Author Topic: Understanding Surf Height and Swell  (Read 10325 times)

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Offline Kalo

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Understanding Surf Height and Swell
« on: September 22, 2015, 02:44 PM »
 Does anyone have a clear understanding of these charts. Even I've read a bit about both SH and Swell and I'm still not exactly sure what the charts mean.  If the surf height is 1ft and swell is 5ft. What type of waves would we see breaking at the beach? Also they have swell 1-6. Does anyone clearly understand what these are and how they play into what breaks at the beach?  I've tried to find something clearly describing this on Surfline website and so far no luck. Thanks!


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Offline surfbrewer

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Re: Understanding Surf Height and Swell
« Reply #1 on: September 22, 2015, 04:44 PM »
Surf height means just that, the height of the surf at the beach or area you are looking at. Things that can impact the surf height and make it appear different from what is predicted are shifting sand bars on the seafloor, reefs, and the direction the beach faces. If you have a south swell hitting a beach that faces due south, it will have larger wave heights generally.

Swell gets a bit more complicated. We need to look at swell type, period, size, and direction. There are 2 types of swell, groundswell and wind swell. Groundswell is generated far offshore from the local spot and is usually generated by large weather systems. Wind swell is generated closer to shore by local weather patterns and winds. Generally groundswell offers better conditions for us to be on the water but, more importantly is the period and direction of swell.

Swell period represents the spacing, in seconds, between waves within the swell. You will hear "long period" and "short period" swell. By definition, long period swell is any swell with wave spacing 16 seconds or greater, while short period swell is less than 16 seconds. For me, in relation to kayak fishing, if I see a forecast calling for a swell at 12 seconds or greater I'm pretty stoked (depending how big it is). Longer period swell = calmer, smoother water. Short period swell becomes less organized and choppier.

That leads us to swell size and direction. The size of a swell is the measurement of wave height within the swell and is measured in deep water. Swell direction is the direction the swell is coming from. So a NW swell is coming from the northwest moving in a southeast direction. These two factors work together to determine wave height. I'll give you an example:

The Estero Coast which runs from Cayucos up towards Cambria is a South facing coastline. The beaches there face south and when a south swell comes into the area it hits that area full on and produces large and fun waves for surfers. South swell, again depending on size, can make spots like Windmills unfishable for most people. But, while that spot is unfishable an area like Leffingwell in Cambria that faces NW can be calm and totally fishable. The opposite is also true and is more common for our area. A NW swell is impacting the area making spots like Leffingwell and MDO less desirable, while Windmills has flat water.

Where it gets tricky is knowing which spots can handle certain swell size and what swell directions impact certain spots more. For me I know that if there is a south swell running, unless its a small one like 2-3 feet or smaller, I am not going to attempt launching at Windmills. The best thing you can do is pay attention to the daily swell reports and when you can visit the various launch spots to see how different swells affect them. Also, look at a map of the coastline and see what direction the spots actually face. You might be surprised at the actual direction of some beaches.

As for swell 1-6 on the chart you posted, swell 1 is the primary or main swell that is impacting the area. Swell 2 is the secondary swell impacting the area, usually from a different direction. Swell 3-6, if they're indicated, are also lesser swells impacting the area. These swells are usually smaller, shorter period wind swells. It is common to have a secondary swell, but you will not always have a third, fourth, fifth, etc. These lesser swells can also affect the surface of the water. If you have a nice small, long period swell you are going to be stoked but, throw in a secondary swell coming from the opposite direction and then a short period wind swell coming from another direction and you can have a big choppy mess out there.

Looking back at the chart you posted you see that the primary swell is WNW 5 feet at 8 seconds. Because you are looking at the surf forecast for Avila, a SW facing beach, you can see that the wave heights are basically flat because this steep (309 degree) WNW swell is missing this beach completely. Only the secondary, long period 1 foot swell is hitting here along with the tertiary swell which is also very small and fairly long.

Another factor that is separate from swell but that affects us greatly, sometimes more than the swell, is the wind. Really pay attention to the wind. I can't stress this enough. While our normal winds can be a pain in the ass, making conditions sloppy and unfishable, east winds or offshore winds can be a serious problem for kayaks. There are more than a few of us on this site and others that have been caught off guard be the wind, if you aren't prepared or at least have the means to call for help it can be a life threatening situation. Don't underestimate the wind. The bottom line is there are a bunch of factors that affect conditions out there. Be safe out there, have a vhf radio, go with a buddy, keep asking questions, and have a great time! I hope that helps and answers some of your questions.

