Two storms will sock the Pacific Northwest between Thursday night and the weekend, unloading over a foot of rain in some areas. The second and much more powerful storm, expected Saturday, is a monster which could unleash destructive winds if it hits the region head-on.
“So much intense weather is going to hit us, that I don’t know where to start,” writes Cliff Mass, a professor of meteorology at the University of Washington.
Mass warns Saturday’s windstorm has the potential to be a “historic event.”
The storm is actually the former Super Typhoon Songda which has transitioned into a potent mid-latitude cyclone. “It poses the threat of a major Western Washington windstorm,” the National Weather Service says.
How high the winds get and where the winds are strongest will depend on its angle of approach and where it makes landfall. Some models, like the European, show the storm smashing into western Washington Saturday evening. Others track it northwest of the Olympic Peninsula over southern Vancouver Island. “All these solutions look pretty threatening,” the Weather Service says.
— NWS Seattle (@NWSSeattle) October 12, 2016
The European model would thrust the strongest winds, exceeding hurricane-force (74 mph), just south of the storm center along the west coast of Oregon, but tropical-storm-force winds would still lash coastal Washington and Puget Sound.
The European model simulation of the storm (see the animation at the top of this post) shows a textbook meteorological “bomb,” defined as a storm whose central pressure falls at least 24 millibars in 24 hours. The lower the pressure, the stronger the storm. It shows this storm’s pressure dropping about 30 millibars between Friday night and Saturday night from 998 mb to 969 mb — a level equivalent to many Category 2 hurricanes.
The GFS model predicts a less severe storm than the European model and would bring tropical storm-force winds to the west coast of Washington rather than Oregon.
In a worst-case scenario on Saturday, “Puget Sound could get a very major hit with massive power outages and damage,” Mass says. “This is a very dangerous storm.”
In addition to howling winds and torrential rain, towering waves of 30 feet or higher are possible along the coast, which could cause beach erosion and coastal flooding, the Weather Service says.
The storm’s predicted evolution shares similarities to the 1962 Columbus Day storm which also began as a typhoon, named Freda. The Seattle Times offers this retrospective on that storm, which killed at least 46 people:
In 1962, wind speeds were recorded at 83 mph at West Point in Seattle and passed 150 mph along the Washington and Oregon coast. But the top gusts are not known because the measuring instruments were damaged or destroyed.
Even the World’s Fair closed due to high wind. Some people were allowed to stay at the Food Circus (now called the Armory) if they lived south of Seattle, where the damage was worse, according to HistoryLink.
While the worst weather is expected Saturday from the second storm, the first storm, expected Thursday night, is no slouch. The National Weather Service forecast office in Seattle is calling for one to three inches of rain and winds up to 40 to 60 miles per hour. It has hoisted a high wind warning for Seattle and says tree damage and scattered power outages are possible.
Thursday night’s storm and the blockbuster feared Saturday are embedded within what’s known as an atmospheric river — a 3,500-mile-long plume of moisture sourced from the tropics. The fire hose is pointed squarely at the Pacific Northwest.
Total rainfall through Sunday could exceed a foot at high elevations and half a foot closer to sea level, which could lead to flooding in some areas.
At high altitudes, a powerhouse jet stream with winds to 200 miles per hour is steering this river of moisture and energizing the storms flowing along it.