Sunday, April 1, 2012

Puget Sound Waterspouts

Sunday April 1, 2012
6:24 P.M.

Waterspout over the Florida Keys. Retrieved from NOAA.

When I was looking at the radar today, I definitely noticed some rather heavy rain showers. I have a house in Cultus Bay on South Whidbey Island, so I wasn't too surprised when my neighbor called me to tell me the skies were looking pretty stormy. But then he told me something else, and my jaw practically dropped to the floor. He said that two HUGE waterspouts had entered formed right off Possession Point, which is more in Puget Sound, and then gone into Cultus Bay before getting out of the bay and passing within 100 yards of his house before dissipating. Waterspouts are pretty rare around here, but they are definitely not unheard of, especially in the spring.

Take a look at the radar below. To prove to you that this is not an April Fool's joke, focus your attention on the precipitation over South Whidbey Island. You can see a pretty well-defined convergence zone over there, and that is probably what caused the waterspouts. My neighbor called me at 6:32 PM, so these waterspouts were definitely associated with this convergence zone.

Convergence zones are often associated with funnel clouds, tornadoes, and waterspouts. Cliff Mass has a great book about weather in the Pacific Northwest that explains why, but I haven't been able to find the diagrams he uses in the book on the web (believe me, I've tried). Anyway, convergence zones form at the boundary between northerly winds and southerly winds, and when these two winds collide, they often produce localized areas of rotation that produce weak tornadoes and waterspouts.

The best metaphor for showing how convergence zones can spin up tornadoes is a pinwheel. Since a convergence zone has air coming in from the north and the south, it spins columns of air like pinwheels, and this rotation leads to waterspouts like the ones my neighbor witnessed on Whidbey Island.

Waterspouts pick up lots of stuff from the water, and my neighbor found clams, sand, some seaweed, and even some baitfish scattered around the neighborhood. Rumor has it a salmon fell at another house in Cultus Bay, but my neighbor wasn't quite sure on this one.

Thanks for reading, and don't be surprised if a herring comes your way in the next hour or two. :)

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