Weather Blog

Surprise Convergence Zone brings stormy night to a few

Surprise Convergence Zone brings stormy night to a few

I'm going to bet there might be some puzzled looks around the water cooler on Friday.

"Wow, Ed, what did you think of that storm last night? I thought our home by Boeing Field was going to wash away. And then the big boom of thunder. Amazing! I thought the forecast was for clear skies."

Ed: "What are you smoking, Joe? It was a calm night at my home in North Seattle. And I heard Mary was out for a jog last night in Des Moines and was remarking on how pleasant an evening it was?"

Even I have to admit when people emailed and Tweeted me asking about the thunderbolt Thursday evening near Boeing Field, I thought the email was lost in time and just now delivered. At my house in Snohomish County, you'd never know there was rain anywhere around.

But lo and behold, there was.  A very narrow -- and sneaky -- Puget Sound Convergence zone spontaneously formed Thursday evening right over south-central King County.

How narrow? Sea-Tac Airport reported just a trace of rain Thursday.  Six miles north at Boeing Field? A whopping 0.47" of rain. But even going further north to the University of Washington campus -- just 8 miles away -- there was zilch in the rain bucket.

But even more amazing was that there was not much moisture to work with even with the favorable wind pattern. It looks like the zone tapped into a little moisture just to the east of the Olympics and it helped feed the zone.  Even had enough instability for one lonely but noticeable lightning strike.

With the rain not measuring at Sea-Tac Airport, May 17 won't go down as an official rainy day in Seattle, but try telling that those who were soaked on the south end of the city.

And just try telling those elsewhere that it actually rained Thursday night!