December 5, 2000
Seattle temperatures won’t drop below zero, UW scientist says
Rumors that record sub-zero temperatures will hit Seattle next week are based on sketchy data and have virtually no chance of coming true, a University of Washington scientist said today.
“This will be the coldest weather we’ve had in Seattle in a few years, but I’d be more worried about pipes freezing and that sort of thing than about having the coldest day in Seattle history,” said Cliff Mass, a UW atmospheric sciences professor.
The coldest-ever temperature in Seattle is zero, recorded at Seattle-Tacoma International Airport on Jan. 31, 1950.
But long-term forecasts posted on at least one Web site on Monday predicted that on Dec. 12 the low would hit minus 7 Fahrenheit and the next day would drop to 12 below zero.
Those numbers had been changed significantly by Tuesday morning, with the web site predicting a low of 14 degrees on Dec. 12 and 4 degrees the following day. However, many people who had seen the original numbers were sending queries to a variety of local agencies, Mass said.
He said it is quite possible that some places in the Seattle region will see the mercury dip into the lower teens during the next few weeks. The faulty forecast, he said, resulted because of a computer model that does not correctly simulate important local effects.
“That model doesn’t have the Cascades, which block cold air coming across from Eastern Washington,” Mass said. “Our skill at forecasting one week ahead of time is relatively low.”
A frigid arctic air mass is taking shape over the Yukon, in far Northwestern Canada, and it will be pushed south by a strong, stable ridge of air over the eastern Pacific. Part of the arctic air mass will spill into Washington and the rest will move east of the Continental Divide into Montana.
Mass expects Seattle to record the coldest temperatures it has had in the last three to five years, but he also expects conditions to remain generally dry. However, he said he and other scientists would have a much better idea later this week, as the crucial time draws nearer. Forecasts are increasingly inaccurate the farther they look into the future, he said.
“We may be able to forecast, but it doesn’t mean it’s skillful for these long time frames,” he said.
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For more information, contact Mass at (206) 685-0910 or cliff@atmos.washington.edu
