The Gulf Coast is the main diurnal tide in the USA. Southeast Asia is another
area.


http://chinook.kpc.alaska.edu/~ifeeb...altidemap.html
http://www.oceanservice.noaa.gov/edu...07_cycles.html


"Bart Senior" wrote in message
.net...
2 pts. Great answer Jeff. an extra point for adding
worthwhile content.

Can you name two places where tides are diurnal?

What are spring and neap tides and how can you tell by
observing the moon, if a tide will be spring or neap?

Jeff Morris wrote

Halfway between moonrise and moonset is 10 pm local time, which is the
time of
transit of the local meridian. To this we must add the "Local
Establishment" or
the "Lunitidal Interval" (actually the proper terms are "high water full
and
change" or "mean high water lunitidal interval") to get the time of the
next
high tide.

This was published on old charts. My 1867 Boston Harbor chart lists the
"Corrected Establishment" (average of all high water intervals) for Boston
Light
as "XIh XIIm". This mean you add 11 hours and 12 minutes to the time of
local
meridian passage of the moon to get the time of the next high tide.

Tides watches usually require setting the Lunitidal Interval for a
particular
spot. Of course, this only works for semidiurnal tides.

I've had trouble finding a nice tide table for the east coast, so I checked out my 1886 Bowditch.
Sure enough, it had the following (plus tables for the rest of the world):

http://www.sv-loki.com/NETides.jpg
http://www.sv-loki.com/SETides.jpg

I'm sure some oceanographer can explain the variations, but there's nothing obvious that would help
me if I landed on a different planet.

--
-jeff

"N1EE" wrote in message
om...
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.

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.

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.

Here is an example for my location:

2004-05-02 5:26 PM EDT Moonrise
2004-05-02 7:51 PM EDT Sunset

2004-05-02 10:09 PM EDT 7.80 feet High Tide

2004-05-03 4:33 AM EDT -0.49 feet Low Tide
2004-05-03 5:06 AM EDT Moonset
2004-05-03 5:47 AM EDT Sunrise

2004-05-03 10:38 AM EDT 7.16 feet High Tide

2004-05-03 4:45 PM EDT -0.14 feet Low Tide
2004-05-03 6:42 PM EDT Moonrise
2004-05-03 7:52 PM EDT Sunset

2004-05-03 10:55 PM EDT 8.06 feet High Tide

2004-05-04 5:21 AM EDT -0.84 feet Low Tide
2004-05-04 5:33 AM EDT Moonset
2004-05-04 5:46 AM EDT Sunrise

2004-05-04 11:27 AM EDT 7.20 feet High Tide

2004-05-04 4:35 PM EDT Full Moon
2004-05-04 5:31 PM EDT -0.26 feet Low Tide
2004-05-04 7:53 PM EDT Sunset
2004-05-04 8:01 PM EDT Moonrise

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

Bart Senior

"Wally" wrote

Bart Senior wrote:
Moonrise 4 pm local time
Moonset 4 am local time

Approximately when is high tide? [ 1 pt ]

I guess it depends on the location. For my area, it's a couple of hours or
so after lunar noon, so about midnight to 1am for the above example.

Bart Senior wrote:

Can you name two places where tides are diurnal?

Always diurnal, i.e. only one tide per day, every day? - No. I don't
think there is one. It'd be a very rare combination of geography and
geography.

Diurnal most of the time, i.e. only one tide per day most days, with
other days showing a smaller second tide? - Lots of places. The
Aleutians and the Gulf of Mexico are two.

What are spring and neap tides and how can you tell by
observing the moon, if a tide will be spring or neap?

Spring tides are bigger than neap tides. Spring tides occur at the full
moon and at the new moon. Neap tides occur at the first and last
quarter.



BTW, I sail on a small inland lake, so this stuff is just trivia for
me. Tides schmides - the real question is which direction is the next
90 degree wind shift coming from.

--
//-Walt
//
// Sigs suck. Oh, the irony.

Bart Senior wrote:

Moonrise 4 pm local time
Moonset 4 am local time

Approximately when is high tide? [ 1 pt ]

Are we right on the ocean, or somewhere up a coastal bay? On the Ocean
the high tide will occur around lunar noon (when the moon is at it's
highest point in the sky) and again about twelve hours and 25 minutes
later. So let's say about 10pm and then about 10:30am the next day.

On a basin like, say, Rehoboth Bay tides can lag by several hours.
Check the local tide charts.

--
//-Walt
//
// Sigs suck. Oh, the irony.

No, I'm trying to get people to think about the relationship between
altitude and period between rise and set for a fixed lunar orbital period.

Cheers

Jeff Morris wrote:

"Navigator" wrote in message
...


Wally wrote:

Navigator wrote:


What location has moon rise and set 12 hours apart?


Virtually anywhere, I'd guess - just had a look at moon rise and set for
some random locations (Glasgow, Jerusalem and Canberra), for today, and
they're all a shade over 12 hours apart. If rise/set are close to due
east/west, then the time for the moon to traverse the sky will be about 12
hours - think about the solar equinoxes, where the sun rises/sets due
east/west. I dare say this princple won't hold at extreme latitudes. The
moon passes the due east/west points twice in its mo(o)nthly cycle.



The devil _is_ in the detail and is it ever 12 hours????



Why not? What's the problem? Or are you making the sophomoric argument that
its very unlikely to be "precisely" 12 hours? It certainly isn't hard to find
places and times where its within a couple of minutes. Certain latitudes are
more favorable than others for this situation to exist, but there's nothing the
precludes it.

Have a go with:
http://aa.usno.navy.mil/ select "Data Services" and then "Table of
sunrise/sunset ..."

