What About Waves, Swells and Tides?

If you have never surfed before, you probably would not have realized that surfing is pretty much a "big ocean" sport. For msot of us, we need the Pacific or Atlantic ocean. You cannot usually do it in Sacramento Delta or Lake Tahoe  (but it is sometimes possible in the Great Lakes). A bit of knowledge about the waves are on order for you to participate in the sport more like experts.

 

Surfable waves happen on shores facing an open ocean. This is the reason why surfing is associated with California, Hawaii, Florida and Australia where such geography exists. Now imagine for a moment, a boat scene in a movie. Why is the boat rocking all the time? This is primarily due to the ocean swells.

 

(Good) Swells are usually generated from big storm (low pressure) systems out in the big ocean with strong winds blowing in a consistent direction for several days. You probably have seen films of a ship in a big storm with agitated seas. If the storm stays in a area for several days, some parts of these rough waves get directed, combined and gain enough energy to travel outwards from the storm area. But, unlike the river flow where water is physically moving from the top of a mountain to the ocean, in ocean waves, the water does not travel from a storm to the shores. Instead, the pure form of energy in the form of up and down (it is actually circular under the water) motions travels at some speed as swells.  Closer to a storm, the waves within it are rough and random (and you can see that near shore when the wind is blowing a lot) but as you get further away enough from it chops from it build up into swells that survive and reach our beaches thousands of miles from it. As the wave travels, smaller choppier waves die down quickly closer to the storm (or later combine with other smaller waves to make bigger ones) and this allows clean smooth big swells to arrive at our shores. When this energy reaches the shore, the speed slows down while more swells to push from the back; kind of like a traffic pile-up. Then there is no longer a place for this energy to escape except to go higher upwards,  then when it gets high enough, the gravity wins, and the top surface of the water begins break up forward. We paddle in from these the wave faces as they are just sufficiently built up, and almost ready to be crashing down creating a steep slope. 

 

Swells are measured in terms of period and height. Period is the time between one and next peak of the swell (in the open ocean) pass through a fixed point such as a buoy. In the picture here, one period is the time between the swell peak 2 passes through where the peak 1 originally was. Swell height is measured from the level ocean surface to the top of the swell peak. So imagine a buoy in the middle of an ocean a there is are pure 15 second 6 ft swells set coming. The buoy will gradually float up to the top ridge of the swell for 5 ft, about shoulder high as the first swell passes by, then it gradually goes down then 15 seconds later you see the same motion. 

 

In reality, as you can see in the picture here, not all the swells are coming at the exactly the regular interval, at the same height, nor from the exactly the same direction so buoy reports indicate the average or certain percentile of most recorded periods and heights. Also usually swells from all directions are mixed in.  In this picture, the average swell period would be the average time for the swells 1-2, 2-3, and 3-4. In this picture, the swells are coming in uniformly from the west, and also you can tell that there is no local wind swells (chops). 

 

This is because you can see that other than the major swells, water is relatively flat between the swells. If there is a lot of wind swells going on, the sea would look rough and from this vantage point, the wave patterns will look like a "weaving, or cross hatch" pattern.  I would say that this is a good smooth condition with about chest to head high (it looks deceptively small from a 100-ft cliff). If the swells get much bigger than this at this location at this direction, it will "close out" as you can see that the swell line is coming all the way across the beach. When a close out occurs, the waves will crash the entire length of the beach all at the same time, and that won't be fun to get out nor surf. In fact this beach has been in the closed out  condition for several days before I took this picture. Now you are looking at the left-over energy from an earlier big swell conditions. 

 

When a storm is cooking far away, the first swells that escape have higher energy and have faster speed (also they have longer periods), then slower less powerful (but often more appreciated by beginners and intermediate surfers) ones arrive later. Depending on the distance of the storm from the shore, this change can occur in a matter of day or even half a day, so when a condition is "big" and good for experts in the morning, towards the end of the day the condition might all change to "small" allowing us to go out. Unless there are several storms going on at the same time when there is a big day, there will be a small day, then a flat day. Then another set of waves arrive from another storm, making the beach suddenly full of high waves.  

