May 04, 2017

Amazing Day of Lightining

Today's thunderstorms brought as much lightning as I have seen in years around western Washington:  at least several hundred strokes, in stark contrast to our  normal lightning-deficient precipitation.

Some of the thunderstorms brought strong winds, gusting to 40-70 mph, as illustrated by the gust map for the past 12-hours.  A few exposed mountain ridges got to 70-80 mph.

Strong wind brought falling trees and damage, particularly from Lacy to Yelm.

Multiple lines of convection came through producing .30-.50 inches over most of the region, but as much as 2-3 inches in the thunderstorm cores (see map from Seattle RainWatch below)

But what was most extraordinary was the massive lightning display and the stunning clouds.

We can start early this morning, with a stunning shot by Peter Benda of Bellevue showing a blanket of fog over lower elevations and some altocumulus clouds aloft hinting at mid-level instability.

Rod Gilbert sent this absolutely stunning picture from near Dupont, WA. Breathtaking.  A rain shaft in the middle with a lower-hanging shelf cloud below.  The lower portion of the cloud was roiling with turbulence.  Something out of a science fiction movie.

Stephen sent me this image from Tacoma--just stunning.

And Allen Jones forwarded some wonderful lightning pictures, like this one:

How good was the forecast?  Well, we did warn of the potential for thunderstorms, but our models suggested they would have hit about 3 hours later then they did.   Perhaps a B?

The 9 PM radar shows one last thunderstorm area is about to hit western Washington, with most of the action moving eastward across the Cascades and eastern Washington.  Cooler, marine air will push in later tonight, which should end the threat of thunderstorms west of the Cascade crest.

Finally, for the skiers in the crowd, the NW Avalanche Center is having their annual fundraiser, this time for improving mountain weather stations.  More information here.  And if you want to join local weather lovers at the Puget Sound American Meteorological Society meeting, check below.

On Saturday May 6th, Larry Schick, lead meteorologist for the US Army Corps of Engineers in Seattle, will talk about Flood Risk Management and Atmospheric Rivers in Western Washington at 3pm at the Seattle Public Library Montlake branch2401 24th Ave. E., Seattle, WA 98112, All are invited.  Refreshments as well.


  1. It was a great weather day. Fog into glorious sun into awesome rainstorms. A little something for everyone.

  2. At 2:10 am, there's yet another thunderstorm hitting the Snoqualmie Valley. Probably the 5th round of storms, since the first one hit at 4:20 pm.

  3. No doubt to be blamed on human-caused climate change.

  4. Those storms reminded me of the ones I grew up with in the mid-west. I was surprised how many people were out walking around in it. I don't think they realize the power of a good thunderstorm since they really don't happen around here very often.

  5. Depressing. The clouds seemed to part as they approached Portland. The "Portland Divergence zone"?

  6. Pretty exciting day yesterday for these parts in SE King County! Storm moved through around 3pm then again 5pm then another at 7pm, yet another at 9pm and to top it off another 1am to about 2am that kept us all up! Not sure I have seen that kind of prolonged activity around here EVER. And, yes I agree with Larchintech. Very surprised to see people acting like it was no big deal when cloud to ground lightening was hitting less than a mile away! You absolutely need to respect that kind of power.

  7. The risks of lightning are very remote, statistically, other than for ground currents, which can be scary. When I used to climb in CO, where daily T-storms are the norm, we often wound up on exposed ridges where our hair stood on end and the rocks under our feet vibrated. That was a bad sign, but not uncommon. But what we really sweated was the ground currents, not an air strike.

    A strike well above you or to either side would travel through the surface rocks. You could tell when that was happening when the flash and a very loud CLICK sound came simultaneously, and the thunder was a fraction of a second delayed. The click was from the ground current running through the rocks beneath your feet, banging them together. Very sobering. Sometimes we'd endure dozens of click-strikes in a matter of minutes.

    The safety rule was to never touch your hands to the ground (or anything conductive that touched the ground). If you wanted to reduce your profile, you did it by kneeling with arms crossed over your chest or up around your head. (Given you were usually in hail and extremely heavy rain at that point, it was natural to be holding something over your head.)

    You can handle a lot of ground current flowing from toes to knees without significant injury, or even being aware of it, but it doesn't take many milliamps through the heart to screw up the rhythm, possibly fatally. Touching your hand to the ground completes the wrong circuit through your body. Worst thing you could possibly do was to lay down. The key was that even if you were the highest thing around, the probability of an air strike was very, very remote.

    Of course, staying away from lone trees was good advice, but the worst advice was to duck under a rock overhang to get out of the hail. What happens when the ground current comes down the rocks from all the strikes just above you? Yeah, it air gaps from the rock overhang over your head to the ground below, using your body to complete the circuit. Same problem can occur around buildings by standing in the entranceway. Current travels on the skin of a structure and can air gap the entranceways.

    Far safer to stand out in the rain and hail and be awed by the lightning than to stand in a doorway. Better yet, get well inside the building and look out a window.


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