Re: double tide cause

["John S. Denker" <jsd@MONMOUTH.COM>]

At 03:03 PM 9/1/01 -0500, Kossom wrote:

> 1. Why does much of the Gulf of Mexico experience only one high and low tide
> per day, rather than the usual two?

What's the evidence for a once-a-day tide?  Evidence available to me
indicates nothing but the usual twice-a-day tide, e.g.
 http://www.cyberangler.com/weather/tide_correction_st_petersburg.html
 http://www.tpwd.state.tx.us/fish/recreat/fishrept/tidetab.htm

The tides in the Gulf are small and weird.  You would expect the tides to
be somewhat attenuated, because the Gulf is fairly small, and connected to
the open ocean only by rather narrow straits.

BTW, if you want tides that are large and weird, try the Bay of Fundy.  I
spent a day sailing near there last month....

> 2. Why does Lake Ponchatrain (a relatively large, but shallow bay with a
> very small connection to the Gulf) not experience tides of its own?

Relatively large?  Relative to the ocean, it's not large at all.

==============================

REMEMBER, FOLKS:  We can expand the moon's gravitational field near the
earth in a Taylor series.
 *) The zeroth-order term applies an acceleration to everything,
independent of position and therefore independent of size.  This term is
uninteresting, because it is cancelled by the earth's orbital motion.
 *) The first-order term applies an acceleration that varies linearly with
position.  In any region of the earth, this is like tilting the definition
of "horizontal" by a certain small angle.  How a body of water responds to
such tilting depends on many factors including
 -- size of body
 -- whether the body has resonances near the driving frequency
 -- damping
 -- et cetera.