N1EE wrote:

1 pt to you Wally.

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

In theory.

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

You need to do some more research. Use the following two resources to
compare moonrise/set times and tides for various locations:

http://www2.shore.net/~mcmorran/tide/tideform.html
http://aa.usno.navy.mil/data/docs/RS_OneYear.html
(be sure to correct for daylight savings time)

For instance, try comparing Virginia Beach, VA and Solomon's Island, MD
.. Moonrise/set times are within a couple of minutes of each other, but
the tides are six hours out of synch.

Why? Well, obviously it takes some time for the large bulge of water
that is the tide to make its way up the Chesapeake Bay. Since water
doesn't move instantly, moonrise is essentially useless for predicting
tides on large bays.


--
//-Walt
//
// Sigs suck. Oh, the irony.

Sounds more like you don't know what you're talking about.



"Navigator" wrote in message
...
No, I'm trying to get people to think about the relationship between
altitude and period between rise and set for a fixed lunar orbital period.

Cheers

Jeff Morris wrote:

"Navigator" wrote in message
...


Wally wrote:

Navigator wrote:


What location has moon rise and set 12 hours apart?


Virtually anywhere, I'd guess - just had a look at moon rise and set for
some random locations (Glasgow, Jerusalem and Canberra), for today, and
they're all a shade over 12 hours apart. If rise/set are close to due
east/west, then the time for the moon to traverse the sky will be about 12
hours - think about the solar equinoxes, where the sun rises/sets due
east/west. I dare say this princple won't hold at extreme latitudes. The
moon passes the due east/west points twice in its mo(o)nthly cycle.



The devil _is_ in the detail and is it ever 12 hours????



Why not? What's the problem? Or are you making the sophomoric argument
that
its very unlikely to be "precisely" 12 hours? It certainly isn't hard to
find
places and times where its within a couple of minutes. Certain latitudes
are
more favorable than others for this situation to exist, but there's nothing
the
precludes it.

Have a go with:
http://aa.usno.navy.mil/ select "Data Services" and then "Table of
sunrise/sunset ..."

Are you saying that the peiod between rise and set is fixed?

Cheers

Jeff Morris wrote:

Sounds more like you don't know what you're talking about.



"Navigator" wrote in message
...

No, I'm trying to get people to think about the relationship between
altitude and period between rise and set for a fixed lunar orbital period.

Cheers

Jeff Morris wrote:


"Navigator" wrote in message
...


Wally wrote:


Navigator wrote:



What location has moon rise and set 12 hours apart?


Virtually anywhere, I'd guess - just had a look at moon rise and set for
some random locations (Glasgow, Jerusalem and Canberra), for today, and
they're all a shade over 12 hours apart. If rise/set are close to due
east/west, then the time for the moon to traverse the sky will be about 12
hours - think about the solar equinoxes, where the sun rises/sets due
east/west. I dare say this princple won't hold at extreme latitudes. The
moon passes the due east/west points twice in its mo(o)nthly cycle.



The devil _is_ in the detail and is it ever 12 hours????



Why not? What's the problem? Or are you making the sophomoric argument

that

its very unlikely to be "precisely" 12 hours? It certainly isn't hard to

find

places and times where its within a couple of minutes. Certain latitudes

are

more favorable than others for this situation to exist, but there's nothing

the

precludes it.

Have a go with:
http://aa.usno.navy.mil/ select "Data Services" and then "Table of
sunrise/sunset ..."

"Walt" wrote

For instance, try comparing Virginia Beach, VA and Solomon's Island, MD
. Moonrise/set times are within a couple of minutes of each other, but
the tides are six hours out of synch.

Why? Well, obviously it takes some time for the large bulge of water
that is the tide to make its way up the Chesapeake Bay. Since water
doesn't move instantly, moonrise is essentially useless for predicting
tides on large bays.

I ask Uncle NOAA for tide info.

Scotty

Are you claiming its broken?

There are a number of factors that determine the time between moonrise and
moonset. However, there is no reason why a 12 hour duration can't occur, and no
reason why it can't happen from 4pm to 4am.

Now you can claim that you were "trying to get people thinking about something"
but I claim you have no idea about lunar noon and it relationship to the tides,
and that you had some bizarre notion that a 12 hour duration was not possible.


"Navigator" wrote in message
...
Are you saying that the peiod between rise and set is fixed?

Cheers

Jeff Morris wrote:

Sounds more like you don't know what you're talking about.



"Navigator" wrote in message
...

No, I'm trying to get people to think about the relationship between
altitude and period between rise and set for a fixed lunar orbital period.

Cheers

Jeff Morris wrote:


"Navigator" wrote in message
...


Wally wrote:


Navigator wrote:



What location has moon rise and set 12 hours apart?


Virtually anywhere, I'd guess - just had a look at moon rise and set for
some random locations (Glasgow, Jerusalem and Canberra), for today, and
they're all a shade over 12 hours apart. If rise/set are close to due
east/west, then the time for the moon to traverse the sky will be about
12
hours - think about the solar equinoxes, where the sun rises/sets due
east/west. I dare say this princple won't hold at extreme latitudes. The
moon passes the due east/west points twice in its mo(o)nthly cycle.



The devil _is_ in the detail and is it ever 12 hours????



Why not? What's the problem? Or are you making the sophomoric argument

that

its very unlikely to be "precisely" 12 hours? It certainly isn't hard to

find

places and times where its within a couple of minutes. Certain latitudes

are

more favorable than others for this situation to exist, but there's nothing

the

precludes it.

Have a go with:
http://aa.usno.navy.mil/ select "Data Services" and then "Table of
sunrise/sunset ..."