The windstorm that swept through the Northwest on Sunday had some of the wind speed and low pressure associated with tropical hurricanes, according to the National Weather Service in Seattle.
We nearly witnessed a hurricane.
The spring storm that rushed through the Northwest on Sunday, bringing wind gusts as high as 80 mph on the coast, showed a classic spiral pattern and extreme low pressures more familiar to Florida.
“Storm looks like a hurricane! The central pressure is deeper than expected, 978 mb,” the National Weather Service vented on Twitter around 1:30 p.m., with a photo of the eye of the storm offshore from Olympic National Park.
The intensity was expected to peak at 4:30 p.m., and dissipate over Vancouver Island in a few hours, said Jay Albrecht, a weather-service meteorologist in Seattle.
The edges of the spiral extended Sunday afternoon from Arlington to just north of Hoquiam, he said, taking in large areas of Puget Sound and the Pacific Coast.
Gusts reached 82 mph at Destruction Island on the north Pacific Coast, 74 mph at Moclips beach just north of Grays Harbor, and 62 mph at Discovery Park in Seattle, he said.
Winds were shifting direction around the epicenter, which passed Forks at around 3:30 p.m. On the Olympic Peninsula, wind directions pivoted during the day from northeast, to northwest, to west, Albrecht said.
The low-pressure center of the storm attracts winds inward, but the rotation of the earth counters that tendency by pulling wind directions “to the right,” he said. So on the coast, winds began from the south, then kept shifting as the eye moved toward Canada.
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On the edge of the storm, the Seattle area received winds from the south, the same direction as during any ordinary rainstorm.
Albrecht called Sunday’s episode an “extratropical storm,” meaning outside the tropics but with similar characteristics. Gusts hovered near the 74 mph benchmark that defines hurricane-force winds, he said.
But there were big differences:
A hurricane can last for weeks, but this Northwest storm took about one day to travel from northern California to British Columbia, Albrecht said. The center of the action sped north at about 40 mph through Washington state, compared to 10 mph or 15 mph for a tropical hurricane.
Also, hurricane winds are sustained in a gulf-type storm. Here, gusts were brief.
The low atmospheric pressure of 978 millibars off the Olympic Peninsula compared to 990 or 1,000 millibars during a basic windstorm, or 1,015 millibars on a nice March day, Albrecht said.
The weather system arrived four hours earlier than meteorologists expected, so the worst phase ended by late afternoon, instead of around 9 p.m. Sunday.
It followed another windstorm last week, when gusts reached 60 mph in the Puget Sound area.
Low pressures are a product of the global water cycle, which produces the familiar jet stream over the Pacific. Winds in the upper atmosphere, at 30,000 to 40,000 feet elevation, have reached 230 mph to 240 mph recently, Albrecht said. The jet stream has been intense, perhaps because of the El Niño seasonal pattern, he said.
As for the spiral effect — winds that gain speed near the storm’s center — he compared that to a figure skater who spins faster by retracting her arms.