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    Re: Tides by bearing of the moon
    From: Hewitt Schlereth
    Date: 2009 Apr 7, 19:35 -0400

    Yup, I mixed up terms: Semi-diurnal is what they are in Long Island
    Sound and the US East Coast. Diurnal (sort of) is what they seem to be
    here in St. John. Thanks for calling me on it, George.
    
    A handy thing about Long Island Sound is its luni-tidal interval of 11
    hours means when the moon is high so is the tide - i.e.,when the moon
    is rising so is the tide, when it's going down so is the tide.
    
    Admittedly, this is a rough-and-ready method but it does give the big
    picture and it stood me in good stead over many years. I'm hoping to
    get a similar handle on the tides here, though it doesn't matter much
    because the range is small.
    
    Hewitt
    
    On 4/7/09, George Huxtable  wrote:
    >
    >  Hewitt wrote-
    >
    >
    >  | Living here in the US Virgin Islands I've dabbled at it, but the tides
    >  | here are not diurnal as they are on the US East Coast but more like
    >  | what I've heard of the tides around England.
    >
    >
    > Those words puzzle me. I have a book here by a American named Marmer, from
    >  1926, "The Tide". Which shows some predictions for Sandy Hook and New York
    >  harbour. And those tides appear to be very semidiurnal (repeating after 12
    >  hours or so), without much daily inequality, between am and pm tide. Those
    >  are just like the tide pattern we have here in UK waters.
    >
    >  Is the pattern very different elsewhere on the US East Coast?
    >
    >  Hewitt added, about tables of luni-tidal intervals-
    >
    >
    >  "In comparing this lunar method with the published tables, I noted that
    >  there were often noticeable differences between what the table would
    >  say and what I actually observed on the water. I figured this was
    >  because the tables are generated by a computer which could not know
    >  what the wind or barometer were going to be on the predicted day and
    >  time. Both wind and barometric pressure affect the tide."
    >
    >
    > ========================
    >  That's certainly true, that weather can affect tide, but it most cases it
    >  calls for rather extreme conditions to have an important effect. Predictions
    >  of luni-tidal intervals are averaged over a wide range of conditions (most
    >  important, phases), and for that reason do not predict tides well on a
    >  particular day.
    >
    >
    >  George.
    >
    >  contact George Huxtable, at  george{at}hux.me.uk
    >  or at +44 1865 820222 (from UK, 01865 820222)
    >  or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    >
    >
    >  >
    >
    
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