — and colder-than-normal temperatures and greater-than-normal rain- and snowfall in Western Washington.
Ni Cushmeer, a National Weather Service meteorologist in Seattle, said residents should expect “classic La Niña” conditions to start in November. The combination of soggy conditions and cold temperatures has emergency planners concerned about floods and snowfall.
“As we go into a La Niña weather pattern, we expect that we’re probably going to have more rain than usual from October to December, it’s going to be colder than normal from January to March and we’re also going to see an increased precipitation potential in those months of January to March,” King County Emergency Management Director Hillman Mitchell said. “Throughout the whole winter, we’re looking at a wetter pattern and a colder pattern toward the latter part of the winter.”
La Niña is considered the opposite of El Niño — a phenomenon defined by unusually warm temperatures in the equatorial Pacific. In the Pacific Northwest, El Niño tends to mean drier winters.
Though a rain-sodden winter is almost a sure bet, Cushmeer said greater-than-normal snowfall could be more difficult to forecast.
“It doesn’t necessarily mean that we’ll get a lot of snow in the lowlands, although during moderate to strong La Niña conditions, there have been instances where there’s been quite a bit of snow in the lowlands, even in the Seattle area,” she said.
In the Seattle area, normal precipitation amounts to 37.07 inches per year. The annual snowfall tally is 8.1 inches per year — though the number can be off, as evidenced by the recent flake-free winter. (Meteorologists use data collected at Sea-Tac International Airport for official climate records in the region.)
“We can count on it end up being cooler than normal, and we can count on above-normal rainfall, but as far as above-normal snowfall, that can go either way,” Cushmeer said.