User:Jpanderson/jan30

Surf forecasting is the process of using offshore swell data to predict onshore wave conditions. It is used by millions of people across the world, including professionals who put their forecasts online, meteorologists who work for news crews, and surfers all over the world. It is impossible to make an exact prediction of the surf(shape and size of breaking waves), but by knowing a few factors a good prediction can be made. One needs to have an understanding of how waves are formed, a basic knowledge of bathymetry, and information (such as tides, location, and weather) about the surf spot being forecasted to accurately forecast the surf.

How waves are made
Waves are created as wind blows over the ocean, transferring its energy into the water The size of the swell is affected by three variables: the velocity of the wind, its duration, and its fetch, or distance the wind blows over.

Swells
There are two different types of swell that affect the surf conditions. In general groundswell produces waves that are much better for surfing. Wind swell is usually smaller, and almost always choppier and harder to surf than groundswell. Although both are present at most surf spots, groundswell creates much better breaking waves and sort of dominates the lineup. This distinct separation occurs because groundswell originates far from the shore it has more time to separate into more organized patterns, which are much easier to surf
 * Groundswell- Groundswell refers to waves generated far off of the coast
 * Wind swell- Wind swell refers to waves formed from local winds to the specific surf spot.

Swell Data
In order to forecast the surf, there is important data from the swells that need to be analyzed. There are three main factors used in surf forecasting:


 * Swell Height- Swell height refers to the height of the swell in deep water.


 * Swell Direction- Swell direction refers to the direction from where the swell is coming from. It is measured in degrees (as on a compass), and often referred to in general directions, such as a NNW or SW swell.
 * Swell Period- Swell period is an extremely important fact in surf forecasting that is often overlooked. It is a measurement of time between successive waves in seconds. If you multiply the swell period by 1.5 you will calculate the speed in knots of the waves. In general waves will be refered to as either short period (15 seconds or less) or long period waves(16 or more seconds). The swell period will give you information about how the swell will affect specific breaks differently.

These three pieces of information are the main key to forecasting the surf. If there is a swell of significant height that is headed in the direction of the break you are forecasting for, then there probably will be good surf. The swell period will tell you how much a swell will wrap into a spot and how much it will grow in deep water.

Wrapping and Refraction
One important fact about waves is that they focus more of their energy towards shallower water. Waves will always turn and refract towards shallower water. This is where swell period can drastically affect the conditions. The longer the period of the swell the more it tends to wrap into a spot. This means that a swell might cause waves in a spot even if it is not directed directly at the spot. Significant underwater irregularities, such as underwater canyons and sea mounts, can also affect how the waves come into a surf spot. Irregularities like these may cause the surf to much larger at one spot near by, while almost nonexistent at another. This is the case in surf spots such as Black's Beach, El Porto, and Mavericks.

Knowing your Break
Using swell data, which is readily available on the internet, you can predict how the surf will be for a fairly large area. However, the waves can differ drastically from spot to spot and from time to time. To accurately forecast the surf for a spot you need to understand how different conditions affect the waves there.

Types of Breaks
The shape of the ocean floor affects the break greatly. In general there are gradual sloping ocean floors which result in a slower crumpling wave (better for long boarding) and steeper sloping floors which result in a faster, hollower breaking wave (better for short boarding). There are also many different types of breaks:
 * Beachbreaks- Beachbreaks are the most common breaks in the world. They have many random qualities in the ocean floor, that can cause the waves to be either very good or very poor, which make them extremely difficult to accurately forecast for. The quality of the waves are decided by the shapes of the sand bars at the bottom. There are some things that can affect the sand bars at a beachbreak:
 * Water sources- Water sources such as a river mouth or sewer drain can create well defined sandbars after a big outflow of water
 * Piers- Piers usually have deep channels directly under them which can form sandbars on the sides, making better waves at the pier
 * Jetties- Smaller Jetties cause sand to build up on the tip that can cause good sandbars to form. Large jetties can actually cause the waves to reflect off the jetty and wedge into the next wave making larger and better waves The impact of jetties is especially evident at the breaks in Newport Beach.
 * Reefs- Reefs are breaks that have rock bottoms instead of sand bottoms. The have deeper channels next to the shallower water which gives a good form to the wave. They can often force waves to shoal quickly from deep to shallow water causing large and hollow surf.
 * Pointbreaks- Pointbreaks are breaks in which the waves bend and break around a specific point, usually resulting in consistent and good shape. Point breaks are usually formed by river mouths with loose rock bottoms

Weather and Tides
There are many other factors that affect the surf at a specific spot such as the wind and the tide. In general the surf is usually better with little to no wind. The surf is usually the best at a spot when there is a slight offshore wind. This wind helps to hold up the breaking wave a little longer, allowing a surfer to have more time on the face of the wave. The tide is an extremely important factor that affects the surf. Tides, which occur from varying gravitational forces between the sun, moon, and the earth, are easy to predict for a large time in advance. The effect of the tide on the waves differs at every spot. Some breaks can be epic on a low tide, while almost nonexistent with a high tide. Other breaks can change have much better shape on higher tide, as opposed to a lower tide.

Putting it all Together
The only way to tell how specific information will affect the surf in a specific spot is to spend time observing that spot. One of the beauties of surfing is that no two waves are the same, yet alone two surf spots. It takes spending a lot of time at a spot to figure out which conditions make that spot good and which conditions don't. Only then can an accurate forecast of the surf for any conditions be made.