Tag: beach break

How to Read a Surf Forecast – How Period Affects Wave Size

on By

waves are affected by Period

At Surf With Amigas Retreats we consistently hear the same remarks… “The surf report said 2-3ft but the waves are flat!” or “The report says 5-7ft tomorrow, is it going to be huge?”  The predicted surf height is arguably the least useful piece of information on the surf report. You should be paying more attention to the swell period!

If you look at a surf forecast you’ll generally see three bits of information:

  1. Swell size
  2. Swell period
  3. Swell direction

All are important. Most people just focus on the predicted swell size, but swell period actually has as much or even more to do with swell size in deciding how big the waves will actually be once they break at your surf spot.

Here’s an example of a surf forecast from Surfline showing three swells. On the left side, you can see the wave size forecast. This column tells you that Surfline predicts that the waves will be 3-4 feet at this specific beach.

How to Read a Surf Report

The next three columns (after the rating) show three different swells in the water. These are heights for the open ocean swells, not the size of the actual breaking waves. The first swell is 2.5ft at 16 seconds The second swell is 2.6ft at 12 seconds, and a third swell that at 6am is predicted to be 2.9ft at 7 seconds. The forecast predicts that the combination of these three swells will lead to waves in the 3-4ft range.

When I look at a surf forecast, I don’t even use that first column showing wave heights other than just as a guide that shows a trend – for example – are the waves predicted to be bigger today than yesterday? To me, the specific size predicted is relatively meaningless. You’ll know if you have ever looked at a surf forecast and then gone to your beach to check the surf, that the wave size predicted can be drastically off from reality.

The forecast given is usually for a general area or even a specific surf spot, but from the beach you’ll see that there may be 1′ waves breaking inside the cove of a point break, and 5′ waves breaking on the very outside even if the forecast says 3-4′. At a beach break, one end of the beach may be twice the size of the other side.

INTERESTED IN WATCHING SURF TUTORIALS? CLICK HERE.

SO HOW IS THIS INFORMATION GENERATED?

Swell forecasts use buoy readings which are then plugged into a computer model to predict readings in the future, usually at maximum up to 10 or 12 days out. A buoy is out there on the ocean measuring the rate and the distance that it is moved up and down by swells. It measures the height of the swell bump (crest) and the distance in time (wavelength) between crests. Since surf forecasts are predictions, they are most accurate within only a couple of days. Forecasts more than 5 days out should be taken with a grain of salt, as a lot can happen to change swells in that time, resulting in smaller or larger surf than first predicted.

HOW ARE WAVES CREATED?

Waves are formed by wind blowing over the surface of the ocean. The further away the storm begins makes a difference. A weak storm far away may dissipate before it creates a very large swell. But if there is a big strong storm originating on the opposite side of the globe, that maintains its strength and high wind speed at it travels, it will transfer a large amount of wind energy into the ocean which creates a long period swell.

If you’re looking at a surf forecast, by “long period” swell we’re usually talking 14” and above. However, where you live plays a factor in what is considered “long period”. In southern California, swells of 16″ or 17″ typically count as “long”. On the east coast or in the caribbean, an 11″ or 12″ period counts as “long” due to the fact that the average period tends to be smaller.

These long period swells contain energy created by wind that gets pushed down into the ocean, which means the swells typically move further below the surface and are more affected by bottom contour but less by winds and swells from other storms. This is why long period swells can maintain their energy over a further distance.

How DO waves travel?

Swells travel as a group of waves or “wave train”. As the swell moves forward, the wave in the front of the wave train will slow down and drop back to the rear of the group while the other waves move forward by one position. Then the next wave in front moves back and another takes its place — much like a rotating conveyor belt that is also moving forward. It’s a process somewhat similar to the “drafting” technique used by bicycle racers, and it enables wave trains to conserve their energy as they travel great distances across the oceans, working together to sustain energy.

SO, WHAT ELSE AFFECTS THE SIZE OF WAVES?

Bottom contour plays a big role in affecting the size of the waves from any swell, and wave height forecasts don’t always take that into account. For that reason, it’s much more useful to understand how to read the swell prediction from the buoy numbers, then after developing familiarity with your local beach you can better predict the actual size of the waves you will encounter that day from looking at the numbers. That’s what we’ll attempt to explain below. Bear with me, there’s some science and math involved!

