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    Re: Big Full Moon and Perigee Spring Tides
    From: Frank Reed
    Date: 2011 Mar 20, 04:22 -0700

    John H, you wrote:
    "I'm at Cape Cod today, and we do have some big tides today, so that much is interesting."

    Also note that there is a lag of about a day for Spring Tides on the Atlantic coast of the US. The ocean tides are like a big set of coupled, driven harmonic oscillators. The driving force has numerous frequencies. The most important frequencies, of course, are the daily rates for the Sun and the Moon to pass over any point on the Earth. Since they're different frequencies, they generate different responses in the driven oscillators with slightly different phases. That yields the delay in the Spring Tides. This delay is different in different parts of the world. As I said, here on the Atlantic coast of the US, it's about a day. In northwest Europe, two days or more. On the Pacific coast of the US, close to zero, and there are even a few spots around the globe where the Spring Tides lead the phase of the Moon by a couple of days. This lag was one of the first things that I brought up on NavList way back in December of 2003. I was interested because early editions of Bowditch still described European conditions and back then there were ZERO 19th century editions of Bowditch available online. Now there are dozens.


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