One Daily Tide vs Two
Country: United States
Date: August 2007
On February 9, 2004, Laura asked why Panama City, Florida
had only two tides a day. David R. Cook answered that there are two
low tides and two high tides everywhere. I was born and lived in
Panama City until I left for college. The local newspapers only
recorded one low and one high tide a day. If only two are recorded a
day, would not the other two tides simply be so small that they are
not measured? I know there appears to be only two a day in Panama
City, Florida. Can someone explain this observation?
When I made the statement in my entry, unfortunately
I was looking at Panama City Beach, not Panama City.
Please let me clarify.
If you go to the web site
you can scroll down to 2 listings of tides for Panama
City and 2 for Panama City Beach. Note that only one low tide
and one high tide are shown for both locations on August 1.
For August 2, 2007, two high and two low tides are shown for
Panama City Beach and only one of each for Panama City.
Panama City Beach normally only receives one high and one low
tide per day. The position of the Sun, Moon, the N/S or E/W
orientation of the coastline, whether the location is on
the ocean or in a bay (such as Panama City in St. Andrews Bay)
or in an enclosed or mostly enclosed gulf, such as the Gulf
of Mexico, local underwater topography, water depth, etc.
determine whether there are two observable or significant
high and low tides or just one of each, and the timing of
the tides at a particular location.
In general, there is one dominant high energy tide per day,
at any location; this occurs typically 1 to several hours
after the Moon sets at your location (this one has the greatest
A smaller energy tide (with lower tide height) occurs several
hours after the Moon rises. The size of the tides and timing
is dependent on the position of the Sun also.
East and west facing locations directly on the large oceans
(Atlantic, Pacific, etc.) consistently experience two high and
low tides per day because the path of the tide is not hindered.
If your location is within a bay with a narrow opening, such
as is the case of St. Andrews Bay for Panama City, it takes a
long time for the bay water level to respond to the high energy
high tide in the Gulf of Mexico; note that the Aug 1, 2007
Panama City high tide occurs some 2 to 3 hours after the Panama City
Beach high tide. St. Andrews Bay then starts emptying, working
towards low tide, but, again, it is delayed in doing so by the
narrow bay opening and so Panama City experiences low tide hours
after Panama City Beach.
Only 5 hours later, on August 2 early morning, Panama City Beach
has low energy high and low tide within a couple of hours of each
other (2:47 and 4:44 respectively), which are hardly different in height.
It's impossible for St. Andrews Bay to respond to these quick
and small tide changes, so the low energy high and low tides
simply do not occur at Panama City. In reality, the low energy
high tide serves only to keep the water level in St. Andrews Bay
higher overall between high energy high tides, than would occur if it
could respond to the low energy tide.
Computer models are used to determine tide tables because of the
complexity of the physical considerations, such as occurs at
David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory
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Update: June 2012