Tide height effect on wave height?

[SoCalSurfing]

On Surfline, tide height and wave height are shown:
http://www.surfline.com/surf-report/sea ... rnia_4217/

What is the tide height relative to?

Does it have any effect on wave height?

For example, at 2AM the tide height is .53ft but the wave height is 2-3 feet.....how does this work?

Thank You.

[oldmansurfer]

Tide hieght is relative to the depth of water in the ocean. Tides are where the level of water in the ocean goes up and down due to gavity of the moon sun and earth acting together and the rotation of the earth and then the topography in the individula area. But more simply at high tide or high tide heights there will be more water over the reefs and sandbars and rocks so the same swell height will either break closer to the shore or result in smaller waves. Here is a resource I found doing a simple google search http://ci.coastal.edu/~sgilman/770Oceansinmotion.htm

[oldmansurfer]

Basically how tide height affects the quality of waves at a particular break is dependant on the break.

[SoCalSurfing]

Hi,

Thanks for the info and link.

So, at a tide height of 0, there is no bulge at any side of the earth ? The level of the water is the same as the rest of the ocean?

Thank You.

[oldmansurfer]

there is always a bulge on the earths oceans since gravity doesn't go away. This bulge on both sides of the world rotates around the world or slightly more correctly stays in place while the world rotates. At zero it is halfway between the maximum and minimum height. It goes through about 2 cycles a day so two highs and two lows a day. The world rotates around it's axis but the bulge stays in place aligned to the gravity of the moon.

[SoCalSurfing]

Interesting... thank you.

Regarding: "At zero it is halfway between the maximum and minimum height."

Why is zero the lowest it goes to on Surfline, if this is not the minimum ?

Thank You.

[oldmansurfer]

I am not sure but we have minus tides where the sea level is below zero. Tides are complicated in some spots because they are not on the equator and the world is not a big ball of water (there are land masses all over) and the world is tilted in orientation to the moon and then there is the gravity from the sun. On a particular day the tides may all be above zero. At other times there will be marked low tides and away from the equator massive huge changes in tide (more than 50 feet difference) in areas with the right geography. And I guess I am not sure if zero is the inbetween spot or if it is the average height. I recently read a book about waves and stuff so I may seem like I know but I sort of know but not exactly. The book is called Surf Science https://surfing-waves.com/Item/AZsurf_science/surf_surf_science_an_introduction_to_waves_for_surfing.htm It's pretty interesting but I am not an expert after reading it

[oldmansurfer]

Is all of surfline like that or just for a locale you are interested in?

[drowningbitbybit]

I am not sure but we have minus tides where the sea level is below zero.

The height of the tide is taken from a "normal zero", which is how low the tide is at it's normal minimum during the lunar cycle.

Occasionally there are conditions when there's a really really big tide (like when there was a "supermoon" a week or two ago) and then it can be a minus number.

You can also get minus numbers due to weather (this won't be shown in the forecast charts though) when a strong offshore blows the water further out at low tide, or when there is a very low pressure nearby "sucking" the water out.

[oldmansurfer]

Where I live minus tides are frequent and common but really low tides are less often. I am also an amature malacologist so the minus tides are cool to get out on reefs and check out the organisms present without having to get wet. As far as surfing goes I pay absolutely no attention to tides or surf forecasts because I can look and see and I am going to go surfing regardless because I have only a little time to go surfing in so I make the most of it.

[jaffa1949]

Tide height is predictable and most meteorology services around the world produce tide charts.
The shape of the coast determines tides too , there are places where tides are very small and place where they are huge the Bay of Fundy having the biggest . There are places where tides come as a series of wave fronts moving up a stream. ( tidal bores) .

Surf waves or swell moves on top of the tides the height of the tide effecting the breaking of the swell into waves.

Swell direction, its period, the fetch over which the swell is created, and local wind conditions create the final atmospheric response.

Then add the nature of the bottom and it's contours, EASY makes all the difference between consistently good breaks and those that only break a couple of times a year.

Look at your local breaks with new eyes, learn the combinations that make it work!

[oldmansurfer]

I found this specific discussion of tide and surf breaks http://www.surfoutlet.com/guides/how-to-choose-the-best-tides-for-surfing