Weathercatch: Pacific Northwest’s ‘bomb cyclones’ tamer than East Coast’s

The Pacific Northwest was blissfully insulated from the recent “bomb cyclone” that clobbered the East Coast on Jan. 4, along with the stunning cold spell that followed. Sure, our region experienced some freezing rain, fog and the heaviest snowfall of the year (six inches in the Spokane and Wenatchee areas on Jan.11), but those conditions pale in comparison to the storm that advanced from North Carolina to Maine.

What are bomb cyclones and could one strike us here in the Northwest? Turns out, they already have.

Scientifically called “bombogenesis,” these monster storms occur when a convergence of warm air and cold air over ocean waters develop into a swirling wind pattern that leads to a rapid lowering of air pressure. This extreme drop in atmospheric pressure causes the storm to draw more air into its circulation, giving it explosive strength.

The storm that hit the East Coast formed in the Gulf Stream, eventually pulling in subzero air from the Arctic as it moved toward land and up the coast. Not only did it bring heavy snowfall but also damaging winds of up to 70 mph in some places.

Bomb cyclones have struck this side of the country as well. In fact, they form over the Pacific Ocean almost as often as the Atlantic waters. Why don’t we hear about them? Most of these pinwheel-pattern storms fizzle before making it to landfall. The ones that do move inland are called by other terms, including big blows, winter blasts and super storms.

The Columbus Day Storm is among the biggest. The Oct. 12, 1962 event was the worst weather disaster to strike the Pacific Northwest in the 20th century, killing 46 people and damaging thousands of homes, schools and businesses. Formed from the remnants of a tropical typhoon that pulled in cool air off the northern California coast, the storm bore down on Vancouver, B.C., Washington and Oregon, bringing torrential rain and wind gusts exceeding 100 mph to some locations.

Another cyclonic windstorm associated with a rapid drop in air pressure occurred Dec.12, 1995, forming off the California coast and steamrolling up the West Coast into Washington and Oregon. Hurricane-force winds battered buildings, brought down trees and killed four people.

More recently was the Hanukkah Eve Storm that occurred the day before the Jewish holiday in 2006. The powerful December storm that brought heavy precipitation and wind gusts as high as 70 mph knocked out power to more than a million people in western Washington and Oregon.

Bomb cyclones or big blows – whatever we call them – these weather systems tend to bring more rain than snow to the Pacific Northwest. Unlike off the Atlantic Coast, they’re characterized by strong southerly winds drawing warm air into our region.

When the storms hit Western Washington, we in the Inland Northwest may have to dodge raindrops and clutch our scarves in the wind, but we can thank the Cascade Mountains for buffering us from their ferocity.