Cheers,
Eric

 

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Offline Kalo

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Re: Understanding Surf Height and Swell
« Reply #2 on: September 23, 2015, 01:13 AM »
Be safe out there, have a vhf radio, go with a buddy, keep asking questions, and have a great time! I hope that helps and answers some of your questions.

Cheers,
Eric

Eric, I can't thank you enough for all that you've written.  Not sure if you've described this type of thing before, but I have to say it is very well done.  I spent a couple days reading other things and didn't see something so good.

Seems obvious, but I hadn't really noticed the swell directions under the various primary or secondary swell heights.

So far I've just launched at Avila (concrete vehicle ramp past the Cal Poly Pier).  The biggest waves breaking at that location have always seemed a bit larger than the what the reports might have said.  One thing I remember reading is that if the period is longer, there is more energy, and when it reaches the shore would produce larger breaking waves.

I just printed 3 local maps from http://www.charts.noaa.gov/PDFs/PDFs.shtml (18700) to keep track of the directions the beaches and launch sites are facing.  Nice to have them printed rather than looking online.

It's so helpful to understand what conditions experienced fishing kayakers consider No Go.

So far I've learned  to watch a bit and WAIT for the bigger waves to break and then be ready to move and do it with some serious intention to get out there quickly during the smaller sets.

Need to get a good VHF radio soon.

Thank you very much! Roger
« Last Edit: September 23, 2015, 01:16 AM by Kalo »
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Offline Ryanimpreza

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Re: Understanding Surf Height and Swell
« Reply #3 on: September 23, 2015, 10:58 AM »
Damn, nice write up!!!

Surf height means just that, the height of the surf at the beach or area you are looking at. Things that can impact the surf height and make it appear different from what is predicted are shifting sand bars on the seafloor, reefs, and the direction the beach faces. If you have a south swell hitting a beach that faces due south, it will have larger wave heights generally.

Swell gets a bit more complicated. We need to look at swell type, period, size, and direction. There are 2 types of swell, groundswell and wind swell. Groundswell is generated far offshore from the local spot and is usually generated by large weather systems. Wind swell is generated closer to shore by local weather patterns and winds. Generally groundswell offers better conditions for us to be on the water but, more importantly is the period and direction of swell.

Swell period represents the spacing, in seconds, between waves within the swell. You will hear "long period" and "short period" swell. By definition, long period swell is any swell with wave spacing 16 seconds or greater, while short period swell is less than 16 seconds. For me, in relation to kayak fishing, if I see a forecast calling for a swell at 12 seconds or greater I'm pretty stoked (depending how big it is). Longer period swell = calmer, smoother water. Short period swell becomes less organized and choppier.

That leads us to swell size and direction. The size of a swell is the measurement of wave height within the swell and is measured in deep water. Swell direction is the direction the swell is coming from. So a NW swell is coming from the northwest moving in a southeast direction. These two factors work together to determine wave height. I'll give you an example:

The Estero Coast which runs from Cayucos up towards Cambria is a South facing coastline. The beaches there face south and when a south swell comes into the area it hits that area full on and produces large and fun waves for surfers. South swell, again depending on size, can make spots like Windmills unfishable for most people. But, while that spot is unfishable an area like Leffingwell in Cambria that faces NW can be calm and totally fishable. The opposite is also true and is more common for our area. A NW swell is impacting the area making spots like Leffingwell and MDO less desirable, while Windmills has flat water.

Where it gets tricky is knowing which spots can handle certain swell size and what swell directions impact certain spots more. For me I know that if there is a south swell running, unless its a small one like 2-3 feet or smaller, I am not going to attempt launching at Windmills. The best thing you can do is pay attention to the daily swell reports and when you can visit the various launch spots to see how different swells affect them. Also, look at a map of the coastline and see what direction the spots actually face. You might be surprised at the actual direction of some beaches.

As for swell 1-6 on the chart you posted, swell 1 is the primary or main swell that is impacting the area. Swell 2 is the secondary swell impacting the area, usually from a different direction. Swell 3-6, if they're indicated, are also lesser swells impacting the area. These swells are usually smaller, shorter period wind swells. It is common to have a secondary swell, but you will not always have a third, fourth, fifth, etc. These lesser swells can also affect the surface of the water. If you have a nice small, long period swell you are going to be stoked but, throw in a secondary swell coming from the opposite direction and then a short period wind swell coming from another direction and you can have a big choppy mess out there.

