Monday, September 26, 2011

Facebook as an oceanographic tool

Today my facebook page was full of accounts, from friends living on Puget Sound proper, of high winds. Here in Port Angeles though it was quite calm, in stark contrast to the apparent wind tunnel effect that turned Admiralty Inlet, just 30 miles away as the crow flies, into a froth of foam and waves. I wasn't there, but I saw the video.

So this told me that this particular wind storm was probably from the south, and while Port Angeles was protected by the mass of the Olympics behind us, Puget Sound was hammered. So, on to the oceanography. The real indicator that this was a region-wide south wind event comes from the tidal gauge in Port Angeles:

Note the little green line at the bottom of the plot - this is the "tidal residual", or the difference between the predicted water level and the actual water level. This is also called "storm surge" - piles of water that move in response to changing atmospheric pressure. Today's residual was almost 50 cm, or over a foot, of extra water - quite a bit when you consider that our normal tidal range is around 8-9 feet.

Now on to the cool part. Where is this extra water coming from? Those strong south winds in Puget Sound were even stronger on the outer coast:

This plot from plots wind observations from Destruction Island offshore of the Washington coast. We see high winds - exceeding 50 knots in some cases - blowing w/o pause from the south.

That strong wind pushes water in front of it but the rotation of the earth causes an apparent diversion (the Coriolis "force") of that water mass to the right - into and up the Strait of Juan de Fuca. So, despite the fact that we didn't feel any of today's strong winds, we certainly experienced them as an extra high-tide.

No comments: