It's a really harmonic probelm with the moon being just one factor. As a
result it's not even a constant delay at a fixed spot.

Cheers

Wally wrote:

N1EE wrote:

1 pt to you Wally.

High Tide will be somewhat close to the
mid point between moonrise and moonset.

I have not researched many lcoations but I'd
estimate +/- an hour for more locations.

In my location High tide occurs about an hour
before that mid point.

Geographical factors will have a big influence.
A body of water might be north-south like the
Bay of Fundy or Gulf or California versus
east-west like Long Island Sound.


Yup, guess the geography is the single biggest factor affecting the
interval between lunar noon and high tide. At least, I'd imagine that a
smooth planet completely covered in water would have a constant interval for
all locations.



I find it handy to be able to judge high tide
by looking at the moon. I can add or subtract
to estimate when the next high or low tide will
be.


That's a habit I might try to develop. That said, I only daysail (club
racing), so I tend to use published tide info and the little program in my
PDA (Tide Tool).



As you can see we have at times nearly a 9
foot swing, so tidal currents coupled with river
current can cause problems with launching if you
are like me, and using a chain hoist. At times
I cannot drop the boat all the way into the river.
I need longer lift straps.


My boat isn't in the water, but the one I crew on has a marina berth, which
is very convenient. We have a similar situation with current - we're at a
narrow on a tidal river a couple of miles across which immediately opens out
to an estuary to the east. On the ebb, the current can get up to 3 knots in
places. There are islands and bridge piers dotted around, a deep channel on
the north side, and shoals to the south, all of which seem to make for a
great variety of water to contend with. Tidal range gets close to 6m at
springs (about 20 feet).




2004-05-04 11:42 PM EDT 8.21 feet High Tide

2004-05-05 5:44 AM EDT Sunrise
2004-05-05 6:06 AM EDT Moonset

You will note that the time of high tide slips
about 50 minutes every day and the interval
between high tides is about 12.5 hours.


A quick scan at my local data suggests slightly less slippage (30-40
minutes), but I'm not sure how reliable the info is. Did you use software to
derive your numbers?



A good sailor will know what these factors are
for his or her location to figure the next
high tide.


Aye, still getting there. :-)