2/14/2018 0 Comments
the ides of the tides (part 1)
by Gritter Griffin
High tide, low tide, neap tide, spring tide, flood tide, ebb tide…that’s a lot of tides!
It is often surprising how many people who regularly fish do not have a basic grasp of how tidal flow works. Even more surprising is that many do not have a real understanding of the effect that tidal movement has on the feeding patterns of fish.
Perhaps it really shouldn’t be that surprising, though, when you consider that nearly every source one can turn to in order to learn how tides work seems to resort to a complex diatribe involving words like syzygy, quadrature, perihelion, obliquity, ecliptic, paragee, evection, and etc.
I was raised in south Alabama and I expect most of those words, if mentioned in mixed company, would get you in social hot water pretty quickly.
Agreed, the movement of the planet’s oceans is an extremely complex study. But, discussions of this subject often degenerate into a one-upsmanship intellectual debate regarding a multitude of the laws of physics as well as hieroglyphic-looking mathematical formulas.
The good news is that you don’t need any of that mumbo jumbo to understand tidal flow and how it works. It is not necessary to understand the complexities behind “why” tides do what they do as long as you can get a grasp on “what” tides do and “when” they do it.
By the time you finish this short article you will have all the information you need to sound like a regular old salt when you are talking about the tides and tide charts. And, you will be able to make practical use of this information.
First, a few simple definitions:
High Tide: as high as the water is going to get before it starts to fall again.
Low Tide: as low as the water is going to get before it starts to rise again.
Neap Tide: the tide at the quarter moon phases.
Spring Tide: the tide at the new moon and the full moon. (It has absolutely nothing to do with the season of the year.)
Flood Tide: the incoming flow of water during the period from low tide to high tide. This term just means the water is “coming in” or “rising”.
Ebb Tide: the outgoing flow of water during the period from high tide to low tide. This term just means the water is “going out” or “falling”.
Remember, for our purposes here, we only want to know what happens and when it happens. We are not concerned with why it happens except for a couple of generalities.
Generally speaking, there are two tides per day. There is a high tide followed in six hours by a low tide which is then followed in six hours by another high tide and then another low, etc, etc. The times of each high and low occur at a progressively later time each day (about 50 minutes).
The amount of rise or fall in the tide is directly related to the moon phase which is where the moon is in relation to the earth and the sun. Only two situations are of any concern. All others are a variation of these two.
In the first situation the earth, moon, and sun are lined up in a row.
When the earth, moon, and sun are all lined up in a row (syzygy) there is an increased “pull” on the water along this line. This causes the “spring” tide which is the highest a tide will get. The spring tide occurs twice each month. Once on the full moon and again on the new moon.
In the second situation, the earth and sun stay in the line but the moon is ‘off to the side’ of the earth at 90 degrees.
When the earth and sun are still in the same line and the moon has moved to the side of the earth perpendicular to this line (quadrature) there is a lessened “pull” on the water along the same line. This causes the “neap” tide during which there is less water movement. There is still a high and a low tide but high tide does not reach the same levels of the spring tide and the low tide is the lowest it will be throughout the cycle. The neap tide occurs twice each month. Once on the first quarter and again on the last quarter of the moon.
Here’s another way to think of the monthly tide cycle that may help you get it straight.
If you could stand in the same spot in the water for 28 days and follow the rise and fall of the tides it would go something like this:
Let’s begin with a full moon and a spring tide. Remember, this tide occurs twice every month during the full moon and new moon phase. At the time of the high tide, the full moon is beautiful and the water is at your kneecaps. About six hours later, at low tide, you are standing on dry ground.
Don’t move. You’ve got to stay right there for 28 days and watch the rise and fall of the water. The next day at high tide the water line at your kneecaps will be slightly lower than it was yesterday and at low tide there will be a little less dry ground at your feet.
Each successive day at the time of the high tide the water will be slightly lower on your kneecaps than it was the preceding day and at low tide it will be slightly higher at your feet.
By the time you have stood there for 7 days and reached the first quarter of the moon you will find that the high tide mark is now below your knees and at low tide the water level is at your ankles. You have now reached the first neap tide of the month. This is when the high tide is not quite as high or the low tide quite as low as during the full and/or new moon phases. This is because the moon is now at a 90 degree angle to the line between the earth and sun and the tidal forces are not as strong as when the earth, moon, and sun are all lined up.
Over the next seven days (days 8 – 14) each daily high tide will now be a little higher and the low tide will be a little lower until the new moon. Now you have been standing there for 14 days. The high tide is back at your kneecaps and the low tide has you standing on dry ground just like it was during the full moon.
Over the next seven days (days 15 -21), between the new moon and the 3rd quarter, each high tide will again be a little bit less high and the low tide a little bit less of a low until you reach the second neap tide of the cycle (3rd quarter of the moon) and the water level is the same as it was on day 7 at the first neap tide.
Over the final seven days (22 – 28) you will again see the gradual rise in each tide until you are back at the full moon with the high tide at your knees and the low tide leaving you on dry ground.
You can now get out of the water and go home with a new appreciation of the tidal cycle (and really wrinkly feet).
This lunar cycle repeats itself over and over every 28 days.
Now that you have a grasp of some of the terminology and how the tide cycle follows the moon, it is time to look at a tide table and learn how to interpret and use the rise and fall of the tides for the area you will be fishing. That all comes up in Part 2.
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