 

When storms or even just high winds occur very close to our shores or if you are inside the storm, we get waves that are really choppy and do not help much in the way of surfing, these are called wind waves. Wind waves usually have shorter periods like 6-8 seconds, and they do not pump as much water so breaks tend to be smaller. So big surfable waves are usually from very far away places 12 seconds or longer periods and from places like such as Alaska, Date Lines, and the South Pacific, and small summer "fun" beginner waves come more close to us.

 

Do not overlook the swell period indicated from buoy or surf reports. The reason is that the break height and where the break occurs is greatly influenced by the wavelength, and in general when the depth of the bottom reaches 5% of the wavelength, that's when the water will start to push upwards. This is relatively independent of the swell height. What you need to remember here is that when the period gets longer the 5% depth will obviously gets deeper and most shores get deeper as you go out, the waves will start breaking further out.

 

The term "Swell size" is not the same as the wave face size which can differ greatly depending on the bottom of the beach area, the swell height,  the swell period, local wind speed, directions and the tide. More on this topic below.

 

Wind is also extremely important. When wind is blowing from the shore to the ocean, the condition is called "offshore" and this usually "hold up" the waves longer so surfers love the offshore condition. When the wind is blowing from the ocean to the shore, the condition is called "onshore" and this tend to blow off the top of the wave causing the waves to be smaller.

 

You will also hear about something called Set Waves, or simply "Sets."  In most surfing situations, set waves are the ones that surfers like to catch. If you are looking at a surfing beach, you will often see many waves coming but once in a while (in 3 to 10 minutes) there is a period where waves gets much bigger than the other times. These waves are the result of set waves. Set waves are created because not all swells are created at the same spot or at the exact same period. All these swells contain different wave periods, sometimes they get combined at the peaks making the wave much bigger. In physics this is called “interference” or "beat" when more than one waves are present on a same medium.

 

The illustration below gives you a very simple case to demonstrate this. Suppose that there are two waves that are coming into the area that you are surfing. One is at 2 ft at 15 seconds and another at 2 ft at 22 seconds. If there is one without the other then you would experience overall 2 ft of swells, but when both come in to the area at same time, both waves combine together and create 3 and 4 ft waves. In real situation, there are many many more waves from various directions (and phases) combine together so the final height and the shape of the sets are much more complex than the illustration below. Another thing you should notice though, even if the swell heights at the buoys are saying average 2 ft, you could get double or even higher sets, because these measurements will take off the bottom and top numbers to average, so you should always be watching out for the sets when you are out in the ocean. You might paddle out what seems to be a calm period only to find out you an overhead monster comes up suddenly! If you are unsure, don't paddle out as soon as you arrive at the beach, but watch for good 10 minutes if there won't be huge set periods.

 

Tides

 

Tide changes contributes very significantly to the surf quality and in some breaks it is a closely guarded secret by local surfers. During a course of a day, the ocean height goes up and down as much as 7-10 ft. As I stated, the break occurs because of the depth, if the depth changes so will be where the waves start to break. Depending on the geography some locations are better surfed at lower tides, and some other locations work better for surfing when the tide is medium to high.

 

Tide changes occur due to the position of the moon and to a lesser extent, gravitational influences from other planets and the Sun. In the Pacific ocean, we normally get two high and low tides per day. Surfers usually talk about the tides in terms of the following,

•  Minus Tide: The low tide is negative height than the 0 ft sea level.
•  Low Tide: 0 to 2 ft
•  Average sea level: Average of high and low tide levels. It is around 3 ft around in our area.
•  Medium Tide: 2 to 4 ft
•  High Tide: 4 ft and above.

In addition we use the term "incoming" or "outgoing".