If you’re a math geek or like numbers keep reading. Otherwise, skip down to “shoaling”…

You can calculate the speed of the waves with this formula: The speed of a swell or “wave train” is 1.5 x period. So looking at our example forecast above the 13” swell will have a speed of 1.5 x 13 or about 19.5 knots and the 22” swell will be 1.5 x 22 = 33 knots. If you want to convert that to mph (because who understand knots anyways?) the conversion is 1 knot = 1.2 mph. A 13” swell moves at 23.4 mph and a 22” swell moves at 39.6 mph. So a 22” period swell is moving at double the speed of a 13” swell. Individual waves move even faster. This is the speed of the wave train. If you want to calculate the speed of an individual wave, it is swell period x 3. So an individual wave in a 13” swell is going to be traveling at 13 x 3 = 39 knots or 46.8 mph vs a 22” period wave traveling at 22 x 3 = 66 x 1.2 = 79.2 mph.

Again, think of the wave train like a rotating conveyor belt that is also moving forward. This is the speed the wave travels through open water, not the speed that the wave will be traveling when you’re sitting in the water waiting to catch it. As the wave train moves into shallower water or encounters a rock shelf, headland, or beach the speed will slow down.

DeptH:

Waves begin to feel the ocean floor at a depth of 1/2 the wave length. To figure it out you take the number of seconds between swells, square it, then multiply by 2.56. The result will equal the depth the waves begin to feel the ocean floor.

So a 13” swell = 13 x 13 = 169 x 2.56 = 432’

But a 22” swell = 22 x 22 = 484 x 2.56 = 1,239’ deep

So longer period swells are more affected by bottom contour and that’s why they are called ground swells (typically over 13” long). We call shorter period swells wind swells because they are always generated by local winds (even though all waves are actually generated by wind), and usually can’t travel more than a few hundred miles before they decay.

Shoaling:

When waves approach shallower water their lower reaches begin to drag across the ocean floor and that friction slows them down. The wave energy below the surface of the ocean is pushed upward causing the waves to increase in height. The longer the period, the more energy under the surface, which is why longer period waves grow bigger than short period waves.

A 3’ wave with a 10″ period may only grow to be a 4’ breaking wave but a 3’ wave with 20 seconds may grow to be a 15’ breaking wave – more than 5 times the deep water height depending on the contours of the ocean floor.

As the waves pass into shallower water they become steeper and unstable as more and more energy is pushed upwards, finally to a point where they break at typically a depth of 1.3 times the wave height. So a 6’ wave will break in about 8’ of water.

A gradually sloping bottom will create a crumbly slow-breaking wave while a wave traveling over a steep ocean floor or hitting a reef result in faster hollower breaking waves. As the waves move into shallower water the speed and wavelength decrease (the waves get slower and closer together). So it isn’t that looking at a swell that is 20” means that the waves will come 20” apart. It’s a more complicated formula affected by so many factors.

Wrapping:

An aerial picture of one of the greatest point breaks – California’s Rincon – aptly called “queen of the coast”, demonstrating how a swell will wrap around a headland.

 

Here you see waves approaching from the right moving in towards shore – the grey area on the left. The black dot is a reef or sandbar. As the waves bend around it they cross up. This is the perfect situation for a peaky beach break and what makes the Northern Nicaragua surf spot “the Boom” work. In that case theres an outer reef that makes the waves cross up.

So from everything we’ve discussed above, you should have an idea of why and how this wrapping happens. The wave train approaches the coast, as it starts to “feel” the bottom it slows down and starts to break. The swell energy that has not yet felt the bottom continues traveling forward but the friction causes it to bend a bit and the lines wrap inwards, creating a very long “perfect” wave for surfers to enjoy.

This wrapping effect is most visible on a point break, but it can happen whenever an obstacle is encountered,whether it is a sandbar, reef, river mouth, bay, or even man made object such as a pier or jetty. If you are looking for waves with better shape, look for a coastline with some feature that will help the swell to wrap. If you have a long straight beach break without anything to break it up you will most likely have long closed-out waves.