Looking back at the chart you posted you see that the primary swell is WNW 5 feet at 8 seconds. Because you are looking at the surf forecast for Avila, a SW facing beach, you can see that the wave heights are basically flat because this steep (309 degree) WNW swell is missing this beach completely. Only the secondary, long period 1 foot swell is hitting here along with the tertiary swell which is also very small and fairly long.

Another factor that is separate from swell but that affects us greatly, sometimes more than the swell, is the wind. Really pay attention to the wind. I can't stress this enough. While our normal winds can be a pain in the ass, making conditions sloppy and unfishable, east winds or offshore winds can be a serious problem for kayaks. There are more than a few of us on this site and others that have been caught off guard be the wind, if you aren't prepared or at least have the means to call for help it can be a life threatening situation. Don't underestimate the wind. The bottom line is there are a bunch of factors that affect conditions out there. Be safe out there, have a vhf radio, go with a buddy, keep asking questions, and have a great time! I hope that helps and answers some of your questions.

Cheers,
Eric
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Offline surfbrewer

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Re: Understanding Surf Height and Swell
« Reply #4 on: September 23, 2015, 04:36 PM »
No problem, glad it helped clarify some things. You nailed it on the head though, have patience whether you are launching or landing. But, once you decide to go, GO! I don't know how many times I've seen guys wait and wait and wait, then finally decide to go only to hesitate or fumble with their paddle or something. When you feel its the right time have your gear ready and do it. As always feel free to ask other questions.

Thanks, Ryan!
 

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Offline RipTide aka Cor-Dawg

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Re: Understanding Surf Height and Swell
« Reply #5 on: September 23, 2015, 04:42 PM »
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Offline Zodiacker

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Re: Understanding Surf Height and Swell
« Reply #6 on: September 23, 2015, 11:58 PM »
Eric did a great job with the descriptive, but don't forget that one's height while sitting atop a kayak and facing an oncoming swell front on, one may end up in a slightly different result than what was read as "predicted swell height". One may be in a trough (in an out going retreat of water) and below the predicted swell height.

...just some of my Co2

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Offline surfbrewer

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Re: Understanding Surf Height and Swell
« Reply #7 on: September 24, 2015, 12:09 AM »
You said it George! Swell and waves always look bigger from the seat of a yak, a few inches off the water. ;)
 

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Offline Dogpound

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Re: Understanding Surf Height and Swell
« Reply #8 on: September 24, 2015, 12:16 AM »
Excellent info there.  Great write up Eric!With time you will find where your comfort zone is and decide what is no go for you.  In addition to all of the swell considerations you also have to take into consideration the wind speed and direction,  and predicted wind forecast for the day you are going.  Swell is important but  so is the wind.



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Offline dernst

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Re: Understanding Surf Height and Swell
« Reply #9 on: December 26, 2016, 06:55 PM »
Nice write-up.

This is a good site to see the swell size and direction.

https://cdip.ucsd.edu/?nav=recent&sub=nowcast&xitem=conception

Offline PJ

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Re: Understanding Surf Height and Swell
« Reply #10 on: December 27, 2016, 04:08 PM »
Great write-up Eric.  Only other thing to mention is that waves typically come in sets.  Sets of 3, 4, 5, 7 or sometimes even more.  The time between sets (not the period between the waves in the set) is typically greater on a longer period swell - which is usually a south swell in the summer & a WNW swell in the fall or winter.  Windswell is almost always short period swell with small amount of time between sets from the NW, which makes it a bitch to get out thru.

I think the thing that gets most people in trouble is when we have a long period southern hemi swell, with a good amount of time between sets.  Meaning it can be flat for 10 minutes, then overhead waves for 3 minutes straight, then flat again for 7 minutes.  You show at the beach, see flat water & think "no problemo".  Then by the time you're launching you're getting creamed.

Lastly, swell on a buoy has the much greater emphasis on the period than the wave height.  A 7 foot swell at 7 seconds isn't really that big.  But, a 7 foot swell at a 20 second period can me a mammoth mama-jamma:)  A lot of our south swells show on the buoys as 3' at 18 sec or similar -  which can translate into 6' surf height at a south facing beach.

They ran the Eddie Big Wave contest on Oahu last winter when the Hanalei buoy hit 20 feet at 20 seconds, a massive swell.

« Last Edit: December 27, 2016, 04:10 PM by PJ »
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Offline Hnfdkyakr

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Re: Understanding Surf Height and Swell
« Reply #11 on: January 18, 2017, 05:01 AM »
Thanks for asking tht great question Kalo, and thanks for that AWESOME answer Eric and everyone else!!!!
 Be safe!
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Be safe out there!
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