Dear Betty,
My friend is always checking her tide chart before we go out for a surf. Why do I need to be concerned with the tides and what do the little numbers on the tide chart mean?
—Morgan, Jacksonville, Florida
Dear Morgan,
Tides are the natural rise and fall of the ocean caused by the gravitational pull of the moon. The tide changes from high to low (or low to high) about every six hours. The whole cycle takes about 25 hours so you can count on the tides shifting about an hour each day. When there is a full moon or a new moon, the swing between high and low is the greatest. Depending on where in the world you live, tides can fluctuate anywhere from one foot (close to the equator) to 25 feet (closer to the poles). In the United States, we see about a six- to seven-foot fluctuation when the tide is at its largest swing (you will usually see numbers on a tide chart ranging from -1 to 6). A negative number is a very low tide, while six feet is very high. Tides affect surfers because they change the conditions at your local break. First, you need to know your surf spot and what kind of tide works best there. You can find this out by observing the conditions and asking other surfers in the water. Some spots close out or expose rocks at low tide while some don't break at all at high tide.
Now you can check the daily tide by looking at your tide chart. You can pick up a yearly printed tide chart at any surf shop or check tides online (try a web search of tides and your area). There is usually an AM and PM high and low, as each day has four tide changes. First, find the date you are planning to surf. Here's an example of what you might find: June 18, 3:00 AM (4.2 high), 9:41 AM (0.4 low), 4:40 PM (5.0 high), 11:04 PM (1.6 low). So, if you are planning to surf at 8 AM, you can expect the tide to be on the low side, reaching its lowest point at 9:41 AM.
Also keep in mind that swell affects the conditions of the surf, so you shouldn't rely on tides alone.
Enjoy the ride,
Betty
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