Amazing Lightning In Seattle Powered By Extraordinary Moisture From Hawaii

May 5, 2017

The lightning storm that hit the Seattle area Thursday afternoon and evening is over now, but it’s one that won’t be forgotten anytime soon. The thunderclaps and light show electrified the skies and brought intense wind to the area.

About 14,000 people were without power Friday morning. But that wasn’t the amazing part to KNKX weather expert Cliff Mass.

“It was the greatest lightning outbreak we’ve had – probably in 5 to 10 years,” he said.

A look at the 24-hour lightening map of the region showed hundreds and hundreds of strikes, he said.

“I couldn’t believe my eyes,” remarked Mass.

“Normally, when we have thunderstorms ... we have one or two lightning strikes from each one of these cells,” he said. “But not this time. It was massive. And we don’t see something like this very often.”

A Plume Of Extreme Wet from Hawaii

Lightning crashes from the sky during Thursday evening's storm.
Credit Allan J. Jones

Mass said the source of the lightening was an unusual plume of very high moisture levels coming into the region. The phenomenon, sometimes called the Pineapple Express, is produced by a jet stream of very wet and warm moisture from the tropics around Hawaii. Often it hits the Pacific Northwest kind of like a fire hose, bringing tropical rain in.

And this time it came with those record-breaking lightning storms too.

But on Friday morning, it was traveling eastward into Idaho and Montana, yielding to a milder but still wet weekend.

He said marine air, which comes with lower pressure, was starting to push back into Western Washington, bringing a band of precipitation and cooler air in with it.

‘So, no lightning when you have cool marine air at low levels," said Mass. "We’ll see some showers [Friday] ... They’ll fade off as we get into evening.”

Mass said come Saturday morning we can expect partly cloudy skies with a few showers in the area, but but that should open up into sunshine.

"I expect temperatures getting up into the mid- to upper 50s on Saturday, maybe even 60 in a few places, so not too bad," he said. "Then a mini-ridge of high pressure develops over the entire region on Sunday, so that will dry it out, temps getting up to 60 or low 60s in a few places. "

Sunday will definitely be the day, said Mass.

"Monday and Tuesday look partly cloudy and temperatures around 60," he said. “So, we’re through it now – it’s over."

To hear the podcast of this segment, with more discussion of the record water year and how lightening is produced,  you can click on the "play" icon at the top of this post. 

The weekly KNKX feature 'Weather with Cliff Mass’ airs every Friday at 9 a.m. immediately following ‘BirdNote’, and twice on Friday afternoons during ‘All Things Considered.' The feature is hosted by KNKX environment reporter Bellamy Pailthorp. Cliff Mass is a University of Washington professor of atmospheric sciences, a renowned Seattle weather prognosticator, and a popular weather blogger. You can also subscribe to podcasts of ‘Weather with Cliff Mass’ shows, via iTunes or Google Play.