In Summary

Swell forecasts tell you a lot more than just what size waves they are predicting for any particular beach, and that other information – including swell height and period can actually be more useful in helping you to predict the size of the waves breaking that day at your local break.

The best way to start understanding surf forecasts is to look at the forecast, then go to your beach to check the wave size. Notice the difference in predicted size vs. the size of the waves you actually see breaking. Then the next day, do the same thing. And the day after that…. Over time you’ll start to see a pattern and figure out which combination of numbers creates the ideal situation for the type of waves YOU like to ride. Then you’ll know which days to call in sick and score!

Special thanks to Surfline.com for assistance with the mathematical formulas quoted above.

FOR MORE SURF TUTORIALS CLICK HERE.

How To Read Waves: Lesson 1 – Types of Breaks

on By

The first thing a new surfer wants to learn (after they’ve learned the very basics of how to stand up on a wave) is how to “read” waves. We practice this in-person during surf sessions at our women’s surf and yoga retreats, and while we wish there was a secret password to unlocking this mystery that we could easily share with you, it’s actually a complicated skill to learn which takes years to grasp and a lifetime to master.

Want to watch a video about how to read waves? CLICK HERE!

When you think about it, reading waves is actually like predicting the future. You have to look at a lump of water and be able to anticipate what it’s going to look like in 5, 10, 15 seconds and then position yourself accordingly. Not an easy task! But, there are some shortcuts and tips that we can share to give you a jumpstart. This is the first lesson in our series, so read on to learn more about the different types of waves. If you want to get the full experience, join us on a retreat to have these features pointed out to you in person!

How do waves work?

Have you ever been watching surfers from beach thinking “man, they make that look so easy” or “why didn’t he go for that wave?” If you’ve never tried surfing it’s easy to think it looks like a paddle out, surf a wave cycle on repeat.  If you have surfed before, you are aware there is much more to surfing than that and 90% of your time in the ocean is spent either paddling (out, over, in, for a wave, to avoid a wave you don’t want) or sitting on your board studying the horizon looking for a wave to ride.

how waves break

To start with the very basics, here’s a graphic showing how waves work. Wind blows over the ocean surface pushing surface water up into waves. The wind-blown waves will travel on indefinitely until they encounter a shallow bottom surface, which slows down the bottom part of the wave, causing the top part of the wave to topple over and form a breaking wave.

The abruptness of the change in bottom contour affects the power of the breaking wave. Imagine yourself jogging. You trip over a speed bump and slightly topple over but are able to keep running. This is a wave encountering a gradually sloping bottom or very small sandbar or with a high tide. Now imagine you trip over a curb. Your fall will be more complete and harder. This is what happens at a medium tide. Finally, imagine tripping over a waist high wall – you would double over with force. This is what happens at low tide or when a wave hits a shallow reef sitting in deep water.

How fast you’re running will make a difference as well. So imagine the speed of your run to equal the strength of the swell, and the thing you trip over to be the ocean bottom contour, whether it’s rock, reef, or sand.

Being able to read waves is one of the most difficult skills to master in surfing. Here is the secret to reading them. The way you approach waves changes from wave to wave, day to day, and surf break to surf break. Only time and experience can get you to know when you should paddle for a wave or skip it. There are many aspects to reading waves but starting with the very basics : knowing what kind of break you are surfing is step one to gaining the knowledge of wave reading. Ok, onto the different types of bottom contours…

three main types of breaks

boom peaks

1. Beach Breaks:

Beach breaks are waves breaking over a sandy bottom. They are usually the most consistent types of breaks – meaning there would be surf-able waves on most days – since little swell is needed for waves to break over the sandy bottom.

Here's a diagram of how a sandbar forms. Wave action pulls sand off the beach to form a bar.
Here’s a diagram of how a sandbar forms. Wave action pulls sand off the beach to form a bar.

Waves break on sandbars that form on the ocean floor due to currents and wave action. The sand bars can shift with different storm and swell patterns which means that waves don’t break in the same spot every time.

With all the water coming towards shore via waves, that water needs a way to get back out to sea. This is how riptides form.

sandbar with rip photo

In the photo above you can see a low tide beach scene. The sand bar is visible along with a break in the bar caused by the water heading back out to sea that pulls sand with it. Since the water is deeper over the break in the bar, waves will be less likely to break there.

