Thursday, March 17, 2011

The tidal data captured the tsunami

I am often told that the tidal data from NOAA doesn't really matter because unexpected things can happen in the Bay. Yes, that's true, the unexpected can happen.  I don't think anyone expected the 8.9 magnitude earthquake to hit Japan late last week, or that the resulting tsunami would make its way to our Western coast -- but that's exactly what happened.

I went to the NOAA's San Francisco and Richmond stations to see just what effect that tsunami had on the water levels.  The tsunami hit the Golden Gate Bridge with 2 foot waves about 8 a.m. on the 11th.  "Water is coming in, going out, coming back in again, " [National Weather Service forecaster Diana] Henderson said.  Source

And that is exactly the way San Francisco's station data looks -- water coming in, going out, coming back in again.  As you can see from the plot, the water level had been a little below predicted.  About 8 a.m. on the 11th, the water level became very erratic, in the initial hours going up and down by as much as 3 feet.

The Richmond station didn't show such dramatic water level ups and downs, as it is 9 miles further north, but still a very noticeable effect.  

I hope this finally convinces the skeptics that the water level data from the NOAA does accurately reflect what's going on in real-time in the Bay.

Luckily for the Bay, the tsunami's arrival had the best timing -- during a LL tide and a period of lower than average H and HH tides.

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