One thing I dont get about surf forecasts in relation to the significant wave chart is why is the forecast flat for the week when it looks like Gloucester will have some type of swell on Sat/Sun of this week? Is the significant wave chart not relevant to rideable waves?
What will a sideshore swell produce in terms of waves. Im trying to really understand the swell charts and not have to rely simply on the forecast. Thank you for your explanations so far.
ahh that is a more complex question than you realize! swell angle can make all kinds of different things happen depending on the bottom conditions, swell period, tide and wind direction. a perpendicular swell can create closeouts or all time conditions. a diagonal angle can create rights where there were once only lefts or nothing at all. beach breaks are always changing too so a spot that works with a given set of conditions might not work with the same conditions a month later or even hours later. it's a science but not an exact one.
i find the forecasters are pretty on it and do the best they can with the data at hand, but it will certainly make you a better surfer to wrap your brain around as much of all this as you can. the best advice is to keep up with the maps and cams but then go out and experience the data by surfing it. there's a lot of nuance that you can't get from just looking at the maps.
it takes a lifetime and there's always something to learn. good luck!
How the angle of the swell affects the surf will depend on the swell period. If you have a very sideshore swell with a very short period, chances are the surf will be weak and gutless. A very perpendicular swell with a very long period will likely create closeouts at most beach breaks. The longer the period, the more angle you want b/c the surf will have plenty of power and you want that sweeping action so you get long lines rather than closeouts. With short period windswells, you don't have to worry so much about closeouts b/c windswells are typically peaky. So to maximize the power of a short period swell, you want the angle to be more perpendicular. On the east coast, swell direction is important, but wind direction and tide tend to have even more pronounced effects. On the west coast and at reefbreak locations prone to deepwater long period swells, swell direction can be the most important factor in determining wave quality. Every spot will have its own "sweet spot" of wind, tide, swell period, and swell direction, and the more you surf a spot you will become more tuned in to all of these variables. Hope that helps and PFS!!!
the significant wave height maps are a great resource to get a quick, overall picture of the upcoming surf, but it is definitely important to understand what you are looking at.
The significant wave height is defined as the average of the top 1/3 of all waves in the wave spectrum. This is defined, as if you were in a boat, and you would notice the bigger waves and not the smaller waves. But, of course, being an average of the biggest 1/3 of all waves, of course there will be bigger waves then this average value.
The wave height is good to know, but so is the wave direction. Use the white arrows on the wave maps to see where the dominant swell direction is coming from. If the arrows are pointing away from the coastline, then the majority of swell is pointing out to see from strong offshore winds.
These 2 variables - significant wave height, and direction are very very useful, but are certainly not the whole picture. To understand the whole picture, we need to realize that the ocean wave field is a spectrum of wave heights at different wave frequencies (or period) and coming from 0 to 360 degrees.
To understand how the waves will be at the beach, we look at organized swells. And, we can use some statistical approaches to partition swells from the entire wave energy spectrum. On Swellinfo, you can use the Surf/Swell Timeline. When you hover over the surf timeline, you will see the 2 primary swells. And, when you view the swell timeline, you can view the top 6 swell categories.
Looking at the individual swells is important, especially, when there are multiple swell sources in the water. For example, there may be a small SE background swell at 3ft @ 10 seconds, which will produce nice waist to stomach high surf. But, the offshore winds may be blowing really hard creating a 7ft @ 7 second swell moving away from the coast. The significant wave height would be around 7ft, while the surf will be only waist to stomach.
I hope this helps, and I didn't utterly confuse you further. I need to get a better knowledge section going. But, take a look at the outdated tutorials if you haven't already.