A rip current is a great place to choose to paddle out. Not only is the current going to take you out to sea, you will also likely have fewer waves coming at you to have to duck-dive or turtle-roll. When sitting in the lineup looking for a wave to catch, you want to avoid sitting in a rip tide for the same reason : waves will be less likely to break there and those that do will usually be choppy from all the outrushing water. 

If it has been a long time since a swell or storm has broken up the sand bottom then the sand can settle and flatten which means that breaking waves will be more likely to close out – meaning to break all at once without any opportunity for a long ride.

Other factors such as piers, jetties, and storm drains may dictate what may happen to a sand bar and also where the rip tides form. Those factors can create a more consistent sand bar which is why you often see surfers crowding these areas.   

Beach breaks are great for learning because there is little to worry about in the way of obstacles such as rocks and reefs. Waves will be breaking in multiple places which helps spread out the crowd. Also the waves are usually consistent, giving beginners plenty of tries to get the hang of surfing and more advanced surfers plenty of waves to practice on.

Our Northern Nicaragua Retreats and Northern Costa Rica Retreats are all primarily held at beach breaks.

reef craziness2. Reef Breaks:

A reef break is a surf spot that has anything from smooth rock to razor sharp reef beneath the breaking waves. Since the reef doesn’t move around, these waves will break in generally the same spot and will be more predictable than a beach break.

Often times waves breaking over a reef have more power because when the swell energy approaches the reef, the abrupt change in bottom (material or depth) creates a more hollow wave. At lower tides reef breaks can be dangerous if the reef is shallow (note photo in the beginning of this section of dry rock visible very close to the surfer!).reef break

Reef breaks are more predictable than beach breaks. The takeoff spot rarely varies very much so you can study where the waves are breaking, look towards the beach, choose a lineup marker (palm tree, hotel, lifeguard tower etc.), and then paddle directly to “the spot” each time, knowing that when the waves come, you’ll be in a good spot to catch one. Reef breaks typically have a consistent channel allowing you to paddle out easily. Since the takeoff spot is so predictable, crowds can often be more of an issue at a reef break than they would be at a shifty beach break.

While the potentially sharp and hard bottom of a reef break makes these spots more suited to more advanced surfers, there are some user-friendly waves that do break over reef. If you are a beginner planning to tackle a reef break, it’s a good idea to have a friend or someone like Surf With Amigas point you in the right direction to help you find the channel and avoid getting stuck inside on the reef.

If you are used to surfing beach breaks reef breaks are a great way to switch it up. They will force you to be more aware of your surroundings (shallow bottoms, line ups on the beach) and often offer better wave shape with the potential for a longer ride so you can practice new maneuvers in your surfing and have more time to think about what you’re doing.

On our Rote Island, Indonesia Retreats you would have an opportunity to surf a variety of reef breaks. If you join us on a Northern Nicaragua Retreat and we have some swell, we’ll get a chance to surf a fun reef break as well.

3. Point Breaks:

Point breaks are the quintessential wave you see in a surfer’s notebook doodles. The longest waves in the world are point breaks. The most well formed points come off of peninsulas that jut out into the ocean or some other feature underwater causing sand to build up to form very very long waves. They can have rock, reef, sand bottoms or a combination of rock or reef and sand (the rock or reef would act to hold the sand in place). Swell energy bends and peels along the peninsulas forming long, sometimes “perfect” waves.

wave drawing

 The waves forming off these points break in the same direction, so they are either all breaking left or all breaking right. Like a reef break, the waves will typically begin breaking in the same spot and are therefore relatively easy to predict.

Point breaks are often times crowded due to their tight takeoff point and very long high quality rides. On a good day, riding a wave from the peak may turn into a slalom course with the surfer on the wave having to maneuver around surfers waiting for their own waves, paddling out, or trying to drop in. Unfortunately, point breaks are usually tucked alongside headlands that can block swell energy making them more fickle and require a larger swell than either reef breaks or beach breaks to make them work.

Pavones is the second longest left point break in the world and if you join us at one of our Southern Costa Rica Retreats you will have a chance to surf the zone! Our retreats in southern Morocco are at an incredibly long right point break- great for longboarding.