he weather word of the day is bombogenesis.
What, you ask, is that?
It’s when a cyclone — a rotating system of clouds and thunderstorms, like the one about 300 miles off the Washington coast — rapidly intensifies over a 24-hour period, according to the National Weather Service.
This already low-pressure system will continue to intensify and drop in pressure over the Pacific Tuesday. Meteorologists expect it to remain well offshore, but the system is strong enough to cause a rapid increase in easterly winds across Western Washington beginning sometime between 4 p.m. and 7 p.m.
“If you notice it’s not very windy yet in the middle of the afternoon, just be patient,” the weather service said.
Easterly winds are expected to gust up to 60 mph along the coast, the western Strait of Juan de Fuca and much of Puget Sound lowlands east of Lake Washington.
High wind warnings are active for these areas through early Wednesday morning, and widespread power outages are expected. Damaging winds will blow down trees and power lines, and travel will be difficult, according to the weather service.
Waves over the outer coastal waters may reach heights of up to 30 feet, with 12- to 18-foot seas closer to the coastline, the weather service said. There’s a storm warning in effect as such.
Wind gusts could be even stronger, up to 70 mph, in the Cascades foothills along the Interstate 90 corridor.
Meteorologists are also watching for mountain waves flowing off the Cascades and into the foothills, which could impact airport terminals near Puget Sound.
Mountain waves are updrafts and downdrafts that occur in mountainous areas when rapidly flowing air runs into a steep front. They can produce very strong wind gusts in narrow areas and turbulence.
Possibility is low — less than 15 to 20% — “but it is something to be aware of,” the weather service said.
For areas outside the high wind warning, such as Seattle, wind advisories for gusts up to 50 mph are in effect Tuesday afternoon through early Wednesday.
Strong easterly windstorms are not common outside the Cascade foothills, the weather service said.Due to the terrain, there are many places, like Edmonds and south of Tacoma, that may be sheltered from winds Tuesday.
Easterly winds in the lowlands do not typically ramp up, the weather service added, but Tuesday afternoon and evening could feature quick accelerations.
Rain, too, will spin out ahead of the system, wetting pavement in the southwest portion of the state Tuesday afternoon. By the evening, rain will greet all of Western Washington.
Snow elevations will remain below pass levels Tuesday, and a rare blizzard warning is in effect for the Cascades above 2,500 feet Tuesday night into Wednesday morning.
Up to a foot of additional snow and winds gusting up to 60 mph will make for white-out conditions. Travel in the passes will be “very difficult to impossible,” the weather service said.
Winds will start to subside by Wednesday morning, the weather service said.
Low-pressure systems are typical for this time of year, although stronger bomb cyclones, like Tuesday’s, are less common. The region has been seeing one or two a year recently, like one early last year that soaked California, flooded neighborhoods, knocked out power for tens of thousands and contributed to two deaths.
This week’s system spans much of the West Coast, from Vancouver Island to Northern California.
The weather service advises people to prepare their homes by trimming trees, repairing loose siding and shutters and securing loose items.
When wind blows, the safest place is indoors in an interior room, and away from windows,