Is this a joke?

Very very basic explanation of how the continental shelf effects us in the SOUTH EAST.

Long period swells send energy very very deep into the ocean. When this energy comes into contact with the sea floor it is pushed up creating a swell. When this swell eventually reaches the beach is creates waves. Due to the continental shelf being WAY offshore especially in the south east of the united states, wave energy decays as it approaches our beaches more so than anywhere else in the US. This along with the angle of the past swell, which was a bit too north of our swell window (blocked mainly by cape Hatteras) caused the bust in not only this but many other surf forecasting sites.

However most of you know that long period swells tend to wrap around points and capes. This would have been the case anywhere else but due to the continental shelf in our region the waves never made it here. This is typical of our region and many seasoned surfers and amateur forecasters saw this bust coming days in advance.

Dont blame the site. Swellinfo.com is by far the most reliable and user friendly surf forecasting site for the EAST COAST that exists.

Here are some images to explain what happened:

 

the continental shelf, if i remember correctly is about 400 feet deep and is fairly flat as the name suggests.

As the wave period increases, the depth at which the wave energy travels beneath the ocean surface increases. So, short period swells aren't influenced as much by the shelf, where as long period swells can lose much of their wave energy off the coast.

Depth(ft) = Period*Period * 2.56ft , where period is in seconds.

10 sec period => 256 ft
12 sec period => 369 ft.
14 sec period => 502 ft.
16 sec period => 655 ft.
18 sec period => 829 ft.
20 sec period => 1024 ft

As you can see, anything around 12 seconds or below will not interact greatly with the continental shelf. Many of the east coast swells stay below this mark.

This is of course a simplified answer,because you also need to take into account he near shore bathymetry, such as offshore shoals, etc...

 

Thanks for the nice write up and pics! I am understanding it more. I see the shelf is close at Hatteras (no wonder it breaks so good).

The Hatteras Diamond shoals buoys were reading; 10+ feet at 16 and 20-25 ft at 16 seconds (20 miles out) last thursday and friday. And at my sse facing beach, inside of a hook (Atlantic Beach, NC)(to the right of the "a" in north carolina in the pic above) it was reading 3.2-4.2 at 14-16 seconds. Went out saturday and it was about knee to waist, light offshore wind but breaking kind of funky, hard to get into, had to take late takeoffs, alot of closeouts, not much shoulder pickings. Tide was fatter than usual even at low tide. NE swell never really wraped like I thought it would.

Now down south at Wilmington, a more eastern in the southeast facing beach, they got more size, but the N wind put more bump in it.

I see the forecast get more accurate 24 hours out...even NOAA. But.Surfline was way off. Even calling today good and it was flat. This site still rocks and is one of the better forecasting sites. Thanks!

 

Thanks, ecoastprock , you are a Star, helped me a lot as well, although it's not me posted the 1st question, I benifited from it.

Cheers man.

 

troy

"swellinfo is always right if you dont see the wave paddle out and it will come" "trust the waves with ja life and ja wife" "you must have faith and the wave will follow" "if all else fails catch the sleeper set to mace" "Hit the lip with a shwak attack" "dont hate when no waves i skate" "frothy mountains are rolling in"

all are quotes to live by brought to us by troy. when you start to question something just think what would troy think and do that. Troy is always right and troy always surfs.

 

i dont smoke weed i smoke fools like you in da line up

 

tides?

Does swellinfo take the tide height into account when posting forcasts? I'm not being a smart a$$ or complaining....just curious. It seems like they don't. I have looked at numerous reports where the wave height is dropping as the tide fills in. I realize that each day/tide/swell/wind/location is different ,however, if there is a swell coming in all day and the tide is filling in....I would think a couple of hours before high tide would be better than low tide in most cases. I have seen the opposite on these reports several times.

 

no, not yet... All local areas will differ with regards to tide influence.

Tide of course will be a huge factor, especially on the longer period swells where water depth is so influential.

The forecasts in time will become more sophisticated to better take into account local factors. Many plans to improve the forecasts in the upcoming year.

 

Thanks for your response. Looking forward to the improved forcast!