The travel section of Sufrline.COM provides detailed information on the best tide and the swell directions for most well surfed breaks in the world. Be sure to check it out, and then you need to invest some of your own time visiting each break and take some notes. There are also guide books that tell you more in detail about how the wind and tide works. Like the preference for food, every person has his or her preference of the spot and the wave quality. It will take sometime for you to gain this knowledge, and a lot of surfers call this "paying the dues." Your preference also will change as you improve your surfing skills.

 

If you are totally unfamiliar with the area, don't know anybody and don't know any information hit the period when the tide is going from low to medium in an incoming shift. This way, you won't miss good low tide (if the spot works for low). In fact, that's mainly you would end up doing as tide won't stay the same for hours (normally).

 

This is a very gross generalization to the point of not worth mentioning but,

•  Beach breaks normally work best in medium incoming tides. Low tide is usually worst.
•  Reef supported bottoms work best in lower tides (like in Santa Cruz).

 

So, to summarize all this, If you are looking for "clean" well formed gentle waves for beginner surfers, look for the later arriving lower energy group than the first "big stuff". So, if you find that one day it is too big for you to surf, then wait half a day or until the next day and you might find the conditions more suitable for your skill level. Waves generated in storms in Alaska, "Down and Under" or Southern Pacific oceans take many days of travel to hit our beaches, so you can be prepared for many days in advance.

 

Please read what I have written a few times, go out to the beach and try to digest what I wrote.

When you are ready to learn more about the surf and the surf forecasting technique, visit the http://www.stormsurf.com web site. This site is one of the most authoritative surf wave forecast sites.

 

And also, you should not go out when Tsunami warning is out. Tsunami travels at speeds upwards of 700 mph, instead of about 10 to 25 mph for the regular swells. Then when it reaches the shore, it just causes a lot of damage. I most cases, Tusnami waves do not hold the surfable shape. 

To see what waves are out there in near the shore, we need to go and take a look at the buoy readings. For surfing the swell direction is very important as Montara and Linda Mar will require good NW to W swells, and the Jetty will require good W to SW swells to break good. But not all buoys can detected this information, and only near-by ones are Pint Reyes and also Monterey buoys. The Scripps map that is pulled in from the site is one of the best in terms quickly figure this out.

 

 

 

The left picture from NOAA and Scripps Institute is showing "current" North and Central California swell conditions, and this is, by far, one of the best charts to quickly tell what is going on near our shores.

• The color of the ocean is showing the swell height. Purple to blue is more flat, green to yellow is pretty big and red is really big 40-50 ft swells. Often the entire map is one color but that means that the swell heights are even in this map section.

• The buoy reading indicates the period and the swell size reading.

• Red arrows are Wind directions (not swell directions)

• Blue arrows and hollow arrows on latitude lines (hard to see) are swell directions.

For more details, you can click on the picture and you can interactively visit each of the buoy that is mentioned.

 

One of the best buoys  I use is the Point Reyes provided by CDIP and this tells you the energy and directions of the swells coming. Generally when we get lots of the waves with the period shorter than 6 seconds, you will see a choppy condition at the shore. This just means be prepared, and verify with the web cam sites.

 

You should also check the National Weather Service site and check the weather. There is a detailed weather discussion section that will usually tells the general wind trend. This is important because gusty 25+ MPH on-shore wind directions are detrimental to surfing as the wind will blow off the top of breaks not allowing them to become big enough. On the other hands the offshore and sideshore directions can help form better shape waves if it is not too much.

 

The STORMSURF Pacific Nor Cal Quick Cast is a valuable site that provide you with the projection for this and next week information based on global atmospheric conditions and estimated calculation of swell arrival. All the hard work is done for you. But if you are not satisfied with it, or if they are on vacation, then you need to use their own Power Tools to figure all this out yourself.

 

You can estimate the swell traveling speed by multiplying the swell period in seconds with 1.5 (resulting in nautical miles per hour).